Profiles of radionuclide left ventricular ejection fraction changes induced by supine bicycle exercise in normals and patients with coronary heart disease

Effect of exercise on left and right ventricular ejection fraction and wall motion

OBJECTIVE

We evaluated the diagnostic value of response of left and right ventricular ejection fraction and wall motion to exercise using electron beam computed tomography.

METHODS AND RESULTS

We attempted to determine the value of exercise electron beam computed tomography for detecting coronary artery disease, including evaluation of the right ventricular ejection fraction and wall motion abnormalities. A study of 35 patients undergoing electron beam tomography exercise cine studies and coronary artery angiography for the evaluation of chest pain was performed. Of the 18 patients with significant coronary disease (> or = 50% luminal diameter stenosis in at least one coronary artery), 17 (94%) had failure to increase global left ventricular ejection fraction with exercise. Fourteen of 18 (78%) developed a wall motion abnormality during peak exercise, and eight (44%) developed a regional right ventricular wall motion abnormality during peak exercise. Of the 17 patients without obstructive disease, 14 (82%) had a increase in ejection fraction > or = 5% and none had an abnormal response in left ventricular wall motion during peak exercise (specificity = 100%). The change in right ventricular ejection fraction with exercise was not a significant predictor of obstructive coronary disease in this study (P=NS). Using different criteria during stress to predict coronary disease, the accuracy was 89% (31/35) using an increase of <5% in ejection fraction, 89% (31/35) using the development of a new or worsened wall motion abnormality, and 91% (32/35) using both left ventricular criteria.

CONCLUSION

Our study suggests that exercise electron beam computed tomography appears to be a useful tool for the detection of coronary disease. A increase of <5% in ejection fraction and abnormal left ventricular response to exercise were important predictors, while the exercise induced changes of right ventricular ejection fraction was not a significant predictor of obstructive disease. Both left and right ventricular wall motion abnormalities are useful and important parameters in identifying patients with obstructive disease from those with normal coronary arteries.

Improved myocardial ischemia detection by combined physical and mental stress testing

The hypothesis that addition of mental stress to physical exercise would modify the circulation response to stress and improve noninvasive detection of myocardial ischemia was tested in a randomized, crossover radionuclide angiocardiographic study. Compared with physical exercise or mental stress alone, combined stress led to higher heart rates and rate-pressure products in early stress stages, to more pronounced symptoms, and to a better discrimination of subjects with and without coronary artery disease by radionuclide angiography.

Diagnostic value of postexercise systolic blood pressure response for detecting coronary artery disease in patients with or without hypertension

To evaluate the diagnostic value of the postexercise systolic blood pressure (SBP) response for detecting and evaluating the presence of coronary artery disease (CAD), treadmill testing was conducted in 130 subjects with normal blood pressure and 51 patients with hypertension, each of whom underwent selective coronary angiography. A total of 48 subjects with normal blood pressure and 27 patients with hypertension had no significant narrowing of the coronary artery (control subjects), whereas 82 subjects with normal blood pressure and 24 patients with hypertension had significant narrowing (patients with CAD). The postexercise SBP response was defined on the basis of the SBP ratio (i.e., the SBP at 3 minutes of recovery divided by that at peak exercise). An SBP ratio that exceeded 0.90 (cutoff point for discriminating control subjects from patients with CAD) was considered to be an abnormal SBP response. In the subjects with normal blood pressure, the abnormal SBP response identified CAD as accurately as did ST-segment depression. In the patients with hypertension, the diagnostic accuracy was increased significantly by combining the abnormal SBP response and ST-segment depression (p < 0.01). The SBP ratio increased with the number of diseased coronary arteries. Ten of the 14 patients with a narrowing of the left main coronary artery had an SBP ratio higher than 1.00. The postexercise SBP response may be useful for detecting CAD in patients with and without hypertension and for evaluating the severity of CAD.

