Previous studies have established that most of the heterogeneity in exercise capacity seen with sedentariness, aging, or physical training can be accounted for by individual differences in the maximal rate of total body oxygen consumption (VO2 max) during dynamic exercise. However, the factors that limit VO2 max in normal subjects remain disputed. To test the hypothesis that differences in left ventricular diastolic performance contribute to the heterogeneity of VO2 max seen in healthy subjects, 57 normal sedentary volunteers (36 +/- 13 yr, range 20-76 yr) and 9 endurance athletes (37 +/- 8 yr, range 26-51 yr) were studied. Aerobic capacity was estimated as VO2 max during a multistage dynamic cycle exercise protocol, whereas resting left ventricular systolic and diastolic function was assessed by two-dimensional and Doppler echocardiography. The relationship of the left ventricular functional indexes with VO2 max was investigated by stepwise multiple regression analysis. VO2 max ranged from 25 to 58 ml.kg-1 x min-1 in sedentary subjects and from 44 to 60 ml.kg-1 x min-1 in athletes. With univariate analysis, significant correlations were observed between VO2 max and age (r = -0.60), maximal heart rate (r = 0.48), maximal work load (r = 0.80), left ventricular volumes at both end diastole (r = 0.51) and end systole (r = 0.62), peak early transmitral filling velocities (r = 0.80), and the ratio of early to late transmitral filling velocities (r = 0.87).(ABSTRACT TRUNCATED AT 250 WORDS)

To determine the effects of a moderately prolonged exercise on left ventricular systolic performance, 23 healthy male subjects, aged 18 to 51 yr (mean 37 yr) were studied. The subjects exercised first on a treadmill (brief exercise) and completed, on a separate day, a 20-km run. M-mode, two-dimensional, and Doppler echocardiography, as well as calibrated carotid pulse tracings, were obtained at rest and immediately on completion of both brief and prolonged exercise. Left ventricular systolic function was assessed by end-systolic stress-shortening relationships. Heart rate increased similarly after brief and prolonged exercise (+30%). Mean arterial pressure decreased from 99 +/- 7 to 92 +/- 8 mmHg (P less than 0.001) after prolonged exercise, but it remained unchanged after brief exercise. Left ventricular end-diastolic volume was decreased after prolonged exercise (130 +/- 23 vs. 147 +/- 18 ml at rest, P less than 0.01). Both ejection fraction and rate-adjusted mean velocity of fiber shortening decreased after prolonged exercise [from 67 +/- 5 to 60 +/- 6% (P less than 0.001) and from 1.12 +/- 0.2 to 0.91 +/- 0.2 cm/s (P less than 0.001), respectively] despite a lower circumferential end-systolic wall stress (133 +/- 23 vs. 152 +/- 20 g/cm2). The relationship between ejection fraction (or mean velocity of fiber shortening adjusted for heart rate) and end-systolic wall stress was displaced downward on race finish (P less than 0.05). These changes were independent of the changes in left ventricular end-diastolic volume and hence those in preload. The data suggest that moderately prolonged exercise may result in depressed left ventricular performance in healthy normal subjects.

Alternative strategies using conditional probability analysis for the diagnosis of coronary artery disease (CAD) were examined in 93 infarct-free women presenting with chest pain. Another group of 42 consecutive female patients was prospectively analyzed. For this latter group, the physician had access to the pretest and posttest probability of CAD before coronary angiography. These 135 women all underwent stress electrocardiographic, thallium scintigraphic, and coronary angiographic examination. The pretest and posttest probabilities of coronary disease were derived from a computerized Bayesian algorithm. Probability estimates were calculated by the four following hypothetical strategies: SO, in which history, including risk factors, was considered; S 1, in which history and stress electrocardiographic results were considered; S2, in which history and stress electrocardiographic and stress thallium scintigraphic results were considered; and S3, in which history and stress electrocardiographic results were used, but in which stress scintigraphic results were considered only if the poststress probability of CAD was between 10% and 90%, i.e., if a sufficient level of diagnostic certainty could not be obtained with the electrocardiographic results alone. The strategies were compared with respect to accuracy with the coronary angiogram as the standard. For both groups of women, S2 and S3 were found to be the most accurate in predicting the presence or absence of coronary disease (p < .05). However, it was found with use of S3 that more than one-third of the thallium scintigrams could have been avoided without loss of accuracy. It was also found that diagnostic catheterization performed to exclude CAD as a diagnosis could have been avoided in half of the patients without loss of accuracy. Studies in the prospective group of 42 women confirmed that S2 and S3 had the best diagnostic accuracy. We also observed a higher prevalence of angiographically documented coronary disease in this group (48% vs 26% in the first group of 93 women). In this prospectively studied group, there was a smaller proportion of patients with a low probability estimate of CAD (29% of the patients with a probability of .10% in the prospective group vs 58% of the patients in the first group). Our results suggest that the treating physician's prior knowledge of probability estimates reduced the number of unnecessary diagnostic coronary angiographic procedures performed. Circulation 71, No. 3, 535-542, 1985. THE APPLICATION of probability methods to the diagnosis of coronary artery disease (CAD) is an important conceptual advance. IA The validity of probability analysis for diagnosing CAD has already been demonstrated by comparison of the calculated probability of disease with coronary angiographic results.5-10 Another potential application of probability analysis is to

