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

Background-The hemodynamic mechanism for the improvement in left ventricle (LV) end-diastolic pressure in cardiomyopathy patients treated with β-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. Methods and Results-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, τ(ln), shortened (P=0.03). In a similar fashion, the LV chamber stiffness constant, κ, decreased (P=0.02), LV volume elastance improved (P=0.04), and the myocardial stiffness constant, κ(e), decreased (P=0.02). A multiple regression analysis revealed that the decrease in LV end-diastolic pressure was indicative of significant improvements in τ(ln) and κ(e) with the relationship: LV end- diastolic pressure=-4.73+0.27 τ(ln)+0.54 κ(e) (r=0.81, P<0.0001). These LV diastolic relaxation properties did not change or worsened in the control cardiomyopathy patients. Conclusions-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.