Pathological effects of alcohol septal ablation for hypertrophic obstructive cardiomyopathy

BACKGROUND

The pathological effects and the mechanisms of action of intracoronary administration of ethanol for alcohol septal ablation (ASA) for the management of hypertrophic obstructive cardiomyopathy (HOCM) are unknown.

METHODS

We examined surgical specimens and, in one case, autopsy specimens from four patients who underwent surgical septal myectomy 2 days to 14 months after unsuccessful ASA.

RESULTS

Pathological examination early after ASA showed coagulative necrosis of both the myocardium and the septal perforator arteries. Affected arteries were distended and occluded by necrotic intraluminal debris, without platelet-fibrin thrombi. Late after unsuccessful ASA, excised septal tissue was heterogeneous, containing a region of dense scar, and adjacent tissue containing viable myocytes and interspersed scar.

CONCLUSIONS

Intracoronary administration of ethanol in patients with HOCM causes acute myocardial infarction with vascular necrosis. The coagulative necrosis of the arteries, their distension by necrotic debris and the absence of platelet-fibrin thrombi distinguish ethanol-induced infarction from that caused by atherosclerotic coronary artery disease. The direct vascular toxicity of ethanol may be an important aspect of the mechanism of successful ASA.

Clinical correlates and reference intervals for pulmonary artery systolic pressure among echocardiographically normal subjects

BACKGROUND

Data in normal human subjects on the factors affecting pulmonary artery systolic pressure (PASP) are limited. We determined the correlates of and established a reference range for PASP as determined by Doppler transthoracic echocardiography (TTE) from a clinical echocardiographic database of 102 818 patients, of whom 15 596 (15%) had a normal Doppler TTE study.

METHODS AND RESULTS

A normal TTE was based on normal cardiac structure and function during complete Doppler TTE studies. The PASP was calculated by use of the modified Bernoulli equation, with right atrial pressure assumed to be 10 mm Hg. Among TTE normal subjects, 3790 subjects (2432 women, 1358 men) from 1 to 89 years old had a measured PASP. The mean PASP was 28.3+/-4.9 mm Hg (range 15 to 57 mm Hg). PASP was independently associated with age, body mass index (BMI), male sex, left ventricular posterior wall thickness, and left ventricular ejection fraction (P<0.001). The estimated upper 95% limit for PASP among lower-risk subjects was 37.2 mm Hg. A PASP >40 mm Hg was found in 6% of those >50 years old and 5% of those with a BMI >30 kg/m(2).

CONCLUSIONS

Among 3790 echocardiographically normal subjects, PASP was associated with age, BMI, sex, wall thickness, and ejection fraction. Of these subjects, 28% had a PASP >30 mm Hg, and the expected upper limit of PASP may include 40 mm Hg in older or obese subjects. These findings support the use of age- and BMI-corrected values in establishing the expected normal range for PASP.

Vascular endothelial function in cyclosporine and tacrolimus treated renal transplant recipients

BACKGROUND

Endothelial dysfunction is an early key event in the development of arteriosclerotic cardiovascular disease (ASCVD), thus an early marker of subclinical ASCVD. Endothelial function is impaired in renal transplant recipients (RTR) treated with cyclosporine (CyA). Tacrolimus is associated with less hyperlipidemia and hypertension than CyA, however, there are no data on endothelial function in tacrolimus-treated RTR.

METHODS

High-resolution brachial ultrasonography was used to assess endothelium-dependent dilatation (EDD), and endothelium-independent dilatation (EID) in 20 stable RTR and a control group of 10 healthy subjects without clinical evidence of ASCVD. The RTR group included patients receiving CyA (n=10) and tacrolimus (n=10). EDD and EID were measured as percent increase in brachial artery diameter in response to reactive hyperemia and nitroglycerin, respectively.

RESULTS AND CONCLUSIONS

EDD was significantly lower in RTR versus controls (1.7+/-0.7 vs. 7.3+/-0.7%, P<0.0001), whereas EID was similar in the two groups. No significant differences were found in EDD or in EID between CyA- and tacrolimus-treated RTR. Glomerular filtration rate, plasma homocysteine, blood pressure, and lipid profiles were similar in CyA- and tacrolimus-treated RTR.

Endothelial nitric oxide synthase limits left ventricular remodeling after myocardial infarction in mice

Background- To investigate the role of endothelial nitric oxide synthase (NOS3) in left ventricular (LV) remodeling after myocardial infarction (MI), the impact of left anterior descending coronary artery ligation on LV size and function was compared in 2- to 4-month-old wild-type (WT) and NOS3-deficient mice (NOS3(-/-)). Methods and Results- Two days after MI, both strains of mice had a similar LV size, fractional shortening, and ejection fraction by echocardiography. Twenty-eight days after MI, both strains had dilated LVs with decreased fractional shortening and lower ejection fractions. Although the infarcted fraction of the LV was similar in both strains, LV end-diastolic internal diameter, end-diastolic volume, and mass were greater, but fractional shortening, ejection fraction, and the maximum rate of developed LV pressure (dP/dt(max)) were lower in NOS3(-/-) than in WT mice. Impairment of diastolic function, as measured by the time constant of isovolumic relaxation (tau) and the maximum rate of LV pressure decay (dP/dt(min)), was more marked in NOS3(-/-) than in WT mice. Mortality after MI was greater in NOS3(-/-) than in WT mice. Long-term administration of hydralazine normalized blood pressure in NOS3(-/-) mice, but it did not prevent the LV dilatation, impaired systolic and diastolic function, and increased LV mass that followed MI. In WT mice, capillary density and myocyte width in the nonischemic portion of the LV did not differ before and 28 days after MI, whereas in NOS3(-/-) mice, capillary density decreased and myocyte width increased after MI, whether or not hydralazine was administered. Conclusions- These results suggest that the presence of NOS3 limits LV dysfunction and remodeling in a murine model of MI by an afterload-independent mechanism, in part by decreasing myocyte hypertrophy in the remote myocardium.

Accelerated atherosclerosis, aortic aneurysm formation, and ischemic heart disease in apolipoprotein E/endothelial nitric oxide synthase double-knockout mice

BACKGROUND

To test whether deficiency in endothelial nitric oxide synthase (eNOS) affects atherosclerosis development, we compared lesion formation in apolipoprotein E (apoE)/eNOS-double knockout (DKO) and apoE-knockout (KO) control animals.

METHODS AND RESULTS

After 16 weeks of "Western-type" diet, apoE/eNOS-DKO males and females showed significant increases in lesion area of 93.6% and 59.2% compared with apoE-KO mice. All apoE/eNOS-DKO animals studied developed peripheral coronary arteriosclerosis, associated with perivascular and myocardial fibrosis, whereas none of the apoE-KO mice did. Transthoracic echocardiography showed a significantly increased left ventricular wall thickness and decreased fractional shortening in DKO animals. Mean arterial pressure was increased in DKO mice and was comparable in degree to eNOS-KO animals. Male DKO animals developed atherosclerotic abdominal aneurysms and aortic dissection.

CONCLUSIONS

eNOS deficiency increases atherosclerosis in Western-type diet-fed apoE-KO animals and introduces coronary disease and an array of cardiovascular complications, including spontaneous aortic aneurysm and dissection. This phenotype constitutes the first murine model to demonstrate distal coronary arteriosclerosis associated with evidence of myocardial ischemia, infarction, and heart failure. Hypertrophy and reduced left ventricular function cannot be explained by increased blood pressure alone, because eNOS-KO animals do not develop these complications.

One-year survival following early revascularization for cardiogenic shock

CONTEXT

Cardiogenic shock (CS) is the leading cause of death for patients hospitalized with acute myocardial infarction (AMI).

OBJECTIVE

To assess the effect of early revascularization (ERV) on 1-year survival for patients with AMI complicated by CS.