Mechanism of abnormal postexercise systolic blood pressure response and its diagnostic value in patients with coronary artery disease

To define the factors that affect an abnormal postexercise systolic blood pressure (SBP) response and to verify the diagnostic value of that response in patients with coronary artery disease (CAD), we studied 33 normal subjects, eight patients with hypertension who had no CAD, and 42 patients with documented CAD who underwent supine leg exercise testing. SBP recovery ratios were derived by dividing the values obtained 1 and 3 minutes after exercise by the peak value. The upper normal limit of the SBP ratio was defined by two standard deviations from the mean for 33 normal subjects. The specificity of this criterion for identifying patients with CAD was 97% and the sensitivity was 60%. None of the eight patients with hypertension showed an abnormal postexercise SBP response. At peak exercise the pulmonary artery wedge pressure was significantly greater in the patients with CAD having an abnormal response. In multiple regression analysis the exercise pulmonary artery wedge pressure, the exercise SBP, and the systemic vascular resistance after exercise were determining factors for an abnormal SBP response. Three-vessel disease was more common in patients with an abnormal response. Results of this study indicate that an abnormal postexercise SBP response appears to be determined by (1) the extent of exercise-induced impairment of left ventricular function and (2) peripheral vascular tone during recovery. This study also suggests that this criterion can increase the specificity of supine exercise testing in patients with CAD including those with hypertension and might provide a marker for the severity of impaired left ventricular function by exercise in CAD.

Quantitative thallium-201 myocardial exercise scintigraphy in normal subjects and patients with normal coronary arteries

Quantitative thallium-201 myocardial exercise scintigraphy was tested in two patient populations representing alternative standards for cardiac normality: group I comprised 18 male uncatheterized patients with a low likelihood of coronary artery disease (CAD); group II contained 41 patients with normal coronary arteriograms. Group I patients were younger, they achieved a higher rate-pressure product than group II patients; all had normal findings by physical examination and electrocardiography at rest and exercise. Group II patients comprised 21 females, 11 patients showed abnormal electrocardiography at rest, and five patients showed ischemic ST depression during exercise. Twelve patients had signs of minimal CAD. Twelve patients revealed abnormal visual and quantitative thallium findings, three of these patients had minimal CAD. Profiles of uptake and washout of thallium-201 were derived from both patient groups, and compared with normal limits developed by Maddahi et al. Furthermore, low likelihood and angiographically normal patients may differ substantially, and both sets of normal patients should be considered when establishing criteria for abnormality in exercise thallium imaging. When commercial software containing normal limits for quantitative analysis of exercise thallium-201 imaging is used in clinical practice, it is mandatory to compare these with normal limits of uptake and washout of thallium-201, derived from the less heterogeneous group of low-likelihood subjects, which should be used in selecting a normal population to define normality.

Effects of exercise tolerance, age, and gender on the specificity of radionuclide angiography: sequential ejection fraction analysis during multistage exercise

We investigated the factors that determine the left ventricular ejection fraction response to exercise in 57 middle-aged, untrained patients with angiographically normal coronary arteries. The ejection fraction was measured by blood pool radionuclide angiography during each stage of exercise. Stepwise regression analysis was applied to 39 variables, and the resulting significant variables were then included in a logistic regression model to determine which of them would predict a normal ejection fraction response. By stepwise regression analysis, the best model (F = 5.6, p = 0.0004) was obtained by combining four variables: achieving 85% of maximal predicted heart rate, peak heart rate, number of exercise stages performed, and resting pulse pressure. Only the latter two variables were significant by logistic regression analysis. The specificity of greater than or equal to 5 ejection fraction unit increase at peak exercise was 42%, 75%, and 100% in patients who exercised one, two, or three stages, respectively. Furthermore, the increase in ejection fraction during each exercise stage was independent of age or gender. Thus the standard criteria of normality during exercise radionuclide angiography have high specificity only when applied to patients with good exercise performance, regardless of age or gender.

