[Detection of risk factors for hemodynamic dysadaptation under physical loading by data of genetic studies...

Examination in 28 pairs of twins who were studied by echocardiography just after their performance of exercise (Stage I) and at the peak of effects produced by oral anapriline (Stage II) have shown that at rest such parameters as end-systolic volume, ejection fraction, relative changes in the internal dimension of the left ventricular cavity during a cardiac cycle, show moderate-to-high genetic predisposition. At the same time, a persistent contribution of heredity to myocardial contractility is found only for end-systolic volume when the conditions of the examination were changed. The lesser extent to which contractility parameters had hereditable signs, the more intensively they varied under different conditions. It is assumed that the contraction rate of circulatory myocardial fibers is less resistant to environmental factors. A significant decrease in this parameter during anapriline administration allows one to suppose that cardiac decompensation in patients with coronary heart disease starts with damages to the very myocardial circulatory muscles.