Effects of digoxin, placebo and ibopamine on exercise tolerance and cardiac rhythm of patients with chronic post-infarct left ventricular failure.

This study compares the effects of digoxin, placebo and ibopamine (SB-7505), the orally active 3,4-diisobutyryl ester of N-methyl-dopamine, on exercise tolerance and cardiac rhythm of 14 patients whose left ventricular heart failure (end-diastolic pressure, 26.3 +/- 5.9 mmHg; ejection fraction, 0.42 +/- 0.10%) depended on a previous myocardial infarction. Patients were admitted to the study while on chronic oral digoxin treatment (serum levels between 1.1 and 1.9 ng/ml). Placebo instead of digoxin was given for the following month. Thereafter ibopamine 50 mg t.i.d. for one month was given. A sequence of one-month treatments with digoxin, placebo and ibopamine was repeated, then ibopamine was administered continuously for the next two months. The concurrent treatment (diuretics in all patients, nitroderivates in twelve, calcium antagonists in two) remained unchanged during the observation period. Symptoms-limited exercise tests and 24-h Holter recordings were obtained at admission, at the end of each one-month treatment and at the end of the observation period. Two patients developed unstable angina without increase of serum creatine phosphokinase while on ibopamine and were withdrawn. Out of the 12 patients that concluded the trial, one required supplementary doses of diuretic at the end of the second period on placebo. The results obtained during the trial suggest that: a) therapeutic plasma levels of digoxin have no deleterious effect on cardiac rhythm nor significantly increase exercise tolerance as compared with placebo; b) diuretics and nitrates appear to sustain the clinical stability of these patients as a group.(ABSTRACT TRUNCATED AT 250 WORDS)