The efficacy of cardiovascular nuclear medicine exercise studies

Radionuclide stress tests were initially introduced into medicine as new diagnostic tests for coronary artery disease (CAD). These tests are very effective for this purpose when applied to populations with an intermediate pre-test probability of coronary artery disease. Radionuclide stress tests, however, also are used now in guiding many management decisions in patients with established CAD, based on the ability of these tests to assess the extent and severity of myocardial ischemia, the functional significance of coronary stenoses, and myocardial viability. Specific uses beyond diagnosis include decisions regarding whom to catheterize, send to coronary bypass surgery, or angioplasty; risk stratification following myocardial infarction or before noncardiac surgery; and evaluation of the results of therapy. This article reviews both the diagnostic efficacy of radionuclide stress tests and their efficacy in guiding management decisions in patients with known coronary artery disease.

Rate of left ventricular functional recovery by radionuclide angiography after exercise in coronary artery disease

To characterize determinants of the rate of recovery of left ventricular (LV) function after exercise-induced ischemia, sequential postexercise radionuclide angiography was performed prospectively in 38 consecutive patients with documented coronary artery disease (CAD). In each patient new or increased regional asynergy developed or absolute ejection fraction decreased at least 4% during exercise. Twenty patients showed immediate recovery of LV function after exercise (group 1) and 18 showed delayed recovery (group 2). Ejection fraction in the first postexercise period was significantly greater in group 1 (65 +/- 12%) than in group 2 (55 +/- 11%) (p less than 0.01). The mean number of coronary arteries with at least 70% diameter narrowing was greater in group 2 (2.7 +/- 0.5) than in group 1 (2.0 +/- 0.9) (p = 0.026); CAD score was also greater in group 2 than in group 1 (p = 0.005). The increase in LV end-diastolic volume from rest to end exercise was greater in group 2 than in group 1 (p = 0.005); neither the change in LV volume nor the change in heart rate or blood pressure after exercise separated the groups. The only independent predictor of the rate of functional recovery was the degree of exercise-induced regional myocardial asynergy (p less than 0.001). Thus, exercise radionuclide angiography in patients with CAD provides a model for evaluating postischemic myocardial function. Delayed functional recovery is associated with extensive exercise-induced regional asynergy as a result of severe CAD and is not primarily influenced by hemodynamic changes.

Relation between coronary anatomy and serial changes in left ventricular function on exercise: a study using first pass radionuclide angiography with gold-195m

Serial changes in left ventricular function on exercise were assessed by first pass radionuclide angiography with gold-195m (half life 30.5 s) in 25 men with known coronary anatomy. In the seven patients with three vessel disease, abnormalities of global left ventricular function and regional wall motion occurred earlier during exercise, were of greater extent at peak exercise, and persisted longer after exercise than in the 11 patients with one and two vessel disease or the seven with normal coronary arteries. Although there were significant differences between the groups in absolute change in ejection fraction and the rate of change in ejection fraction related to exercise duration and heart rate, a considerable overlap of values between groups precluded the accurate prediction of coronary anatomy in individuals. These data suggest that the amount of myocardium at risk from ischaemia in some patients with one and two vessel disease may resemble that in patients with three vessel disease. This study shows that an anatomical classification based solely on the number of diseased vessels will not predict the extent of the impairment of left ventricular function on exercise.

Changes in rest and exercise myocardial perfusion and left ventricular function 3 to 26 weeks after clinically uncomplicated acute myocardial infarction: effects of exercise training

The effects of exercise training on exercise myocardial perfusion and left ventricular (LV) function in the first 6 months after clinically uncomplicated acute myocardial infarction (AMI) were assessed in 53 consecutive men aged 55 +/- 9 years. Symptom-limited treadmill exercise with thallium myocardial perfusion scintigraphy and symptom-limited upright bicycle ergometry with equilibrium gated radionuclide ventriculography were performed 3, 11 and 26 weeks after AMI by 23 men randomized to training and 30 randomized to no training. Peak cycle capacity increased in both groups between 3 and 26 weeks (p less than 0.01), but reached higher levels in trained than in untrained patients (803 +/- 149 vs 648 +/- 182 kg-m/min, p less than 0.01). Reversible thallium perfusion defects were significantly more frequent at 3 than at 26 weeks: 59% and 36% of patients, respectively (p less than 0.05), without significant inter-group differences. Values of LV ejection fraction at rest, submaximal and peak exercise did not change significantly in either group. The increase in functional capacity, i.e., peak treadmill or bicycle workload, that occurred 3 to 26 weeks after infarction was significantly correlated with the increase in peak exercise heart rate (p less than 0.001), but not with changes in myocardial perfusion or LV function determined by radionuclide techniques. Changes in myocardial perfusion or LV function do not appear to account for the improvement in peak functional capacity that occurs within the first 6 months after clinically uncomplicated AMI.

