A-Hamid Hakki

The use of rest and exercise radionuclide ventriculography in risk stratification in patients with suspected coronary artery disease

The study examined the value of rest and exercise radionuclide ventriculography in risk stratification in patients with suspected coronary artery disease. There were 604 patients, 474 men and 130 women, aged 55 +/- 11 years (mean +/- standard deviation). At a follow-up of 18 +/- 10 months, there were 43 hard cardiac events: 27 patients died of cardiac causes and 16 had nonfatal acute myocardial infarctions. Univariate and multivariate survival analysis of the 10 most important clinical and exercise variables identified the exercise left ventricular ejection fraction as the most important predictor of death and total cardiac events (chi 2 = 18.1 and 29.6, respectively). The exercise heart rate was a significant, independent, but much weaker predictor of cardiac death and total events (chi 2 = 8.4 and 3.9, respectively), while exercise tolerance was a significant independent predictor of cardiac death only (chi 2 = 6.4). Actuarial life table analysis showed that the risk for future cardiac events increased in stepwise fashion as the exercise ejection fraction decreased. Thus, the exercise left ventricular ejection fraction is a useful prognosticator in patients with suspected coronary artery disease. This finding has important implications in patient management.

Tricuspid regurgitation: Noninvasive techniques for determining causes and severity

Tricuspid regurgitation is often not apparent on physical examination and several methods are now available to aid in this difficult assessment. Cardiac catheterization using right ventriculography, previously considered the diagnostic standard, has several limitations. Currently available noninvasive tools such as M-mode and two-dimensional echocardiography (with or without contrast), Doppler techniques and even radionuclide cardiologic imaging have added significantly to the precise assessment of the presence and severity of tricuspid regurgitation. This review examines the comparative use and limitations of these various techniques.

Resting thallium-201 myocardial perfusion patterns in patients with severe left ventricular dysfunction: Differences between patients with primary cardiomyopathy, chronic coronary artery disease, or acute myocardial infarction

This study examined the value of resting thallium-201 imaging in differentiating patients with primary cardiomyopathy from those with ischemic cardiomyopathy. There were 15 patients with primary cardiomyopathy (group I); 20 with chronic CAD (group II); and 25 with acute Q wave myocardial infarction (group III). All patients had LVEF less than or equal to 35%. The thallium score was less than 50 (maximum 60) in one patient (7%) in group I, in 17 patients (85%) in group II, and in 25 patients (100%) in group III (p less than 0.0001, I vs II and III). The number of normal segments was 11.4 +/- 4.9 in group I, 6.9 +/- 2.9 in group II, and 7.0 +/- 2.2 in group III (p less than 0.0001, I vs II, III). Reversible defects were present in three patients in group II, three in group III, and none in group I. Abnormal right ventricular thallium uptake was observed in 27% of patients in group I, 25% in group II, and 40% in group III (p = NS). Abnormal lung thallium uptake was observed in 33% in group I, 20% in group II, and 20% in group III (p = NS). Thus, rest thallium imaging is useful in separating patients with primary cardiomyopathy from those with ischemic cardiomyopathy.

Relation between electrocardiographic and scintigraphic location of myocardial ischemia during exercise in one-vessel coronary artery disease

The purpose of this study was to determine the usefulness of exercise electrocardiography in predicting the site of myocardial ischemia. Fifty-two patients were studied who had angiographically documented 1-vessel coronary artery disease (CAD) and exercise-induced reversible thallium-201 perfusion defects. The patients were divided into 2 groups: group I (28 patients) had left anterior descending CAD and group II (24 patients) had left circumflex or right CAD. There were no significant differences between the 2 groups in severity of coronary stenosis, heart rate and systolic blood pressure during exercise. The size of the perfusion defect was larger in group I than II (28 +/- 12% vs 19 +/- 10%, p less than 0.02). There was no significant difference between the 2 groups in the frequency of ST depression in the anterior, inferior or lateral electrocardiographic leads. ST depression occurred in 16 patients (57%) in group I and 11 patients (46%) in group II (difference not significant). The sensitivity of the exercise electrocardiogram was 52% using 12 leads, 50% using 3 leads (V3, V5 and aVF) and 50% using V5 alone (difference not significant). Thus, the site of ST depression during exercise is not a good predictor of the site of exercise-induced perfusion defect or anatomic site of CAD. The use of 12 leads does not improve the sensitivity of exercise electrocardiography in patients with CAD.

Effects of esmolol on cardiac function: Evaluation by noninvasive techniques

In a double-blind, randomized, crossover study, the effects of esmolol and propranolol were examined at rest and during peak upright exercise in 15 patients. At rest, both esmolol and propranolol significantly decreased heart rate, systolic blood pressure, rate-pressure product, left ventricular ejection fraction, cardiac index and right ventricular ejection fraction. During exercise, significant decreases were also found in heart rate, systolic blood pressure and cardiac index in both treatment groups. No significant differences were found between mean esmolol and mean propranolol measurements at rest and during exercise, except for the exercise systolic blood pressure, which was lower during esmolol infusion. Blood levels of esmolol decreased markedly by 30 minutes postinfusion, as did its beta-blocking action. Esmolol was well tolerated with no important local, systemic or laboratory abnormalities. Thus, the effects of esmolol on cardiovascular performance at rest and during exercise are similar to those of propranolol.

