Vasopressin administration facilitates fluid removal during hemodialysis

Inadequate secretion of vasopressin during fluid removal by hemodialysis may contribute to the cardiovascular instability that complicates this therapy and administration of exogenous hormone, by supporting arterial pressure, may facilitate volume removal. To test this, we measured plasma vasopressin in patients with end-stage renal disease (ESRD) during hemodialysis and found that despite significant fluid removal, plasma vasopressin concentration did not increase. We further found that ESRD did not alter the endogenous removal rate of plasma vasopressin and that plasma hormone is not dialyzed. Finally, in a randomized, double-blinded, placebo-controlled trial in 22 hypertensive patients, we examined the effect of a constant infusion of a non-pressor dose of vasopressin on the arterial pressure response during a hemodialysis in which the target fluid loss was increased by 0.5 kg over the baseline prescription. We found that arterial pressure was more stable in the patients receiving vasopressin and that while only one patient (9%) in the vasopressin group had a symptomatic hypotensive episode, 64% of the patients receiving placebo had such an episode (P=0.024). Moreover, increased fluid removal was achieved only in the vasopressin group (520+/-90 ml vs 64+/-130 ml, P=0.01). Thus, administration of non-pressor doses of vasopressin to hypertensive subjects improves cardiovascular stability during hemodialysis and allows increased removal of excess extracellular fluid. Inadequate vasopressin secretion during hemodialysis-induced fluid removal is a likely contributor to the intradialytic hypotension that limits fluid removal.

Predictors of hemorrhage in patients with untreated brain arteriovenous malformation

BACKGROUND

Intracranial hemorrhage is a serious possible complication in patients with brain arteriovenous malformation (AVM). Several morphologic factors associated with hemorrhagic AVM presentation have been established, but their relevance for the risk of subsequent AVM hemorrhage remains unclear.

METHODS

The authors analyzed follow-up data on 622 consecutive patients from the prospective Columbia AVM database, limited to the period between initial AVM diagnosis and the start of treatment (i.e., any endovascular, surgical, or radiation therapy). Univariate and multivariate logistic regression and Cox proportional hazard models were applied to analyze the effect of patient age, gender, AVM size, anatomic location, venous drainage pattern, and associated arterial aneurysms on the risk of intracranial hemorrhage at initial presentation and during follow-up.

RESULTS

The mean pretreatment follow-up was 829 days (median: 102 days), during which 39 (6%) patients experienced AVM hemorrhage. Increasing age (hazard ratio [HR] 1.05, 95% CI 1.03 to 1.08), initial hemorrhagic AVM presentation (HR 5.38, 95% CI 2.64 to 10.96), deep brain location (HR 3.25, 95% CI 1.30 to 8.16), and exclusive deep venous drainage (HR 3.25, 95% CI 1.01 to 5.67) were independent predictors of subsequent hemorrhage. Annual hemorrhage rates on follow-up ranged from 0.9% for patients without hemorrhagic AVM presentation, deep AVM location, or deep venous drainage to as high as 34.4% for those harboring all three risk factors.

CONCLUSIONS

Hemorrhagic arteriovenous malformation (AVM) presentation, increasing age, deep brain location, and exclusive deep venous drainage appear to be independent predictors for AVM hemorrhage during natural history follow-up. The risk of spontaneous hemorrhage may be low in AVMs without these risk factors.

Recurrent stroke and cardiac risks after first ischemic stroke: The Northern Manhattan Study

BACKGROUND

Few population-based studies with long-term follow-up have compared risk of recurrent stroke and cardiac events after first ischemic stroke. The relative risk of these two outcomes may inform treatment decisions.

METHODS

In the population-based Northern Manhattan Study, first ischemic stroke patients age 40 or older were prospectively followed for recurrent stroke, myocardial infarction (MI), and cause-specific mortality. Fatal cardiac events were defined as death secondary to MI, congestive heart failure, sudden death/arrhythmia, and cardiopulmonary arrest. Risk of events (with 95% CIs) was calculated using Kaplan-Meier survival analysis and adjusted for sex and age using Cox proportional hazard models.

RESULTS

Mean age (n = 655; median follow-up 4.0 years) was 69.7 +/- 12.7 years. The risk of recurrent stroke was more than twice that of cardiac events (including nonfatal MI) at 30 days and approximately twice cardiac risk at 5 years. The age- and sex-adjusted 5-year risk of fatal or nonfatal recurrent stroke was 18.3% (14.8 to 21.7%), and the 5-year risk of MI or fatal cardiac event was 8.6% (6.0 to 11.2%). The adjusted 5-year risk of nonfatal stroke (14.8%, 11.6 to 17.9%) was approximately twice as high as fatal cardiac events (6.4%, 4.1 to 8.6%) and four times higher than risk of fatal stroke (3.7%, 2.1 to 5.4%).

CONCLUSIONS

Cardiac mortality is nearly twice as high as mortality owing to recurrent stroke, but long-term risk of all stroke, fatal or nonfatal, is approximately twice the risk of all cardiac events. The high risk of nonfatal recurrent stroke reinforces the importance of therapies aimed at preventing stroke recurrence in addition to preventing cardiac events.

Relative elevation in baseline leukocyte count predicts first cerebral infarction

BACKGROUND

Atherosclerosis is an inflammatory disease, and leukocyte levels are associated with future risk of ischemic cardiac disease.

OBJECTIVE

To investigate the hypothesis that relative elevations in leukocyte count in a stroke-free population predict future ischemic stroke (IS).

METHODS

A population-based prospective cohort study was performed in a multiethnic urban population. Stroke-free community participants were identified by random-digit dialing. Leukocyte levels were measured at enrollment, and participants were followed annually for IS, myocardial infarction (MI), and cause-specific mortality. Cox proportional hazards regression models were used to calculate hazard ratios (HRs) and 95% CIs for IS, MI, and vascular death after adjustment for medical, behavioral, and socioeconomic factors.

RESULTS

Among 3,103 stroke-free community participants (mean age 69.2 +/- 10.3 years) with baseline leukocyte levels measured, median follow-up was 5.2 years. After adjusting for stroke risk factors, each SD in leukocyte count (1.8 x 10(9) cells/L) was associated with an increased risk of IS (HR 1.22, 95% CI 1.05 to 1.42), and IS, MI, or vascular death (HR 1.13, 95% CI 1.02 to 1.26). Compared with those in the lowest quartile of leukocyte count, those in the highest had an increased risk of IS (adjusted HR 1.75, 95% CI 1.08 to 2.82). The effect on atherosclerotic and cardioembolic stroke was greater than in other stroke subtypes.

CONCLUSION

Relative elevations in leukocyte count are independently associated with an increased risk of future ischemic stroke and other cardiovascular events.

Association of Infratentorial Brain Arteriovenous Malformations With Hemorrhage at Initial Presentation

Background and Purpose— The goal of this study was to analyze the association of hemorrhagic presentation with infratentorial brain arteriovenous malformations (AVMs).

Methods— The 623 consecutive, prospectively enrolled patients from the Columbia AVM Databank were analyzed in a cross-sectional study. Clinical presentation (diagnostic event) was categorized as intracranial hemorrhage or nonhemorrhagic presentation. From brain imaging and cerebral angiography, AVM location was classified as either infratentorial or supratentorial. Univariate and multivariate statistical models were applied to test the effect of age, sex, AVM size and location, venous drainage pattern, and associated (ie, feeding artery or intranidal) arterial aneurysms on the likelihood of hemorrhage at initial AVM presentation.

Results— Of the 623 patients, 72 (12%) had an infratentorial and 551 (88%) had a supratentorial AVM. Intracranial hemorrhage was the presenting symptom in 283 patients (45%), and infratentorial AVM location was significantly more frequent (18%) among patients who bled initially (6%; odds ratio [OR], 3.60; 95% confidence interval [CI], 2.09 to 6.20). This difference remained significant (OR, 1.99; 95% CI, 1.07 to 3.69) in the multivariate logistic regression model controlling for age, sex, AVM size, deep venous drainage, and associated arterial aneurysms. In the same model, the effect of other established determinants for AVM hemorrhage—ie, AVM size (in 1-mm increments; OR, 0.95; 95% CI, 0.94 to 0.96), deep venous drainage (OR, 3.09; 95% CI, 1.87 to 5.12), and associated aneurysms (OR, 2.78; 95% CI, 1.76 to 4.40)—remained significant.

Conclusions— Our findings suggest that infratentorial AVM location is independently associated with hemorrhagic AVM presentation.

Effect of Age on Clinical and Morphological Characteristics in Patients With Brain Arteriovenous Malformation

Background and Purpose— The goal of this work was to determine the effect of age at initial presentation on clinical and morphological characteristics in patients with brain arteriovenous malformation (AVM).

Methods— The 542 consecutive patients from the prospective Columbia AVM database (mean±SD age, 34±15 years) were analyzed. Univariate statistical models were used to test the effect of age at initial presentation on clinical (AVM hemorrhage, seizures, headaches, neurological deficit, other/asymptomatic) and morphological (AVM size, venous drainage pattern, AVM brain location, concurrent arterial aneurysms) characteristics.

Results— Hemorrhage was the presenting symptom in 46% (n=247); 29% (n=155) presented with seizures, 13% (n=71) with headaches, 7% (n=36) with a neurological deficit, and 6% (n=33) without AVM-related symptoms. Increasing age correlated positively with intracranial hemorrhage ( P =0.001), focal neurological deficits ( P =0.007), infratentorial AVMs ( P <0.001), and concurrent arterial aneurysms ( P <0.001); an inverse correlation was found with seizures ( P <0.001), AVM size ( P =0.001), and lobar ( P <0.001), deep ( P =0.008), and borderzone ( P =0.014) location. No age differences were found for sex, headache, asymptomatic presentation, and venous drainage pattern.

Conclusions— Our data suggest a significant interaction of patient age and clinical and morphological AVM features and argue against uniform AVM characteristics across different age classes at initial presentation. In particular, AVM patients diagnosed at a higher age show a higher fraction of AVM hemorrhage and are more likely to harbor additional risk factors such as concurrent arterial aneurysms and small AVM diameter. Longitudinal population-based AVM data are necessary to confirm these findings.

The New York Islands AVM Study: design, study progress, and initial results

BACKGROUND AND PURPOSE

Prospective population-based data on the incidence of brain arteriovenous malformation (AVM) hemorrhage are scarce. We studied lifetime detection rates of brain AVM and incident AVM hemorrhage in a defined population.

METHODS

The New York islands (ie, Manhattan Island, Staten Island, and Long Island) comprise a 9,429,541 population according to the 2000 census. Since March 15, 2000, all major New York islands hospitals have prospectively reported data on consecutive patients living in the study area with a diagnosis of brain AVM and whether the patient had suffered AVM hemorrhage. Patients living outside the ZIP code-defined study area were excluded from the study population.