DESIGN

The SHOCK (Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock) Trial, an unblinded, randomized controlled trial from April 1993 through November 1998.

SETTING

Thirty-six referral centers with angioplasty and cardiac surgery facilities.

PATIENTS

Three hundred two patients with AMI and CS due to predominant left ventricular failure who met specified clinical and hemodynamic criteria.

INTERVENTIONS

Patients were randomly assigned to an initial medical stabilization (IMS; n = 150) group, which included thrombolysis (63% of patients), intra-aortic balloon counterpulsation (86%), and subsequent revascularization (25%), or to an ERV group (n = 152), which mandated revascularization within 6 hours of randomization and included angioplasty (55%) and coronary artery bypass graft surgery (38%).

MAIN OUTCOME MEASURES

All-cause mortality and functional status at 1 year, compared between the ERV and IMS groups.

RESULTS

One-year survival was 46.7% for patients in the ERV group compared with 33.6% in the IMS group (absolute difference in survival, 13.2%; 95% confidence interval [CI], 2.2%-24.1%; P<.03; relative risk for death, 0.72; 95% CI, 0.54-0.95). Of the 10 prespecified subgroup analyses, only age (<75 vs >/= 75 years) interacted significantly (P<.03) with treatment in that treatment benefit was apparent only for patients younger than 75 years (51.6% survival in ERV group vs 33.3% in IMS group). Eighty-three percent of 1-year survivors (85% of ERV group and 80% of IMS group) were in New York Heart Association class I or II.

CONCLUSIONS

For patients with AMI complicated by CS, ERV resulted in improved 1-year survival. We recommend rapid transfer of patients with AMI complicated by CS, particularly those younger than 75 years, to medical centers capable of providing early angiography and revascularization procedures.

Intracardiac echocardiography: current uses and future directions

Advances in transducer technology have enabled development of catheter-based ultrasound imaging devices that produce very high resolution images of vessels and cardiac structures. Although the majority of clinical use has been in the evaluation of the coronary and peripheral vasculature, a broad spectrum of cardiac applications continue to develop, including evaluations of the ventricles, valves, and great vessels, as well as the guidance of electrophysiological procedures. Specifically, introduction of the ultrasound catheter into the heart results in dynamic, real-time images for assessment and quantitation of ventricular systolic function, severity of valve stenosis, and extent of regurgitant orifices. The intracardiac applications have the potential to become the gold standard for quantitation of valve dynamics and a critical tool in the ICU for prolonged monitoring of cardiac physiology.

Evidence of reduced resting blood flow in viable myocardial regions with chronic asynergy

OBJECTIVES

We tested the hypothesis in patients (n = 24) with ischemic heart disease that chronic contractile dysfunction occurs in myocardial regions with true reduction in rest blood flow.

BACKGROUND

Whether viable myocardial regions with chronic contractile dysfunction have true reduction in rest myocardial blood flow is controversial.

METHODS

Positron emission tomography (PET) 13N-ammonia was used to measure myocardial blood flow in combination with 18F-fluorodeoxyglucose (18FDG) to assess myocardial viability. Viability also was assessed by dobutamine echo and recovery of function after coronary artery bypass grafting (CABG). Segments (n = 252) were selected based on PET measured reduced resting blood flow and rest asynergy on echo.

RESULTS

Regional myocardial viability was present in 20 of 23 patients by PET, 13 of 23 by dobutamine echo and 10 of 11 by postrevascularization criteria. Rest blood flow in normal regions was 1.14+/-0.52 ml/min/g and by definition exceeded (p < 0.005) that in both viable (0.48+/-0.15; n = 8 patients) and nonviable (0.45+/-0.14; n = 8 patients) regions (post-CABG criteria), which did not differ. Correction of rest myocardial blood flow in viable asynergic segments, only, for fibrosis and incomplete tracer recovery raised the level to 0.67+/-0.21 (p < 0.005 vs. normal). Finally, evidence of both stunning (rest asynergy with normal flow) and hibernation was present in 15 of 23 (65%) patients.

CONCLUSIONS

Reduced rest blood flow in viable myocardial regions with chronic asynergy is common and cannot be accounted for by partial volume effect. Thus, hypotheses concerning physiologic mechanisms underlying chronic contractile dysfunction should consider the role played by chronic reduction of basal myocardial blood flow.

Transmitral Doppler: a new transthoracic contrast method for patent foramen ovale detection and quantification

OBJECTIVES

This study compared a new transthoracic echocardiographic (TTE) method for detection of right to left bubble passage, transmitral Doppler (TMD), against two-dimensional (2D) TTE contrast study and the gold standard, of transesophageal echocardiography (TEE), and assessed its utility in quantitative assessment of patent foramen ovales (PFO).

BACKGROUND

Current TTE methods are relatively insensitive in PFO detection and do not allow quantitative assessment of right to left shunt.

METHODS

In 44 patients (59 years, range 34 to 76 years) saline contrast and color Doppler studies were performed in three conditions--TTE TMD, TTE 2D and TEE. Bubble transit on the TMD was measured semiquantitatively by a visual bubble score and objectively by integrating the acoustic power within the mitral velocity envelope.

RESULTS

By TEE it was determined that 17 patients (39%) had PFOs; 16 had right to left contrast passage, and only 1 had left to right flow by color Doppler. Against TEE contrast study, the sensitivity of TMD and 2D contrast studies were 100% and 75%, respectively, with specificity of 96% and 100%. Greater than 10 bubbles on a single beat of the resting contrast TMD identified patients with a maximum resting TEE PFO opening diameter >2 mm with 78% sensitivity and 100% specificity. There was a strong correlation (r2 = 0.72, p<0.01) between the TMD acoustic power and PFO opening diameter.

CONCLUSIONS

Transmitral Doppler is a sensitive and specific method for TTE PFO detection that allows quantification of right to left bubble passage and may obviate the need for TEE in many patients after stroke.

Transesophageal echocardiographic (TEE) evaluation of the mitral and tricuspid valves

In skilled hands, multiplane TEE provides a comprehensive assessment of the anatomy and function of the mitral and tricuspid valves. TEE is uniquely effective in the evaluation of the diverse pathophysiologic processes that cause valvular heart disease.

Congenital deficiency of nitric oxide synthase 2 protects against endotoxin-induced myocardial dysfunction in mice

BACKGROUND

Sepsis can be complicated by severe myocardial dysfunction and is associated with increased nitric oxide (NO) production by inducible NO synthase (NOS2). To investigate the role of NOS2 in endotoxin-induced myocardial dysfunction in vivo, we studied wild-type and NOS2-deficient mice.

METHODS AND RESULTS

Serial echocardiographic parameters of myocardial function were measured before and at 4, 7, 16, and 24 hours after an endotoxin challenge. Seven hours after challenge with either endotoxin or saline, systemic and left ventricular pressures were measured, and the first derivative of left ventricular developed pressure (dP/dt), slope of the end-systolic pressure-dimension relationship (Slope(LVESPD)), and time constant of isovolumic relaxation (tau) were calculated. Endotoxin challenge in wild-type mice decreased left ventricular fractional shortening, velocity of circumferential shortening, dP/dt(max), Slope(LVESPD), and dP/dt(min) and increased time constant tau. Endotoxin-induced myocardial dysfunction was associated with increased ventricular NOS2 gene expression and cGMP concentrations. Seven hours after endotoxin challenge, NOS2-deficient mice had greater fractional shortening, dP/dt(max), and Slope(LVESPD) than did endotoxin-challenged wild-type mice. Measures of diastolic function, dP/dt(min) and time constant tau, were preserved in endotoxin-challenged NOS2-deficient mice. After endotoxin challenge in wild-type mice, early (3-hour) inhibition of NOS2 with L-N:(6)-(1-iminoethyl)lysine hydrochloride prevented, whereas later (7-hour) inhibition could not reverse, endotoxin-induced myocardial dysfunction.

