The Cardiac Cycle: Mitral Flow and Valve Motion

Abstract

Illustrations of the “Events of the Cardiac Cycle” have traditionally included the electrocardiogram and heart sounds, (obtained non-invasively) as well as left ventricular, left atrial, and aortic pressures (obtained invasively). With the development of electromagnetic flowmetry, phasic aortic flow was added to the picture. Our understanding of the cardiac cycle was further enhanced by measurements of phasic mitral flow and finally by aortic and mitral valve motion. It is interesting to note that although more than a decade has elapsed since publication of the first mitral flow measurement (1) the standard textbook diagrams of the cardiac cycle still do not include a mitral flow trace; nor do they include a trace of mitral valve motion, despite the fact that simultaneous flow and valve motion were measured ten years ago (2). This paper will attempt to fill this gap by focusing on transmitral pressure-flow relations and mitral valve motion. We will analyze and discuss illustrative oscillographic records obtained by highly invasive, but accurate, methods (Fig. 1) in both anesthetized and conscious dogs with normal and pathological diastolic function and mitral valves. We seek to provide a scientific basis for analyzing the physiology and pathophysiology of mitral flow and valve motion so that the users of non–invasive diagnostic methods can understand the ambiguities inherent in these measurements and thereby more meaningfully interpret their data.