This study represents the first systematic evaluation of dysrhythmias during extravehicular activity (EVA). Twenty-four-hour electrocardiograph (ECG) tracings of Shuttle crew members (n=7) were recorded before, during and after spaceflight including EVA. A comparison of the incidence and severity of dysrhythmias across subjects and time was performed.
Participating crewmembers were required to wear either a Holter ECG recorder or the standard operational bio-instrumentation system (OBS) ECG monitors. The protocol involved 3 specific phases: Phase 1, before flight - acquisition of 3 separate 24-hour Holter recordings; Phase 2, during flight - 24 hours of data collection during and after each EVA (including one 24-hour period within 2 days of landing). Phase 3, after flight - 24 hours of Holter monitoring on postflight days R+0, R+7, and R+30.
Although limited by sample size, the data suggested that the incidence of dysrhythmias is no greater during EVA than in any other phase of a mission. The cardiac response during EVA was statistically no different from the response during the preflight and postflight phases. With the advent of Space Station and the necessity for increased EVA, knowledge of both electrophysiologic and cardiovascular changes will be needed. The data from this study suggested that EVA does not precipitate deleterious cardiac events during space flight.