CONCLUSIONS

These results suggest that NOS2 is required for the development of systolic and diastolic dysfunction in murine sepsis.

Echocardiographic determinants of left ventricular ejection fraction after acute myocardial infarction

OBJECTIVE

This study was performed to determine if factors other than the size of regional dysfunction influence the global left ventricular ejection fraction after acute myocardial infarction.

BACKGROUND

Left ventricular ejection fraction is an important prognostic variable after acute myocardial infarction. Although infarct size is known to affect the subsequent global left ventricular ejection fraction, it remains unclear whether other factors such as site or severity of the wall motion abnormality influence the ejection fraction after acute myocardial infarction.

METHODS

Sixty-nine consecutive patients (mean age 61 +/- 14 years, 46 [67%] male) who did not receive thrombolytic therapy or undergo early revascularization were studied by echocardiography 1 week after Q-wave myocardial infarction. The absolute size of the region of abnormal wall motion (AWM) and the percentage of the endocardium involved (%AWM) were quantitated along with the wall motion score. A severity index was then derived as the mean wall motion score within the region of AWM. Site of myocardial infarction was classified as either anterior or inferior from the endocardial map. Left ventricular ejection fraction was measured by Simpson's method with 2 apical views.

RESULTS

Twenty-nine (42%) patients had anterior and 40 had inferior myocardial infarction. The mean left ventricular ejection fraction was significantly lower in anterior than in inferior myocardial infarction (44.8% +/- 11.5% vs 53% +/- 8.6%; P =. 001). The mean %AWM was greater in anterior than in inferior myocardial infarction (32.1 +/- 15.5 vs 22.4 +/- 14.1; P =.01). The mean wall motion score was greater in anterior than in inferior myocardial infarction (9.8 +/- 6.4 vs 6.4 +/- 4.4; P =.01). The mean severity index did not differ by site. Multiple regression analysis demonstrated that, in descending order of importance, %AWM, extent of apical involvement, and site of myocardial infarction were independent determinants of global left ventricular ejection fraction.

CONCLUSIONS

For myocardial infarctions of similar size, left ventricular ejection fraction is lower when apical involvement is extensive and the site of infarction is anterior. This site-dependent difference may be related to characteristics specific to the apex.

Regional patterns of left ventricular systolic dysfunction after subarachnoid hemorrhage: evidence for neurally mediated cardiac injury

Although left ventricular (LV) dysfunction has been described after subarachnoid hemorrhage (SAH), its pathophysiology, regional distribution, and reversibility remain uncertain. To test the hypothesis that regional wall motion patterns in SAH patients do not match the typical patterns observed in coronary artery disease, a segmental wall motion analysis was performed in 30 SAH patients with LV dysfunction. Both regional (n = 21) and global (n = 9) wall motion patterns were observed. Preservation of apical function relative to the base was observed in 17 (57%) of the 30 patients. Many of the wall motion patterns were atypical of coronary artery disease but correlated with the distribution of the myocardial sympathetic nerve terminals. Five subjects had follow-up echocardiograms with resolution of LV dysfunction in all cases. In conclusion, a previously unreported, apex-sparing pattern of LV dysfunction is described, providing indirect evidence for a neurally mediated mechanism of cardiac injury. Limited data indicate that LV dysfunction in SAH patients is potentially reversible.

Myocardial perfusion and wall motion in infarction border zone: assessment by myocardial contrast echocardiography

Several mechanisms have been proposed to explain the decreased wall motion (WM) at the borders of myocardial infarction (MI). We used myocardial contrast echocardiography (MCE) to investigate the relation of perfusion to WM in infarcted border zones (BZs) 6 weeks after MI in 5 sheep. After quantifying the extent of WM abnormality and the perfusion defect, normal (NL), infarcted, and BZs were defined. Peak intensity after contrast was measured in acoustic units (AU). Radiolabeled microspheres were injected to measure regional blood flow. The heart was stained with 2,3, 5-triphenyltetrazolium chloride (TTC). The perfusion defect on MCE was 33% +/- 7% of the total myocardial area and correlated well with TTC (r = 0.92, P <.03). The BZ was 8% +/- 5% of the total myocardial area. Peak intensity after contrast was decreased in MI compared with BZ and NL (MI: 2.5 +/- 1.9 AU, BZ: 8.0 +/- 3.8 AU, P <.005; NL: 10.2 +/- 6.9 AU, P <.02) and comparable in NL and BZ. The blood flow measured by microspheres was not different in NL and BZ but was decreased in MI (NL: 1.6 mL/g/min, BZ: 1.5 +/- 0.5 mL/g/min, MI: 0.7 +/- 0.5 mL/g/min; P <.0001). In this model of chronic ovine MI, the BZ was small and its perfusion was preserved. These findings support the hypothesis that tethering of normal myocardial segments explains the abnormal wall motion noted at the borders of MI.

Regional myocardial perfusion after experimental subarachnoid hemorrhage

BACKGROUND AND PURPOSE

The pathophysiology of cardiac injury after subarachnoid hemorrhage (SAH) remains controversial. Data from animal models suggest that catecholamine-mediated injury is the most likely cause of cardiac injury after SAH. However, researchers also have proposed myocardial ischemia to be the underlying cause, as a result of coronary artery disease, coronary artery spasm, or hypertension and tachycardia. To test the hypothesis that SAH-induced cardiac injury occurs in the absence of myocardial hypoperfusion, we developed an experimental canine model that reproduces the clinical and pathological cardiac lesions of SAH and defines the epicardial and microvascular coronary circulation.

METHODS

Serial ECG, hemodynamic measurements, coronary angiography, regional myocardial blood flow measurements by radiolabeled microspheres, 2D echocardiography, and myocardial contrast echocardiography were performed in 9 dogs with experimental SAH and 5 controls.

RESULTS

Regional wall motion abnormalities were identified in 8 of 9 SAH dogs and 1 of 5 controls (Fisher's Exact Test, P=0.02) but no evidence was seen of coronary artery disease or spasm by coronary angiography and of significant myocardial hypoperfusion by either regional myocardial blood flow or myocardial contrast echocardiography.

CONCLUSIONS

In this experimental model of SAH, a unique form of regional left ventricular dysfunction occurs in the absence of myocardial hypoperfusion. Future studies are justified to determine the cause of cardiac injury after SAH.

The echocardiographic diagnosis, characterization, and extraction guidance of cardiac foreign bodies

Echocardiography is ideal for localizing cardiac foreign bodies and for characterizing associated cardiac and vascular injury before and during extraction. We report 5 cases of traumatic and iatrogenic cardiac foreign bodies that illustrate the central role of transthoracic and transesophageal ultrasonography in the management of these patients.

Moderate-high intensity exercise training after myocardial infarction: effect on left ventricular remodeling

BACKGROUND

Regular exercise increases exercise capacity and physical fitness, but questions remain about the effects of exercise on left ventricle (LV) remodeling after myocardial infarction. This study investigated the effects of moderate to high intensity exercise training on LV remodeling after a first myocardial infarction.

METHODS

An exercise group of 68 patients in cardiac rehabilitation after a first myocardial infarction had an initial echocardiogram and exercise stress test. Thirty patients completed the 12 weeks of training and had echocardiograms suitable for quantitative analysis. Follow-up echocardiograms and exercise tests were performed. A carefully matched control group of 30 patients with echocardiograms at fixed intervals after myocardial infarction and no formal exercise training were also studied. LV size was expressed as the endocardial surface area-to-body surface area (ESAi), whereas infarct size was characterized by the percent abnormal wall motion (%AWM) by echocardiography using an endocardial surface area mapping technique. Indices of LV shape (sphericity) were also assessed.

