The lungs as receptor sites for cardiovascular regulation

Improved long-term survival associated with stent deployment during percutaneous coronary interventions: results from a registry of 3399 patients

INTRODUCTION

The use of stents in percutaneous coronary intervention (PCI) improves procedural success and reduces restenosis. However, few studies have had a sufficient sample size or adequate follow-up to determine whether this advantage results in a positive effect on mortality.

METHODS

A total of 3399 patients undergoing PCI (stented [with dual antiplatelet therapy]: n = 2456, nonstented [balloon PCI or rotational atherectomy]: n = 942) at a single institution from 1994 to 2001 were followed up prospectively (43 +/- 22 and 54 +/- 25 months, respectively) for acute and long-term clinical outcomes.

RESULTS

Angiographic success (< 50% residual stenosis) (99.7% vs 97.7%, P < .001) and acute gain (3.02 +/- 0.55 vs 2.08 +/- 0.62 mm, P < .001) were both greater for stented lesions. Likewise, procedural complications of death (0.04% vs 0.4%, P = .02) and dissection (4.9% vs 8.0%, P = .001) were lower in the stent group, as were rates of 6-month clinical restenosis (10.3% vs 16.3%, P < .001). Eight-year mortality (12.0% vs 18.2%, hazard ratio = 0.78, P = .009) was lower among the stent group, as was long-term major adverse cardiac events (36.2% vs 50.6%, P < .001), but no difference in long-term myocardial infarction was found (6.5% vs 7.6%, P = .28). In multivariable Cox regression, stent use (hazard ratio = 0.76, 95% CI [0.58-0.99], P = .04) remained associated with significantly reduced mortality.

CONCLUSION

This large prospective study demonstrates that, in addition to a general improvement in procedural success and a reduced need for repeat revascularization, the use of stents with dual antiplatelet therapy was associated with a significant reduction in long-term mortality. Consideration should be given for the use of stents whenever feasible during PCI.

Coronary Artery Stenoses: Detection with Calcium Scoring, CT Angiography, and Both Methods Combined

PURPOSE

To investigate prospectively the relative accuracy of computed tomographic (CT) angiography, calcium scoring (CS), and both methods combined in demonstrating coronary artery stenoses by using conventional angiography as the reference standard.

MATERIALS AND METHODS

The study was approved by the institutional review board Human Research Ethics Committee, and all patients completed written informed consent. Fifty patients (40 men, 10 women) aged 62 years +/- 11 (+/- standard deviation) who were suspected of having coronary artery disease underwent both conventional coronary angiography and multisection coronary CT angiography with CS. Sensitivity and specificity of CS, CT angiography, and both methods combined in demonstrating luminal stenosis greater than or equal to 50% were determined for each arterial segment, coronary vessel, and patient. Receiver operating characteristic (ROC) curves were generated for CS prediction of significant stenosis, and the Mann-Whitney U test was used for comparison of CS between groups.

RESULTS

When used with segment-specific electrocardiographic phase reconstructions, CT angiography demonstrated stenosed segments with 79% sensitivity and 95% specificity. Mean calcium score was greater in segments, vessels, and patients with stenoses than in segments, vessels, and patients without stenoses (P < .001 for all); nine (16%) of 56 stenosed segments, however, had a calcium score of 0. The patient calcium score correlated strongly with the number of stenosed arteries (Spearman rho = 0.75, P < .001). CS was more accurate in demonstrating stenosis in patients than in segments (areas under ROC curve were 0.88 and 0.74, respectively). CT angiography, however, was more accurate than CS in demonstrating stenosis in patients, vessels, and segments. The sensitivity and specificity of CS varied according to the threshold used, but when the calcium score cutoff (ie, >150) matched the specificity of CT angiography (95%), the sensitivity of CS in demonstrating stenosed segments was 29% (compared with 79% for CT angiography). Combining CT angiography with CS (at threshold of 400) improved the sensitivity of CT angiography (from 93% to 100%) in demonstrating significant coronary disease in patients, without a loss of specificity (85%); this finding, however, was not statistically significant.

CONCLUSION

CT angiography is more accurate than CS in demonstrating coronary stenoses. A patient calcium score of greater than or equal to 400, however, can be used to potentially identify patients with significant coronary stenoses not detected at CT angiography.

Coronary artery spatial distribution of acute myocardial infarction occlusions

BACKGROUND

Acute coronary occlusions leading to ST-segment elevation myocardial infarctions (STEMIs) are due primarily to rupture of atherosclerotic plaques. Present "vulnerable plaque" detection technology focuses on identifying individual plaques with no clear therapeutic plan beyond conventional risk factor reduction. We developed a spatial map of the distribution of acute coronary occlusions to test our hypothesis that plaque ruptures do not occur uniformly throughout the coronary tree.

METHODS AND RESULTS

We analyzed 208 consecutive patients who presented to the Brigham and Women's Hospital with STEMI and mapped the location of the acute coronary occlusion. These occlusions were not uniformly distributed throughout each of the major epicardial coronary arteries but tended to cluster within the proximal third of each of the vessels (right coronary artery, P=0.001; left anterior descending artery, P=0.003; left circumflex artery, P=0.001). Furthermore, Poisson regression showed that for each 10-mm increase in distance from the ostium, the risk of an acute coronary occlusion was significantly decreased by 13% in the right coronary artery, 30% in the left anterior descending artery, and 26% in the left circumflex artery.

CONCLUSIONS

Acute coronary occlusions leading to STEMI tend to cluster in predictable "hot spots" within the proximal third of the coronary arteries. Identification of these high-risk zones for acute coronary occlusions will lead to future advances in vulnerable plaque detection technology and potentially locally directed preventive strategies.

Noninvasive imaging of coronary arteries: current and future role of multi-detector row CT

While invasive imaging techniques, especially selective conventional coronary angiography, will remain vital to planning and guiding catheter-based and surgical treatment of significantly stenotic coronary lesions, the comprehensive and serial assessment of asymptomatic or minimally symptomatic stages of coronary artery disease (CAD) for preventive purposes will eventually need to rely on noninvasive imaging techniques. Cardiovascular imaging with tomographic modalities, including computed tomography (CT) and magnetic resonance imaging, has great potential for providing valuable information. This review article will describe the current and future role of cardiac CT, and in particular that of multi-detector row CT, for imaging of atherosclerotic and other pathologic changes of the coronary arteries. It will describe how tomographic coronary imaging may eventually supplement traditional angiographic techniques in understanding the patterns of atherosclerotic CAD development.