Noninvasive prediction of the angiographic extent of coronary artery disease after myocardial infarction: comparison of clinical, bicycle exercise electrocardiographic, and ventriculographic parameters

To assess alternative criteria for the prediction of multivessel coronary artery disease after myocardial infarction, we compared the clinical, bicycle electrocardiographic, and radionuclide ventriculographic (ejection fraction and wall motion) responses in 110 patients undergoing coronary angiography after myocardial infarction. Ninety-seven of the 110 patients had multivessel coronary artery disease (two or more diseased vessels). Clinical or electrocardiographic abnormalities were observed in 41 of 97 (sensitivity = 43%) patients with multivessel disease, and in only two of 13 (specificity = 85%) patients without multivessel disease. The average information content of these combined clinical and electrocardiographic variables relative to perfect discrimination was 5%. Among the scintigraphic parameters, the conventional criterion for ejection fraction abnormality, a rise of less than 5% had a sensitivity of 72% and a specificity of 62% for multivessel coronary artery disease, while a fall in ejection fraction of 5% or more had a sensitivity of 39% and specificity of 92% for multivessel coronary artery disease. The presence of an exercise wall motion abnormality in the nonadjacent noninfarcted (remote) region had a sensitivity of 82% and specificity of 55% for multivessel coronary artery disease. A more stringent criterion, worsening of remote wall motion with exercise, had a sensitivity of 52% and specificity of 75%. When this latter criterion was combined with a fall in ejection fraction, the sensitivity for multivessel coronary artery disease increased to 62%, specificity remained 75%, and information content increased from 5% to 10%. We conclude that conventional diagnostic criteria for abnormal clinical, bicycle electrocardiographic, or scintigraphic results do not identify patients with additional coronary artery disease after infarction with high accuracy. Two alternative ventriculographic parameters--a fall in ejection fraction and wall motion worsening--are similar to clinical parameters in specificity, but have a higher sensitivity and information content.

Sensitivity and specificity of nuclear phase analysis versus ejection fraction in coronary artery disease

Phase standard deviation (SD) and skew characteristics of the first Fourier harmonic of equilibrium radionuclide volume curves were examined and compared during rest and during supine bicycle exercise with ejection fraction (EF) changes and the development of ischemia in 17 control subjects and in 2 groups of patients (n = 57) with coronary artery disease (CAD). Group I comprised 37 patients with CAD; IA was a subgroup of 20 patients with previous myocardial infarction (MI) and IB a subgroup of 17 patients with CAD without MI (all with coronary stenosis greater than 75% diameter narrowing). Group II comprised 20 patients with CAD who had undergone coronary bypass surgery. In the Group I subjects, phase SD was the most sensitive indicator of CAD at rest (Group I, 56%; Group IA, 70%, and Group IB, 29%), and the EF was the most sensitive indicator at submaximal (Group I, 78%; Group IA, 86%, and Group IB, 64%) and maximal exercise (Group I, 70%; Group IA, 93%, and Group IB, 53%). When phase SD and skewness were combined with EF changes, little increase in sensitivity occurred in Group I (rest 61%, submaximal exercise 88% and maximal exercise 76%). The results from Group II subgroups were qualitatively similar to those observed with Group I subgroups. These data reveal a marginally improved sensitivity for detection of CAD during supine bicycle radionuclide ventriculography when phase measurements were added to changes in global EF values.

