INTRODUCTION: Future commercial spaceflight participants (SFPs) with conditions requiring personal medical devices represent a unique challenge. The behavior under stress of cardiac implanted devices (CIDs) such as pacemakers is of special concern. No known data currently exist on how such devices may react to the stresses of spaceflight. We examined the responses of two volunteer subjects with CIDs to G forces in a centrifuge to evaluate how similar potential commercial SFPs might tolerate the forces of spaceflight.
CASE REPORT: Two subjects, 75- and 79-yr-old men with histories of atrial fibrillation and implanted dual-lead, rate-responsive pacemakers, underwent seven centrifuge runs over 2 d. Day 1 consisted of two +Gz runs (peak = +3.5 Gz, run 2) and two +Gx runs (peak = +6.0 Gx, run 4). Day 2 consisted of three runs approximating suborbital spaceflight profiles (combined +Gx/+Gz). Data collected included blood pressures, electrocardiograms, pulse oximetry, neurovestibular exams, and postrun questionnaires regarding motion sickness, disorientation, greyout, and other symptoms. Despite both subjects' significant medical histories, neither had abnormal physiological responses. Post-spin analysis demonstrated no lead displacement, damage, or malfunction of either CID.
DISCUSSION: Potential risks to SFPs with CIDs include increased arrhythmogenesis, lead displacement, and device damage. There are no known prior studies of individuals with CIDs exposed to accelerations anticipated during the dynamic phases of suborbital spaceflight. These cases demonstrate that even individuals with significant medical histories and implanted devices can tolerate the acceleration exposures of commercial spaceflight. Further investigation will determine which personal medical devices present significant risks during suborbital flight and beyond.
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