Building off of his ground-based studies in orthostatic intolerance, Dr. Richard J. Cohen is working with NASA investigators to study the effects of weightlessness on the cardiovascular system by studying astronauts pre- and post-flight. The group will use two non-invasive technologies developed in Dr. Cohen’s laboratory in this study. Microvolt T-wave alternans testing will be used to determine whether space flight can make the heart susceptible to serious heart rhythm disturbances. Microvolt T-wave alternans testing equipment has been cleared by the FDA and is now in widespread clinical use to identify patients at risk of sudden cardiac death. Cardiovascular system identification will be used to assess the effects of space flight on cardiovascular regulation. The researchers also will study the drug midrodrine to determine its effectiveness as a countermeasure to the development of orthostatic intolerance following space flight.
Effects of Spaceflight on Cardiovascular Stability (Flight Study)
Richard J. Cohen, M.D., Ph.D.
Massachusetts Institute of Technology
In previous ground-based bed-rest studies sponsored by NSBRI, we have applied two new techniques that we have developed to study the effects of simulated microgravity on the cardiovascular system. Cardiovascular system identification (CSI) has been used a noninvasive means of measuring alterations in closed-loop cardiovascular regulation and the measurement of Microvolt level T-Wave Alternans (TWA) has been used as a noninvasive measure of susceptibility to ventricular arrhythmias. We have also successfully tested the alpha-l sympathetic agonist midodrine as a countermeasure to the development of orthostatic intolerance. We have found that 16 days of bed rest results in altered cardiovascular regulation. In particular, we have demonstrated alterations in baroreceptor sensitivity, altered electrical stability of the heart, and that midodrine is an effective countermeasure to the development of orthostatic intolerance.
In this proposal, we plan to apply the same measurement techniques of CSI and TWA to astronauts pre- and postflight and to test midodrine as a countermeasure to the development of orthostatic intolerance. This study will allow us to determine if the changes in cardiovascular regulation and cardiac electrical stability measured in a ground-based model also occur during actual space flight. In addition, we will test for the first time a potentially effective countermeasure for the development of postflight orthostatic intolerance.