Association of the PURSUIT risk score with predischarge ejection fraction, angiographic severity of coronary artery disease, and mortality in a nonselected, community-based population with non-ST–elevation acute myocardial infarction

BACKGROUND

The Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) risk score was derived from the PURSUIT trial population for 30-day mortality prediction.

METHODS

The PURSUIT risk score was calculated for 337 consecutive Olmsted County residents with non-ST-elevation acute myocardial infarction admitted to the coronary care unit of our institution from 1988 through 1998. Predischarge ejection fraction (EF) measurement was available for 246 patients (73%). After excluding patients with prior coronary artery bypass graft surgery (n = 42), 219 patients (65%) had coronary angiography within 30 days of admission. Mortality at 30 days was 8.9%. Among 30-day survivors, mortality at 1 year was 7.9%.

RESULTS

Mean age was 70 +/- 13 years, and 37% of patients were women. Mean predischarge EF was 52% +/- 16%. Patients with higher PURSUIT risk score had lower EF (P <.001). Three-vessel (> or =70% stenosis in all 3 coronary arteries) or left main (> or =50% stenosis) coronary artery disease was present in 60 of 219 patients (27%) who had coronary angiography. Higher PURSUIT risk score was associated with greater likelihood of 3-vessel or left main disease (P <.001). The PURSUIT risk score had very good predictive accuracy for both early (30-day, C-statistic = 0.78) and late (30-day to 1-year, C-statistic = 0.77) mortality.

CONCLUSIONS

The PURSUIT risk score correlates with EF, angiographic severity of coronary artery disease, and short- and long-term mortality of nonselected patients with non-ST-elevation acute myocardial infarction.

Autonomic responses during inhalation of natural fragrance of “Cedrol” in humans

It is well known that odors affect behaviors and autonomic functions. Previous studies reported that some compounds in cedar wood essence induced behavioral changes including sedative effects. In the present study, we analyzed cardiovascular and respiratory functions while subjects were inhaling fumes of pure compound (Cedrol) which was extracted from cedar wood oil. Vaporized Cedrol (14.2+/-1.7 microg/l, 5 l/min) and blank air (5 l/min) were presented to healthy human subjects (n=26) via a face mask, while ECGs, heart rate (HR), systolic blood pressure (SBP), diastolic BP (DBP), and respiratory rates (RR) were monitored. Statistical analyses indicated that exposure to Cedrol significantly decreased HR, SBP, and DBP compared to blank air while it increased baroreceptor sensitivity. Furthermore, respiratory rate was reduced during exposure to Cedrol. These results, along with the previous studies reporting close relationship between respiratory and cardiovascular functions, suggest that these changes in respiratory functions were consistent with above cardiovascular alterations. Spectral analysis of HR variability indicated an increase in high frequency (HF) component (index of parasympathetic activity), and a decrease in ratio of low frequency to high frequency components (LF/HF) (index of sympathovagal balance) during Cedrol inhalation. Furthermore, Cedrol inhalation significantly decreased LF components of both SBP and DBP variability, which reflected vasomotor sympathetic activity. Taken together, these patterns of changes in the autonomic parameters indicated that Cedrol inhalation induced an increase in parasympathetic activity and a reduction in sympathetic activity, consistent with the idea of a relaxant effect of Cedrol.

Bradykinin causes hypotension by activating pulmonary sympathetic afferents in the rabbit

Bradykinin (BK) activates sympathetic afferents in the heart, intestine, and kidney, and it alters hemodynamics. However, we know little about the influence of pulmonary sympathetic afferents on circulation. Activation of pulmonary afferents by directly injecting stimulants into the lung parenchyma permits examination of reflexes that originate in the lung without confounding effects from the systemic circulation. In the present study, we tested the hypothesis that pulmonary sympathetic afferents exert a significant influence on hemodynamics. We examined reflex effects of injecting BK (1 microg/kg in 0.1 ml) into the lung parenchyma on circulation in anesthetized, open-chest, artificially ventilated rabbits. BK significantly decreased mean arterial blood pressure (BP) (27 +/- 3 mmHg) and heart rate (19 +/- 4 beats/min). Both effects remained after bilateral vagotomy. To rule out possible direct systemic vasodilation by BK, we examined renal sympathetic nerve activity (RSNA) in response to BK injection and examined BP responses to injection of ACh (0.1 ml of 10-4 M). BK suppressed the RSNA before and after vagotomy. ACh did not change BP when injected into the lung parenchyma, but it decreased BP (31 +/- 3 mmHg) when injected into the right atrium. Our data indicate that activating pulmonary sympathetic afferents reflexly suppresses hemodynamics.

The relation of QT dispersion and localized QT difference to coronary pathology in a population with unstable coronary artery disease

BACKGROUND

QT dispersion (QTd) contains prognostic information in several patient groups. The variable increases in several conditions with ischemia. Originally, it was thought to reflect the local repolarization inhomogeneity. Even though this explanation has been questioned lately, it continues to be put forward. In order to elucidate a possible local mechanism, we investigated the relation between QT dispersion, an ECG parameter reflecting the local dispersion, and angiographical measures in a population with unstable coronary artery disease.

METHODS

The 276 patients were recruited from the FRISC II trial. As the QTd parameter we used the mean value of automatically measured QTd during 27 hours after admission (QTdMean). As a local repolarization measure we used the maximal difference in QT between two adjacent ECG leads (QTdiffMean). The computations were performed on all available ECG leads and on a restricted set without the V1-V2 combination. Previously published angiographic scoring tools were adapted for rating and localizing the coronary pathology by two approaches and applied on 174 patients undergoing angiography.

RESULTS

QTdMean was significantly higher than that reported in previous material with unselected chest pain patients (55 vs 40 ms). QTdiffMean correlated strongly with QTdMean. No differences in QTdMean were detected between patients with different angiographical scores. No relation could be shown between the region with dominating coronary pathology as expressed by the scoring tools and the localization of QTdiffMean.

CONCLUSIONS

QTd in ischemia seems to be increased by a mechanism unrelated to localization and severity of coronary disease.