RESULTS

As of June 14, 2002, 284 prospective AVM patients (mean+/-SD age, 35+/-18 years; 49% women) were encountered during 21,216,467 person-years of observation, leading to an average annual AVM detection rate of 1.34 per 100,000 person-years (95% CI, 1.18 to 1.49). The incidence of first-ever AVM hemorrhage (n=108; mean age, 31+/-19 years; 45% women) was 0.51 per 100,000 person-years (95% CI, 0.41 to 0.61). The estimated prevalence of AVM hemorrhage among detected cases (n=144; mean age, 33+/-19 years; 50% women) was 0.68 per 100,000 (95% CI, 0.57 to 0.79).

CONCLUSIONS

Our prospective data, spanning 27 months, suggest stable rates for AVM detection and incident AVM hemorrhage. Approximately half of AVM patients may suffer intracranial hemorrhage.

Concurrent arterial aneurysms in brain arteriovenous malformations with haemorrhagic presentation

OBJECTIVE

To assess the effect of concurrent arterial aneurysms on the risk of incident haemorrhage from brain arteriovenous malformations (AVMs).

METHODS

In a cross sectional study, 463 consecutive, prospectively enrolled patients from the Columbia AVM Databank were analysed. Concurrent arterial aneurysms on brain angiography were classified as feeding artery aneurysms, intranidal aneurysms, and aneurysms unrelated to blood flow to the AVM. Clinical presentation (diagnostic event) was categorised as intracranial haemorrhage proved by imaging or non-haemorrhagic presentation. Univariate and multivariate statistical models were applied to test the effect of age, sex, AVM size, venous drainage pattern, and the three types of aneurysms on the risk of AVM haemorrhage at initial presentation.

RESULTS

Arterial aneurysms were found in 117 (25%) patients with AVM (54 had feeding artery aneurysms, 21 had intranidal aneurysms, 18 had unrelated aneurysms, and 24 had more than one aneurysm type). Intracranial haemorrhage was the presenting symptom in 204 (44%) patients with AVM. In the univariate model, the relative risk for haemorrhagic AVM presentation was 2.28 (95% confidence interval (CI) 1.12 to 4.64) for patients with intranidal aneurysms and 1.88 (95% CI 1.14 to 3.08) for those with feeding artery aneurysms. In the multivariate model an independent effect of feeding artery aneurysms (odds ratio 2.11, 95% CI 1.18 to 3.78) on haemorrhagic AVM presentation was found. No significant effect was seen for intranidal and unrelated aneurysms. The attributable risk of feeding artery aneurysms for incident haemorrhage in patients with AVM was 6% (95% CI 1% to 11%).

CONCLUSIONS

The findings suggest that feeding artery aneurysms are an independent determinant for increased risk of incident AVM haemorrhage.

Risk of endovascular treatment of brain arteriovenous malformations

BACKGROUND AND PURPOSE

Independently assessed data on frequency, severity, and determinants of neurological deficits after endovascular treatment of brain arteriovenous malformations (AVMs) are scarce.

METHODS

From the prospective Columbia AVM Study Project, 233 consecutive patients with brain AVM receiving > or =1 endovascular treatments were analyzed. Neurological impairment was assessed by a neurologist using the Rankin Scale before and after completed endovascular therapy. Multivariate logistic regression models were used to identify demographic, clinical, and morphological predictors of treatment-related neurological deficits. The analysis included the components used in the Spetzler-Martin risk score for AVM surgery (AVM size, venous drainage pattern, and eloquence of AVM location).

RESULTS

The 233 patients were treated with 545 endovascular procedures. Mean follow-up time was 9.6 months (SD, 18.1 months). Two hundred patients (86%) experienced no change in neurological status after treatment, and 33 patients (14%) showed treatment-related neurological deficits. Of the latter, 5 (2%) had persistent disabling deficits (Rankin score >2), and 2 (1%) died. Increasing patient age [odds ratio (OR), 1.04; 95% confidence interval (CI), 1.01 to 1.08], number of embolizations (OR, 1.41; 95% CI, 1.16 to 1.70), and absence of a pretreatment neurological deficit (OR, 4.55; 95% CI, 1.03 to 20.0) were associated with new neurological deficits. None of the morphological AVM characteristics tested predicted treatment complications.

CONCLUSIONS

From independent neurological assessment and prospective data collection, our findings suggest a low rate of disabling treatment complications in this center for endovascular brain AVM treatment. Risk predictors for endovascular treatment differ from those for AVM surgery.

Dysplastic vessels after surgery for brain arteriovenous malformations

BACKGROUND AND PURPOSE

The cause and clinical significance of residual dysplastic vessels after surgery for brain arteriovenous malformations (AVM) are unclear. We studied predictors and frequency of residual dysplastic vessels on cerebral angiography after AVM surgery.

METHODS

The 240 prospectively enrolled surgical patients from the New York AVM Databank underwent 269 AVM-related surgical procedures. Reported postoperative brain angiographic findings were classified post hoc as showing (1) persistent dysplastic vessels, (2) a residual AVM, (3) focal hyperemia in the surgical bed, (4) other changes, or (5) a normal angiogram. Univariate and multivariate models were applied to test for an association between residual dysplastic vessels and patient age, sex, preoperative AVM size, anatomic AVM location, number of embolization procedures before surgery, and the time interval between AVM surgery and the postoperative angiogram.

RESULTS

Of the 224 documented postoperative angiograms, 78 (35%) showed dysplastic vessels, 24 (11%) had evidence for a residual AVM, 16 (7%) showed focal hyperemia, 6 (2%) revealed other findings, and 100 (45%) were normal. The number of cases showing angiographic evidence for dysplastic vessels was significantly associated with increasing size of the AVM (in millimeter increments; P=0.0001); the mean diameter of AVMs in patients showing dysplastic vessels after surgery was significantly larger (41 mm, SD +/-14) than in those without residual dysplastic vessels (27 mm, SD +/-13; P<0.001). Symptomatic postoperative intracerebral hemorrhage occurred in 4 patients (1%), in 2 of whom dysplastic vessels were seen on the postoperative angiogram.

CONCLUSIONS

The findings suggest that persistent dysplastic vessels may be found in approximately one third of angiograms after AVM surgery. Preoperative AVM size was found to be an independent predictor for the occurrence of dysplastic vessels on the postoperative angiogram.

Acute cardiac allograft rejection in nitric oxide synthase-2(-/-) and nitric oxide synthase-2(+/+) mice: effects of cellular chimeras on myocardial inflammation and cardiomyocyte damage and apoptosis

BACKGROUND

The contribution of nitric oxide synthase (NOS)-2 to myocardial inflammation and cardiomyocyte necrosis and apoptosis during allograft rejection was investigated through heterotopic cardiac transplantation in mice.

METHODS AND RESULTS

In the first experiments, hearts from C3H donor mice were transplanted into NOS-2(-/-) and NOS-2(+/+) C57BL/6J.129J recipients. A second series of experiments included NOS-2(-/-) donor hearts transplanted into NOS-2(-/-) recipients and wild-type NOS-2(+/+) donor hearts transplanted into wild-type NOS-2(+/+) recipients. (All donors were C57BL/6J and recipients were C57BL/6J.129J.) In the first series of experiments, no significant differences were observed in allograft survival, rejection score, total number of apoptotic nuclei (TUNEL), total number of apoptotic cardiomyocytes, or graft NOS-2 mRNA and protein. Positive NOS-2 immunostaining occurred in endothelial cells and cardiomyocytes in the allografts; the inflammatory infiltrate was NOS-2 positive only when recipients were NOS-2(+/+). In the second series of experiments, cardiac allograft survival was significantly increased in the NOS-2(-/-) mice (26+/-13 versus 17+/-8 days, P<0.05), along with significant reductions in inflammatory infiltrate, rejection score, and total number of apoptotic nuclei (23.5+/-9.5 versus 56.4+/-15.3, P<0.01) and of apoptotic cardiomyocytes (2.9+/-1.6 versus 6.9+/-2.7, P<0.05). No NOS-2 or nitrotyrosine, a marker of peroxynitrite exposure, was detected in NOS-2(-/-) allografts transplanted into NOS-2(-/-) recipients.

CONCLUSIONS

The data suggest that NO derived from NOS-2 contributes to the inflammatory response and to cardiomyocyte damage and apoptosis during acute cardiac allograft rejection.

Direct coronary artery perfusion from the left ventricle

OBJECTIVES

Trends in coronary bypass surgery require less invasive techniques and more conduits. We investigated the ability of direct coronary perfusion from the left ventricle to support regional and global cardiac function.

METHODS

A conduit was established between the left ventricle and left anterior descending coronary artery (n = 6) with an interposed Starling resistor that allowed for graded regulation of backward flow. Changes of coronary flow, regional function in the territory of the left anterior descending coronary artery, and reactive hyperemia were studied. In 3 separate dogs, functional tolerance to increased heart rate was tested. In another 3 dogs, left ventricle-left anterior descending and left ventricle-left circumflex coronary artery conduits were established simultaneously (double conduit), and global function was tested.

RESULTS

Without flow regulation, flow through the left ventricle-left anterior descending conduit exhibited high peaking (102 +/- 35 mL/min), midsystolic forward flow, and large pandiastolic backward flow (peaking at -47 +/- 22 mL/min). Mean coronary flow and regional function were maintained at 46.0% +/- 7.1% (35.8%-54.2%) and 45.3% +/- 29.1% (-1.8%-74.2%) of their respective normal values. When the Starling resistor was used to regulate backward flow, these values increased to 70.8% +/- 12.5% (56.8%-90.4%) and 70.2% +/- 27.8% (23.6%-107.7%), respectively. Coronary and functional reserve with a left ventricle-left anterior descending conduit were not observed. With the double conduit, global ventricular contractility indexed by end-systolic pressure-volume relation averaged 46% +/- 35% of its normal value.

CONCLUSIONS

A left ventricle-coronary artery conduit supplied approximately 45% of normal blood flow and regional function, and both were improved by regulation of backward flow. Therefore, a conduit from the left ventricle to an epicardial vessel could serve as a rapidly deployable means of revascularizing totally occluded coronary vessels for which suitable natural conduits are not available.

Quantification of myocardial perfusion in human subjects using 82Rb and wavelet-based noise reduction

Quantification of myocardial perfusion with 82Rb has been difficult to achieve because of the low signal-to-noise ratio of the dynamic data curves. This study evaluated the accuracy of flow estimates after the application of a novel multidimensional wavelet-based noise-reduction protocol.