The relation between myocardial ischemia and the ejection fraction response to exercise in patients with normal or abnormal resting left ventricular function

This study examines the relation between myocardial ischemia and the left ventricular (LV) ejection fraction (EF) response to exercise in patients with normal or abnormal resting EF. We studied 69 patients aged 25 to 78 years (mean 52 years) by radionuclide ventriculography (at rest and during peak upright exercise) and by exercise thallium-201 imaging. In 27 patients with resting EF less than 50%, the EF response to exercise was normal (greater than or equal to 5% increase) in 13 patients and abnormal in 14. The thallium scans showed reversible defects in 11 of the 14 patients (79%) with abnormal response but none in any of the patients with normal responses (p = 0.0001). In the 42 patients with resting EF greater than or equal to 50%, the EF response to exercise was normal in 23 and abnormal in 19. Reversible defects were present in 13 of the 19 patients (68%) with abnormal response and in only 3 of 23 patients (13%) with normal response (p = 0.0001). Therefore, an abnormal EF response to exercise was seen in 11 of 11 patients with resting EF less than 50% and in 13 of 16 patients (81%) with resting EF greater than or equal to 50% who had reversible thallium defects; normal EF responses were seen in 13 of the 16 patients (81%) with resting EF less than 50% and in 20 of 26 patients (77%) with resting EF greater than or equal to 50% who had no reversible thallium defects. Thus, in patients with abnormal resting LV function an abnormal EF response to exercise suggests the presence of myocardial ischemia rather than a nonspecific response to stress.

The effects of aging after coronary arterial bypass grafting on the regulation of cardiac output during upright exercise

We examined the effects of age on cardiac performance and the mechanisms that regulate cardiac output during upright exercise in patients free of myocardial ischemia after coronary revascularization. There were 90 subjects, aged 36 to 75 years, of whom 27 were greater than or equal to 60 years. There were no age-related changes in resting heart rate, systolic blood pressure, left ventricular end-diastolic volume index, left ventricular end-systolic volume index, stroke volume index, cardiac index and left ventricular ejection fraction. There were, however, age-related changes in exercise capacity (y = 20 - 0.21x, r = -0.52, P less than 0.001); exercise heart rate (y = 185 - 1x, r = -0.42, P less than 0.001); exercise end-systolic volume index (y = 11 + 0.46x, r = 0.28, P less than 0.01) and exercise ejection fraction (y = 81 - 0.31x, r = -0.28, P less than 0.01). In a subgroup of 54 patients with comparable exercise workload (27 aged less than 60 and 27 greater than or equal to 60 years), the age-related differences in exercise end-systolic volume index, exercise ejection fraction and exercise cardiac index were not observed, but the exercise heart rate was still higher in the younger patients (y = 168 - 0.76x, r = -0.34, P less than 0.01). Thus, age modifies the compensatory mechanisms that regulate the cardiac output during exercise. Young and old patients alike show increases in end-diastolic volume and ejection fraction to maintain exercise cardiac output. The higher exercise heart rate in the younger subjects suggests a decrease in cardiac responsiveness to adrenergic stimulation associated with aging.

Age- and gender-related changes in exercise left ventricular function in mitral valve prolapse

The correlates of exercise left ventricular (LV) performance were examined in 45 patients with isolated mitral valve prolapse (no associated mitral regurgitation or coronary artery disease). There were 18 men and 27 women, aged 16 to 73 years; 20 patients were 40 years or younger and 25 were older than 40. The response of the LV ejection fraction (EF) to symptom-limited upright exercise was normal (at least a 5% increase) in 27 patients (60%) and abnormal in 18 (40%). There were no significant differences between patients with normal and abnormal EF response in clinical presentation, electrocardiographic findings (at rest or during exercise), medications, rest EF, heart rate (at rest or during exercise) and systemic arterial pressure (at rest and during exercise). A normal EF response was observed more frequently in patients 40 years or younger than in those older than 40 (80 vs 44%, p less than 0.01), and more often in men than in women (78 vs 48%, p less than 0.04). The change in EF from rest to exercise was 18 +/- 9% in men and 5 +/- 10% in women 40 years or younger (p less than 0.01), and 9 +/- 8% in men and 2 +/- 8% in women older than 40 (p less than 0.04). Thus, patients (especially women and those older than 40 years) with isolated mitral valve prolapse may have abnormal LV functional reserve. Genetic differences in the expression of the disease in both sexes and age-related irreversible myocardial changes may explain these observations.

Radionuclide evaluation of exercise left ventricular performance in patients with coronary artery disease

Rest and exercise radionuclide angiography is a useful technique to study the cardiac adaptation during exercise in patients with coronary artery disease. Most patients with coronary artery disease have an abnormal EF response to exercise, although the magnitude of the change in EF may not correlate with the extent of coronary artery disease. The resting end-diastolic volume maybe the most important determinant of the presence and degree of left ventricular dilation during exercise in such patients. The exercise left ventricular EF improves after revascularization, but the EF response to exercise often remains abnormal. Evaluation of the regional and global left ventricular performance and the pressure-volume relationship during systole and diastole, as well as changes in these parameters after revascularization are possible. The exercise EF is also an important prognosticator in patients with known or suspected coronary artery disease.