Effect of the cardiac arrhythmias on the renal and mesenteric circulations

Abstract

A new accurate method of direct measurement of renal and mesenteric blood flow is described using a new electromagnetic flowmeter technic with an integrator-computer apparatus. Using this technic, the effect on the renal circulation of various experimentally produced cardiac arrhythmias was studied. There was a significant reduction in renal arterial flow and a consistent and prolonged rise in the renal vascular resistance. This reduction in renal blood flow due to the increased resistance appears to be a homeostatic mechanism which helps to provide “available” blood for the myocardial and cerebral circulations during arrhythmias. The decrease in renal blood flow often persisted even after conversion to sinus rhythm and a return to normal of the systemic blood pressure and cardiac output. This phenomenon is most likely due to prolonged renal vasoconstriction. Arrhythmias of long duration may result in renal damage due to ischemia. The results in the mesenteric circulation were more variable. It has been shown that the mesenteric circulation is extremely important in maintaining circulatory homeostasis during arrhythmic shock and is a labile mechanism. For this reason, the mesenteric circulation could be called the “homeostatic watchdog” of the systemic circulation. The term “mesenteric vascular insufficiency” describes the functional state of reduced mesenteric flow due to mesenteric vasospasm and reduced cardiac output and blood pressure which occurs in arrhythmias and other circulatory disturbances. A correlation has been made between these experimental findings and with clinical states seen in patients at the bedside and the autopsy table who present with symptoms of “mesenteric vascular insufficiency.”