RESULTS

In the exercise group, no significant changes were seen in ESAi (57.95 +/- 13.1 vs 57.80 +/- 12.04 cm2/m2) or in %AWM (19.33 +/- 15.27 vs 20.11 +/- 15.95) from the initial to the final echo. The indices of sphericity were also unchanged. None of these parameters changed in the control group. Within each group was found heterogeneity in LV remodeling. Multivariate regression analysis revealed initial ESAi and initial %AWM to predict change in ESAi over time.

CONCLUSIONS

In this study of patients with predominately small infarcts, exercise training did not adversely affect LV remodeling after myocardial infarction. Remodeling is heterogeneous and appears related to infarct and LV size.

Three-dimensional echocardiographic assessment of left ventricular wall motion abnormalities in mouse myocardial infarction

We applied 3-dimensional echocardiographic reconstruction to assess left ventricular (LV) volumes, function, and the extent of wall motion abnormalities in a murine model of myocardial infarction (MI). Consecutive parasternal short-axis planes were obtained at 1-mm intervals with a 13-MHz linear array probe. End-diastolic and end-systolic LV volumes were calculated by Simpson's rule, and the ejection fraction and cardiac output were derived. Echocardiography-derived cardiac output was validated by an aortic flow probe in 6 mice. Echocardiography was then performed in 9 mice before and after the left anterior descending coronary artery was ligated. Wall motion was assessed, and the ratio of the abnormally to normally contracting myocardium was calculated. After MI occurred, LV end-diastolic volume and LV end-systolic volume increased (33 +/- 10 vs 24 +/- 6 microL, P <.05 and 24 +/- 9 vs 10 +/- 4 microL, P <.001), whereas cardiac output decreased (4.2 +/- 1.5 mL/min vs 6.6 +/- 2.3 mL/min, P <.01). Forty percent of the myocardium was normokinetic, 24% was hypokinetic, and 36% was akinetic. Echocardiography can measure LV volumes and regional and global function in a murine model of myocardial infarction, thereby providing the potential to quantitate and compare the responses of various transgenic mice to MI and its therapies.

Echocardiographic determination of risk area size in a murine model of myocardial ischemia

Genetically altered mice are useful to understand cardiac physiology. Myocardial contrast echocardiography (MCE) assesses myocardial perfusion in humans. We hypothesized it could evaluate murine myocardial perfusion before and after acute coronary ligation. MCE was performed before and after this experimental myocardial infarction (MI) in anesthetized mice by intravenous injection of contrast microbubbles and transthoracic echo imaging. Time-video intensity curves were obtained for the anterior, lateral, and septal myocardial walls. After MI, MCE defects were compared with the area of no perfusion measured by Evans blue staining. In healthy animals, intramyocardial contrast was visualized in all the cardiac walls. The anterior wall had a higher baseline video intensity (53 +/- 17 arbitrary units) than the lateral (34 +/- 13) and septal (27 +/- 13) walls (P < 0.001) and a lower increase in video intensity after contrast injection [50 +/- 17 vs. 60 +/- 24 (lateral) and 65 +/- 29 (septum), P < 0.01]. After MI, left ventricular (LV) dimensions were enlarged, and the shortening fraction was decreased. A perfusion defect was imaged with MCE in every mouse, with a correlation between MCE perfusion defect size (35 +/- 13%) and the nonperfused area by Evans blue (37 +/- 16%, y = 0.77x + 6.1, r = 0.93, P < 0. 001). Transthoracic MCE is feasible in the mouse and can accurately detect coronary occlusions and quantitate nonperfused myocardium.

A murine model of myocardial microvascular thrombosis

Disorders of hemostasis lead to vascular pathology. Endothelium-derived gene products play a critical role in the formation and degradation of fibrin. We sought to characterize the importance of these locally produced factors in the formation of fibrin in the cardiac macrovasculature and microvasculature. This study used mice with modifications of the thrombomodulin (TM) gene, the tissue-type plasminogen activator (tPA) gene, and the urokinase-type plasminogen activator (uPA) gene. The results revealed that tPA played the most important role in local regulation of fibrin deposition in the heart, with lesser contributions by TM and uPA (least significant). Moreover, a synergistic relationship in fibrin formation existed in mice with concomitant modifications of tPA and TM, resulting in myocardial necrosis and depressed cardiac function. The data were fit to a statistical model that may offer a foundation for examination of hemostasis-regulating gene interactions.

Ventricular remodeling in active myocarditis. Myocarditis Treatment Trial

BACKGROUND

Remodeling of the left ventricle with the development of a spherical cavity occurs in dilated cardiomyopathy and is associated with a poor long-term prognosis. The early effects of myocarditis on left ventricular geometry have not been previously described or correlated with clinical outcome.

METHODS

The baseline echocardiograms of 35 patients with biopsy-confirmed myocarditis were compared with 20 normal controls. Left ventricular end-diastolic volume, long axis length, and mid-cavity diameter were measured. The degree of sphericity was expressed as the ratio of the mid-cavity diameter to the long axis length. Left ventricular ejection fraction was assessed by radionuclide angiography.

RESULTS

In patients with myocarditis, mean left ventricular volume of 81 +/- 29 mL/m(2) was significantly greater than 50 +/- 8 mL/m(2) in controls (P =.001). Chamber dilatation occurred primarily along the mid-cavity diameter, which measured 5.3 +/- 0.8 cm in patients with myocarditis versus 4.2 +/- 0.4 cm in controls (P =.001). The degree of left ventricular sphericity in patients with myocarditis, 0.64 +/- 0.08, was significantly greater than that of controls, 0.54 +/- 0.04 (P =.001). When patients were stratified according to left ventricular volume, patients with increased left ventricular volume (>75 mL/m(2)) were associated with a more spherical chamber and lower left ventricular ejection fraction than patients with a more normal left ventricular volume (</=75 mL/m(2)).

CONCLUSIONS

Active myocarditis is associated with early left ventricular remodeling and the development of a spherical chamber. These changes correlate with ventricular dilatation and reduced left ventricular ejection fraction.

Relation between coronary "steal" and contractile function at rest in collateral-dependent myocardium of humans with ischemic heart disease

BACKGROUND

We tested the hypothesis that rest asynergy in collateral-dependent myocardium correlates with coronary steal.

METHODS AND RESULTS

PET with [13N]ammonia measured myocardial blood flow and flow reserve in 15 patients with symptomatic chronic ischemic heart disease. Coronary angiography assessed stenosis severity and collateral blood supply. Echocardiography or contrast ventriculography evaluated regional wall motion. Collateral-dependent segments with normal flow at rest and supplied by coronary vessels having </=50% diameter stenosis were studied. Steal was defined as a decline in myocardial blood flow with adenosine >/=0.15 mL. min-1. g-1 versus rest. Blood flow at rest in asynergic, collateral-dependent segments with steal (1.15+/-0.35 mL. min-1. g-1) exceeded (P<0.0001) that of asynergic segments without steal (0.81+/-0.24) and those with normal contraction (0.77+/-0.18). Although the flow reserve ratio of segments with normal contraction (1.8+/-0.8) exceeded that of asynergic ones with (0.6+/-0.1) or without (1.3+/-0.4) steal, overlap was great. Correlation between basal contraction and flow reserve ratio in collateral-dependent myocardium was significant but weak (r=0.45, P<0.001). However, segments demonstrating "steal" with adenosine manifested asynergy in 22 of 23 collateral-dependent segments versus 24 of 39 nonsteal segments (chi2=7.10, P<0.01).

CONCLUSIONS

Although myocardial flow reserve in collateral-dependent segments with normal contraction exceeded that of asynergic segments, overlap was great. However, in patients with angina or congestive heart failure, left ventricular segments demonstrating steal with adenosine almost always exhibit asynergy at rest. Thus, coronary steal may play an important role in the pathogenesis of chronic contractile impairment at rest, whereas simple reduction of flow reserve may be less important in selected patients.

