Effects of enhanced coronary flow during cardiopulmonary bypass: development of myocardial edema

Abstract

Coronary blood flow, left ventricular diastolic stiffness, ventricular water content and ventricular thiocyanate space were investigated in empty fibrillating and empty beating dog hearts during cardiopulmonary bypass. In empty fibrillating hearts coronary blood flow was considerably enhanced even at levels of normal perfusion pressure. A close correlation was demonstrated between enhanced coronary flow, left ventricular diastolic stiffness, tissue water content and thiocyanate space. Left ventricular end-diastolic pressure considerably increases during myocardial ischaemia (2, 14), while the motion of the posterior left ventricular wall decreases (8). These changes indicate that during myocardial ischaemia enhanced diastolic stiffness of the left ventricular wall occurs. According toSzentiványi andJuhász-Nagy (18) collateral myocardial blood flow is significantly enhanced in the nonischaemic part of the heart muscle during myocardial ischaemia. Recently it has been shown that abnormally enhanced coronary blood flow induces myocardial edema and enhances diastolic ventricular stiffness (15, 16). It is evident that coronary flow is usually elevated in the fibrillating heart during cardiopulmonary bypass even at normal perfusion pressure (1). The correlation between coronary blood flow and myocardial water content as well as left ventricular diastolic stiffness was, therefore, studied in empty beating and empty fibrillating hearts. Der Zusammenhang zwischen der Koronardurchströmung und dem Wassergehalt, dem Thiocyanat-Raum sowie der diastolischen Steifheit der linken Herzkammerwand wurde in leer fibrillierenden und leer schlagenden Hundeherzen während kardiopulmonaler Bypass-Operation untersucht. Es wurde bewiesen, daß eine strenge Korrelation zwischen der erhöhten Koronardurchströmung und dem Wassergehalt, dem Thiocyanat-Raum sowie der diastolischen Steifheit der linken Herzkammerwand existiert. Die Beobachtung läßt vermuten, daß eine erhöhte Koronardurchströmung in den leer fibrillierenden Herzen ein Myokardödem, eine erhöhte Steifheit der linken Kammerwand in Diastole und eine verminderte Leistung des linken Ventrikels auch bei normalem Perfusionsdruck verursachen kann.