New Concepts in the Pathophysiology of Diastole

pp 121-127

Abstract

In this study we have analized some past and present concepts about diastole. Although this phase of the cardiac cycle is known from ancient times, it was not until the last decades that it was studied more carefully. The cardiac cycle in general, and the diastole in particular, were not always understood in the same way. Since the XVII century the cardiac cycle has been divided in phases that are still modifying nowadays. For example, the limits of systole and diastole are still uncertain. A new concept emerged during the last years is that isovolumic relaxation is an important determinant of the ventricular filling, since the ventricle is still relaxing after the mitral valve opening. On the other hand, it is well known that relaxation begins very early during the ejection period, before the aortic valve closure. If we recognized that the filling of the ventricle has an important active component we must assume the necessity of an alter-native way to calculate the real passive properties. This alternative consists in calculating the passive filling pressure from the measured left ventricular pressure and the active relaxation pressure. Two additional relatively new concepts are discussed in the study: the acute changes in diastolic stiffness, and the dissociation between isovolumic relaxation and stiffness that occurs during the reperfusion of a stunned myocardium. The role of a giant intrasarcomeric protein called titin (or connectin) in the regulation of diastolic stiffness is also discussed.