Regional wall motion assessment in stress echocardiography by tissue Doppler bull's-eyes

Quantification of regional myocardial wall velocities is needed in stress echocardiography for transition from subjective to quantitative assessment. Tissue Doppler allows quantitation of wall velocities, but interpretation is difficult and angle-dependent. Calculating the ratios of velocities with similar angles to the beam may overcome angle dependency. We measured left ventricular wall velocities during stress echocardiography with tissue Doppler. Regional peak systolic and early (E) and late (A) diastolic velocities were constructed in a "bull's-eye" format. Regional stress/rest and E/A ratios were calculated. Bull's-eye map construction demanded only minimal manual interaction, and the maps showed the left ventricular velocity distribution, simplifying wall motion reading markedly. Still, apical velocities appeared lower as a result of Doppler angle-dependency. With velocity ratios, angle-dependency was no longer noted. In stress echocardiography, wall motion abnormalities at rest and contractility changes with dobutamine became readily apparent. Bull's-eye display of quantitative tissue Doppler velocity allows rapid assessment of regional wall motion. Calculating the ratio of regional velocities circumvents the angle-dependency of Doppler. This novel technique has the potential for simplified and automated quantitative analysis in stress echocardiography.

Dynamic holographic imaging of the beating human heart

Background--Currently, the reporting and archiving of echocardiographic data suffer from the difficulty of representing heart motion on printable 2-dimensional (2D) media. Methods and Results--We studied the capability of holography to integrate motion into 2D echocardiographic prints. Images of normal human hearts and of a variety of mitral valve function abnormalities (mitral valve prolapse, systolic anterior motion of the mitral leaflets, and obstruction of the mitral valve by a myxoma) were acquired digitally on standard echocardiographic machines. Images were processed into a data format suitable for holographic printing. Angularly multiplexed holograms were then printed on a prototype holographic "laser" printer, with integration of time in vertical parallax, so that heart motion became visible when the hologram was tilted up and down. The resulting holograms displayed the anatomy with the same resolution as the original acquisition and allowed detailed study of valve motion with side-by-side comparison of normal and abnormal findings. Comparison of standard echocardiographic measurements in original echo frames and corresponding hologram views showed an excellent correlation of both methods (P<0.0001, r2=0.979, mean bias=2.76 mm). In this feasibility study, both 2D and 3D holographic images were produced. The equipment needed to view these holograms consists of only a simple point-light source. Conclusions--Holographic representation of myocardial and valve motion from echocardiographic data is feasible and allows the printing on a 2D medium of the complete heart cycle. Combined with the recent development of online holographic printing, this novel technique has the potential to improve reporting, visualization, and archiving of echocardiographic imaging.

Abnormal global left ventricular relaxation occurs early during the development of pharmacologically induced ischemia

In animal and human models, left ventricular (LV) diastolic function has been observed to be highly sensitive to myocardial ischemia. The response of LV diastolic parameters to pharmacologically induced ischemia, however, has not been characterized and might be important in the interpretation of dobutamine stress echocardiography. Eight mongrel dogs, in which were inserted a high-fidelity micromanometer LV catheter, coronary sinus sampling catheter, and ultrasonic coronary artery flow probe, underwent intravenous dobutamine infusion at escalating doses both before (control protocol) and after (ischemia protocol) creation of left anterior descending coronary artery stenosis with a hydraulic cuff occluder adjusted to maintain resting coronary artery flow but attenuate reactive hyperemia. At each dobutamine dose, epicardial short-axis 2-dimensional echocardiographic images and hemodynamic measurements were obtained. LV diastolic function was examined by calculation of peak (-)dP/dt and the time constant of isovolumic relaxation (tau). The dobutamine infusion protocol was terminated on the earliest recognition of an anterior wall motion abnormality. Peak (+)dP/dt normalized for developed isovolumetric pressure was calculated as a relatively load-independent index of global LV contractile function. Dobutamine infusion with and without ischemia resulted in comparable changes in heart rate and (+)dP/dt/IP, with no change in LV end-diastolic or -systolic pressure. The magnitude of peak (-)dP/dt increased less during the ischemia (1231 +/- 109 to 1791 +/- 200 mm Hg/sec) versus the control (1390 +/- 154 to 2432 +/- 320 mm Hg/sec) protocol (P <.05). Similarly, the observed decrease in tau was less during the ischemia (53 +/- 3 to 38 +/- 4 msec) than the control (51 +/- 5 to 23 +/- 3 msec) protocol, corresponding to a slower rate of relaxation (P <.05). In addition, the smaller decrease in tau was observed at the dobutamine dose before the dose at which an echocardiographic wall motion abnormality was first recognized. Dobutamine-induced ischemia is associated with abnormal LV diastolic function. In addition, these abnormalities seem to occur early in the development of ischemia. These observations extend to pharmacologically induced ischemia prior findings from other models of ischemia, suggesting the high sensitivity of LV diastolic function to the development of myocardial ischemia.

Effect of vesnarinone on cardiac function in patients with severe congestive heart failure

BACKGROUND

Vesnarinone has yielded controversial results on morbidity in patients with congestive heart failure. We tested the hypothesis that vesnarinone may have a beneficial effect on cardiac remodeling and function.

METHODS

Thirty-four patients with left ventricular ejection fraction (LVEF) <30% (17 treated with vesnarinone) underwent an echocardiography at baseline and at 12+/-5 months. Left ventricular end-diastolic and end-systolic volume, mitral regurgitation, diastolic filling, and right ventricular area change were quantified and compared.

RESULTS

When the vesnarinone group was considered as a whole, there was no significant effect of vesnarinone on cardiac systolic and diastolic function or remodeling. However, an increase in LVEF >7% was observed in six of the vesnarinone patients and none of the control group. Vesnarinone improved right and left ventricular systolic function significantly in patients with initial LVEF <25%.

CONCLUSIONS

In severe congestive heart failure, vesnarinone induces variable responses but improves biventricular performance in patients with the most impaired initial function.

Effect of atenolol or metoprolol on arbutamine stress echocardiography in patients suspected of having coronary artery disease

Arbutamine stress echocardiography was performed in 81 patients with suspected coronary artery disease. Arbutamine infusion, using a dedicated closed-loop delivery device, provided comparable myocardial stress in patients receiving beta-1 blockers versus those who were not.

Determination of right ventricular structure and function in normoxic and hypoxic mice: a transesophageal echocardiographic study

BACKGROUND

Noninvasive cardiac evaluation is of great importance in transgenic mice. Transthoracic echocardiography can visualize the left ventricle well but has not been as successful for the right ventricle (RV). We developed a method of transesophageal echocardiography (TEE) to evaluate murine RV size and function.

METHODS AND RESULTS

Normoxic and chronically hypoxic mice (F(IO2)=0.11, 3 weeks) and agarose RV casts were scanned with a rotating 3.5F/30-MHz intravascular ultrasound probe. In vivo, the probe was inserted in the mouse esophagus and withdrawn to obtain contiguous horizontal planes at 1-mm intervals. In vitro, the probe was withdrawn along the left ventricular posterior wall of excised hearts. The borders of the RV were traced on each plane, allowing calculation of diastolic and systolic volumes, RV mass, RV ejection fraction, stroke volume, and cardiac output. RV wall thickness was measured. Echo volumes obtained in vitro were compared with cast volumes. Echo-derived cardiac output was compared with measurements of an ascending aortic Doppler flow probe. Echo-derived RV free wall mass was compared with true RV free wall weight. There was excellent agreement between cast and TEE volumes (y=0.82x+6.03, r=0.88, P<0.01) and flow-probe and echo cardiac output (y=1.00x+0.45, r=0.99, P<0.0001). Although echo-derived RV mass and wall thickness were well correlated with true RV weight, echo-derived RV mass underestimated true weight (y=0.53x+2.29, r=0.81, P<0.0001). RV mass and wall thickness were greater in hypoxic mice than in normoxic mice (0.78+/-0.19 versus 0.51+/-0.14 mg/g, P<0.03, 0.50+/-0.03 versus 0.38+/-0.03 mm, P<0.04).