METHODS

Myocardial perfusion was estimated using 82Rb and a two-compartment model from dynamic PET scans on 11 healthy volunteers at rest and after hyperemic stress with dipyridamole. Midventricular planes were divided into eight regions of interest, and a wavelet transform protocol was applied to images and time-activity curves. Flow estimates without and with the wavelet approach were compared with those obtained using H2(15)O.

RESULTS

Over a wide flow range (0.45-2.75 mL/g/min), flow achieved with the wavelet approach correlated extremely closely with values obtained with H2(15)O (y = 1.03 x -0.12; n = 23 studies, r = 0.94, P < 0.001). If the wavelet noise-reduction technique was not used, the correlation was less strong (y = 1.11 x + 0.24; n = 23 studies, r = 0.79, P < 0.001). In addition, the wavelet approach reduced the regional variation from 75% to 12% and from 62% to 11% (P < 0.001 for each comparison) for resting and stress studies, respectively.

CONCLUSION

The use of a wavelet protocol allows near-optimal noise reduction, markedly enhances the physiologic flow signal within the PET images, and enables accurate measurement of myocardial perfusion with 82Rb in human subjects over a wide range of flows.

Measurement of myocardial blood flow with PET using 1-11C-acetate

11C-acetate has been used extensively for the noninvasive assessment of myocardial oxygen consumption and viability with PET. The use of early uptake of acetate by the heart to measure myocardial perfusion has been proposed. This study evaluated the application of 11C-acetate for absolute measurement of myocardial blood flow using a simple compartmental model that does not require blood sampling.

METHODS

Eight healthy volunteers and 13 subjects with concentric left ventricular hypertrophy were studied under resting conditions with both 11Cacetate and 15O-water. Myocardial blood flow with 11C-acetate was obtained by fitting the first 3 min of the blood and tissue tracer activity curves to a two-compartment model. Flows obtained were compared with a validated approach using 15O-water.

RESULTS

In healthy volunteers, regional myocardial perfusion at rest estimated with 11C-acetate was comparable with values obtained with 15O-water (1.06 +/- 0.25 and 0.96 +/- 0.12 mL/g/min, respectively). Perfusion in subjects with left ventricular hypertrophy was also comparable if the recovery coefficient (FMM) used was corrected for ventricular mass. If a fixed FMM was used, flow was greatly overestimated. FMM could be estimated from left ventricular mass (FMM = 0.46 + 0.002 x mass, r = 0.86, P < 0.0001).

CONCLUSION

The results of this study suggest that 11C-acetate can be applied to quantitatively estimate myocardial perfusion under resting conditions using a two-compartment model without the need for blood sampling, provided that an appropriate FMM is chosen. This approach should increase the usefulness of this tracer and obviate administration of a separate tracer to independently measure perfusion.

Absolute quantitation of coronary steal induced by intravenous dipyridamole

OBJECTIVE

The study was done to determine whether coronary steal (defined as an absolute decrease in perfusion from resting blood flow) is induced by intravenous (IV) dipyridamole in patients with severe coronary artery disease (CAD).

BACKGROUND

Myocardial ischemia during coronary vasodilation is usually attributed to coronary steal. However, there is limited data on the absolute magnitude of coronary steal in humans.

METHODS

Eighteen patients with multivessel CAD underwent dynamic positron emission tomography (PET) imaging with 13NH3 at rest and after infusion of IV dipyridamole. Eight myocardial sectors were analyzed per short axis slice and myocardial blood flow calculated with a two-compartment model in absolute terms.

RESULTS

Coronary steal occurred in 8 of the 18 patients. In the 8 patients with coronary steal, myocardial blood flow decreased from 90 +/- 18 ml/100 g/min at rest to 68 +/- 27 ml/100 g/min following dipyridamole in the segments with steal, and increased from 87 +/- 19 to 138 +/- 16 ml/100 g/min following dipyridamole in the segments without steal. Significant clinical correlates of coronary steal were either ST elevation or the combination of ST depression and angina.

CONCLUSIONS

Coronary vasodilation with IV dipyridamole is associated with significant reductions in blood flow to collateral-dependent myocardium consistent with coronary steal in about 45% of patients with severe CAD.

The Effect of Concurrent Arterial Aneurysms on the Risk of Hemorrhagic Presentation in Brain Arteriovenous Malformations

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Background and Purpose: To assess the effect of concurrent arterial aneurysms on the risk of hemorrhagic presentation in brain arteriovenous malformations (AVMs). Methods: The 463 consecutive, prospectively enrolled patients from the New York AVM Databank were analyzed. Concurrent arterial aneurysms on brain angiography were classified as (1) flow-related feeding artery aneurysms, (2) intranidal aneurysms, and (3) aneurysms unrelated to blood flow to the AVM. Clinical presentation (diagnostic event) was categorized as (1) intracranial hemorrhage proven by imaging or (2) non-hemorrhagic presentation. Univariate and multivariate statistical models were applied to test the effect of age, gender, AVM size, venous drainage pattern, and the three different types of aneurysms on the risk of AVM hemorrhage at initial presentation. Results: Arterial aneurysms were found in 117 (25%) AVM patients. In 93 cases, a single aneurysm type was found (54 had feeding artery aneurysms, 21showed intranidal aneurysms, 18 had unrelated aneurysms), 24 patients had more than one aneurysm type. Overall, 204 (44%) patients presented with hemorrhage. Concurrent arterial aneurysms were significantly more frequent in patients with incident AVM hemorrhage (34%) as compared to those without hemorrhage (18%, p=0.001). In the multivariate model an independent effect for flow-related aneurysms (OR 2.1 , 95% CI: 1.2 to 3.8) on hemorrhagic AVM presentation was found. No effect was seen for intranidal and unrelated aneurysms. The attributable risk of incident hemorrhage in AVM patients harbouring flow-related aneurysms is 0.059 (95% CI: 0.01 to 0.105). Conclusions: The findings suggest that flow-related arterial aneurysms are an independent determinant for increased risk of incident AVM hemorrhage.

The New York Islands AVM Study: Detection rates for brain AVM and incident AVM hemorrhage

P159

Background: Population-based data on the incidence of brain AVM hemorrhage is scarce. We studied detection rates of brain AVM and AVM hemorrhage in a defined population. Methods: The New York islands (Manhattan, Staten Island, and Long Island) are a ZIP-code defined area comprising a 8,898,000 population. In a retrospective investigation, major NY islands hospital centers retrieved the number of patients who lived in the study area and were discharged with a diagnosis of brain AVM between 1996 and 1999. Starting March 15, 2000, all major NY islands hospitals prospectively reported data on consecutive NY islands patients with a diagnosis of brain AVM and whether or not the patient had suffered AVM hemorrhage. Referral patients living outside the study area were excluded from the sample. Results: The retrospective detection rate of brain AVMs in patients living in the study area (Table 1) was estimated to be 1.2/100,000 person-years (95% CI:1.1–1.4). As of July 14, 2000, 37 prospective AVM patients were encountered leading to a calculated AVM detection rate of 1.25/100,000 pers-yrs (95% CI: 0.9–1.7) with an estimated incidence for first-ever AVM hemorrhage (n=6) of 0.2/100,000 pers-yrs (95% CI:0.1 to 0.5). The prevalence of AVM hemorrhage (n=14) was 0.5/100,000 pers-yrs (95% CI:0.3 to 0.8). Conclusions: Our preliminary data suggest similar prospective and retrospective AVM detection rates. More than one third of AVM patients may suffer intracranial hemorrhage.

Gender differences in the risk of ischemic stroke associated with aortic atheromas

BACKGROUND AND PURPOSE

Atherosclerotic plaque of the proximal portion of the aorta is associated with an increased risk of ischemic stroke in the elderly. Different cutoffs of plaque thickness have been used in the literature for risk stratification and have been applied to both men and women. However, the assumption that the relationship between plaque thickness and stroke risk is the same in the 2 genders has not been proven. The aim of this study was to evaluate whether the prevalence of different degrees of aortic plaque thickness differed in men and women with ischemic stroke.

METHODS

We performed transesophageal echocardiography in 152 patients aged >59 years with acute ischemic stroke (76 men and 76 women) and in 152 control subjects of similar age (70 men and 82 women). Odds ratios (ORs) for ischemic stroke with 95% CIs for different plaque thickness definitions were calculated for the overall group and separately for men and women by logistic regression analysis after adjusting for age, arterial hypertension, and hypercholesterolemia.

RESULTS

Aortic plaques >/=4 mm were significantly more frequent in men than in women (31.5% versus 20.3%, respectively; P:=0.025) and were associated with ischemic stroke in both men (adjusted OR 6.0, CI 2.1 to 16.8) and women (adjusted OR 3. 2, CI 1.2 to 8.8). However, plaques 3 to 3.9 mm in thickness had a significant association with stroke in women (adjusted OR 4.8, CI 1. 7 to 15.0) but not in men (adjusted OR 0.8, CI 0.2 to 3.0). Plaques <3 mm were not associated with a significantly increased stroke risk for either sex.

CONCLUSIONS

Smaller aortic plaques are significantly associated with ischemic stroke in women but not in men. If the increased prevalence of smaller plaques in women is confirmed to be associated with increased risk for embolic stroke, different cutoff points may have to be adopted in men and women for risk stratification and for decisions regarding medical intervention.

Normal limits for left ventricular ejection fraction and volumes estimated with gated myocardial perfusion imaging in patients with normal exercise test results: influence of tracer, gender, and acquisition camera

BACKGROUND

Myocardial imaging with tracers such as technetium-99m sestamibi or thallium-201 is extensively used as a means of measuring myocardial perfusion. With gated acquisition, these tracers can also be used as a means of measuring left ventricular ejection fraction (EF) and end diastolic and end systolic volumes (EDV and ESV, respectively). The objective of this study was to determine the normal range of EF, EDV, and ESV and to evaluate differences caused by either the tracer used, the gender of the patient, or the acquisition camera used.