Diagnosis and treatment of neurally mediated syncope

BACKGROUND

Syncope is caused by a severe but reversible reduction in blood flow to the brain stem neurons responsible for supporting consciousness (reticular activating system). Neurally mediated syncope, also referred to as vasovagal or reflex syncope, is the most frequent cause of loss of consciousness in apparently normal subjects.

REVIEW SUMMARY

Neurally mediated syncope is believed to be a reflex response with afferent, central, and efferent pathways. Characteristic autonomic changes in neurally mediated syncope are an increase in parasympathetic efferent activity causing bradycardia and a reduction in sympathetic vasoconstrictor outflow causing vasodilatation. Premonitory symptoms, such as nausea, diaphoresis, abdominal discomfort, and blurred vision, are caused by autonomic activation and are distinguishing features of neurally mediated syncope. Neurally mediated syncope frequently has a characteristic trigger, although this may not be apparent. Testing orthostatic tolerance during passive head-up tilt is the best available diagnostic procedure to evaluate patients with syncope in whom a cardiac cause has been excluded. In many cases, once the diagnosis of neurally mediated syncope is confirmed, it may suffice to reassure the patient and teach him to avoid known triggers and to recognize and act upon early warning symptoms. Because subjects with neurally mediated syncope may potentially be sodium depleted, increasing salt intake can be beneficial in improving their orthostatic intolerance.

CONCLUSIONS

Neurally mediated syncope is the most common form of syncope in healthy adults. The best diagnostic tools are the clinical history and passive head-up tilt. The best treatment strategies are the avoidance of triggering factors as well as intravascular volume expansion.

Influence of vestibular activation on respiration in humans

The purpose of this study was to determine the effects of the semicircular canals and otolith organs on respiration in humans. On the basis of animal studies, we hypothesized that vestibular activation would elicit a vestibulorespiratory reflex. To test this hypothesis, respiratory measures, arterial blood pressure, and heart rate were measured during engagement of semicircular canals and/or otolith organs. Dynamic upright pitch and roll (15 cycles/min), which activate the otolith organs and semicircular canals, increased respiratory rate (Delta2 +/- 1 and Delta3 +/- 1 breaths/min, respectively; P < 0.05). Dynamic yaw and lateral pitch (15 cycles/min), which activate the semicircular canals, increased respiration similarly (Delta3 +/- 1 and Delta2 +/- 1, respectively; P < 0.05). Dynamic chair rotation (15 cycles/min), which mimics dynamic yaw but eliminates neck muscle afferent, increased respiration (Delta3 +/- 1; P < 0.05) comparable to dynamic yaw (15 cycles/min). Increases in respiratory rate were graded as greater responses occurred during upright (Delta5 +/- 2 breaths/min) and lateral pitch (Delta4 +/- 1) and roll (Delta5 +/- 1) performed at 30 cycles/min. Increases in breathing frequency resulted in increases in minute ventilation during most interventions. Static head-down rotation, which activates otolith organs, did not alter respiratory rate (Delta1 +/- 1 breaths/min). Collectively, these data indicate that semicircular canals, but not otolith organs or neck muscle afferents, mediate increased ventilation in humans and support the concept that vestibular activation alters respiration in humans.

Anandamide induces cardiovascular and respiratory reflexes via vasosensory nerves in the anaesthetized rat

1. We tested the hypothesis that sensory nerves innervating blood vessels play a role in the local and systemic regulation of the cardiovascular and respiratory (CVR) systems. We measured CVR reflexes evoked by administration of anandamide (86 - 863 nmoles) and capsaicin (0.3 - 10 nmoles) into the hindlimb vasculature of anaesthetized rats. 2. Anandamide and capsaicin each caused a rapid dose-dependent reflex fall in blood pressure and an increase in ventilation when injected intra-arterially into the hindlimb. 3. Action of both agonists at the vanilloid receptor (VR1) on perivascular sensory nerves was investigated using capsazepine (1 mg kg(-1) i.a.) a competitive VR1 antagonist, ruthenium red (1 mg kg(-1) i.a.), a non-competitive antagonist at VR1, or a desensitizing dose of capsaicin (200 nmoles i.a.). The cannabinoid receptor antagonist SR141716 (1 mg kg(-1) i.a.) was used to determine agonist activity at the CB(1) receptor. 4. Capsazepine, ruthenium red, or acute VR1 desensitization by capsaicin-pretreatment, markedly attenuated the reflex CVR responses evoked by anandamide and capsaicin (P< 0.05; paired Student's t-test). Blockade of CB(1) had no significant effect on the responses to anandamide. 5. Local sectioning of the femoral and sciatic nerves attenuated CVR responses to anandamide and capsaicin (P< 0.05). Vagotomy or carotid sinus sectioning had no significant effect on anandamide- or capsaicin-induced responses. 6. These data demonstrate that both the endogenous cannabinoid, anandamide, and the vanilloid, capsaicin, evoke CVR reflexes when injected intra-arterially into the rat hindlimb. These responses appear to be mediated reflexly via VR1 located on sensory nerve endings within the hindlimb vasculature.

Transesophageal echocardiographic assessment of pulmonary arterial and venous flow during high-frequency jet ventilation

STUDY OBJECTIVE

To evaluate high-frequency jet ventilation (HFJV) effects on pulmonary arterial and venous flow compared to those of intermittent positive-pressure ventilation (IPPV) by using pulsed Doppler transesophageal echocardiography.

DESIGN

Prospective clinical study.

SETTING

University-affiliated hospital operating room.

PATIENTS

13 ASA physical status I and II patients undergoing lower abdominal or lower extremity surgery.

INTERVENTIONS

PATIENTS had total IV anesthesia with propofol and fentanyl. After anesthesia induction, a transesophageal echocardiography probe was inserted into the esophagus. IPPV (TV, 8-10 mL/kg; respiratory rate, 10-12 cycles/min; I/E ratio, 1:2; FIO(2), 1.0) and HFJV (driving pressure, 0.5-0.6 kgf/cm(2); frequency,3 Hz; I/E ratio, 1:1; FIO(2), 1.0) were performed under hemodynamically stable conditions.