SUMMARY The clinical value of combining exertional ECG and postexertional thallium (201T1) scintigraphy was assessed in 160 patients (130 men and 30 women) suspected of having coronary artery disease (CAD) who underwent a coronary arteriography. Based on sex and history, the patients were subdivided in two groups with different prevalences of CAD: Group 1 (high prevalence of CAD = 90%) included 98 men with typical angina pectoris (AP) and group 2 (low prevalence of CAD = 18%) included 32 men and 30 women with atypical AP.Compared with the exertional ECG, myocardial scintigraphy was more sensitive (87% vs 74%) and more specific (89% vs 70%) for the diagnosis of CAD. The combination of the ECG and scintigraphic data was useful if both tests gave concordant results: 100% of true positives (n = 67) and 84% of true negatives (n = 43). In case of discordant results (n = 50), no firm diagnostic conclusion could be made due to the many false-positive (27%) and false-negative (25%) scintigrams.These results are easier to interpret when the prevalence of CAD is taken into account. According to Bayes' theorem, abnormal exercise results confirm CAD when the prevalence is high and normal results rule out CAD when the prevalence is low; also, a normal response to exercise has no predictive value when the prevalence is high. When the prevalence is low, an abnormal ECG or thallium has low predictive value but concordant abnormal responses are highly predictive for CAD (100% of true positives).EXERCISE myocardial perfusion scintigraphy with thallium-201 is useful for detecting myocardial ischemia due to coronary artery disease (CAD) and seems more reliable than the exertional ECG. '-5 In symptomatic patients, the characteristics of the complaints are important and, from a well-taken history, one can evaluate the likelihood of CAD.8 12 Several reports on exertional ECG have indicated that the diagnostic information provided by the test was largely determined by the prevalence of the disease within the population.9" [13][14][15][16][17] This study was undertaken to assess the diagnostic value of exercise thallium scintigraphy and its combination with exertional ECG; in order to analyze the influence of the prevalence of CAD, the patients were subdivided in groups according to the information provided by the history. The prevalence of CAD is almost 100% after an acute myocardial infarction, so patients with a history of infarction were excluded. Material One hundred sixty patients, 130 men and 30 women, suspected of CAD but without evidence of a previous myocardial infarction, were studied. They underwent a multistage maximal exercise test 1 to several days before the arteriographic study. These patients were studied because of the presence of chest pain. Before the exercise test, the patients were carefully questioned by the same physician. From the clinical history, the complaints were subjectively judged to be typical or atypical of angina pectoris (AP). As in a previous study,9 this judgment was based on the location, qualit...

The value of exercise testing for the diagnosis of coronary artery disease is disputed but very few studies have taken advantage of all recent improvements, namely computer averaging of the ECG signals, multivariate analysis of the data, a compartmental diagnostic approach and probabilistic interpretation of the results. These methods were tested in a group of 387 men who had a computer-assisted multistage maximal exercise test; none had a history of myocardial infarction. In 284 symptomatic patients, the diagnosis was made by arteriography; 103 ostensibly healthy men were also included. The computer-averaged ECG signals (X, Y, Z) recorded at maximal exercise, maximal heart rate, blood pressure and workload, and the onset of angina pectoris during exercise were submitted to a multivariate stepwise discriminant analysis. The pretest likelihood for CAD was calculated from age and history; the post-test likelihood was calculated from Bayes' theorem and the average information content of several diagnostic methods was assessed in categorical and compartmental models. By multivariate analysis, 5 variables collected at maximal exercise were selected, namely the heart-rate, the ST60 segment level, the onset of angina during the test, the workload and the slope of the ST segment in lead X. The average information content of the analysis using 5 variables was 44% in a categorical model versus 55% in a compartmental model (P less than 0.001). For comparison, the information content of the analysis using the ST60 segment level alone was only 16% in the categorical model and 27% in the compartmental model. The clinical value of these diagnostic methods (categorical versus compartmental, univariate versus multivariate) was assessed by a probabilistic classification of the patients. The classification provided by the analysis of the ST60 segment changes was barely better than that one provided by the simple history. The probabilistic use of a multivariate and compartmental analysis of the data led to a significantly better and more accurate classification of the patients (83% of correct classification).