METHODS AND RESULTS

A total of 1513 consecutive patients (mean age, 60+/-12 years [SD]) who had normal results on Bruce exercise tests had either Tc-99m sestamibi (n = 884) or Tl-201 (n = 629) injected at peak stress. Although all patients were referred for the evaluation of chest pain or dyspnea and many had cardiac risk factors, all had normal exercise capacity corrected for age, no electrocardiographic signs of ischemia, normal results on perfusion scans, and normal wall motion determined by means of quantitated gated single photon emission computed tomography (QGS). Scans were acquired on 1 of 3 different cameras. The mean EF for all patients who had gated Tc-99m sestamibi scans was 63% +/- 9%, not different from patients who had gated Tl-201 scans (63% +/- 9%). However, when the gender of the patient was considered, the mean EF for women was 66% +/- 8% with Tc-99m sestamibi (n = 519), higher than the mean EF for men (58% +/- 8%, n = 365, P<.0001). Similarly, the mean EF for women studied with Tl-201 (67% +/- 8%, n = 326) was higher than that of men (59% +/- 7%, n = 303,P<.0001). Patients with diabetes mellitus (n = 153) had a slightly reduced EF (62% +/- 10%, P<.001). In a subset of 240 patients, 140 patients studied with Tc-99m sestamibi and 100 studied with Tl-201, the EDV and ESV for women (n = 124) was estimated by means of QGS to be lower (57 +/- 17 mL and 19 +/- 11 mL, respectively) than those for men (74 +/- 22 mL-and 29 +/- 13 mL, respectively; n = 116; P<.001 for each comparison). No clinically significant differences in EF or volumes were noted based on tracers used or acquisition camera. For patients with normal results on exercise treadmill tests and perfusion imaging, the lower limit of normal for EF with gated perfusion imaging with QGS was 50% for women and 43% for men. For EDV and ESV, the upper limit of normal was 91 mL and 40 mL, respectively, for women and 119 mL and 55 mL, respectively, for men.

CONCLUSIONS

No significant differences related to either tracer or acquisition camera used were noted for EF, suggesting equivalency for clinical trials for patients with normal results on exercise tests. However, EF, EDV, and ESV determined by means of gated perfusion imaging need to be corrected for gender.

Elevated levels of plasma C-reactive protein are associated with decreased graft survival in cardiac transplant recipients

BACKGROUND

Inflammation may be involved in the origin of transplant coronary artery disease. We hypothesized that plasma levels of C-reactive protein (CRP) and interleukin-6 (IL-6), markers for systemic inflammation, would correlate with cardiac transplant graft survival.

METHODS AND RESULTS

We studied 99 consecutive cardiac transplant recipients who were referred for routine endomyocardial biopsy and/or surveillance coronary angiography. Plasma levels of CRP and IL-6 were measured by their respective ELISAs. Patients were divided into 2 groups: those who died or required retransplantation and those who survived without the need for retransplantation. During the follow-up period of 5.0+/-2.7 years (range, 0.2 to 15.1 years) after transplant, 20 patients died and 9 required retransplantation. There was no significant difference in age, race, sex, cause of native myopathy, presence of diabetes, or use of aspirin, statins, or calcium channel blockers between the 2 groups. Although IL-6 did not relate to graft failure, CRP level was predictive of allograft failure (P:=0.003). The risk of allograft failure increased 36% for every 2-fold increase in CRP level. Moreover, CRP levels also correlated significantly with the frequency of grade 3 rejection (P:=0.02). In multivariate analysis, when combined with other significant predictors such as donor age and sex mismatching of the graft, CRP still significantly predicted graft failure (P:=0.025) with a 32% increase in the risk of graft failure for every 2-fold increase in CRP level.

CONCLUSIONS

These findings suggest that elevated plasma levels of CRP are associated with subsequent allograft failure in cardiac transplant recipients.

Incident hemorrhage risk of brain arteriovenous malformations located in the arterial borderzones

BACKGROUND AND PURPOSE

We sought to assess the relative risk of hemorrhagic presentation of brain arteriovenous malformations (AVMs) located in the arterial borderzone territories.

METHODS

The 464 consecutive, prospectively enrolled patients from the New York AVM Databank were analyzed. AVM borderzone location was coded positive when the malformation was supplied by branches of at least 2 of the major circle of Willis arteries (anterior, middle, and/or posterior cerebral arteries). AVMs fed by branches of only 1 major pial or any other single artery served as a comparison group. Clinical presentation (diagnostic event) was categorized as (1) intracranial hemorrhage, proven by brain imaging, or (2) seizure, focal neurological deficit, headache, or other event with no signs of AVM hemorrhage on brain imaging.

RESULTS

In 48% (n=222) of the patients, AVMs were located in the arterial borderzone territories; in 52% (n=242) a non-borderzone location was found. Hemorrhage was the presenting symptom in 44% (n=205); 28% (n=132) presented with seizures, 11% (n=52) with headaches, 7% (n=34) with a neurological deficit, and 9% (n=41) with other or no AVM-related symptoms. The frequency of incident AVM hemorrhage was significantly lower in borderzone AVMs (27%, n=61) than in non-borderzone malformations (60%, n=144; P:<0.001). This difference remained significant in a multivariate model controlling for age, sex, AVM size, deep venous drainage, and presence of aneurysms (odds ratio, 0.4; 95% CI, 0.25 to 0.66).

CONCLUSIONS

Our findings suggest that borderzone location is an independent determinant for a lower risk of AVM hemorrhage at initial presentation.

Determinants of neurological outcome after surgery for brain arteriovenous malformation

BACKGROUND AND PURPOSE

We sought to define determinants of neurological deficit after surgery for brain arteriovenous malformation (AVM).

METHODS

One hundred twenty-four prospective patients (48% women, mean age 33 years) underwent microsurgical brain AVM resection. Patients were examined by 3 study neurologists immediately before surgery, postoperatively in-hospital, by in-person long-term follow-up, and with a structured telephone follow-up. They were classified according to the 5-point Spetzler-Martin grading system, with its 3 elements: size, venous drainage pattern, and location. The functional neurological status was classified with the modified Rankin scale. Multivariate logistic regression models were applied to test the effect of patient age, gender, and the 3 Spetzler-Martin elements on early and long-term postoperative neurological complications.

RESULTS

Twelve patients (10%) were classified as Spetzler-Martin grade 1; 36 (29%) as grade 2; 47 (38%) as grade 3; 26 (21%) as grade 4; and 3 (2%) as grade 5. Postoperatively, in-hospital, 51 patients (41%) showed new neurological deficits (15% disabling [ie, Rankin scale score >2] and 26% nondisabling [ie, Rankin 1 or 2]). At long-term follow-up (mean follow-up time 12 months), 47 patients (38%) revealed surgery-related neurological deficits (6% disabling; 32% nondisabling). The rate of neurological complications increased by Spetzler-Martin grade. Female gender, AVM size, and deep venous drainage were significantly associated with neurological deficits at in-hospital and long-term evaluation. For patient age and AVM location, no significant association was found.

CONCLUSIONS

The findings suggest that female gender, AVM size, and AVM drainage into the deep venous system may be determinants of neurological deficit after microsurgical AVM resection.

Maximizing hemodynamic effectiveness of biventricular assistance by direct cardiac compression studied in ex vivo and in vivo canine models of acute heart failure

OBJECTIVE

Direct cardiac compression improves effective ventricular contractility. However, associated reductions in filling volumes and increases in arterial pressure occurring at the onset of direct cardiac compression limit the degree to which cardiac output is augmented. We tested the hypothesis that active preload and afterload control maximizes the hemodynamic effectiveness of direct cardiac compression.

METHODS AND RESULTS

Studies in isolated canine hearts loaded with a computer-controlled volume servo system that mimicked heart failure were used to clearly define the hemodynamic effects of direct cardiac compression. Immediately on initiation of direct cardiac compression, ventricular end-diastolic pressure and volume decreased substantially, arterial pressure increased, but stroke volume did not change significantly. When end-diastolic pressure was restored to about 20 mm Hg, stroke volume doubled; decreasing afterload resistance further increased stroke volume by about 30%. Such load adjustments were then tested in vivo in a canine model of acute heart failure induced by coronary artery microembolizations titrated to decrease cardiac output to 33% +/- 9% of control as end-diastolic pressure rose to 20.6 +/- 2.2 mm Hg. Direct cardiac compression decreased end-diastolic pressure to 11.4 +/- 2.6 mm Hg while increasing cardiac output from 0.8 +/- 0.2 to 1. 4 +/- 0.5 L/min (to only approximately 55% of normal). Restoring end-diastolic pressure to 19.6 +/- 2.2 mm Hg by infusions of saline solution increased cardiac output to 1.9 +/- 0.5 L/min. Afterload reduction (nitroprusside), while maintaining end-diastolic pressure at 19.8 +/- 1.3 mm Hg, increased cardiac output to its baseline, 2.8 +/- 1.1 L/min.

CONCLUSIONS

Direct cardiac compression significantly improves ventricular pumping capacity and can restore cardiac output to about 60% of normal in the setting of acute heart failure. When combined with active preload and afterload manipulations, direct cardiac compression can restore cardiac output to normal.

The epidemiology of brain arteriovenous malformations

OBJECTIVE

Common estimates of the prevalence rate for pial arteriovenous malformations (AVMs) of the brain vary widely, and their accuracy is questionable. Our objective was to critically review the original sources from which these rates were derived and to establish best estimates for both the incidence and prevalence of the disease.

METHODS

We reviewed all of the relevant original literature: autopsy series, the Cooperative Study of Intracranial Aneurysms and Subarachnoid Hemorrhage and related analyses, and other population-based studies. We also modeled the confidence intervals of estimates for a process of low prevalence such as AVMs.

RESULTS

Many of the prevalence estimates (500-600/100,000 population) were based on autopsy data, a source that is inherently biased. Other estimates (140/100,000 population) originated from an inappropriate analysis of data from the Cooperative Study. The most reliable information comes from a population-based study of Olmsted County, MN, but prevalence data specific to AVMs was not found in that study.

CONCLUSION

The estimates for AVM prevalence that are published in the medical literature are unfounded. Because of the rarity of the disease and the existence of asymptomatic patients, establishing a true prevalence rate is not feasible. Owing to variation in the detection rate of asymptomatic AVMs, the most reliable estimate for the occurrence of the disease is the detection rate for symptomatic lesions: 0.94 per 100,000 person-years (95% confidence interval, 0.57-1.30/100,000 person-years). This figure is derived from a single population-based study, but it is supported by a reanalysis of other data sources. The prevalence of detected, active (at risk) AVM disease is unknown, but it can be inferred from incidence data to be lower than 10.3 per 100,000 population.

Demographic, morphological, and clinical characteristics of 1289 patients with brain arteriovenous malformation

BACKGROUND AND PURPOSE

The purpose of this study was to assess demographic, clinical, and morphological characteristics of patients with brain arteriovenous malformations (AVMs).

METHODS

Prospectively collected data of 1289 consecutive AVM patients from 3 independent databases (1 multicenter [Berlin/Paris/Middle and Far East, n=662] and 2 single centers [New York, n=337, and Toronto, n=290]) were analyzed. The variables assessed were age at diagnosis, sex, AVM size, AVM drainage pattern, AVM location in functionally important brain areas ("eloquence"), and type of presentation (hemorrhage, seizure, chronic headache, or focal neurologic deficit). Comparisons were made by ANOVA, contingency tables, and log-linear models.