Peak exercise and immediate postexercise imaging for the detection of left ventricular functional abnormalities in coronary artery disease

Eleven patients without significant coronary artery disease (CAD) (group A), 22 patients with significant CAD and no prior myocardial infarction (MI) (group B), and 10 patients with CAD and a previous MI (group C) were imaged at rest, at peak exercise and immediately after exercise by first-pass radionuclide angiography. At peak exercise, mean left ventricular (LV) ejection fraction (EF) did not change significantly in group A or C and decreased significantly in group B. However, in all groups mean LVEF increased significantly immediately after exercise. Examination of potential criteria for an abnormal LVEF response showed that changes from rest to peak exercise were sensitive for detection of CAD but were not specific. Postexercise criteria were more specific but relatively insensitive: 15 of 32 patients (47%) with CAD showed a normal (greater than 5% increase over rest) response after exercise. Similarly, a regional abnormality at peak exercise was 100% sensitive, compared with a sensitivity of 78% after exercise for the whole group, and only 68% in patients without prior MI. Seven patients would have been misclassified as normal if postexercise imaging alone had been performed. The likelihood of an abnormal postexercise EF response was related to the extent of CAD: No patient with 1-vessel, 8 of 17 with 2-vessel and 9 of 12 with 3-vessel CAD showed such a response. Peak exercise imaging is necessary to achieve maximal sensitivity for the detection of CAD, and a high false-negative rate will be obtained if postexercise imaging only is used. The combination of peak exercise and postexercise imaging may be of value in assessing the severity of CAD.

Radionuclide imaging correlatives of heart rate impairment during maximal exercise testing

A lower than normal heart rate response to maximal dynamic exercise, known as chronotropic incompetence or heart rate impairment, has been demonstrated to have a poor prognosis. In order to better describe patients with this finding, 156 men with coronary heart disease were evaluated. All patients were studied with maximal exercise testing, including measurements of oxygen consumption, exercise electrocardiograms, thallium scintigraphy and radionuclide ventriculography. Chronotropic incompetence was defined as a maximal heart rate 1 standard error of the estimate below the regression line of age versus maximal heart rate on two separate exercise tests. In patients so defined, mean maximal oxygen consumption was significantly lowered and angina was the major reason for stopping exercise on the treadmill. Patients with chronotropic incompetence not limited by angina had more evidence of myocardial scar and dysfunction and had a greater prevalence of three vessel coronary disease than did patients with a normal heart rate response. Radionuclide testing results suggest that among patients with chronotropic incompetence, those with angina have a better prognosis than those who do not have angina but who may have myocardial dysfunction.

The declining specificity of exercise radionuclide ventriculography

Although exercise radionuclide ventriculography was initially reported to be a highly specific test for coronary-artery disease, later studies reported a high false-positive rate. To verify this turnabout, we analyzed the responses in 77 angiographically normal patients; 32 were studied from 1978 to 1979 (the early period), and 45 from 1980 to 1982 (the recent period). Most patients studied in the early period had normal responses (94 per cent for ejection fraction and 84 per cent for wall motion). In contrast, normal responses were less frequent in patients studied in the recent period (49 per cent for ejection fraction and 36 per cent for wall motion, P less than 0.001). The probability of coronary disease before testing was higher in these patients (38 vs. 7 per cent, P less than 0.001). More patients studied in the recent period underwent radionuclide ventriculography before angiography (78 vs. 22 per cent, P less than 0.001), and more of these prior studies had abnormal results than those performed after angiography (55 vs. 6 per cent, P less than 0.0001). Thus, two factors are responsible for the temporal decline in specificity: a change in the population being tested (pretest referral bias) and a preferential selection of patients with a positive test response for coronary angiography (post-test referral bias).

