The Causes of Postural Cardiovascular Disorders Ziegler , Michael G.; Rizos, Demetri P. Shibao et al. describe a series of tests that elucidate mast cell activation as a novel cause of postural orthostatic tachycardia syndrome (POTS) and orthostatic hypotension (OH). Because blood pressure control systems are redundant, patients with OH often have more than a single cause of their postural symptoms, and elucidating these causes can be challenging. The study by Shibao et al illustrates this because all but one of their subjects were premenopausal females. Estrogen and histamine vasodilate, and the patients who developed POTS were predominantly those made more susceptible to excessive vasodilation by age and sex. There are so many syndromes that cause orthostatic symptoms that approaching the problem through differential diagnosis is needlessly difficult. Analysis of the cardiovascular physiology of patients with OH is a better way to elucidate etiology and is also more likely to reveal when there are multiple reasons for impaired blood pressure control. The cardiovascular systems used to maintain blood pressure during upright posture are most simply pictured as a volume of fluid, a pump, vessels that resist fluid flow, and a system that regulates pump speed and resistance to flow. The corresponding anatomic parts of this system are blood volume, the heart, resistance blood vessels, and the autonomic nervous system. It is possible to test each of these components responsible for maintenance of blood pressure to determine the defect(s) causing POTS or OH. This simple physiological approach is useful in the outpatient setting to diagnose a single patient and in the clinical research laboratory. | |
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