RESULTS

Overall, mean age at diagnosis was 31.2 years (95% CI 30.2 to 32.2 years), and 45% of the patients were female (95% CI 42% to 47%). AVM maximum diameter was <3 cm in 38% (95% CI 35% to 41%). Deep venous drainage was present in 55% (95% CI 52% to 59%). An eloquent AVM location was described in 71% (95% CI 69% to 74%). AVM hemorrhage occurred in 53% (95% CI 51% to 56%). Generalized or focal seizures were described in 30% (95% CI 27% to 33%) and 10% (95% CI 8% to 12%), respectively. Chronic headache was recorded in 14% (95% CI 12% to 16%). Persistent neurological deficits were found in 7% (95% CI 6% to 9%), and progressive neurological deficits in 5% (95% CI 4% to 6%). Significant differences between centers were found for age (P<0.001), sex (P=0.04), eloquence (P=0.04), size (P<0.001), hemorrhage (P=0.006), persistent neurological deficit (P<0.001), and reversible neurological deficit (P=0.013). The intercenter difference found for hemorrhage frequency did not remain after adjustment for AVM size.

CONCLUSIONS

Baseline characteristics differed considerably between centers. The differences found in patient age and AVM size may be explained by center-specific referral patterns and the influence of access to treatment resources, whereas those found for other characteristics may be attributable to center-specific definitions. Analysis of natural history data from tertiary referral center databases may be improved by consistent definitions applicable to the entire population of AVM patients.

Aortic atheroma morphology and the risk of ischemic stroke in a multiethnic population

BACKGROUND

Protruding atheromas in the aortic arch are an independent risk factor for ischemic stroke in the elderly. However, the role of atheroma morphologic characteristics (ulceration and mobility) has been less well characterized. Moreover, data have been obtained in predominantly white populations, and little is known about the association between atheromas and stroke in minorities.

METHODS AND RESULTS

We performed transesophageal echocardiography in 152 elderly patients with stroke (58 white, 45 black, 49 Hispanic) and in 152 age- and race/ethnicity-matched control patients. Atheromas were classified as small (<4 mm in thickness), large noncomplex (> or =4 mm, no ulceration or mobility), and complex (ulcerated or mobile). Logistic regression analysis was performed to assess the risk of stroke associated with different definitions of atheroma in the overall group and in the race-ethnic strata after adjusting for the presence of other stroke risk factors. Complex atheromas were strongly associated with stroke in the overall group (22.4% in cases, 2.6% in control patients; adjusted odds ratio [OR] 17.1, 95% confidence intervals [CI] 5.1 to 57.3), whereas large noncomplex atheromas conferred a mildly increased stroke risk (22.4% vs 16.5%; adjusted OR 2.4, 95% CI 1.1 to 5.1). Complex atheromas also were strongly associated with stroke in whites (adjusted OR 24. 3, 95% CI 3.9 to 150.6) and Hispanics (adjusted OR 13.9, 95% CI 1.4 to 136). In blacks, complex atheromas were significantly more frequent in cases (15.6% vs 0%; P =.006), but their absence in control patients precluded the calculation of the OR. Complex atheromas were twice as frequent in white patients with stroke (32. 3%) than in black or Hispanic patients (15.6% and 16.3%, respectively; P =.05).

CONCLUSIONS

Aortic atheroma complexity rather than size is strongly associated with ischemic stroke in the elderly. Complex atheromas are significantly associated with stroke in all 3 race-ethnic subgroups.

Upregulation of COX-2 during cardiac allograft rejection

BACKGROUND

The hypothesis that cyclooxygenase-2 (COX-2) is involved in the myocardial inflammatory response during cardiac allograft rejection was investigated using a rat heterotopic abdominal cardiac transplantation model.

METHODS AND RESULTS

COX-2 mRNA and protein in the myocardium of rejecting cardiac allografts were significantly elevated 3 to 5 days after transplantation compared with syngeneic controls (n=3, P<0.05). COX-2 upregulation paralleled in time and extent the upregulation of iNOS mRNA, protein, and enzyme activity in this model. COX-2 immunostaining was prominent in macrophages infiltrating the rejecting allografts and in damaged cardiac myocytes. Prostaglandin (PG) levels in rejecting allografts were also higher than in native hearts. Because NO has been reported to modulate PG synthesis by COX-2, additional transplants were performed using animals treated with a selective COX-2 inhibitor (SC-58125) and a selective inhibitor of the inducible nitric oxide synthase (iNOS) N-aminomethyl-L-lysine. At posttransplant day 5, inhibitor administration resulted in a significant reduction of COX-2 mRNA expression (3764+/-337 versus 5110+/-141 arbitrary units, n=3, P<0.05) and iNOS enzymatic activity (1.7+/-0.4 versus 22.8+/-14. 4 nmol/mg protein, n=3, P<0.01) compared with vehicle-treated allogeneic transplants. Allograft survival in treated animals was increased modestly from 5.4 to 6.4 days (P<0.05). However, apoptosis of cardiac myocytes (TUNNEL method) was only marginally reduced relative to vehicle controls in treated graft recipients. The intensity of allograft rejection was also similar in the treated and untreated allografts.

CONCLUSIONS

The data indicates that COX-2 expression is enhanced in parallel with iNOS in the myocardium during cardiac allograft rejection.

Association between large aortic arch atheromas and high-intensity transient signals in elderly stroke patients

BACKGROUND AND PURPOSE

Aortic arch atheromas (AAs) have been shown to be a risk factor for ischemic stroke (IS) in the elderly because of their potential for cerebral embolization. However, the association between AAs and the presence of cerebral microemboli has not been clearly established. The aim of this study was to determine whether large AAs are associated with an increased frequency of high-intensity transient signals (HITS) in elderly patients with IS.

METHODS

We performed bitemporal simultaneous HITS monitoring of both middle cerebral arteries in 62 consecutive elderly patients with acute IS (mean age 72.5+/-8.8 years, 65% men). In 16 patients, one or both temporal windows were inadequate; therefore, the analysis of HITS was performed in the remaining 46 patients. All patients underwent omniplane transesophageal echocardiography (TEE), and they had no significant extracranial or intracranial artery disease and no cardiac prosthetic valves. Large AA was defined as > or = 4 mm in thickness. Complex AA was defined as ulcerated or mobile, regardless of plaque thickness. HITS monitoring was performed within 24 hours of TEE and analyzed by an experienced neurologist-sonographer blinded to TEE findings. A 9-dB threshold was chosen to discriminate HITS from background Doppler signal. The HITS counts in the left and in the right middle cerebral arteries were added and reported as a total number of HITS in 30 minutes.

RESULTS

HITS were detected in 14 (78%) of 18 patients with large AAs versus 8 (29%) of 28 patients with no or small AAs (odds ratio [OR] 8.8, 95% CI 2.2 to 34.8; P=0. 001). The association was also present in 27 patients with no other cardiac embolic sources, such as atrial fibrillation, patent foramen ovale, spontaneous echo contrast, and thrombus (7 of 10 patients with large AAs versus 3 of 17 patients with small or no AA; OR 10.9, 95% CI 1.7 to 68.5; P=0.013). Complex AAs were associated with a higher frequency of HITS than were noncomplex AAs (6 of 6 patients with complex AAs versus 15 of 39 patients with noncomplex AAs; OR 2. 6, 95% CI 1.7 to 3.9; P=0.005).

CONCLUSIONS

HITS are significantly associated with large AAs in elderly stroke patients. This observation may support the causal role of large AAs in IS.

Effect of age on the exercise response in normal postmenopausal women during estrogen replacement therapy

Postmenopausal estrogen replacement therapy (ERT) has been associated with a reduced risk of coronary artery disease (CAD). Whether this apparent cardioprotective effect is mediated by a cardiovascular benefit during exercise, however, has not been clearly defined. To evaluate rest and exercise variables with and without ERT, a randomized crossover trial was conducted in 23 postmenopausal women, ranging in age from 44 to 75 years, mean age 57+/-8 years. The rest and exercise variables were compared on ERT and during a drug-free period. The baseline measure was compared to the effects after 4 weeks of ERT and after 4 drug-free weeks. Echocardiographic treadmill exercise variables of heart rate (HR), blood pressure, rate-pressure product (RPP), and cardiac dimensions were determined at baseline and at the end of each treatment period. In response to ERT, there was a decrease in low-density lipoprotein (LDL) cholesterol (drug-free: 142+/-40 mg/dl, ERT: 124+/-34 mg/dl) and an increase in high-density lipoprotein (HDL) cholesterol (drug-free: 52+/-14 mg/dl, ERT: 62+/-15 mg/dl, both p<0.01). At rest, the study population had no overall significant change in HR, blood pressure, RPP, or left ventricular end-systolic and end-diastolic diameters when ERT was compared to the drug-free period. However, subjects with the fastest baseline resting HR had the greatest decrease in HR with ERT relative to the drug-free period (p<0.05). During exercise, ERT effected no change in peak HR, blood pressure, or RPP, although end-systolic diameter decreased slightly (p<0.05). With ERT, subject age correlated negatively with systolic blood pressure (p<0.05) and RPP (p<0.01); both blood pressure and RPP decreased in older subjects. In conclusion, ERT has differential effects dependent on baseline HR and age.

Determinants of resource utilization in the treatment of brain arteriovenous malformations

BACKGROUND AND PURPOSE

Preoperative embolization of arteriovenous malformations (AVMs) is thought to improve outcome following surgical resection of these lesions. The purpose of this study was to examine the cost associated with preoperative embolization and different surgical risk categories in the surgical treatment of brain AVMs.

METHODS

In a review of 126 patients treated surgically for resection of AVMs, we noted the total days spent in the hospital and calculated the associated costs (from hospital and estimated professional fees). Surgical risk category was determined using the Spetzler-Martin grading system. We examined the effect of risk category, preoperative embolization, and outcome (Rankin score) on cost and inpatient days.

RESULTS

Preoperative embolization and greater surgical risk were independently associated with higher total costs. Average adjusted cost for embolization and surgery was $78,400 +/- $4,900 versus $49,300 +/- $5,800 for surgery alone. Patients ranged in preoperative risk category from Spetzler-Martin grades II through V, with an average increase of $20,100 in total cost per Spetzler-Martin grade (95% CI, $13,500 to $28,100). Higher surgical risk category was also associated with more days spent in hospital, with an average increase of 6 days per increment in Spetzler-Martin grade (95% CI, 4 to 8). After surgical resection of an AVM, new neurologic deficits were associated with large differences in cost: $68,500 +/- $6,100 and 15 +/- 2 days in hospital for patients who were neurologically worse after surgery, versus $44,700 +/- $3,900 and 10 +/- 1 days for patients who were unchanged.

CONCLUSION

Preoperative embolization in the treatment of AVMs is associated with higher cost but not more days in the hospital. Patients with higher Spetzler-Martin grade AVMs utilize more hospital resources, in part because they have poorer neurologic outcome, and postoperative deficits are associated with higher costs and more days in the hospital.

