Authors: Convertino, Victor A.; Cooke, William H.

Source: Aviation, Space, and Environmental Medicine, Volume 76, Number 9, September 2005 , pp. 869-876(8)

Publisher: Aerospace Medical Association

Abstract:

Convertino VA, Cooke WH. Evaluation of cardiovascular risks of spaceflight does not support the NASA Bioastronautics Critical Path Roadmap. Aviat Space Environ Med 2005; 76:869–876.

Introduction: Occurrence of serious cardiac dysrhythmias and diminished cardiac and vascular function are the primary cardiovascular risks of spaceflight identified in the 2005 NASA Bioastronautics Critical Path Roadmap. Methods : A review of the literature was conducted on experimental results and observational data obtained from spaceflight and relevant ground simulation studies that addressed occurrence of cardiac dysrhythmias, cardiac contractile and vascular function, manifestation of asymptomatic cardiovascular disease, orthostatic intolerance, and response to exercise stress. Results : Based on data from astronauts who have flown in space, there is no compelling experimental evidence to support significant occurrence of cardiac dysrhythmias, manifestation of asymptomatic cardiovascular disease, or reduction in myocardial contractile function. Although there are post-spaceflight data that demonstrate lower peripheral resistance in astronauts who become presyncopal compared with non-presyncopal astronauts, it is not clear that these differences are the result of decreased vascular function. However, the evidence of postflight orthostatic intolerance and reduced exercise capacity is well substantiated by both spaceflight and ground experiments. Although attenuation of baroreflex function(s) may contribute to postflight orthostatic instability, a primary mechanism of orthostatic intolerance and reduced exercise capacity is reduced end-diastolic and stroke volume associated with lower blood volumes and consequent cardiac remodeling. Conclusion : Data from the literature on the current population of astronauts support the notion that the primary cardiovascular risks of spaceflight are compromised hemodynamic responses to central hypovolemia resulting in reduced orthostatic tolerance and exercise capacity rather than occurrence of cardiac dysrhythmias, reduced cardiac contractile and vascular function, or manifestation of asymptomatic cardiovascular disease. These observations warrant a critical review and revision of the 2005 Bioastronautics Critical Path Roadmap.

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Keywords: blood volume; BP; heart rate; stroke volume; cardiac output; peripheral vascular resistance; orthostatic intolerance; exercise capacity

Document Type: Research article

Publication date: 2005-09-01

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• The peer-reviewed monthly journal, Aviation, Space, and Environmental Medicine (ASEM) provides contact with physicians, life scientists, bioengineers, and medical specialists working in both basic medical research and in its clinical applications. It is the most used and cited journal in its field. ASEM is distributed to more than 80 nations.
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