DOSE-RESPONSE OF CHRONIC BETA-BLOCKER TREATMENT IN HEART-FAILURE FROMEITHER IDIOPATHIC DILATED OR ISCHEMIC CARDIOMYOPATHY

Background Small-scale clinical investigations have demonstrated that single doses of beta-blocking agents can improve left ventricular func tion in heart failure from idiopathic dilated cardiomyopathy (IDC). Th e purpose of this multicenter clinical trial was to determine the dose -effect characteristics of beta-blockade in a heart failure population that includes ischemic dilated cardiomyopathy (ISCD). Methods and Res ults Bucindolol is a nonselective beta-blocking agent with mild vasodi latory properties. One hundred forty-one subjects with class II or III heart failure, left ventricular ejection fraction (LVEF) less than or equal to 0.40, and background therapy of angiotensin-converting enzym e inhibitors, digoxin, and diuretics were given an initial challenge d ose of bucindolol 12.5 mg. One hundred thirty-nine subjects (99 with I DC, 40 with ISCDC) tolerated challenge and were randomized to treatmen t with placebo or bucindolol 12.5 mg/d (low dose), 50 mg/d (medium dos e), or 200 mg/d (high dose). At the end of 12 weeks, left ventricular function and other parameters were measured and compared with baseline values. There was a dose-related improvement in left ventricular func tion in bucindolol-treated subjects. In the high-dose bucindolol group , radionuclide-measured LVEF improved by 7.8 EF units (%) compared wit h 1.8 units in the placebo group (P<.05), and compared with the placeb o group, a greater percentage of subjects had an increase in LVEF by g reater than or equal to 5 units. In contrast, all three bucindolol dos es prevented deterioration of myocardial function as defined by an LVE F decline of greater than or equal to 5 units. Conclusions In heart fa ilure from systolic dysfunction, beta-blockade with bucindolol produce s a dose-related improvement in and prevents deterioration of left ven tricular function.