MEASUREMENTS

Pulmonary-arterial-flow velocity, pulmonary-venous-flow velocity, left ventricular short-axis view, and airway-pressure curve were recorded simultaneously. Parameters measured were: hemodynamic variables, arterial blood gases, inspiratory airway pressure; [from pulmonary-arterial-flow velocity] pre-ejection period (PEP), acceleration time (AT), right ventricular ejection time (RVET), and their ratios (PEP/AT, AT/RVET); [from pulmonary-venous-flow velocity] time-velocity integral of the first systolic wave (S1), second systolic wave (S2), and diastolic wave (D), and systolic fraction (integral S1 + S2/S1+ S2 + D); [from M-mode] left-ventricular-end systolic volume, left-ventricular-end diastolic volume (LVEDV), stroke volume, cardiac output, and ejection fraction, using Teichholz's method.

MAIN RESULTS

Peak inspiratory airway pressure during HFJV was significantly lower than that during IPPV. HFJV significantly decreased PEP/AT, correlating positively with pulmonary arterial pressure, and significantly increased AT and AT/RVET, correlating negatively with pulmonary arterial pressure. Systolic fraction, correlating negatively with left atrial pressure, increased significantly during HFJV, as did LVEDV, stroke volume, cardiac output, and ejection fraction.

CONCLUSIONS

Our results suggest that, in comparison to IPPV, HFJV significantly decreases pulmonary arterial pressure and left atrial pressure, resulting in significant increases in cardiac output and ejection fraction in healthy anesthetized adults.

Repeated 3D coronary MR angiography with navigator echo gating: technical quality and consistency of image interpretation

The purpose of this study was to evaluate the technical quality of 3D coronary MR angiography (CMRA) with navigator echo and the consistency of image interpretation in repeated imaging sessions. Fourteen subjects underwent CMRA, 10 of whom were imaged twice. The coronary arteries (96 segments) were analyzed twice for hemodynamically significant stenoses. Signal-to-noise and contrast-to-noise ratios varied considerably between the two imagings. Fat saturation was poor or satisfactory in 37%; in 15% of the slabs, the severity of artifacts was moderate; and the overall quality was good to excellent in only 42% of the imagings. The intraobserver reproducibility was good (kappa = 0.54), but the consistency of interpretation for repeated CMRA was only satisfactory (kappa = 0.43). Sensitivities of 84 and 84% and specificities of 70 and 62% were obtained for the two readings. Although the reproducibility of image reading is good, 3D CMRA with navigator echo provides only fair technical consistency, and the frequently compromised image quality impairs the clinical utility of this technique.

Kawasaki disease

Kawasaki disease is a leading cause of acquired heart disease in children in the USA. An acute vasculitis of unknown etiology, it occurs predominantly in infancy and early childhood, and more rarely in teenagers. Coronary artery aneurysms or ectasia develop in approximately 15-25% of children with the disease. Treatment with intravenous gamma globulin, 2 g per kg, in the acute phase reduces this risk three- to fivefold. Angiographic resolution occurs in approximately one-half of aneurysmal arterial segments, but these show persistent histologic and functional abnormalities. The remainder continue to be aneurysmal, often with development of progressive stenosis or occlusion. The worst prognosis occurs in children with so-called 'giant aneurysms', i.e. those with a maximum diameter greater than 8 mm, because thrombosis is promoted both by sluggish blood flow within the massively dilated vascular space and by the frequent development of stenotic lesions. Serial stress tests with myocardial imaging are mandatory in the management of patients with Kawasaki disease and significant coronary artery disease to determine the need for coronary angiography and transcatheter interventions or coronary bypass surgery. Continued long-term surveillance in patients with and without detected coronary abnormalities is necessary to determine the natural history of Kawasaki disease.

Cardiovascular measurements relevant to heart size in copper-deficient rats

Dietary copper deficiency in animals is often associated with cardiac enlargement and anemia. In this study we examined the hypothesis that anemia leads to a high cardiac output state that results in work-induced (physiological) cardiac hypertrophy. Blood pressure was measured by carotid cannulation and cardiac output was measured by aortic flow probe in anesthetized, open-chested rats that had been subjected to various degrees of dietary copper deficiency for five weeks. Cardiac output was unaffected by dietary copper deficiency. However, the components of cardiac output were found to vary reciprocally, heart rate decreasing and stroke volume increasing with copper deficiency. Further, total peripheral resistance, calculated as the ratio of mean arterial blood pressure and cardiac output, was depressed by dietary copper deficiency. These findings suggest that bradycardia and depression of vascular resistance induced by copper deficiency contribute to increased venous filling and a resultant increase in stroke volume; these factors may lead to cardiac hypertrophy. A significant correlation between stroke volume and heart weight in rats of varying copper status supports this conclusion.

Pulmonary complications of mechanical ventilation

Although life-saving, mechanical ventilation may be associated with many complications, including consequences of positive intrathoracic pressure, the many aspects of volutrauma, and adverse effects of intubation and tracheostomy. Optimal ventilatory care requires implementing mechanical ventilation with attention to minimizing adverse hemodynamic effects, averting volutrauma, and effecting freedom from mechanical ventilation as quickly as possible so as to minimize the risk of airway complications.

Cost-effectiveness of cardiac rehabilitation after myocardial infarction

BACKGROUND

Cardiac rehabilitation is commonly prescribed after myocardial infarction (MI) to coordinate exercise training and secondary preventive services. Cost-effectiveness analysis allows the quantitative comparison of the relative economic worth of cardiac rehabilitation in relation to other common interventions.

METHODS

The cost-effectiveness of cardiac rehabilitation, in dollars per year of life saved ($/YLS), was calculated by combining published results of randomized trials of cardiac rehabilitation on mortality rates, epidemiologic studies of long-term survival in the overall postinfarction population, and studies of patient charges for rehabilitation services and averted medical expenses for hospitalizations after rehabilitation.

RESULTS

Cardiac rehabilitation participants experienced an incremental life expectancy of 0.202 years during a 15-year period. In 1988, the average cost of rehabilitation and exercise testing was $1,485, partially offset by averted cardiac rehospitalizations of $850 per patient. A cost-effectiveness value of 2,130 $/YLS was determined for the late 1980s, projected to a value of 4,950 $/YLS for 1995. A sensitivity analysis supports the study results.