Evaluation of left ventricular function by radionuclide angiography during exercise in normal subjects and in patients with chronic coronary heart disease

Radionuclide angiography permits evaluation of left ventricular performance during exercise. There are several factors that may affect the results in normal subjects and in patients with chronic coronary heart disease. Important among these are the selection criteria: age, sex, level of exercise, exercise end points, ejection fraction at rest and effects of pharmacologic agents. An abnormal ejection fraction response to exercise is not a specific marker for coronary heart disease but may be encountered in other cardiac diseases. In addition to the diagnostic considerations, important prognostic data can be obtained. Further studies are needed to determine the prognostic implications of anatomic findings versus the functional abnormalities induced by exercise in patients with coronary artery disease.

Improvement of resting myocardial asynergy with cessation of upright bicycle exercise

Exercise generally aggravates ischemic myocardial dysfunction, presumably by increasing tissue oxygen demand out of proportion to the increase in supply. Nevertheless, resting left ventricular (LV) wall motion abnormalities can improve dramatically after upright exercise. To investigate this "paradoxical" phenomenon, we performed upright bicycle exercise equilibrium radionuclide ventriculography in 93 patients with angiographic coronary artery disease. Immediately after exercise, LV end-diastolic volume was similar to the resting level (1 +/- 22% of rest value), but end-systolic volume (ESV) was significantly below (p less than 0.05) that at rest (-11 +/- 32%) and LV ejection fraction increased significantly compared with rest (0.57 +/- 0.16 vs 0.51 +/- 0.13, p less than 0.05). Improvement in resting myocardial asynergy was frequent (115 of 330 abnormal segments), and was observed more commonly in patients without pathologic Q waves and in segments manifesting mild rather than severe asynergy. In 60 additional patients with resting asynergy who were also studied after nitroglycerin (NTG), there was 89% concordance of wall motion response in asynergic segments after exercise and NTG: 71 of 85 segments manifesting improvement with NTG also improved after exercise, and 157 of 172 segments without improvement with NTG also failed to improve after exercise. Despite the similar wall motion response, the mechanism of improvement is probably different from that produced by NTG. With NTG, preload (end-diastolic volume) and afterload (systolic blood pressure) were significantly lower than their resting control levels (p less than 0.05). These changes did not occur after exercise. Instead, an isolated, significant reduction in ESV was noted. These data support the hypothesis that catecholamine stimulation is responsible for paradoxical wall motion improvement after upright exercise.

Noninvasive assessment of changes in myocardial perfusion and ventricular performance following exercise training

Seventeen coronary patients (CAD) underwent thallium (TI-201) treadmill and radionuclide (RNV) ejection fraction supine bicycle testing before and after 5.6 +/- 1.6 (mean +/- SD) months of an exercise program. Thallium data were assessed both using analog images and a computerized circumferential profile technique. Patients exercised on the treadmill to a higher workload after the exercise program, but achieved a similar pressure-rate product. When interpreting the analog thallium images, only 50% agreement was obtained for the assessment of changes in myocardial perfusion (pre/post-training). The computer technique, however, had low inter-intraobserver variability (6%) and better agreement (90.5%). Using the circumferential profile method, five patients improved (a total of 11 regions) and one patient worsened (with two regions). Before the exercise program, the ejection fraction (EF) response to supine bike exercise was normal (an increase greater than 11%) in four, flat in seven, and severely abnormal (a decrease of more than 4%) in six patients. After the exercise program, even though achieving similar or higher pressure-rate products, six patients improved their EF response, nine did not change, and two worsened. Of the five patients who improved their thallium images, one improved his EF response, two remained normal, and two did not change. One patient worsened both his thallium study and the EF response after the exercise program. Changes in thallium exercise images and the EF response to supine exercise occurred in our patients after an exercise program, but were not always concordant. Indeed, of five patients with exercise-induced ischemic ST changes before and after training, the EF response improved in three whereas myocardial perfusion was unchanged. Reasons for this lack of agreement are discussed, and have been considered in the planning of a randomized trial of the effects of an exercise program on myocardial perfusion and function.

