Left ventricular diastolic function of remodeled myocardium in dogs with pacing-induced heart failure.
In patients with heart failure, decreased contractility resulting in high end-diastolic pressures and a restrictive pattern of left ventricular filling produces a decrease in early diastolic filling, suggesting a stiff ventricle. This study investigated the elastic properties of the myocardium and left ventricular chamber and the ability of the heart to utilize elastic recoil to facilitate filling during pacing-induced heart failure in the anesthetized dog. Elastic properties of the myocardium were determined by analyzing the myocardial stress-strain relation. Left ventricular chamber properties were determined by analyzing the pressure-volume relation using a logarithmic approach. Elastic recoil was characterized using a computer-controlled mitral valve occluder to prevent transmittral flow during diastole. We conclude that, during heart failure, the high end-diastolic pressures suggestive of a stiff ventricle are due not to stiffer myocardium but to a ventricle whose chamber compliance characteristics are changed due to geometric remodeling of the myocardium. The restrictive filling pattern is a result of the ventricle being forced to operate on the stiff portion of the diastolic pressure-volume relation to maintain cardiac output. Slowed relaxation and decreased contractility result in an inability of the heart to contract to an end-systolic volume below its diastolic equilibrium volume. Thus the left ventricle cannot utilize elastic recoil to facilitate filling during heart failure.
Solomon
S B
SB
Department of Cardiothoracic Surgery, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Nikolic
S D
SD
Glantz
S A
SA
Yellin
E L
EL
D000818:Animals; D003971:Diastole; D004285:Dogs; D004452:Echocardiography; D004548:Elasticity; D006321:Heart / Q000503:physiopathology*; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate; D006349:Heart Valve Diseases / Q000503:physiopathology; D006439:Hemodynamics; D008943:Mitral Valve; D009200:Myocardial Contraction