CONCLUSIONS

TEE with an intravascular ultrasound catheter is a simple, accurate, and reproducible method to study RV size and function in mice.

Phase III multicenter trial comparing the efficacy of 2% dodecafluoropentane emulsion (EchoGen) and sonicated 5% human albumin (Albunex) as ultrasound contrast agents in patients with suboptimal echocardiograms

OBJECTIVES

This study was performed to compare the safety and efficacy of intravenous 2% dodecafluoropentane (DDFP) emulsion (EchoGen) with that of active control (sonicated human albumin [Albunex]) for left ventricular (LV) cavity opacification in adult patients with a suboptimal echocardiogram.

BACKGROUND

The development of new fluorocarbon-based echocardiographic contrast agents such as DDFP has allowed opacification of the left ventricle after peripheral venous injection. We hypothesized that DDFP was clinically superior to the Food and Drug Administration-approved active control.

METHODS

This was a Phase III, multicenter, single-blind, active controlled trial. Sequential intravenous injections of active control and DDFP were given 30 min apart to 254 patients with a suboptimal echocardiogram, defined as one in which the endocardial borders were not visible in at least two segments in either the apical two- or four-chamber views. Studies were interpreted in blinded manner by two readers and the investigators.

RESULTS

Full or intermediate LV cavity opacification was more frequently observed after DDFP than after active control (78% vs. 31% for reader A; 69% vs. 34% for reader B; 83% vs. 55% for the investigators, p < 0.0001). LV cavity opacification scores were higher with DDFP (2.0 to 2.5 vs. 1.1 to 1.5, p < 0.0001). Endocardial border delineation was improved by DDFP in 88% of patients versus 45% with active control (p < 0.001). Similar improvement was seen for duration of contrast effect, salvage of suboptimal echocardiograms, diagnostic confidence and potential to affect patient management. There was no difference between agents in the number of patients with adverse events attributed to the test agent (9% for DDFP vs. 6% for active control, p = 0.92).

CONCLUSIONS

This Phase III multicenter trial demonstrates that DDFP is superior to sonicated human albumin for LV cavity opacification, endocardial border definition, duration of effect, salvage of suboptimal echocardiograms, diagnostic confidence and potential to influence patient management. The two agents had similar safety profiles.

Sustained pulmonary hypertension and right ventricular hypertrophy after chronic hypoxia in mice with congenital deficiency of nitric oxide synthase 3

Chronic hypoxia induces pulmonary hypertension and right ventricular (RV) hypertrophy. Nitric oxide (NO) has been proposed to modulate the pulmonary vascular response to hypoxia. We investigated the effects of congenital deficiency of endothelial NO synthase (NOS3) on the pulmonary vascular responses to breathing 11% oxygen for 3-6 wk. After 3 wk of hypoxia, RV systolic pressure was greater in NOS3-deficient than in wild-type mice (35+/-2 vs 28+/-1 mmHg, x+/-SE, P < 0.001). Pulmonary artery pressure (PPA) and incremental total pulmonary vascular resistance (RPI) were greater in NOS3-deficient than in wild-type mice (PPA 22+/-1 vs 19+/-1 mmHg, P < 0.05 and RPI 92+/-11 vs 55+/-5 mmHg.min.gram.ml-1, P < 0.05). Morphometry revealed that the proportion of muscularized small pulmonary vessels was almost fourfold greater in NOS3-deficient mice than in wild-type mice. After 6 wk of hypoxia, the increase of RV free wall thickness, measured by transesophageal echocardiography, and of RV weight/body weight ratio were more marked in NOS3-deficient mice than in wild-type mice (RV wall thickness 0.67+/-0.05 vs 0.48+/-0.02 mm, P < 0.01 and RV weight/body weight ratio 2.1+/-0.2 vs 1.6+/-0.1 mg. gram-1, P < 0.05). RV hypertrophy produced by chronic hypoxia was prevented by breathing 20 parts per million NO in both genotypes of mice. These results suggest that congenital NOS3 deficiency enhances hypoxic pulmonary vascular remodeling and hypertension, and RV hypertrophy, and that NO production by NOS3 is vital to counterbalance pulmonary vasoconstriction caused by chronic hypoxic stress.

Accurate localization of mitral regurgitant defects using multiplane transesophageal echocardiography

BACKGROUND

Appropriate patient selection for surgical repair of the mitral valve depends on the specific location and mechanism of regurgitation, which, in turn, has necessitated a more detailed method to accurately describe mitral pathology. This study tests a strategy of using multiplane transesophageal echocardiography to systematically localize mitral regurgitant defects and compares these results with the surgical findings.

METHODS

Fifty patients with mitral regurgitation underwent intraoperative transesophageal echocardiography for the evaluation of mitral pathology and potential repair. Mitral regurgitant defects were localized using a systematic strategy and a simple nomenclature that divides each mitral valve into six sections (three sections per leaflet) and each prosthetic sewing ring into six sections (60 radial degrees = one section).

RESULTS

Thirty-nine patients with native mitral valves were studied, for a total of 234 sections evaluated. Eighty-seven of these sections contained regurgitant defects by transesophageal echocardiography (mean number of regurgitant defects per valve, 2.2; range, 1 through 6). There was agreement between the transesophageal echocardiographic and surgical localizations in 96% (224/234; p < 0.0001) of the sections. Eleven patients with prosthetic mitral valves were studied, for a total of 66 sections evaluated. Twenty-three of these sections contained paravalvular leaks by transesophageal echocardiography (mean number of leaks per prosthesis, 2.1; range, 1 through 6). There was agreement between the transesophageal echocardiographic and surgical localizations in 88% (58/66; p < 0.001) of the sections.

CONCLUSIONS

This transesophageal echocardiographic strategy provides a systematic method to accurately localize mitral regurgitant lesions and has the potential to improve the preoperative assessment of patients with significant mitral regurgitation.

Effects of dobutamine at maximally tolerated dose on myocardial blood flow in humans with ischemic heart disease

BACKGROUND

This study tests the hypothesis in humans with ischemic heart disease that myocardial blood flow response to dobutamine is linearly correlated with blood flow response to adenosine.

METHODS AND RESULTS

PET with [13N]ammonia was used to measure myocardial blood flow at rest and during adenosine and dobutamine at the maximally tolerated dose. Myocardial segments were defined physiologically on the basis of blood flow response to adenosine: normal, > or = 2 mL x min(-1) x g(-1); abnormal, < 2 mL x min(-1) x g(-1); and "steal," decline versus baseline > or = 0.15 mL x min(-1) x g(-1). The patient population consisted of 11 men and 2 women. Dobutamine increased heart rate (79+/-22 to 115+/-28 bpm) and rate-pressure product (9748+/-2862 to 15,157+/-3433 mm Hg/min) significantly (both P<.01). Myocardial blood flow at rest in abnormal segments (0.50+/-0.23 mL x min(-1) x g(-1)) was reduced (P<.001) versus normal (0.90+/-0.45) and steal (0.92+/-0.60). Nevertheless, in abnormal segments, blood flow increased versus rest (P<.001) with dobutamine (0.83+/-0.43) and adenosine (0.90+/-0.49). In steal segments, myocardial blood flow declined versus baseline (P<.001) with dobutamine (0.68+/-0.46) and adenosine (0.50+/-0.45). In normal segments, myocardial blood flow increased (P<.001) with dobutamine (2.16+/-0.99) and adenosine (3.10+/-0.90). Over the range of flows, the correlation between adenosine and dobutamine was good (r=.78, P<.0001). Although flow with dobutamine in normal segments correlated with rate-pressure product (r=.81, P<.05), the slope of the line was 2.7+/-0.8 (P<.02), and normalized blood flow (3.3+/-2.5 x rest) exceeded normalized rate-pressure product (1.9+/-0.8 x rest; P<.05).