CONCLUSIONS

Compared with other post-MI treatment interventions, cardiac rehabilitation is more cost-effective than thrombolytic therapy, coronary bypass surgery, and cholesterol lowering drugs, though less cost-effective than smoking cessation programs. Cardiac rehabilitation should stand alongside these therapies as standard of care in the post-MI setting.

Dipyridamole-induced angina pectoris during sestamibi stress test in patients with significant coronary artery disease: clinical, angiographic, and nuclear determinants

Intravenous dipyridamole induces angina pectoris (AP) in some patients with significant coronary artery disease (CAD). The aim of this prospective study was to identify the angiographic, nuclear, and clinical determinants. The authors examined 50 patients consecutively with significant CAD on coronary angiography. All antiischemic medications were stopped twenty-four hours (nitrates only 6 hours) before injection of dipyridamole (0.84 mg/kg). ECGs were taken before, during, and after this injection. The regional myocardial activity of Tc-99m-Sestamibi at rest and after dipyridamole injection was measured with single-photon emission computed tomography (SPECT). During dipyridamole injection 20 patients had AP, of whom 15 had ST segment depression on ECG (P < 0.001). The only significant difference on coronary angiography between patients with dipyridamole-induced AP and those without AP was the presence of collaterals (P < 0.05). In patients with AP and collaterals, ECG and SPECT changes were always noted in the collateralized territory. Subgroup analysis showed that patients without previous myocardial infarction (MI, n = 17, P < 0.05) or nontransmural MI (n = 17, P < 0.05) had a good correlation between collaterals and AP, whereas patients with a history of transmural MI (n = 16) did not. No further significant variables could be found as a predictor of AP after dipyridamole injection. These findings suggest that AP during dipyridamole stress test is due to ischemia, which is not related to the severity of CAD. Ischemia is probably due to coronary steal to the collateralized territory in patients without transmural MI. Dipyridamole-induced angina pectoris is predictive for collaterals and may indicate viability in patients with MI.

Atropine premedication attenuates heart rate variability during high thoracic epidural anesthesia

BACKGROUND

Atropine premedication is used as it possesses an anticholinergic effect on the cardiac autonomic nervous system (CANS). The aim of this study was to investigate the effect of atropine premedication on the CANS during thoracic epidural anesthesia (TEA) by assessing power spectral analysis of heart rate (HR) variability.

METHOD

Female patients (n = 28) undergoing elective mammary biopsy were randomly allocated into two groups; one received intramuscular premedication of 0.01 mg/kg of atropine 30 min before the procedure (group A: n = 14), and the other did not (group N: n = 14). Each electrocardiogram was digitally recorded before and during TEA, and played back off-line to detect R-R intervals. As a power spectrum required R-R intervals of 256 s, this was analysed before TEA and repeated thereafter for 25 min. The spectra were quantified by determining the peak areas of the spectral density by integrating low frequency (Lo: 0.04-0.15 Hz) and high frequency (Hi: 0.15-0.40 Hz) bands as they showed sympathetic and parasympathetic nervous activity in the CANS. The neural balance was assessed by calculating Hi:Lo ratio.

RESULTS

Decreases in Lo and increases in Hi:Lo ratio were observed, suggesting sympathectomy and vagotonia with TEA in both groups. For 10 min after commencement, TEA maintained Hi:Lo ratios lower in group A than in group N, suggesting a vagolytic effect of premedication with atropine. With TEA, cardiac slowing was observed, which was dependent on the level of dermal analgesia.

CONCLUSION

Power spectral analysis revealed that TEA had the effect of making CANS relatively vagotonic, and that atropine premedication would attenuate the effect of TEA.

Inhibition of muscle sympathetic nerve activity during yawning

Yawning is a complex event that depends largely on the autonomic nervous system. Microneurographic techniques were used to study the mechanism involved in yawning. A series of spontaneous yawns displayed by a healthy 39-year-old male offered us the opportunity to study the muscle sympathetic nerve activity (MSNA) during this phenomenon. It was found that 2 s of yawning inhibited the MSNA recorded at the right peroneal nerve in the lateral knee area, while 3 s of slow expiration succeeding a yawn provoked an MSNA discharge. Blood pressure decreased with each slow expiration by 5-6 mmHg, and increased again with the renewed MSNA discharge. We conclude that yawning is associated with a sympathetic suppression that favours a parasympathetic dominance, as indicated by the MSNA and the decrease in blood pressure. The slow expiration following a yawn is associated with a sympathetic activation marked by an MSNA discharge and an increase in blood pressure.

Adherence in the training levels comparison trial

In the Training Levels Comparison Trial, 197 male coronary heart disease patients were randomized to low or high intensity training with target heart rates, which corresponded to 50% and 85% of the VO2max achieved on the previous exercise test, respectively. Patients were to exercise at their assigned intensity level at three 1-h long supervised sessions per week for 2 yr. This paper reports on two components of adherence: attendance at exercise sessions and achievement of heart rates in the target range. During the first year of training, the average percent of exercise sessions attended (mean +/- SE) for the low intensity group (64.0 +/- 2.5%) was significantly higher than for the high intensity group (55.5% +/- 2.7%). At the end of 1 yr of training, 54% and 37% of the low and high intensity patients, respectively, achieved heart rates within 5 beats.min-1 of their target heart rates. Although the low intensity program was preferable to achieve maximum attendance, attenders on the high intensity program achieved higher heart rates. These results suggest that to maximize the achieved heart rate, it would be optimal to motivate a cardiac rehabilitation patient to train at the high intensity level for a prolonged period of time.

Interactions between hemodynamic and hormonal modifications during PEEP-induced antidiuresis and antinatriuresis

The interactions between hemodynamic and hormonal modifications during antidiuresis and antinatriuresis induced by positive end-expiratory pressure (PEEP) were studied in six patients under 15 cm H2O PEEP before PEEP and after the addition of lower body positive pressure (LBPP) to PEEP (PEEP+LBPP). We measured or calculated the following: cardiac index, systemic arterial, right atrial, pulmonary arterial, and pulmonary artery occlusive pressures; indexed renal blood flow (iodohippurate 131 sodium clearance); total blood volume (chromium 51 radiolabeled RBCs); glomerular filtration rate; urinary output; fractional excretion of sodium (FE Na+); plasma concentrations of antidiuretic hormone (ADH), plasma renin activity (PRA), norepinephrine and epinephrine; urinary concentration of PGE2 (PGE2u). Although LBPP application corrected PEEP deleterious effects on systemic and renal hemodynamics, sustained fall in Vu and in FE Na+ were observed. Antidiuresis was not due to ADH release. Sympathetic activation and high PRA appeared the main determinants of renal function alterations in PEEP ventilation.

