Determinants of afterload-induced diastolic dysfunction.
Severe left ventricular (LV) afterload elevations induce diastolic dysfunction (DD). This decompensatory response, observed in both dogs and rabbits, seems to be related to cytosolic calcium levels. As rats have different calcium kinetics, we investigated the effects of acute LV afterload elevation in rats. Anaesthetized Wistar rats (n = 10) were instrumented in order to record simultaneously LV pressure and septal-free wall dimensions. Afterload was elevated through partial or total occlusions of the ascending aorta. In afterloaded heartbeats, we measured the time constant tau, the necessary (NTR) and the available (ATR) time intervals to complete LV relaxation. DD was evaluated through analysis of the position of the end-diastolic pressure-volume relation. Afterload elevations elicited acceleration of relaxation and DD was observed only in isovolumetric heartbeats. This DD could be explained by the deficit in time to complete relaxation in isovolumetric heartbeats. We conclude, therefore, that the time constant tau and ATR are the major determinants of afterload-induced DD. The calcium kinetics of the rat provide a better adaptation to afterload elevations in this than in other species.
Correia-Pinto
Jorge
J
Serviço de Fisiologia, Faculdade de Medicina da Universidade do Porto, Porto.
Henriques-Coelho
Tiago
T
Oliveira
Sílvia Marta
SM
Leite-Moreira
Adelino
A
D000818:Animals; D003971:Diastole; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*