Stephen K. Rerych

Cardiac Function at Rest and During Exercise in Normals and in Patients with Coronary Heart Disease: Evaluation by Radionuclide Angiocardiography

This study demonstrates that radionuclide angiocardiography provides a simple and noninvasive approach for evaluation of myocardial function. Previous work concerning myocardial performance has been generally conducted with the patient in the supine position. Radionuclide angiocardiograms were performed in the present study at rest and during exercise in 30 normal subjects and in 30 patients with ischemic coronary artery disease. There were 30 normal controls (Group I), ten with single coronary artery disease (Group II), and 20 patients with multiple vessel coronary disease (Group III). All subjects were studied in the erect posture on a bicycle ergometer. In the normal controls, the mean heart rate doubled and the cardiac output tripled during exercise. Intensive training can lead to extraordinary levels of cardiac performance as shown in a world-class athlete who during peak exercise attained a heart rate of 210, an ejection fraction of 97%, and a cardiac output of 56 liters per minute. In the patients with coronary artery disease, both groups were able to increase cardiac output to approximately twice the resting value. The magnitude of increase in blood pressure during exercise was not significantly different in the three groups. However, definite changes were present in the end-diastolic volume at rest compared with exercise. The mean end-diastolic volume at rest was 116 and rose to 128 ml in Group I, 93 rising to 132 ml in Group II, and 138 increasing to 216 ml in Group III. The stroke volume increased comparably in all three groups, but the ejection fraction from rest to exercise showed a marked contrast in the controls compared to those with multivessel coronary disease. The ejection fraction rose in Group I from 66 to 80% during exercise, while in Group II it fell from 69 to 67%, and in Group III from 60 to 46%. These findings indicate that patients with ischemic myocardial disease respond to the stress of exercise by cardiac dilatation to maintain or increase stroke volume at increased heart rates. Moreover, the magnitude of this response appears to be greatest in patients with left main coronary artery stenosis. This approach for evaluating myocardial function during exercise provides useful data of importance in selecting medical versus surgical management of patients with ischemic coronary artery disease.

Accuracy of diagnosis of coronary artery disease by radionuclide management of left ventricular function during rest and exercise.

Rest and exercise radionuclide angiocardiographic measurements of left ventricular function were obtained in 496 patients who underwent cardiac catheterization for chest pain. Two hundred forty-eight of these patients also had an exercise treadmill test. An ejection fraction less than 50% was the abnormality of resting left ventricular function that provided the greatest diagnostic information. In patients with normal resting left ventricular function, exercise abnormalities that were optimal for diagnosis of coronary artery disease were an ejection fraction at least 6% less than predicted, an increase of greater than 20 ml in end-systolic volume and the appearance of an exercise-induced wall motion abnormality. The sensitivity and specificity of the test were lower in patients who were taking propranolol at the time of study and in patients who failed to achieve an adequate exercise end point. In the 387 patients with an optimal study, the test had a sensitivity of 90% and a specificity of 58%. Radionuclide angiocardiography was more sensitive and less specific than the exercise treadmill test. The high degree of sensitivity of the radionuclide test suggests that it is most appropriately applied to patient groups with a high prevalence of disease, including those considered for cardiac catheterization.

Detecting abnormalities in left ventricular function during exercise before angina and ST-segment depression.

To determine if abnormalities in left ventricular function precede angina pectoris and electrocardiographic evidence of myocardial ischemia, we used radionuclide angiocardiography to measure left ventricularejection fraction, volumes, cardiac output and wall motion in 10 normal subjects and 25 patients with coronary artery disease at rest and during two levels of upright bicycle exercise. In the patients with coronary artery disease, the first radionuclide study during exercise was performed before and the second after the onsetof ST-segment depression. In all normal subjects, the ejection fraction increased more than 5%, the end-diastolic volume increased less than 25% and the end-systolic volume decreased from rest to both levels of exercise. Wall motion was normal at rest and increased with exercise. No patient with coronary artery disease had chest pain or ST-segment depression during the first level of exercise. The ejection fraction either decreased or increased less than 5% in 18 patients, the end-diastolic volume increased more than 25% in nine, the end-systolic volume increased in 19 and a segmental contraction abnormality developed in 14. Hemodynamic and wall motion abnormalities occurred in all patients during the second level of exercise when ST-segment depression was present. During exercise in patients with coronary artery disease, abnormalities in left ventricular function frequently develop before angina pectoris and electrocardiographic evidence of myocardial ischemia.

Effects of exercise training on left ventricular function in normal subjects: a longitudinal study by radionuclide angiography.