Left atrial size and the risk of ischemic stroke in an ethnically mixed population

BACKGROUND AND PURPOSE

The association between left atrial size and ischemic stroke is controversial and has been suggested to exist only in men and to be mediated by left ventricular mass. Data are available almost exclusively for white patients. The purpose of this study was to evaluate the association between left atrial size and ischemic stroke in a multiethnic population.

METHODS

A population-based case-control study was conducted in 352 patients aged >39 years with first ischemic stroke and in 369 age-, gender-, and race-ethnicity-matched community controls. Left atrial diameter was measured by 2-dimensional transthoracic echocardiography and indexed by body surface area. Conditional logistic regression analysis was performed to assess the risk of stroke associated with left atrial index in the overall group and in the age, gender, and race-ethnic strata after adjustment for the presence of other stroke risk factors.

RESULTS

Left atrial index was associated with ischemic stroke in the overall group (adjusted OR 1.47 per 10 mm/1.7 m(2) of body surface area; 95% CI 1.03 to 2.11). The association was present in men (adjusted OR 2.81, 95% CI 1.42 to 5.57) but not in women (adjusted OR 1.08, 95% CI 0.70 to 1.66), and in patients aged <60 years (adjusted OR 3.78, 95% CI 1.36 to 10.54) but not >60 years (adjusted OR 1.23, 95% CI 0.84 to 1.81). Subgroup analyses showed the risk to be present in men across all age subgroups. In women, the lack of association between left atrial index and stroke was most strongly influenced by left ventricular hypertrophy. A trend toward an association between left atrial index and stroke was observed in whites (adjusted OR 1.81, 95% CI 0.81 to 4.09) and Hispanics (adjusted OR 1.61, 95% CI 0.98 to 2.65) but was less evident in blacks (adjusted OR 1.25, 95% CI 0.74 to 2.14).

CONCLUSIONS

Left atrial enlargement is associated with an increased risk of ischemic stroke after adjustment for other stroke risk factors, including left ventricular hypertrophy. The association is observed in men of all ages, whereas in women it is attenuated by other factors, especially left ventricular hypertrophy. Interracial differences in the stroke risk may exist that need further investigation.

A prospective evaluation of clinical tests for placement of laryngeal mask airways

BACKGROUND

Reliable tests of correct anatomic placement of the laryngeal mask airway (LMA) may enhance safety during use and minimize the need for fiberoptic instrumentation during airway manipulation through the device. This study assessed the correlation between the outcomes of nine clinical tests to place the LMA and the anatomic position of the device as graded on a standard fiberoptic scale.

METHODS

During 150 anesthetics, the outcome of nine clinical tests of correct placement was individually scored as satisfactory (positive) or unsatisfactory (negative) for clinical use of the LMA. Anatomic placement was assessed (by fiberoptic evaluation) by an anesthesiologist, who was blinded to the placement of the device, as grade 1, vocal cords not seen; grade 2, cords plus the anterior epiglottis seen; grade 3, cords plus the posterior epiglottis seen; and grade 4, only vocal cords seen. The outcomes of clinical tests were correlated with fiberoptic grade.

RESULTS

Tests that correlated with the fiberoptic grade were the ability to generate an airway pressure of 20 cm water, the ability to ventilate manually, a black line on the LMA in midline, anterior movement of the larynx, outward movement of the LMA on inflation of the cuff, and movements of the reservoir bag with spontaneous breathing. Two tests, ability to generate airway pressure of 20 cm water and ability to ventilate manually, correlated with fiberoptic grades 4 and 3 combined (i.e., the epiglottis was supported by the LMA) and grade 2 (the epiglottis was not supported by the LMA). Tests with poor correlation with fiberoptic grade were the presence of resistance at the end of insertion, inability to advance LMA after inflation of the cuff, and presence of a capnographic trace.

CONCLUSIONS

The outcome of clinical tests correlates with the anatomic placement of LMAs, as judged by fiberoptic examination. Two tests that best correlated with the fiberoptic grade were the ability to generate airway pressure of 20 cm water and the ability to ventilate manually.

Theoretical modelling of arteriovenous malformation rupture risk: a feasibility and validation study

PURPOSE

To explore the feasibility of using a theoretical computational model to simulate the risk of spontaneous arteriovenous malformation (AVM) haemorrhage.

METHODS

Data from 12 patients were collected from a prospective databank which documented the angioarchitecture and morphological characteristics of the AVM and the feeding mean arterial pressure (FMAP) measured during initial superselective angiography prior to any treatment. Using the data, a computational model of the cerebral circulation and the AVM was constructed for each patient (patient-specific model). Two model risk (Risk(model)) calculations (haemodynamic- and structural-weighted estimates) were performed by using the patient-specific models. In our previously developed method of haemodynamic-weighted estimate, Risk(model) was calculated with the simulated intranidal pressures related to its maximal and minimal values. In the method of structural-weighted estimate developed and described in this paper, the vessel mechanical properties and probability calculation were considered in more detail than in the haemodynamic-weighted estimate. Risk(model) was then compared to experimentally determined risk which was calculated using a statistical method for determining the relative risk of having initially presented with AVM haemorrhage, termed Risk(exp).

RESULTS

The Risk(model) calculated by both haemodynamic- and structural-weighted estimates correlated with experimental risks with chi2 = 6.0 and 0.64, respectively. The risks of the structural-weighted estimate were more correlated to experimental risks.

CONCLUSIONS

Using two different approaches to the calculation of AVM haemorrhage risk, we found a general agreement with independent statistical estimates of haemorrhagic risk based on patient data. Computational approaches are feasible; future work can focus on specific pathomechanistic questions. Detailed patient-specific computational models can also be developed as an adjunct to individual patient risk assessment for risk-stratification purposes.

Psychosocial outcome after ICD implantation: a current perspective

Depression and reduced sexual functioning have been identified as problems following ICD placement. We examined these issues, and multiple other quality-of-life measures, and their relationship to ICD and ICD discharge. Patients were 64 +/- 11 years old, 72% male, and had undergone ICD 20 +/- 14 months previously. Fifty-eight patients responded to a confidential biopsychosocial questionnaire. Positive attitudes toward the procedure increased from 52% before to 76% after implantation. Satisfaction correlated most strongly with less anger (P = 0.002, r = 0.45), less worry about ICD size (P = 0.007, r = 0.38), less sadness (P = 0.01, r = 0.37), and perceived better health (P = 0.01, r = 0.35). Of these ICD patients, 20%-58% reported measures of depression, and sexual frequency was reduced in 45%. Despite successful ICD placement, health concern increased in 62% of the respondents. Thirty-nine percent attended support groups; 96% found them very helpful. Mean number of ICD discharges described by responders was 5 +/- 11. Fifty percent of our sample reported > or = 1 shock; equal numbers had 1, 2-5, 6-10, and more than 10 shocks. Sixty-two percent of men had at least one discharge compared to 13% of women. After controlling for cardiac clinical variables, experiencing > or = 1 ICD shock was strongly associated with anxiety about family (odds ratio = 7.3), reduced new activities (odds ratio = 6.9), increased sadness (odds ratio = 6.2), and health worry (odds ratio = 5.8). Experiencing > or = 5 ICD shocks was strongly associated with increased health concern (odds ratio = 13.6), increased sadness (odds ratio = 12.5), increased fatigue (odds ratio = 6.1), current sadness (odds ratio = 5.8), and increased nervousness (odds ratio = 5.3). ICD implantation powerfully affects quality-of-life. Postimplantation health concern is paradoxically increased despite improvement in actual health. Negative emotions are associated with defibrillator discharge.

CNI-1493 prolongs survival and reduces myocyte loss, apoptosis, and inflammation during rat cardiac allograft rejection

Cytokines and cytotoxic agents, including nitric oxide (NO) released by macrophages, play important roles during cardiac allograft rejection. In contrast to agents that suppress T-lymphocyte function, CNI-1493 is a multivalent guanylhydrazone compound that inhibits the synthesis and release of proinflammatory cytokines and NO from macrophages. This study investigated the effects of CNI-1493 on rejecting rat cardiac allografts by using Lewis to Wistar-Furth heterotopic cardiac transplants. CNI-1493 (2 mg/kg i.p., b.i.d.) or vehicle (water) was administered beginning the day before surgery. Rat cardiac allograft survival to cessation of heart beat, apoptosis of cardiac myocytes, degree of myocardial inflammation, and inducible nitric oxide synthase (iNOS) messenger RNA (mRNA), protein, and enzyme activity were studied at days 1, 3, 5, and 7 after transplantation. Allograft survival was increased significantly by 26% from 7.5 +/- 0.8 days in vehicle-treated rats (n = 6) to 9.5 +/- 1.2 days in CNI-1493-treated rats (n = 8, p < 0.05). Apoptotic cells per mm2 myocardium decreased from 2.25 +/- 1.25 to 0.84 +/- 0.49 at day 3 and 31.2 +/- 2.9 to 17.6 +/- 5.43 at day 5 after transplantation with CNI-1493 treatment (p < 0.05). The number of apoptotic myocytes and loss of cardiac muscle cells also decreased significantly at day 5 in the treated animals (p < 0.05). The reduction of myocyte loss at day 5 coincided with a significant decrease of the inflammatory response and reduced macrophage influx (p < 0.05). Myocardial iNOS mRNA, protein, and enzyme levels increased during the course of allograft rejection, and CNI-1493 did not significantly reduce iNOS expression in the rejecting rat allograft. CNI-1493 prolongs allograft survival and reduces myocyte loss, apoptosis, and inflammation during rat cardiac allograft rejection. These effects of CNI-1493 appear to be unrelated to altered NO synthesis but may be related to effects of the drug to inhibit macrophage synthesis of cytokines.

Feeding artery pressure and venous drainage pattern are primary determinants of hemorrhage from cerebral arteriovenous malformations

PURPOSE

The purpose of this study was to define the influence of feeding mean arterial pressure (FMAP) in conjunction with other morphological or clinical risk factors in determining the probability of hemorrhagic presentation in patients with cerebral arteriovenous malformations (AVMs).

METHODS

Clinical and angiographic data from 340 patients with cerebral AVMs from a prospective database were reviewed. Patients were identified in whom FMAP was measured during superselective angiography. Additional variables analyzed included AVM size, location, nidus border, presence of aneurysms, and arterial supply and venous drainage patterns. The presence of arterial aneurysms was also correlated with site of bleeding on imaging studies.

