[Status of cardiodynamics in long-term weightlessness]

This paper presents data on the phasic structure of the cardiac cycle of the left ventricle of cosmonauts who flew for 96 to 237 days on Salyut-6-Soyuz and Salyut-7-Soyuz. Cardiodynamic changes at rest that developed largely during the first month of flight involved a mild preload syndrome. During flight months 2 to 8 the cardiac function became relatively stabilized. Provocative tests, i. e. LBNP and exercise tests, presented inflight modified the relationship between cardiac cycle phases when compared to the Earth observations. The modifications are suggestive of predominant adrenergic effects on the heart. Analysis of the phasic structure of the cardiac cycle has revealed no cardiovascular deconditioning. All the variations can be regarded as adaptive reactions to microgravity.