POSTPRANDIAL HYPOTENSION IN ELDERLY PATIENTS WITH UNEXPLAINED SYNCOPE

Background: Syncope in older patients may be caused by a variety of di sorders, including hypotension, but frequently remains unexplained. Po stprandial hypotension is a common disorder of blood pressure regulati on in the elderly. Objective: To determine the pathogenic mechanisms a nd potential role of postprandial hypotension in elderly patients with otherwise unexplained syncope. Methods: We studied 16 elderly patient s with unexplained syncope and nine elderly controls. Blood pressure, heart rate, forearm vascular resistance, plasma norepinephrine level, and cardiac and splanchnic blood volumes were measured be-fore and aft er a 1680-kJ meal. Results: Eight elderly patients with syncope had po stprandial hypotension, with a decline in supine mean arterial blood p ressure of 17+/-2 mm Hg after a meal (P<.001). The blood pressure rema ined unchanged after the meal in the other patients with syncope and t he controls. In patients with postprandial hypotension, systemic vascu lar resistance fell after the meal, while it remained unchanged in the other groups. Heart rate and plasma norepinephrine level increased to a similar extent in all three groups. Forearm vascular resistance inc reased only in the control subjects. Splanchnic blood volume increased by 26% (P<.01) in patients with syncope who had postprandial hypotens ion and by 22% (P<.01) in control, subjects. Splanchnic blood volume r emained unchanged in the patients with syncope without postprandial hy potension. Conclusions: Postprandial hypotension may be an important c ausative factor in elderly patients with unexplained syncope. The eval uation of syncope in elderly patients should therefore include blood p ressure measurements surrounding a meal. Elderly patients with syncope who have postprandial hypotension fail to maintain systemic vascular resistance, probably because of splanchnic blood pooling without a com pensatory increase in peripheral vascular resistance.