The acute and chronic effects of the dihydropyridine calcium antagonist nisoldipine were studied in patients with chronic heart failure (LV EF < .35; peak VO2 < 25 ml/kg/min) caused by idiopathic or postinfarction cardiomyopathy. The study group initially consisted of 16 patients; two patients were excluded from the acute study due to side effects of the drug and two more patients were excluded during the chronic part of the study because of excessive tachycardia or worsening heart failure, respectively; therefore, the final study group consisted of 12 patients. Each patient was evaluated at rest, in the supine and sitting positions, and during maximal bicycle exercise, before and after acute and chronic (2-3 months) oral nisoldipine therapy (20 mg bid). Plasma levels of renin activity, aldosterone, norepinephrine, and epinephrine were measured before and 1 hour after nisoldipine in 10 patients. Concomitant therapy with digitalis and diuretics was kept constant throughout the study. At rest, in the supine position, nisoldipine (20 mg orally) induced an acute increase of cardiac index from 2.87 +/- 0.52 to 3.93 +/- 1.52 l/min/m2, with a reduction of mean arterial pressure from 97 +/- 7 to 85 +/- 9 mmHg and systemic vascular resistance from 1417 +/- 201 to 968 +/- 257 dynes sec/sec cm5 without significant changes of right atrial and pulmonary pressures. Hemodynamic effects peaked 1 hour after its administration and persisted for 6 hours. Similar changes were observed in the resting sitting position.(ABSTRACT TRUNCATED AT 250 WORDS)