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Effects of Simulated Microgravity on Cardiovascular Stability

Principal Investigator:
Richard J. Cohen, M.D., Ph.D.

Massachusetts Institute of Technology
Harvard-MIT Division of Health Sciences and Technology

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.

NASA Taskbook Entry

Technical Summary

The purpose of this investigation is to evaluate and test countermeasures to the development of microgravity-induced orthostatic intolerance and susceptibility to ventricular dysrhythmias. We will apply the Cardiovascular System Identification (CSI) technique for assessing closed-loop cardiovascular regulation and Microvolt T-Wave Alternans (MTWA) technique for assessing susceptibility to ventricular dysrhythmias.

The specific aims of the project are:

  1. 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;
  2. 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;
  3. 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;
  4. 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;
  5. To further develop and enhance the methodology of CSI, MTWA and Plethysmography analyses.

Earth Applications

Specifically, the research has direct application to the study of mechanisms of and treatment for orthostatic hypotension here on Earth. Orthostatic hypotension is an important and prevalent clinical problem that can lead to syncope and falls, which particularly in the elderly, may be life threatening.

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.

Cardiovascular system identification is a technology that has potential widespread applications for a variety of disease states such as heart failure, hypertension and diabetes, etc., which involve alterations in cardiovascular regulation.

Continuous cardiac output monitoring is a technology that may have widespread clinical importance particularly in intensive care-type situations. It may be particularly important for combat casualty care.

Mathematical analysis of venous plethysmography data may play an important role in diagnosing mechanisms of orthostatic intolerance.

This project's funding ended in 2006