Weightlessness can have negative effects on the human body, making astronauts possibly susceptible to symptoms of fainting and light-headedness (orthostatic intolerance), and irregular heartbeats (ventricular dysrhythmias). Dr. Richard Cohen is developing a program to preempt these problems by testing a panel of countermeasures through a series of bed-rest studies involving both men and women. These studies may also provide new diagnostic and therapeutic approaches to treating patients with similar problems here on earth.
Effects of Simulated Microgravity on Cardiovascular Stability
Richard J. Cohen, M.D., Ph.D.
Massachusetts Institute of Technology
Harvard-MIT Division of Health Sciences and Technology
The specific aims of the project are:
- To test a panel of countermeasures to orthostatic intolerance in subjects intolerant to pre-bed rest head-up tilt, in conjunction with the evaluation of CSI and other cardiovascular measures as a potential means of predicting orthostatic intolerance and countermeasure effectiveness;
- To test in a 16-day head-down tilt bed rest study the effectiveness of the orthostatic intolerance countermeasure identified for each individual during pre- bed rest screening, in conjunction with the evaluation of CSI and other cardiovascular measures as a means of predicting orthostatic intolerance and countermeasure effectiveness;
- To utilize MTWA analysis in older men and post-menopausal women in order to measure the effects of a panel of countermeasures for reducing cardiac electrical instability, and to study the effects of these countermeasures on baseline orthostatic tolerance and closed-loop cardiovascular regulation as measured by CSI and other cardiovascular measures;
- To test utilizing MTWA analysis in a 16-day head-down tilt bed rest study the effectiveness of the cardiac electrical instability countermeasure identified for each individual during pre-bed rest screening, and;
- To further develop and enhance the methodology of CSI, MTWA and Plethysmography analyses.
In addition, this study also focuses on mechanisms and treatment of life-threatening ventricular dysrhythmias. Sudden cardiac death from ventricular dysrhythmias accounts for one-half of all cardiac deaths and one in seven of all deaths.
The technologies developed in the context of this project all have direct application to Earth-based medicine.
The Microvolt T-Wave Alternans testing technique has already been successfully commercialized, cleared by the FDA, is reimbursed for by Medicare, and is in widespread clinical used to identify patients at high and low risk of sudden cardiac death so that they may be appropriately treated. Just recently the Center for Medicare and Medicaid Services (CMS) announced an extremely broad proposed National Coverage Decision for Microvolt T-Wave Alternans testing. National Coverage Decisions are limited to the five to ten percent of covered procedures that CMS deems is of greatest importance to Medicare beneficiaries. This action by CMS demonstrates the broad national significance of this technology developed under NASA/NSBRI sponsorship and represents the contribution of space medicine to health care here on Earth.
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Mathematical analysis of venous plethysmography data may play an important role in diagnosing mechanisms of orthostatic intolerance.