RESULTS

By univariate analysis, exclusively deep venous drainage, periventricular venous drainage, posterior fossa location, and FMAP predicted hemorrhagic presentation. When we used stepwise multiple logistic regression analysis in the cohort that had FMAP measurements (n = 129), only exclusively deep venous drainage (odds ratio [OR], 3.7; 95% confidence interval [CI], 1.4 to 9.8) and FMAP (OR, 1.4 per 10 mm Hg increase; 95% CI, 1.1 to 1.8) were independent predictors (P < 0.01) of hemorrhagic presentation; size, location, and the presence of aneurysms were not independent predictors. There was also no association (P = 0.23) between the presence of arterial aneurysms and subarachnoid hemorrhage.

CONCLUSIONS

High arterial input pressure (FMAP) and venous outflow restriction (exclusively deep venous drainage) were the most powerful risk predictors for hemorrhagic AVM presentation. Our findings suggest that high intranidal pressure is more important than factors such as size, location, and the presence of arterial aneurysms in the pathophysiology of AVM hemorrhage.

Psychosocial outcome after ICD implantation: a current perspective

Depression and reduced sexual functioning have been identified as problems following ICD placement. We examined these issues, and multiple other quality-of-life measures, and their relationship to ICD and ICD discharge. Patients were 64 +/- 11 years old, 72% male, and had undergone ICD 20 +/- 14 months previously. Fifty-eight patients responded to a confidential biopsychosocial questionnaire. Positive attitudes toward the procedure increased from 52% before to 76% after implantation. Satisfaction correlated most strongly with less anger (P = 0.002, r = 0.45), less worry about ICD size (P = 0.007, r = 0.38), less sadness (P = 0.01, r = 0.37), and perceived better health (P = 0.01, r = 0.35). Of these ICD patients, 20%-58% reported measures of depression, and sexual frequency was reduced in 45%. Despite successful ICD placement, health concern increased in 62% of the respondents. Thirty-nine percent attended support groups; 96% found them very helpful. Mean number of ICD discharges described by responders was 5 +/- 11. Fifty percent of our sample reported > or = 1 shock; equal numbers had 1, 2-5, 6-10, and more than 10 shocks. Sixty-two percent of men had at least one discharge compared to 13% of women. After controlling for cardiac clinical variables, experiencing > or = 1 ICD shock was strongly associated with anxiety about family (odds ratio = 7.3), reduced new activities (odds ratio = 6.9), increased sadness (odds ratio = 6.2), and health worry (odds ratio = 5.8). Experiencing > or = 5 ICD shocks was strongly associated with increased health concern (odds ratio = 13.6), increased sadness (odds ratio = 12.5), increased fatigue (odds ratio = 6.1), current sadness (odds ratio = 5.8), and increased nervousness (odds ratio = 5.3). ICD implantation powerfully affects quality-of-life. Postimplantation health concern is paradoxically increased despite improvement in actual health. Negative emotions are associated with defibrillator discharge.

Apoptosis and increased expression of inducible nitric oxide synthase in human allograft rejection

BACKGROUND

The mechanisms of myocyte death during cardiac allograft rejection are incompletely understood. In a previous study using a rat heterotopic cardiac allograft model, we showed that cardiac myocyte apoptosis, inducible nitric oxide synthase (iNOS) mRNA, protein and enzyme activity, and nitrotyrosine increased simultaneously during cardiac allograft rejection. This study was designed to investigate whether apoptosis and expression of iNOS occur in human cardiac allograft rejection.

METHODS

Right ventricular endomyocardial biopsies from 30 cases of allograft rejection (International Society of Heart and Lung Transplantation grade 3A/B) were compared with 12 biopsies with no rejection (International Society of Heart and Lung Transplantation grade 0). Samples were co-labeled for apoptosis and muscle actin. Serial sections were stained for iNOS, nitrotyrosine, and the leukocyte markers CD3, CD4, CD8, and CD68 to identify T-cell subpopulations and macrophages.

RESULTS

Biopsies with cardiac allograft rejection showed a 30-fold increase of apoptotic cells when compared with controls. Most apoptotic cardiac myocytes were found in proximity to macrophage (CD68+)-rich inflammatory infiltrates. iNOS immunoreactivity was strongest in macrophages and adjacent myocytes, which also showed high levels of nitrotyrosine, representing damage by peroxynitrite.

CONCLUSIONS

Apoptosis is a major form of myocyte death during human cardiac allograft rejection. Cardiac myocyte apoptosis is closely associated with expression of iNOS in macrophages and myocytes and with nitration of myocyte proteins by peroxynitrite.

Surgical closure of patent foramen ovale in cryptogenic stroke patients

BACKGROUND AND PURPOSE

Patents foramen ovale (PFO) is associated with stroke of unknown etiology or cryptogenic stroke. However, optimal treatment to prevent recurrence in cryptogenic stroke patients with PFO is not clearly defined. Since PFO represents a surgically repairable lesion, interest in closing it is high. This report reviews our experience with cryptogenic stroke patients with PFO who underwent surgical PFO closure and were followed for recurrence of neurological events.

METHODS

We followed 28 cryptogenic stroke patients (17 men, 11 women; mean age, 41 +/- 13 years) with transesophageal echocardiography-defined PFO who had undergone PFO closure by open thoracatomy. All patients selected for surgery refused, could not take, or failed warfarin therapy. They were followed by physician visits and telephone interviews.

RESULTS

There were no surgical complications. With a mean follow-up of 19 months, four patients experienced neurological event recurrence, one stroke, and three transient ischemic attacks. Kaplan-Meier survival analysis demonstrated that the actuarial rate of recurrence was 19.5% (95% confidence limit 2.2-36.8%) at 13 months of follow-up. None of the 17 patients (0%) younger than 45 years suffered a recurrence, whereas four of 11 patients (35%) aged 45 or older experienced a recurrence of neurological event (P < .02). Using a proportional hazards regression model, the increase in relative risk with increasing age was 2.76 per 10 years (95% confidence interval 1.07 to 7.16).

CONCLUSIONS

Although PFO is easily repairable in patients with crytogenic stroke, its closure does not consistently prevent recurrence of ischemic events. The recurrence appears to occur more frequently in older cryptogenic stroke patients.

Valvular strands and cerebral ischemia. Effect of demographics and strand characteristics

BACKGROUND AND PURPOSE

Valvular strands, thin filamentous material attached to the mitral or aortic valve, are seen during transesophageal echocardiography and have been associated with stroke. Little is known about this association in different age, sex, and race-ethnic subgroups and the effect of various strand characteristics on this association.

METHODS

From patients referred for transesophageal echocardiography, 73 patients with recent ischemic stroke (68) or transient ischemic attack (5) were age matched to 73 stroke- and transient ischemic attack-free control subjects. The association between valvular strands and cerebral ischemia was evaluated for the overall group and demographic subgroups. The effect of strand location, length, number, and valve thickness was also determined.

RESULTS

An association between cerebral ischemia and valvular strands was observed (odds ratio [OR] = 4.4; 95% confidence interval [CI] = 2.0 to 9.6). The association was found for both men and women and among all three race-ethnic groups. The OR was greater in those who were younger (12.5 [95% CI = 2.4 to 64.5] for age < 60, 4.8 [95% CI = 1.3 to 18.2] for age 60 to 69, and 1.8 [95% CI = 0.5 to 6.4] for age > or = 70 years). Strands on both the mitral (OR = 3.5; 95% CI = 1.5 to 7.9) and aortic (OR = 3.7; 95% CI = 1.1 to 11.9) valve were associated with cerebral ischemia, whereas the number and length of strands were not. The effect of strands was independent of mitral or aortic valve thickness.

CONCLUSIONS

Valvular strands, whether mitral or aortic, are associated with ischemic stroke, especially among younger persons.

Risk of spontaneous haemorrhage after diagnosis of cerebral arteriovenous malformation

BACKGROUND

A small proportion of strokes are caused by cerebral arteriovenous malformations (AVM). Treatment to prevent intracranial haemorrhage itself carries risks, and untreated AVM may in many cases have a good prognosis. We investigated the risk of subsequent symptomatic bleeding in the clinical course of AVM in patients with and without an initial haemorrhage.

METHODS

281 unselected, consecutive, prospectively enrolled patients with cerebral AVM were grouped according to their initial clinical presentation--142 presented with and 139 without haemorrhage. The frequency of AVM haemorrhages during the subsequent clinical course (before the start of endovascular, surgical, or radiation treatment) in the two groups was compared by means of Kaplan-Meier life-tables, log-rank test, and multivariate proportional-hazards regression models. Haemorrhage was defined as a clinically symptomatic event with signs of acute bleeding on computed tomography or magnetic resonance brain imaging.

FINDINGS

During mean follow-up of 8.5 months for the haemorrhage group and 11.9 months for the non-haemorrhage group, haemorrhages occurred in 18 (13%) of the former patients and in three (2%) of the latter (p=0.0002). The annual risk of haemorrhage was 17.8% and 2.2%, respectively. In the multivariate regression model, the adjusted hazard ratio for haemorrhage at initial presentation was 13.9 (95% CI 2.6-73.8; p=0.002). Deep venous drainage (hazard ratio 4.1 [1.2-14.9], p=0.029) and male sex (9.2 [2.1-41.3], p=0.004) were also significantly associated with subsequent haemorrhage, but no significant association was found for age or AVM size. The annual rate of spontaneous haemorrhage was 32.6% for men and 10.4% for women in the haemorrhage group compared with 3.3% for men and 1.3% for women in the non-haemorrhage group. Among patients with haemorrhage at initial presentation, the risk of haemorrhage fell from 32.9% in year 1 to 11.3% in subsequent years (34.2% to 31.0% in men; 31.1% to 5.5% in women).

INTERPRETATION

In AVM, patients initially presenting with haemorrhage have a higher risk of subsequent bleeding than those presenting with other symptoms. The risk is higher in men than in women.

Lack of effect of estrogen on rest and treadmill exercise in postmenopausal women without known cardiac disease

To assess the peripheral vascular effects of estrogen in women without coronary disease, normal postmenopausal women (mean age 56 +/- 8 years) participated in a randomized, crossover trial using treadmill exercise echocardiography, and received oral conjugated estrogen, 0.625 mg/day or underwent a drug-free period. There was no significant effect on heart rate, blood pressure, double product, left ventricular end-systolic and end-diastolic diameters, or electrocardiographic measures after estrogen. In contrast to the profound effects reported in patients with cardiac disease, oral estrogen in normal women does not bestow significant benefit on treadmill exercise echocardiographic variables at rest or during modest levels of exercise.

Intra-arterial nitrovasodilators do not increase cerebral blood flow in angiographically normal territories of arteriovenous malformation patients

BACKGROUND AND PURPOSE

The mechanism of adaptation to chronic cerebral hypotension in normal brain adjacent to cerebral arteriovenous malformations (AVMs) is unknown. To clarify these mechanisms, we performed cerebral blood flow (CBF) studies in structurally and functionally normal vascular territories during 53 distal cerebral angiographic procedures in 37 patients with AVMs.

