Rest and exercise hemodynamic and hormonal effects of nicorandil, a nicotinamide-nitrate vasodilator, were assessed in 9 patients with New York Heart Association class II or III congestive heart failure (CHF) and left ventricular ejection fraction less than or equal to 40%. Single oral doses of placebo and 40 and 60 mg of nicorandil were given in a double-blind, randomized trial. Hemodynamic measurements were assessed at rest, up to 8 hours after dose and at peak exercise performed on an upright cycloergometer 1 hour after the dose. Forearm blood flow and venous capacitance were measured by plethysmography 45 minutes after dose. Plasma noradrenaline and plasma renin activity were assessed 1 hour and 2 hours after dose, respectively. Data were analyzed by analysis of variance. Peak effects were observed between 30 and 60 minutes after dose. Mean blood pressure decreased from 86 +/- 7 mm Hg after placebo to 78 +/- 7 mm Hg after 40 mg (p less than 0.05) and to 78 +/- 7 mm Hg after 60 mg (p less than 0.05) of nicorandil. Mean pulmonary artery pressure decreased from 24 +/- 11 to 15 +/- 17 mm Hg (p less than 0.05) and to 17 +/- 7 mm Hg (p less than 0.05) and mean pulmonary wedge pressure decreased from 15 +/- 8 to 9 +/- 4 mm Hg (p less than 0.05) and to 10 +/- 5 mm Hg (p less than 0.05). The changes were significant up to 6 to 8 hours after both doses.(ABSTRACT TRUNCATED AT 250 WORDS)