Effect of habitual exercise on left ventricular response to exercise.

To evaluate the effects of chronic physical exercise on left ventricular ejection fraction (LVEF) and ejection rate (LVER), radionuclide angiography was performed at rest and during upright-bicycle exercise in 45 healthy men. The subjects varied widely in exercise habits and working capacity. They were divided into three subgroups on the basis of habitual physical activity. Aerobic training was done more than 7, 2-4, and less than 1 h/wk by subgroups of athletes, trained, and untrained men, respectively. The results indicate marked differences in work capacity (298, 233, and 181 W in the athletes, trained, and untrained groups, respectively). Resting LVEF (72, 69, and 68%) and LVER (4.1, 3.4, and 3.6 s-1) were not significantly different among the groups. With maximal exercise, however, small but statistically significant differences in LVEF (75, 69, and 68%; P less than 0.05 athletes vs. trained and athletes vs. untrained) and in LVER (7.5, 6.3, and 5.2 s-1; P less than 0.05 among all groups) were observed. Work capacity was, however, poorly correlated with exercise LVEF (r = 0.18) and LVER (r = 0.47). The results of this study indicate that the enhanced working capacity observed secondary to increases in habitual physical activity can be attributed to differences in LVEF and LVER only in the most general terms. Accordingly the results agree with previous suggestions based primarily on echocardiographic data that the primary cardiac adaptation to exercise is dimensional rather than functional in character.

Left ventricular function during sudden strenuous exercise.

Strenuous exercise without warm-up has been shown to produce ischemia-like electrocardiographic (ECG) abnormalities in 60-70% of healthy subjects. These abnormalities appeared to be related to the development of an unfavorable myocardial supply/demand balance and, in chronically instrumented dogs, to transient decreases in coronary blood flow. A mechanism involving subendocardial ischemia has been proposed to explain the response to sudden strenuous exercise (SSE). To determine whether the response to SSE included the development of changes in myocardial pump performance typical of ischemia, left ventricular (LV) function at rest, during graded exercise and during SSE was evaluated in nine young (26.6 +/- 3.4 years), well-trained male volunteers using first-pass radionuclide angiography. During graded exercise, the LV ejection fraction increased from 66.9 +/- 9.4% at rest to 73.0 +/- 7.1% during peak exercise, and the LV ejection rate increased from 3.36 +/- 0.67 sec-1 at rest to 6.58 +/- 1.10 sec-1 during peak exercise. Segmental wall motion was normal in all studies. During SSE, the LV ejection fraction decreased in very subject, from an average 72.2 +/- 8.6% at rst to 57.3 +/- 8.1% during exercise. The LV ejection rate remained relatively constant (3.98 +/- 0.92 sec-1 at rest vs 4.33 +/- 0.74 sec-1 during SSE). No segmental wall motion abnormalities were observed during SSE; however, LV wall motion appeared to be diffusely hypokinetic during SSE. In contrast to previous reports, few ECG abnormalities were observed during SSE. These results support the hypothesis that subendocardial ischemia is an important mechanism in the response to SSE. However, the lack of ECG changes and segmental wall motion abnormalities and the relatively high absolute value of the LV ejection fraction suggest that if subendocardial ischemia occurs during SSE, it is attributable to physiologic rather than pathologic mechanisms.

Improvement in left ventricular function after myocardial revascularization: assessment by first-pass rest and exercise nuclear angiography.

Thirty-six patients with coronary artery disease were studied by first-pass radionuclide angiography to assess the effects of myocardial revascularization on exercise-induced myocardial ischemia. The radionuclide studies were performed in the 30 degree right anterior ablique position, at rest and during exercise, 1 to 3 days preoperatively and 10 to 14 days postoperatively. The mean population age was 53 years; the mean number of grafts placed was 4.0 per patient. Fifteen normal male volunteers were tested by rest and exercise radionuclide angiography to serve as normal control subjects. In all exercise radionuclide studies, progressive upright bicycle exercise was performed to symptoms of fatigue, dyspnea, or chest pain. The parameters of ejection fraction (EF), end-diastolic volume (EDV), and regional wall motion (RWM) were determined. Twenty-nine of the 36 patients had postoperative coronary arteriography that was correlated with radionuclide determinations. The results showed that in the normal subjects with maximal exercise the mean EF rose, the mean EDV increased 19%, and there was no exercise-induced regional wall motion dysfunction (ERWMD). In the patients with coronary artery disease prior to operation, the mean EF fell significantly, the mean EDV rose 24%, and 26 of 36 patients had ERWMD. After operation, the mean EF of the group rose, the EDV increased only 15%, and only two of 36 patients continued to show ERWMD. Of the eight patients who demonstrated on abnormal response postoperatively, seven had what was considered to be inadequate revascularization, and in one there was no explanation. The data demonstrate that myocardial revascularization does improve ventricular function by abolishing exercise-induced evidence of ischemia (decreased EF, increased EDV, and ERWMD) as assessed by radionuclide angiography. Failure to abolish the exercise-induced functional instability suggests incomplete revascularization.