Relationship of resting ejection fraction and extent of coronary arterial disease with changes of QRS amplitude during exercise stress testing

To further elucidate the value of the R wave criteria during the exercise stress test (EST), we studied the direction and magnitude of the changes of the QRS amplitude (delta R) as well as the extent of ST segment depression in 75 patients with coronary artery disease (CAD) and 26 normal subjects (NLS). Results were analyzed in relation to severity of the disease (number of vessels involved) and left ventricular EF. In NLS, there was an average decrease of the QRS amplitude of --1.9 +/- 0.6 mm (mean +/- SE) compared to an average increase of 0.6 +/- 0.35 mm for CAD patients. Mean delta R for 1VD was --0.28 +/- 0.75 mm; for 2VD, it was 0.27 +/- 0.54 mm, and for 3VD, it was 1.37 +/- 0.55 mm. Mean delta R for NLS was significantly different (Duncan's multiple range test, p less than 0.05) from 2VD and 3VD but not from 1VD. Although there was no statistically significant difference of mean delta R among CAD groups, a significant linear trend was observed (p less than 0.008). Resting EF did not correlate either with extent of ST segment depression or with the direction or magnitude of delta R induced by exercise. We conclude that the direction of changes in delta R during exercise is related to the presence or absence of CAD. The magnitude of delta R appears to correlate with the severity of coronary arterial involvement. We did not detect any relationship between R wave changes and left ventricular function. The use of R wave criteria may slightly improve the sensitivity of EST but detracts from specificity.

Rest and exercise electrocardiograms and radionuclides in patients presenting for cardiac rehabilitation

The rest and exercise ECG, 201thallium myocardial scintigram (201T1), and radionuclide ventriculography are noninvasive procedures which can be used to evaluate myocardial damage and ischemia. To compare these procedures and to obtain baseline information, 85 male patients with coronary heart disease were evaluated prior to beginning an exercise program. Findings at rest included Q waves or bundle branch block in 54%; 47% had 201T1 redistribution defects and 33% an abnormal ejection fraction (EF). Of the 39 patients with normal ECGs, 31 had no 201T1 defects and only of these 31 (3%) had an abnormal EF. Abnormal EF or 201T1 redistribution defects did not occur in patients without a history of myocardial infarction. Abnormal resting EF occurred in 63% of patients with abnormal versus 7% of those with normal 201T1 redistribution scans. Exercise test results included an abnormal ST-segment response in 80%, an abnormal EF response in 65%, and a 201T1 ischemic defect in 37%. Twenty patients had exercise-induced ST elevation, and this phenomenon was more related to ventricular aneurysms than to ischemia. 201Thallium imaging, radionuclide ventriculography, and the ECG provide results regarding myocardial damage that agree by more than chance, while the exercise induced ST-segment changes did not agree with the radionuclide indications of exercise-induced ischemia.

Response of the left ventricle to stress: effects of exercise, atrial pacing, afterload stress and drugs

A variety of tests are being utilized today to diagnose the presence of ischemic heart disease, assess the prognosis of myocardial and valvular heart disease and evaluate the effects of various pharmacologic agents on cardiac performance. This review summarizes the current evidence regarding the response of left ventricular performance and size to atrial pacing, afterload stress and various forms of exercise. The responses in normal persons and in subjects with coronary heart disease is reviewed and, when applicable, the effects of various pharmacologic agents on exercise performance in these patient groups are examined.

Improvement in ventricular function during exercise studied with radionuclide ventriculography after cardiac rehabilitation

A heterogeneous group of 19 consecutive patients with coronary artery disease were studied with radionuclide ventriculography before and after a mean of 6 months of exercise training. Ejection fraction was measured at rest, at matched submaximal supine work loads and during maximal supine bicycle exercise. After training there was no change in mean ejection fraction at rest or during maximal exercise, but a higher maximal mean systolic blood pressure, heart rate and work load were achieved. At equivalent submaximal work loads after training, similar levels of mean heart rate and systolic blood pressure were reached but a statistically greater mean ejection fraction was obtained. These preliminary results suggest that exercise training may improve cardiac function during exercise in selected patients with coronary disease. A randomized study using similar techniques has been initiated.