Orthostatic Intolerance and the Chronic Fatigue Syndrome

http://www.mc.vanderbilt.edu/gcrc/space/#OI

One of the closest models of the cardiovascular complications of the microgravity environment is orthostatic intolerance. In this disorder, blood pressure may fall slightly on assumption of upright posture, remain the same, or even increase. However, heart rate commonly rises more than 30 beats per minute on standing. Orthostatic intolerance is common and as many as 500,000 Americans may experience it sometime in their lives.

In recent investigations, the staff of the Autonomic Dysfunction Center, including Drs. Italo Biaggioni, Andrew Ertl, Giris Jacob, John Shannon and Jens Jordan, have identified several different pathophysiologic mechanisms underlying orthostatic intolerance. These include partial dysautonomia, central hyperadrenergia, and norepinephrine transporter deficiency. These recent findings should lead to better understanding of this disorder and similar disorders such as the chronic fatigue syndrome. Orthostatic intolerance goes under many different names (mitral valve prolapse syndrome, postural orthostatic tachycardia syndrome, idiopathic hypovolemia, and vasoregulatory asthenia) but all probably share a common pathophysiology.