Abstract Radionuclide angiocardiography provides accurate hemodynamic information during maximal exercise in erect subjects. Cardiac function was studied with this noninvasive technique in 12 male and 6 female college athletes before (BT) and after (AT) 6 months of swimming training. Measurements at rest and during maximal exercise of heart rate, left ventricular ejection fraction, end-diastolic volume, cardiac output and total body blood volume were determined from first pass and equilibrium precordial counting techniques. The results were as follows: Heart Rate (beats/ min) Ejection Fraction (%) End-Diastolic Volume (ml) Cardiac Output (liters/ min) Total Body Blood Volume (liter) Rest BT 74 ± 11 73 ± 6 133 ± 35 6.9 ± 1.1 8.7 ± 0.8 AT 61 ± 7 67 ± 7 167 ± 40 6.7 ± 1.0 11.4 ± 2.2 Exercise BT 185 ± 10 87 ± 4 166 ± 34 25.5 ± 5.7 8.0 ± 0.9 AT 181 ± 14 86 ± 5 204 ± 39 32.0 ± 8.7 10.8 ± 2.3 Total body blood volume increased after training (p −4 ) and ejection fraction (p −3 ) was associated with an increase in end-diastolic volume (p −5 ). Cardiac output at maximal exercise increased (p −4 ) with a constant heart rate and ejection fraction. Individual variation was observed in the performance level achieved, and the maximal cardiac output at exercise achieved after training (56.6 liters/min) was attained by an Olympic athlete. Exercise training appears to enhance cardiac performance primarily by inducing cardiac dilatation.

The reproducibility of radionuclide angiographic measurements of left ventricular function in normal subjects at rest and during exercise.

SUMMARYIn this investigation we determined the reproducibility of radionuclide measurements of left ventricular ejection fraction, end-diastolic volume, end-systolic volume, stroke volume, pulmonary transit time, pulmonary blood volume and cardiac output in 10 normal subjects. First-pass radionuclide angiocardiograms were performed at rest and during upright, submaximal bicycle exercise on day 1 and day 3. The resting heart rate for the group decreased from 79 ± 17 beats/min on day 1 to 71 ± 14 beats/min on day 3 (p < 0.01). This biologic variation probably contributed to the small but significant decreases in ejection fraction (62 ± 7 to 59 ± 7%, p < 0.05) and cardiac output (7.7 ± 1.9 to 6.6 ± 1.5 l/min, p < 0.02), and the increase in pulmonary transit time (5.8 1.6 to 6.2 ± 1.3 seconds, p < 0.05) between day 1 and day 3. The mean variabilities in ejection fraction, cardiac output and pulmonary transit time were 4.0 ± 3.8%, 1.24 ± 1.23 1/min and 0.65 ± 0.64 second, respectively. No significant differences between studies were observed in resting end-diastolic volume, end-systolic volume and stroke volume. The mean variability in enddiastolic volume was 9.9 ± 5.1 ml. Heart rate varied less during exercise to the same work load, and only pulmonary transit time and blood volume differed significantly between studies. During exercise the mean variabilities in ejection fraction, enddiastolic volume, cardiac output and pulmonary transit time were 3.2 ± 2.5%, 9.8 ± 6.2 ml, 1.59 ± 0.67 1/min and 0.25 ± 0.25 second, respectively. Radionuclide measurements of left ventricular function are highly reproducible if obtained under comparable hemodynamic conditions.

Effect of brief and prolonged exercise on left ventricular function

Abstract Left ventricular function during brief (10 minutes) and prolonged (2 hours) upright bicycle exercise was studied in nine young men. Left ventricular ejection fraction and volumes and cardiac output were measured by radionuclide angiocardiography at rest, during submaximal effort at 10 minutes of the prolonged exercise period and during maximal effort at the conclusion of both exercise periods. The cardiac Output Increased from 6.2 ± 1.6 at rest to 17.4 ± 2.9 liters/min during submaximal effort at 10 minutes as a result of a 93 percent increase in heart rate (70 ± 13 to 135 ± 12 beats/min, p

Comparison of electrocardiographic and left ventricular functional changes during exercise.

The diagnostic accuracy of the Bruce multistage exercise treadmill test (ETT) and changes in left ventricular function assessed by radionuclide angiocardiography (RNA) during rest and maximal exercise were compared in 72 patients who underwent coronary arteriography for evaluation of chest pain. Significant coronary artery disease was defined as a 75% or greater stenosis of the diameter of any of the three major coronary arteries. The coronary arteriographic results were used to categorize each patient according to the number of vessels with a significant lesion. As a result, 15 patients had insignificant disease and 57 had significant lesions of one or more coronary arteries. ETT results were defined as positive if ST-segment changes occurredwith exercise, negative if ST-segment changes did not occur at target heart rate, and indeterminate if ST-segment abnormalities existed at rest or if no ST-segment changes developed at a heart rate below the target heart rate. Abnormal changes in left ventricular function by RNA were an exercise-induced wall motion abnormality, a less than 5% increase in ejection fraction, and a greater than 25% increase in end-diastolic volume and an increase in end-systolic volume with exercise.RNA results were normal in 11 of 15 patients with insignificant disease and abnormal in four, all of whom had 50% lesions of a major coronary artery. In this group, ETT results were indeterminate in seven patients, negative in six and positive in two. In the 57 patients with significant coronary disease, RNA results were abnorinal in 55 and normal in two. ETT results were indeterminate in 12 patients, negative in nine and positive in 36.RNA had a sensitivity of 97% and a specificity of 73% for the 72 patients. By comparison, ETT had a sensitivity of 80% and a specificity of 66% for the 53 patients with adequate studies. These results suggest that exercise-induced changes in left ventricular function defined by RNA have a greater diagnostic accuracy than the ST-segment response during ETT in the patient population studied.