[Dynamics of the phasic structure of left ventricular systole on prolonged (140-185 days) space flights]

Kinetocardiographic studies of the left ventricular systolic time intervals at rest in space flights of 140, 175 and 185 days in duration revealed functional changes reflecting cardiovascular adaptation to weightlessness. The typical changes were: shortening of isometric contraction, decrease of the tension index, irregular decline of the ejection time, and a slight increase in the intrasystolic index. These changes in the systolic time intervals are indicative of an enhanced strength of cardiac contraction. This may in turn be associated with cephalad fluid shifts and reduced activity of the peripheral muscular heart.