SEASONAL RESPONSE OF THE HEART TO HEMODYNAMIC CHANGES IN MEN LIVING IN THE EUROPEAN NORTH OF RUSSIA
Residents of the European North of Russia are twice as likely as the national average to suffer from cardiovascular pathology. Thus, the study of seasonal response of autoregulation mechanisms of the heart in northerners is of special scientific interest. Ten male residents of the Komi Republic (mean age 21 years) not getting regular strenuous physical exercise were examined. We studied cardiac hemodynamics and chronotropic function of the heart after changes in venous return and during circulatory homeostasis in two contrasting seasons of the year (in December and May). To simulate changes in venous return to the heart, orthostatic tests were used (from supine to standing position and vice versa). Using Doppler echocardiography, we measured (in the starting position, on the 1st and 4th minute after the test) the aortic root diameter, linear velocity of blood flow through the aortic valve and recorded the heart rate. The stroke volume and cardiac output were calculated. In the standing position, the heart rate, stroke volume and cardiac output in December and May did not differ. The increase in linear velocity of blood flow, stroke volume and cardiac output and the decrease in heart rate induced by the change from standing to supine position persisted for 4 minutes after the test. The decrease in linear velocity of blood flow, stroke volume and cardiac output and the increase in heart rate induced by the change from supine to standing position stayed unchanged for 4 minutes after the test. According to the results obtained, men living in the north and not taking regular strenuous physical exercise showed no differences in cardiac hemodynamics, chronotropic function and cardiac efficiency in standing position in contrasting seasons of the year. Regardless of the impact produced by natural and climatic factors on the bodies of men living in the north, the functioning of autoregulation mechanisms of the heart after postural changes in venous return retain its characteristics even during the restoration of circulatory homeostasis.