Functional importance of myocardial relaxation in patients with congestive heart failure.

The factors that determine left ventricular end-diastolic pressure (LVEDP) are not completely understood. While many investigators measure relaxation in patients with heart failure, its relative functional importance remains unclear. The authors studied 22 patients with cardiomyopathy before and after 3 months of therapy with metoprolol or placebo. At catheterization, LVEDP, isovolumic relaxation rates not normalized for load (tau), the slope of the tau-end-systolic pressure relation (R), the constant of chamber stiffness (k), left ventricular ejection fraction, stroke volume, and coronary sinus norepinephrine levels were measured using micromanometer pressure measurements and digital ventriculography. The myocardial respiratory quotient was measured using blood gas analysis of the coronary sinus and left ventricular blood. Univariate analysis demonstrated that changes in LVEDP correlated with changes in relaxation rates, R, and the myocardial respiratory quotient. However, multivariate stepwise regression analysis demonstrated that only changes in R independently correlated with changes in LVEDP. These data suggest that relaxation may play some role in the determination of LVEDP in patients with heart failure. Changes in glycolytic activity may also play a role in the determination of LVEDP in patients with congestive heart failure.