Improved left ventriculography with the new 5F helical-tip Halo catheter

The purpose of this study was to evaluate the incidence of ventricular ectopy and catheter movement during left ventriculography with a new 5F halo angiographic catheter that has a unique helical-tip design unlike the design of standard 5F and 6F pigtail catheters. The pigtail catheter is presently preferred for left ventriculography, although its use is associated with a high incidence of ventricular ectopy, which often limits precise interpretation of data. In this study, 155 patients (in 145 unpaired and 10 paired studies) underwent left ventriculography during diagnostic cardiac catheterization. In the unpaired group, the 5F Halo catheter was used in 63 studies and standard 5F and 6F pigtail catheters in 40 and 42 studies, respectively. An additional 10 patients had two consecutive left ventriculograms with 5F Halo and pigtail catheters. Ventriculograms were performed with the same technique in the 30-degree right anterior oblique projection. The left ventricle was divided into a basal zone, midzone, and apical zone. Catheter movement within the ventricle was scored as significant if there was at least one zone change. Ventricular ectopy was quantified by a simultaneous electrocardiographic recording during contrast injection. There were no significant differences in the left ventricular systolic or end-diastolic pressures, left ventricular score, or diagnostic quality of the ventriculograms between the 5F Halo catheter group and the 5F and 6F pigtail catheter groups. Mean ventricular ectopy with the 5F Halo catheter was significantly less (0.9 +/- 1.4 ventricular premature beats [VPBs]) than with the 5F pigtail catheter (2.3 +/- 2.5 VPBs, p < 0.001) or the 6F pigtail catheter (2.9 +/- 2.9 VPBs, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of shortening with timing of wall motion in detecting regional abnormalities of the left ventricle in coronary disease

Clinical observations suggest that ischemic myocardium may demonstrate delayed wall motion while absolute shortening remains normal. Wall motion timing and percent shortening were examined in 25 patients (7 normal, 18 coronary disease) with 35 mm biplane left ventriculograms and coronary arteriography. Mean age was 63 +/- 2.4 years. Of 17 males and 8 females, 13 had 3 vessel, 4 had 2 vessel, and 1 had 1 vessel disease. Left ventricular regions were analyzed using the Coronary Artery Surgery Study nomenclature and quantitative computer-based analysis as well as visual based qualitative analysis. Regional percent shortening and ejection fraction were calculated from end systolic and end diastolic frames. Regional shortening times were related to global ejection time from 30 frame/sec, frame by frame analysis. Feeder arteries were stenosed ( > 70%) in 135 of 225 left ventricular regions analyzed. Computer detection (shortening and timing) identified 97/225 as abnormal (p < 0.01 vs. feeder artery stenosis) while physicians identified 79/225 as abnormal (p < 0.01 vs. feeder artery stenosis). Of the 97 computer detected abnormal regions, shortening alone detected 47, timing alone detected 39, and 11 showed both abnormalities. Timing analysis increased detection of wall motion abnormalities from 58/225 (26%) to 97/225 (43%) (p < 0.001). Timing abnormalities were noted more (92%) in basal segments, while shortening abnormalities dominated (88%) in apical segments (p < 0.001). Use of temporal measurements in wall motion analysis significantly increases the likelihood of detecting abnormal left ventricular regional wall motion when compared to shortening measurements alone.

Short and long term outcome of percutaneous transluminal coronary angioplasty in unstable versus stable angina pectoris: a report of the 1985-1986 NHLBI PTCA Registry

In a cohort of 1,720 consecutive patients from the National Heart, Lung, and Blood Institute, Percutaneous Transluminal Coronary Angioplasty (PTCA) Registry (August 1985-May 1986), we compared 768 patients (45%) with stable angina and 952 patients (55%) with unstable angina pectoris. Unstable angina patients exhibited at least one of the following characteristics: new onset angina, rapidly progressing angina, angina at rest, angina refractory to medication, variant angina, acute coronary insufficiency, or angina recurring shortly after an acute myocardial infarct. The distribution of single- and multi-vessel disease was similar among stable and unstable angina patients; multi-vessel disease predominated. Average severity of stenosis and incidence of tubular and diffuse stenosis morphology were higher among patients with unstable angina (both p less than 0.001). Patient success rates were similar in stable and unstable patients. However, on a per lesion basis, overall angiographic success rate and average reduction of severity of stenosis in successfully dilated lesions were significantly higher among patients with unstable angina (both p less than 0.001). Incidence of major patient complications (p less than 0.01) and of emergency coronary bypass surgery (p less than 0.05) were also higher in patients with unstable angina but consistent with their more precarious clinical condition and stenosis morphology. During a two year follow-up, the cumulative distributions of death, myocardial infarct, repeat PTCA, and coronary bypass surgery were not significantly different in patients with stable angina compared to patients with unstable angina. Comparison of the current PTCA Registry cohort with the cases reported in the 1979-1982 Registry revealed a 19% higher success rate for both stable and unstable angina patients. Major complication rates decreased between time periods for stable but not for unstable angina patients. Incidence of emergency bypass surgery decreased more for stable than for unstable angina patients. Coronary angioplasty is indicated in properly selected patients with unstable angina and both single- and multi-vessel coronary disease.

Severe non-hypoxic bradycardia during disconnection from the ventilator during the recovery phase of ARDS

Four patients with adult respiratory distress syndrome developed sinus bradycardia during weaning procedures with no evidence of hypoxemia. Bradycardia occurred immediately after the patients' endotracheal tubes were disconnected from the ventilator and most of the time resolved after reconnection. However, 3 patients eventually deteriorated, requiring advanced life support and for one of them, cardiac pacing. The precise mechanism of these bradycardic episodes remains unclear but was unrelated to hypoxemia or acid-base disorder.

