Changes in cardiovascular function: Weightlessness and ground-based studies

Echocardiographic measurements were taken on members of four Space Shuttle missions before (F-10 to F-12) and twice after (L+0 and L+7 to 14 days) 7- to 9-day space flight missions. Such recordings allowed for determination of left ventricular chamber dimensions and subsequent calculations of left ventricular volume and stroke volume. Resting ventricular volume could be shown to significantly decrease 23% on L+) and to be associated with a significant 28% decrease in stroke volume. Studies 7 to 14 days layer showed amelioration of effects, but persistence of end diastolic volume change. Such findings occurred despite ability to fully ambulate and exercise during the postflight period. Comparison of findings with bed rested subjects (athletic and nonathletic) showed similar changes, but changes after bed rest were of smaller magnitude compared to the flight crews. It is concluded that space flight induces significant changes in heart volume even after short duration (7-9 days) missions. Heavy athletic conditioning preflight may contribute to the severity of the observed changes in the flight crews and to the apparent slow postflight process of recovery.