CONCLUSIONS

In humans with ischemic heart disease, myocardial blood flow responses to dobutamine and adenosine are linearly correlated over a wide range. The hyperemic response to dobutamine is in excess of that predicted by rate-pressure product and reflects the unmeasured inotropic, oxygen-wasting, and beta2-agonist effects of the drug. Dobutamine induces coronary steal with a frequency approaching that of adenosine.

Effects of prolonging peak dobutamine dose during stress echocardiography

OBJECTIVES

This study sought to test whether the physiologic advantage of a prolonged dobutamine stage during stress echocardiography can be effectively combined with a clinically practical infusion protocol.

BACKGROUND

Dobutamine has a half-life of 2 min and requires up to 10 min to achieve steady state. Despite these known pharmacodynamics, dobutamine stress echocardiography is routinely performed by advancing doses at 3-min intervals. Canine studies have shown that dobutamine stress echocardiography end points will occur at a lower dose if each stage is prolonged, but these findings have yet to be used in the clinical setting.

METHODS

The standard 3-min dobutamine dose stage during stress echocardiography was modified by extending the peak dose (40 micrograms/kg body weight per min) for an additional 2 min. Consecutive patients underwent this modified protocol to test whether the requirement for atropine could be reduced. According to this modified protocol, if a dobutamine stress echocardiographic end point (85% of maximal predicted heart rate, new wall motion abnormalities, hypotension, arrhythmia or intolerable symptoms) was not reached at 3 min of the peak dose, this dose was prolonged for an additional 2 min. If a doubtamine stress echocardiographic end point was still not attained, atropine (up to 1.0 mg intravenously) was administered.

RESULTS

The study included 84 patients, 22 of whom (26.2%) achieved a dobutamine stress echocardiographic end point using the standard 3-min stage. Of the 62 patients who did not reach an end point in the initial 3 min of peak dobutamine dose, the additional 2 min of dobutamine increased heart rate (from 99.6 +/- 23.8 to 107.2 +/- 23.2 beats/min, p < 0.01) and allowed 20 patients (32.3%, p < 0.01) to attain an end point. Of the remaining 42 patients, 23 never achieved a stress echocardiographic end point, despite 1.0 mg of atropine. One patient developed supraventricular tachycardia during the additional 2 min of dobutamine, and one developed nonsustained ventricular tachycardia after receiving atropine.

CONCLUSIONS

These data demonstrate that a significant number of patients (32%) who do not reach a dobutamine stress echocardiographic end point with the standard protocol can safely attain an end point solely by extending the duration of the peak dose. Adoption of this strategy may reduce the need for supplemental atropine and its potential adverse effects.

Percutaneous transvenous intracardiac ultrasound imaging in dogs: a new approach to monitor left ventricular function

OBJECTIVE

To evaluate the feasibility and ability of percutaneous transvenous intracardiac echocardiography (ICE) to image the left ventricle (LV) and monitor its function from the right ventricular (RV) cavity.

METHODS

A 10 MHz catheter was advanced into the RV from the jugular vein and positioned along the septum at the LV papillary muscle level in five dogs. The catheter was manipulated until a stable catheter position along the septum, which provided on-axis images of LV, was obtained. Different states of LV size and systolic function (n = 80) were created with dobutamine or esmolol, both in the presence and absence of coronary stenoses. LV stroke area (cm2) obtained by ICE was measured at the mid-ventricular level and compared with stroke volume (cm3) obtained simultaneously with a transaortic flow probe. LV end diastolic, end systolic, and stroke areas obtained by ICE were also compared with those obtained by short-axis epicardial echocardiography.

RESULTS

In 96% of the stages, short axis images of the LV could be obtained and measured by ICE. LV end diastolic, end systolic, and stroke areas measured by ICE were not significantly different from epicardial echocardiographic values. Stroke area correlated with stroke volume in each dog (mean correlation coefficient 0.79 (SEE 0.19) cm2) (P < 0.001).

CONCLUSIONS

Percutaneous intracardiac ultrasound imaging allows monitoring of LV function from the RV with an accuracy comparable to a short-axis epicardial echocardiogram. The present device can be used in closed chest experimental studies. With the development of lower frequency devices, this technique may be valuable for continuous monitoring of LV function in patients in the intensive care unit or operating room.

Prevalence and timing of regional myocardial dysfunction after rotational coronary atherectomy

OBJECTIVES

This study aimed to evaluate the prevalence and time course of wall motion abnormalities associated with rotational coronary atherectomy.

BACKGROUND

Although initial clinical studies found evidence of transient wall motion abnormalities after rotational coronary atherectomy, the prevalence and duration of these wall motion abnormalities are unknown.

METHODS

Using simultaneous echocardiography, we prospectively evaluated 22 patients undergoing rotational atherectomy and compared their wall motion abnormalities with those of 10 patients undergoing coronary angioplasty alone. The extent of wall motion abnormality was quantified and plotted against time to produce curves of abnormal wall motion development and recovery for the two groups.

RESULTS

The cumulative ischemic time was similar for the two groups ([mean +/- SD] 10.3 +/- 6 min for rotational atherectomy vs. 9.6 +/- 4.2 min for coronary angioplasty, p = 0.73). The rate of return to baseline function was significantly lower in the rotational atherectomy group than in the coronary angioplasty group (rotational atherectomy rate constant 0.069 +/- 0.079/min vs. coronary angioplasty rate constant 1.250 +/- 0.47/min, p = 0.0001). The mean time to recovery of baseline wall motion in the rotational atherectomy group (153 min, 95% confidence interval [CI] 6.5 to 3,600) was significantly longer than in the coronary angioplasty group (2.6 min, 95% CI 1.3 to 5.5, p = 0.0001). Rotational atherectomy burr time was longer in the patients who developed myocardial infarction than in those without myocardial infarction (4.7 +/- 2.4 vs. 3 +/- 1.4 min, p = 0.045).

CONCLUSIONS

Transient wall motion abnormalities are common after rotational coronary atherectomy and have a longer duration than those observed after coronary angioplasty. This disparity may be a consequence of differences in the mechanisms by which rotational coronary atherectomy and coronary angioplasty produce their effect.

Factors influencing regional myocardial contractile response to inotropic stimulation. Analysis in humans with stable ischemic heart disease

BACKGROUND

We hypothesized that the response of a myocardial segment to maximal dobutamine reflects not only maximal blood flow but also tethering, metabolic, and beta-blocker status.

METHODS AND RESULTS

Patients with stable ischemic heart disease (n = 27) had positron emission tomographic measurement of blood flow at rest and with adenosine, and echocardiography at rest and with dobutamine. Positron emission tomographic measurement of [18F]fluorodeoxyglucose myocardial distribution also was made. Adenosine blood flow in segments that contracted normally at peak dobutamine was similar to that of segments that became hypokinetic (1.06 +/- 0.72 versus 1.02 +/- 0.77 mL.g-1.min-1). Segments that became akinetic failed to augment blood flow (0.68 +/- 0.30 mL.g-1.min-1). Fluorodeoxyglucose-blood flow mismatch was more common in segments with abnormal wall motion at peak dobutamine (24 of 59, 41%) versus those that contracted normally (63 of 269, 23%; chi 2, 7.40; P < .01). In patients off beta-blockers, segments that contracted normally at peak dobutamine increased blood flow with adenosine (0.70 +/- 0.31 to 0.86 +/- 0.46 mL.g-1.min-1; P < .05), whereas those that became abnormal did not (0.63 +/- 0.24 to 0.65 +/- 0.19 mL.g-1.min-1; P = NS). Segments of patients on beta-blockers that contracted normally at peak dobutamine increased blood flow with adenosine (0.78 +/- 0.31 to 1.10 +/- 0.70 mL.g-1.min-1; P < .05), as did segments that became abnormal (0.74 +/- 0.34 to 1.06 +/- 0.82 mL.g-1.min-1; P = NS). However, segments adjacent to ones with abnormal wall motion at rest had higher frequency of abnormal response at peak dobutamine in groups on (48% versus 16%; chi 2, 14.1; P < .001) and off (51% versus 21%; chi 2, 10.9; P < .01) beta-blockers.

