[Evaluation of cardiac reserve in patients with angina pectoris by dynamic exercise echocardiography]

To evaluate cardiac reserve in patients with angina pectoris, 10 healthy control subjects and 15 patients with angina pectoris were examined by exercise echocardiography. Exercise on the bicycle ergometer in supine position was imposed at 25 watts per min initially and the exercise was increased by 25 watts every 3 min until attainment of either maximal predicted heart rate or ST segment depression in the electrocardiogram (ECG) or appearance of severe chest pain. Blood pressure, two-dimensional echocardiogram at the level of the papillary muscle in the short-axis view (Fig. 1) and 12 leads ECG were recorded at the end of each exercise level. Cardiac response to the exercise was evaluated by blood pressure, areas of left ventricular cavity at the end diastole and end systole, percent change of the area, ejection fraction and mVCF, as shown in Figs. 2, 3 and 4. From these parameters, the behavior of cardiac response to exercise was divided into four types (cf. Fig. 5). Type A: left ventricular volume was increased slightly at the initial stage of exercise, and thereafter, the cardiac response was maintained by a gradual increase of myocardial contractility. Type B: initial response to exercise was similar to type A, but cardiac output was maintained only with an increase of heart rate in further exercise load. Type C: left ventricular contractility and increased left ventricular volume were observed from 25 watts load of exercise. Most of the control subjects responded as type A. Patients with angina who underwent 125 watts exercise showed type B response, while those who tolerated only 75 watts exercise revealed type C or type D (Table 1). The latter indicates decreased cardiac reserve to exercise. From the results of 10 patients who showed ST depression during exercise, deterioration of left ventricular contractile function appeared before ST segment depression, indicating that a change in mechanical pump function preceded electrical function of the myocardium (Fig. 6). It may be concluded that serial changes of cardiac parameters obtained from dynamic exercise echocardiography with an area-based method is useful to identify decreased cardiac reserve in patients with angina pectoris.