Dual purpose computer aided program for cardiac catheterization laboratory data management

This communication describes the design criteria used in the early systems analysis activity of the cardiac laboratory. This analysis activity required an understanding of the cardiology laboratory environment, the establishment of needs to be answered by the program, and the goals of the entire system. The rationale for inclusion of various cardiologic, demographic, quality assurance, and personnel safety parameters is discussed. The input forms used, the database structure created, and the information provided by an applications system are described. Since the system is built around a general-purpose computer (the IBM PC or compatible) and widely available powerful general purpose software, the entire system may be used for many other cardiology laboratory data management tasks.

Respiratory variability and associated cardiovascular changes in adults at rest

Breathing patterns and associated circulatory fluctuations may reflect the action of various regulatory mechanisms as well as mechanical influences of breathing on the circulation. Thus, the study of such patterns can enhance our knowledge of these mechanisms, both in normal and pathological conditions. In this review, literature is evaluated that provides insight into the breath-to-breath variation of respiration in quietly breathing adults. Also when respiration is seemingly random, deterministic patterns in the respiratory variability can often be discerned. The various methods used in the recognition of such patterns and their possible interpretation are discussed. Furthermore, the question is addressed how respiratory variability can affect the circulation and how this can be studied by analysing the time relationships of respiratory and circulatory parameters. This may add to both the understanding of normal cardiovascular regulation and to insight into cardiovascular disturbances under unstable respiratory conditions. As examples of such circumstances, some common conditions are discussed that are often, though not always, associated with pathology, viz. Cheyne-Stokes respiration, snoring and the sleep apnoea syndrome.

Multi-Hospital Eastern Atlantic Restenosis Trial: design, recruitment, and feasibility. M-HEART Investigators

A randomized control trial was set up to examine factors that influence restenosis and determine the effects of corticosteroids on restenosis following successful PTCA. The rationale for the study agent chosen, design, recruitment, and feasibility, as well as initial patient demographic data and initial results are presented.

Cardiovascular reflexes from cardiac sensory receptors

The mammalian heart, especially its left ventricle, is densely innervated by sensory nerves. One set of these travels to the brainstem in the vagus nerves; the other to the spinal cord in sympathetic nerves. Excitation of vagal cardiac afferents, especially unmyelinated afferents from the left ventricle, cause a reflex bradycardia and fall in blood pressure and, under some conditions, a massive release of AVP. The sympathetic afferents convey the sensation of cardiac pain, but innocuous stimuli may cause a reflex tachycardia and rise in blood pressure. Both sympathetic and vagal cardiac afferents can be excited by mechanical distension of the heart (mechanoreceptors), and by a variety of foreign and endogenous chemical substances (chemosensitive receptors). It is not yet clear whether the effective natural stimulus to these receptors is mechanical, or through the chemical products of myocardial metabolism. Neither is it clear whether information from the heart exerts a minute-to-minute regulatory effect on the circulation, or whether it has a purely defensive role in the face of extreme disturbances of cardiac function. Cardiogenic reflexes are also thought to be the cause of haemodynamic and humoral disturbances that occur in clinical conditions such as myocardial ischaemia or infarction, left ventricular outflow obstruction, and acute reduction in central blood volume as well as during coronary angiography.

Hemodynamic effects of high-frequency jet ventilation in dogs with acute right coronary arterial ligation and pulmonary arterial banding

The hemodynamic effects of high-frequency jet ventilation (HFJV), synchronized with diastole, and intermittent positive-pressure ventilation (IPPV) were studied in 10 dogs with acute right-sided myocardial ischemia and elevated right ventricular pressure. Myocardial ischemia was produced by ligation of the proximal right coronary artery (RCA), then the right ventricular pressure was elevated to facilitate the ischemia by banding the main pulmonary artery. Before and 1, 2, 3, and 5 hr after the RCA ligation, cardiorespiratory variables for each ventilatory mode and creatine phosphokinase MB isoenzyme (CPK-MB) were measured. During HFJV compared with IPPV: there were significant increases in stroke index and left ventricular stroke work index at all ischemic periods, and decreases in peak and mean airway pressures and pulmonary vascular resistance at all ischemic periods, and in the product of systolic right ventricular pressure and heart rate at 2 hr, 3 hr, and 5 hr. The difference in mean airway pressure between IPPV and HFJV correlated significantly with those in cardiac index and stroke index (r = 0.575 and 0.779, respectively). CPK-MB was significantly greater at 3 hr and 5 hr than that before RCA ligation. These findings suggest that HFJV synchronized with diastole offers hemodynamic advantages over IPPV to ischemic right ventricle with constricted pulmonary artery, mainly due to lowering the mean airway pressure.

Weighted ventriculographic wall motion score for improved survival prediction in patients with coronary artery disease. Coronary Artery Surgery Study

Global ventricular function parameters such as the ejection fraction and the sum of wall motion scores for segments of the left ventricle are excellent predictors of long-term survival in patients with coronary heart disease. These are usually determined from a monoplane right anterior oblique view. It was hypothesized that a biplane weighted wall motion score that included the left anterior oblique projection might better predict survival. A new score (BISCORE) was derived for 1,433 Mayo Clinic ventriculograms coded by the methods of the Coronary Artery Surgery Study (CASS). Weighting coefficients for each left ventricular segment were derived by the proportional hazards technique, and this resulted in the equation BISCORE = 120 - (8.6 x anterobasal + 3.4 x basal septum + 2.9 x apical + 2.7 x posterolateral + 2.4 diaphragmatic), which yielded a score from 0 (all segments aneurysmal) to 100 (all segments normal). This score stratified the original 1,433 patients into distinct groups by survival. As a single variable it was better than previous wall motion scores and ejection fraction at predicting survival. When prospectively applied to 5,172 Coronary Artery Surgery Study patients, this new score again proved to be a better predictor of survival than previous unweighted scores. Since the new score contains terms from the left anterior oblique ventriculographic projection, it is concluded that this projection adds information to that of the right anterior oblique projection regarding survival. Furthermore, this weighted score appears more highly associated with survival than unweighted scores.