METHODS

CBF was measured using the superselective intra-arterial 133Xe method before and after a 3-minute infusion of either verapamil (1 mg.min-1, n = 23), acetylcholine (1.33 micrograms.kg-1.min-1, n = 7), nitroprusside (0.5 microgram.kg-1.min-1, n = 16) or nitroglycerin (0.5 microgram.kg-1.min-1, n = 7).

RESULTS

Mean +/- SD systemic (76 +/- 13 mm Hg) and distal cerebral arterial (55 +/- 16 mm Hg; range, 20 to 97 mm Hg) pressures were not different among groups. Verapamil increased CBF (45 +/- 12 to 65 +/- 21 mL.100 g-1.min-1, P < .001). There was no effect of acetylcholine (no change [46 +/- 9 to 46 +/- 9 mL.100 g-1.min-1], NS) or nitroglycerin (36 +/- 14 to 36 +/- 13 mL.100 g-1.min-1, NS). Nitroprusside decreased CBF (40 +/- 12 to 31 +/- 11 mL.100 g-1.min-1, P < .001). The percent change in CBF after drug administration was proportional to cerebral arterial pressure for verapamil only (r = .57, P = .0051).

CONCLUSIONS

When infused intra-arterially in clinically relevant doses in both hypotensive and normotensive normal vascular territories remote from an AVM nidus, calcium channel blockade caused vasodilation, but there was an absence of response to nitric oxide-mediated vasodilators. These data suggest that (1) the nitric oxide pathway probably is not involved in the adaptation to chronic cerebral hypotension in AVM patients and (2) if our findings in vessels remote from or contralateral to the AVM are applicable to vessels of patients with other forms of cerebrovascular disease, clinically relevant doses of intra-arterial nitrovasodilators may not be useful in the manipulation of cerebrovascular resistance.

QT dispersion as a marker of risk in patients awaiting heart transplantation

OBJECTIVES

The objectives of this study were to determine whether a signal-averaged electrocardiogram (SAECG) or measurement of interlead variability of QT intervals on an electrocardiogram (ECG) obtained at the time of wait-listing could provide prognostic value with respect to cardiac death during the waiting period.

BACKGROUND

Because heart transplantation is a life-saving but limited resource, there remains an urgent need to identify those patients at greatest risk of dying while awaiting heart transplantation as part of the strategy to optimize the allocation of donor organs to those in greatest need. This study was undertaken to prospectively identify clinical, ECG or SAECG variables that might predict mortality during the waiting period.

METHODS

Of 108 consecutive patients referred for heart transplant evaluation, 80 were placed on a waiting list, at which time a standard 12-lead ECG and a SAECG were recorded. In this cohort of 80 patients, QT dispersion was characterized from the 12-lead ECG as either the maximal-minimal QT interval (QTDISP) or as the coefficient of variation of all QT intervals (QTCV).

RESULTS

During the 25-month follow-up period (mean time on waiting list, 201 days), the mortality rate was 27%/year, divided equally between heart failure and sudden deaths. No clinical variable identified at entry predicted mortality. QTDISP and QTCV were strong mortality predictors, with a 4.1-fold increase in mortality in patients with QTDISP > 140 ms compared with those patients with QTDISP < or = 140 ms (95% CI 1.1 to 14.9), whereas a QTCV > or = 9% also predicted a 4.1-fold increased risk of death (95% CI 1.4 to 11.8). Although 88% of all SAECGs were abnormal, no patient with a normal SAECG died suddenly during the waiting period.

CONCLUSIONS

Indexes of QT dispersion provide a means of stratifying a patient's risk of dying while awaiting heart transplantation and may help to establish priority on a heart transplant waiting list.

L-arginine prevents xanthoma development and inhibits atherosclerosis in LDL receptor knockout mice

BACKGROUND

The potential antiatherosclerotic actions of NO were investigated in four groups of mice (n = 10 per group) lacking functional LDL receptor genes, an animal model of familial hypercholesterolemia. Group 1 was fed a regular chow diet. Groups 2 through 4 were fed a 1.25% high-cholesterol diet. In addition, group 3 received supplemental L-arginine and group 4 received L-arginine and N omega-nitro-L-arginine (L-NA), an inhibitor of NO synthase (NOS).

METHODS AND RESULTS

Animals were killed at 6 months; aortas were stained with oil red O for planimetry and with antibodies against constitutive and inducible NOSs. Plasma cholesterol was markedly increased in the animals receiving the high-cholesterol diet. Xanthomas appeared in all mice fed the high-cholesterol diet alone but not in those receiving L-arginine. Aortic atherosclerosis was present in all mice on the high-cholesterol diet. The mean atherosclerotic lesion area was reduced significantly (P < .01) in the cholesterol-fed mice given L-arginine compared with those receiving the high-cholesterol diet alone. The mean atherosclerotic lesion area was significantly larger (P < .01) in cholesterol-fed mice receiving L-arginine + L-NA than in those on the high-cholesterol diet alone. Within the atherosclerotic plaques, endothelial cells immunoreacted for endothelial cell NOS; macrophages, foam cells, and smooth muscle cells immunostained strongly for inducible NOS and nitrotyrosine residues.

CONCLUSIONS

The data indicate that L-arginine prevents xanthoma formation and reduces atherosclerosis in LDL receptor knockout mice fed a high-cholesterol diet. The abrogation of the beneficial effects of L-arginine by L-NA suggests that the antiatherosclerotic actions of L-arginine are mediated by NOS. The data suggest that L-arginine may be beneficial in familial hypercholesterolemia.

Apoptosis of cardiac myocytes during cardiac allograft rejection. Relation to induction of nitric oxide synthase

BACKGROUND

Apoptosis is a distinct form of programmed cell death characterized by activation of endonucleases that cleave nuclear DNA, condensation and fragmentation of nuclear chromatin, blebbing of intact membranes, and cell shrinkage and fragmentation. The mechanisms responsible are unclear, but nitric oxide (NO) generated by inducible NO synthase (iNOS) has been demonstrated to induce apoptosis in macrophages in vitro. This study investigated whether apoptosis occurs during cardiac allograft rejection and examined the relationship of apoptosis to iNOS expression.

METHODS AND RESULTS

Heterotopic abdominal transplantation from Lewis to Wistar-Furth rats was used as a model of cardiac allograft rejection; Lewis-to-Lewis grafts served as controls. Apoptosis was identified by DNA ladders after electrophoresis on agarose gels and by in situ labeling of DNA fragments; cell types were determined by immunohistochemistry. The number of apoptotic cardiac myocytes increased sharply from day 3 (0.31/mm2 ventricular tissue) to day 5 (1.27/mm2) after transplantation. At day 5, allografts showed a significant increase (P < .01) in apoptotic cardiac myocytes, macrophages, and endothelial cells compared with syngeneic grafts. The expression of iNOS mRNA, protein, and enzyme activity paralleled in time and extent the apoptosis of cardiac myocytes. iNOS immunostaining of infiltrating macrophages and cardiac muscle fibers increased significantly in the allografts at days 3 to 5 and was accompanied by immunostaining of both cell types for nitrotyrosine, which is indicative of peroxynitrite formation.

CONCLUSIONS

Apoptosis of myocardial cells occurs during cardiac allograft rejection. Apoptosis during rejection parallels the expression of iNOS, which suggests that apoptosis may be triggered by NO and peroxynitrite.

Oxidized low density lipoproteins alter macrophage lipid uptake, apoptosis, viability and nitric oxide synthesis

Uptake of oxidized low density lipoproteins (LDL) by monocyte macrophages to form "foam" cells occurs during formation of atherosclerotic lesions. Inducible nitric oxide synthase (iNOS) has been identified in foam cells. To investigate interactions between oxidized LDL, monocyte macrophage viability and iNOS, studies were performed with J774.Al macrophages. iNOS mRNA, protein and enzyme activity were induced in J774.Al macrophages by IFN-gamma lipopolysaccharide (LPS). Neither iNOS induction nor inhibition of nitric oxide (NO) formation was associated with significant alterations in the binding, uptake or degradation of native or oxidized LDL. Nontoxic doses of native LDL or of oxidized LDL did not influence iNOS mRNA or protein in macrophages. However, oxidized LDL, but not native LDL or acetyl LDL, inhibited NO production by macrophages in a dose- and time-dependent fashion. Inhibition of iNOS was not correlated with cholesteryl ester formation but with the degree of LDL oxidation. Inhibition of iNOS did not require the scavenger receptor or directed endocytosis and exhibited noncompetitive kinetics. Inhibition of iNOS activity in J774.Al macrophages was produced by lipid from oxidized LDL but not by lipid from native LDL and by PC vesicles containing LPC but not by PC vesicles alone. Inhibition of NO formation diminished apoptosis of the activated macrophages. The data suggest NO production by iNOS and inhibition of the enzyme by oxidized LDL lipid may influence cell viability, cell-cell interactions and vasomotor tone during atherogenesis.

Calreticulin, an antithrombotic agent which binds to vitamin K-dependent coagulation factors, stimulates endothelial nitric oxide production, and limits thrombosis in canine coronary arteries

Coagulation Factor IX/IXa has been shown to bind to cellular surfaces, and Factor IXa expresses its procoagulant activity by assembling into the intrinsic Factor X activating complex (Factors IXa/VIIIa/X), which also forms on membrane surfaces. This led us to identify cellular proteins which bind Factor IX/IXa; an approximately 55-kDa polypeptide was purified to homogeneity from bovine lung extracts based on its capacity to bind 125I-Factor IX in a dose-dependent and saturable manner. From protein sequence data of the amino terminus and internal peptides, the approximately 55-kDa polypeptide was identified as calreticulin, a previously identified intracellular calcium-binding protein. Recombinant calreticulin bound vitamin K-dependent coagulation factors, 125I-Factor IX, 125I-Factor X, and 125I-prothrombin (Kd values of approximately 2.7, 3.2, and 8.3 nM, respectively), via interaction with its C-domain, although it did not affect the coagulant properties of these proteins. 125I-Calreticulin also bound to endothelial cells in vitro (Kd approximately 7.4 nM), and mouse infusion studies showed an initial rapid phase of clearance in which calreticulin could be localized on the vascular endothelium. Exposure of endothelial cells to calreticulin led to dose-dependent, immediate, and sustained increase in the production of nitric oxide, as measured using a porphyrinic microsensor. In a canine electrically induced thrombosis model, intracoronary infusion of calreticulin (n = 7) prevented occlusion of the left circumflex coronary artery in a dose-dependent manner compared with vehicle-treated controls (n = 5). These results indicate that calreticulin interacts with the endothelium to stimulate release of nitric oxide and inhibit clot formation.