Effects of beta-adrenergic blocking therapy on left ventricular diastolic relaxation properties in patients with dilated cardiomyopathy.

Abstract

The hemodynamic mechanism for the improvement in left ventricle (LV) end-diastolic pressure in cardiomyopathy patients treated with beta-adrenergic blocking agents is controversial. We hypothesized that the salutary effect of this kind of therapy on LV end-diastolic pressure would be indicative of an improvement in late, passive diastolic relaxation properties. We studied 14 cardiomyopathy patients in normal sinus rhythm with no arteriographic evidence of coronary artery disease and an LV ejection fraction of </=40% by radionuclide angiography both before and after 6 months of metoprolol therapy with simultaneous micromanometry and biplane cineventriculography. Four comparable patients who were not treated with metoprolol were studied in a similar fashion and served as control subjects. In those receiving metoprolol, LV end-diastolic pressure decreased (P=0.001). The isovolumic relaxation index, tau(ln), shortened (P=0.03). In a similar fashion, the LV chamber stiffness constant, kappa, decreased (P=0.02), LV volume elastance improved (P=0.04), and the myocardial stiffness constant, kappa(e), decreased (P=0.02). A multiple regression analysis revealed that the decrease in LV end-diastolic pressure was indicative of significant improvements in tau(ln) and kappa(e) with the relationship: LV end-diastolic pressure=-4.73+0.27 tau(ln)+0.54 kappa(e) (r=0.81, P<0.0001). These LV diastolic relaxation properties did not change or worsened in the control cardiomyopathy patients. We conclude that the decrease in LV end-diastolic pressure in cardiomyopathy patients treated with metoprolol is an indicator of improvement in LV diastolic properties resulting from more complete myocardial relaxation.