CONCLUSIONS

Augmented contraction at maximal dobutamine depends not only on increased myocardial blood flow but also on tethering, metabolic, and beta-blocker status. Furthermore, impaired flow reserve does not preclude a normal response to maximal dobutamine, since blood flow need not increase greatly to meet demand.

Biopsy-induced flail tricuspid leaflet and tricuspid regurgitation following orthotopic cardiac transplantation

Damage to the tricuspid valve apparatus has been described after endomyocardial biopsy and may be associated with hemodynamically significant tricuspid regurgitation (TR). This study was performed to determine the prevalence of TR and flail tricuspid leaflet in cardiac transplant recipients and to evaluate the use of a 45 cm sheath placed directly in the right ventricle during endomyocardial biopsy to reduce the incidence of these complications. Echocardiograms and right heart catheterization data of 72 orthotopic cardiac transplant recipients were assessed for the presence of flail tricuspid leaflet, TR, and right-sided cardiac dysfunction 29 +/- 20 months (mean +/- SD) after transplantation. Moderate or severe TR was present in 23 patients (32%). Ten patients (14%) had flail tricuspid leaflet, with 7 of these having severe TR. Right atrial pressure (10 +/- 5 vs 6 +/- 5 mm Hg, p < 0.05) was higher, cardiac index (2.0 +/- 0.2 vs 2.5 +/- 0.7 L/min/m2, p < 0.05) was lower, and right-sided cardiac dimensions were greater in patients with flail leaflets than in those without flail leaflets. Both the prevalence of flail tricuspid leaflet (41% to 6%, p < 0.0001) and mean grade of TR (2 to 1, p < 0.0001) were reduced after the use of a 45 cm sheath. We conclude that TR secondary to biopsy-induced damage to the valve apparatus occurs in cardiac transplant recipients and is associated with signs of early right-sided heart failure. Use of a 45 cm sheath during endomyocardial biopsy reduces the prevalence of flail tricuspid leaflet and the severity of TR.

Absence of Q waves after thrombolysis predicts more rapid improvement of regional left ventricular dysfunction

Although the natural history of regional left ventricular (LV) dysfunction after Q-wave and non-Q-wave myocardial infarction (MI) was well defined in the prethrombolytic era, the functional and structural implications of the absence of Q waves after thrombolysis are less clear. Echocardiography was performed within 48 hours of admission (entry) in 86 patients treated with thrombolysis for their first MI. The extent of abnormal wall motion (AWM; square centimeters) and LV endocardial surface area index (ESA; square centimeters per square meters) were quantified by using a previously validated echocardiographic endocardial surface-mapping technique. Electrocardiography (ECG) performed at 48 hours after thrombolysis was used to classify patients into groups with (Q; n=70) and without (non-Q; n=16) Q waves. All patients in the Q group had regional LV dysfunction on initial echocardiogram compared with 69 percent of those in the non-Q group (p<0.001). When the patients in the non-Q group without AWM were excluded from analysis, there was no significant difference in the extent of AWM between the Q and non-Q groups. Among those patients with AWM on entry, follow-up echocardiography at 6 to 12 weeks demonstrated a significant reduction in extent of AWM for both the Q and non-Q groups. However, the fractional change in AWM was significantly greater in the non-Q than in the Q group (-0.74 +/- 0.28 vs -0.29 +/- 0.44; p<0.02), with a trend toward less AWM at follow-up in the non-Q than in the Q group. The mean ESAi was not significantly different between the two groups at entry or at follow-up. In conclusion, failure to develop Q waves after thrombolysis predicts a lower likelihood of developing regional LV dysfunction and, when such dysfunction is present, predicts a greater degree of recovery.

Effect of beta-blockade on dobutamine stress echocardiography

Dobutamine is an effective pharmacologic stress used in conjunction with echocardiography because of its beta-agonist properties. Concurrent beta-blockade might alter this effectiveness; however, current clinical experience has been variable. The purpose of this study is to determine whether concurrent beta-blockade alters the ability of a dobutamine stress echocardiogram to detect a fixed coronary stenosis by preventing the onset of a wall motion abnormality or by altering the dose at which the wall motion abnormality appears. Paired dobutamine stress tests with and without beta-blockade (esmolol 500 microgram/kg initial bolus, 100 microg/kg/min infusion) were performed in a canine model (n = 8) with a fixed single-vessel coronary stenosis. Heart rate, systolic pressure, proximal left anterior descending coronary flow, myocardial thickening (by sonomicrometry), and left ventricular area change (by epicardial echocardiography) were monitored. Simultaneous beta-blockade resulted in (1) a delayed and diminished increase in hemodynamic parameters (peak heart rate 164.1 +/- 22.3 without beta-blockade vs 110.1 +/- 28.9 beats/min with beta-blockade, p < 0.001, and peak systolic blood pressure 137.9 +/- 26.8 mm Hg without beta-blockade vs 107.3 +/- 15.3 mm Hg with beta-blockade, p = 0.01), (2) an elimination of the physiologic effects of low-dose (5 and 10 microg/kg/min) dobutamine (-0.7 percent +/- 16.7 percent change in myocardial thickening from baseline with beta-blockade, p = NS), and (3) an elimination or alteration in timing of inducible wall motion abnormalities caused by severe coronary artery stenoses (mean termination dose 28.8 +/- 9.9 with beta-blockade vs 15.6 +/- 6.1 microg/kg/min without beta-blocker, p < 0.01). The findings in this canine model suggest that the competitive antagonist markedly attenuates the ability of dobutamine stress echocardiography to detect a significant coronary lesion and may alter its ability to detect viable myocardium at low-dose testing. Further clinical studies to determine the sensitivity of dobutamine stress echocardiography in the presence of beta-blockers and to establish protocol standards are necessary.

Three-dimensional echocardiography: the influence of number of component images on accuracy of left ventricular volume quantitation

One approach to three-dimensional echocardiography is to reconstruct the surface of cardiac structures from two-dimensional images positioned in three-dimensional space. This approach has yielded accurate measures; however, the relationship between the number of nonparallel images used in three-dimensional echocardiographic reconstruction to the accuracy of the volume calculated has not been determined. With a canine model in which instantaneous left ventricular volume could be measured in vivo, images were obtained from intersecting long- and short-axis scans and stored with their spatial coordinates. The left ventricle was reconstructed and its volume calculated. The difference between three-dimensional echocardiographic and true volume was determined in 84 different cavitary volumes (4 to 85 ml). In each case, long- and short-axis images were deleted serially from the original data set (maximum of 27) until there were only three images left in the reconstruction. After each set of deletions, left ventricular volume was recalculated with the remaining images. Three-dimensional echocardiography accurately quantified ventricular volume with eight to 12 intersecting images, with a mean error of less than 1 ml and an SD of 5 ml. With a reduction of component images below eight, there were progressive increases in both absolute and mean percentage error. Accurate assessment of stroke volume and ejection fraction in this beating heart model also required eight to 12 images. Left ventricular volume and systolic function can be quantitated by three-dimensional echocardiography with as few as eight to 12 intersecting or nonparallel images.