Patterns of autonomic response during laboratory stressors

The present study was designed to include an index reflecting the influence of parasympathetic nervous system activity on the heart, respiratory sinus arrhythmia, in addition to measures reflecting primarily sympathetic nervous system activity. The inclusion of the parasympathetic index was considered important for two reasons:(a) Past studies have suggested different patterns of autonomic response to qualitatively different laboratory stressors but have had to infer parasympathetic influences more indirectly, and (b) there is evidence that borderline hypertensives may have reduced vagal tone at rest when compared to normotensives. This last point is important for the study of individual differences in cardiovascular reactivity because excessive responsiveness in young normotensives (beta-adrenergic reactors) has been suggested as a model for studying the precursors of some types of hypertension. Fifty-one male college students were given a reaction time task, a mental arithmetic task, a cold pressor task, and graded bicycle exercise. A variety of cardiovascular and respiratory measures were collected on each subject. Results indicated significant differences in levels of respiratory sinus arrhythmia during the three tasks and the rest period, giving additional evidence for parasympathetic differences (along with sympathetic differences) in these conditions. Additionally, high beta-adrenergic reactors did not differ in mean level of respiratory sinus arrhythmia from low reactors either at rest or during the task periods. These results are discussed in the context of previous research.

Quantitative regional contraction analysis of cineventriculography: reporting, filing, and retrieval functions using a personal computer

A new method for the semiobjective evaluation of left ventricular wall contraction is proposed that uses a percent reduction of areas. The calculation model uses orthogonal coordinates, an internal reference system, and the concept of nonuniform reduction of the cavity, with its obliteration at the apex. From a normal patient population (ten males, four females; aged 45 +/- 13 years), a "normal reference curve" of contraction was obtained. A second patient group (56 males, two females, aged 56 +/- 7 years) with definite contraction abnormalities was then analyzed. A third group (eight males, one female, aged 56 +/- 10 years) was studied before and after nifedipine administration (1 mg over 2 min IV). Specific algorithms compare individual patient contraction curves with the normal reference curve and compute the score point system of contraction analysis. Data are automatically codified and filed during introduction. This saves time and allows a rapid retrieval of data grouped under different coded features. These features include the location and type of wall contraction abnormalities. This method of reading ventriculograms has been shown to be in accordance with the diagnosis of experienced observers and can detect small contraction changes that are induced pharmacologically. The method is proposed as a valuable tool for semiobjective evaluation of left ventricle wall contraction and to facilitate data collection in multicenter collaborative studies.

Survival patterns in clinical and angiographic subsets of medically treated patients with combined proximal left anterior descending and proximal left circumflex coronary artery disease (CASS)

Baseline, clinical, and angiographic features of 1014 Coronary Artery Surgery Study (CASS) registry patients with combined proximal left anterior descending and proximal left circumflex coronary disease were examined to define determinants of prognosis in this clinical high-risk patient subset. A stepwise Cox regression analysis identified congestive heart failure score, left ventricular contraction score, mitral regurgitation, age, and digitalis usage as independent variables predictive of 8-year survival. When patients were stratified by left ventricular contraction score, the 8-year survival rate was 62%, 49%, and 19%, respectively, for patients with a left ventricular score of 5 to 9, 10 to 14, and greater than or equal to 15 (p less than 0.0001). The presence of a stenosis greater than or equal to 70% in the right coronary artery was associated with worse survival (47% versus 54% at 8 years; p = 0.051). In conclusion, the diagnosis of combined proximal left anterior descending and left circumflex coronary artery disease represents a large prognostic spectrum that needs to be considered when counselling individual patients.

Doppler evaluation of changing cardiac dynamics during Cheyne-Stokes respiration

For the purpose of elucidating the mechanisms and/or effects of the cardiovascular changes occurring during Cheyne-Stokes respiration, we utilized Doppler echocardiography to determine intracardiac flow velocity profiles during the changing phases. Left ventricular inflow (LVI) and outflow (LVO) were examined in ten patients, nine with heart failure and one with a cerebrovascular accident. The mean LVI, peak early (E) and late diastolic (A) and LVO velocities were measured at the end of both the hyperpneic and apneic phases. The phasic hemodynamic changes observed during Cheyne-Stokes respiration by Doppler profile could be explained by the development of LV diastolic dysfunction and a decrease in LV stroke volume during the apneic phase of Cheyne-Stokes respiration. Alternatively, an increase in PCO2 during the apneic phase may increase pulmonary vascular resistance lowering preload and stroke volume, whereas during the hyperpneic phase, pulmonary vascular resistance is reduced with resultant increase in left ventricular preload and increase in stroke volume. Both theories are speculative and the precise hemodynamic changes associated with Cheyne-Stokes respiration requires further investigation.

The possibility of using celiac trunk branches as coronary artery bypass grafts

The internal mammary artery has proved to be superior to the saphenous vein for coronary artery bypass grafting, because of its arterial nature and closer approximation in size to the coronary arteries. But the internal mammary artery cannot reach the posterior surface of the heart as a pedicled graft. Two suitable intra-abdominal grafts can reach that surface, viz. the right gastroepiploic artery and the splenic artery. In experiments on eight dogs (weight 9-13.5 kg), the gastroepiploic artery was found to be too small for coronary artery anastomosis, and therefore the splenic artery was used. The size approximation with coronary artery (diameter less than 1 mm) was good. Four dogs survived the month of the study. In two of them the anastomosis was patent, in another the splenic artery was patent despite occlusion of the anastomosis, and in the fourth dog both anastomosis and graft were thrombosed. The possibility of using visceral arterial grafts in coronary surgery is discussed.

Beneficial six-year outcome of smoking cessation in older men and women with coronary artery disease. Results from the CASS registry

We investigated the effects of cigarette smoking and cessation of smoking in a cohort of 1893 men and women from the Coronary Artery Surgery Study (CASS) registry who were 55 years of age or older and had angiographically documented coronary artery disease. The six-year mortality rate was greater among continuing smokers (n = 1086) than among those who quit smoking during the year before enrollment in the study and abstained throughout the study (n = 807) (relative risk, 1.7 [95 percent confidence limits, 1.4, 2.0]). Continuing smokers were also at higher risk of either myocardial infarction or death (1.5 [1.2, 1.7]). There was no diminution of the beneficial effect with increasing age. The relative risks of death were 1.7 (1.4, 2.1) and 1.6 (1.1, 2.3) for the groups 55 to 64 years old and 65 or older, respectively, and 1.6 (1.4, 1.9) for comparable subgroups among CASS subjects 35 to 54 years of age. When subjects were arrayed according to risk quartile, the benefits of smoking cessation were greatest in those at moderate risk. We conclude that smoking cessation lessens the risk of death or myocardial infarction in older as well as younger persons with coronary artery disease.