The central and renal hemodynamic effects and the hormonal response to single doses of 60 mg and 90 mg of diltiazem were evaluated in 10 patients with severe chronic left ventricular (LV) systolic dysfunction (ejection fraction 0.22 +/- 0.08). Diltiazem administration resulted in only mild and mostly statistically insignificant changes. After 60 mg, only heart rate (from 86 +/- 10 beats/min at baseline to 79 +/- 14 beats/min at 4 hours) and pulmonary vascular resistance (from 231 +/- 108 to 165 +/- 74 dynes s cm-5 at 4 hours) changed significantly. Administration of 90 mg of diltiazem resulted in no significant change in any of the measured or calculated central hemodynamic variables. Individual data, however, revealed an increase stroke volume index in 3 patients but a decrease in 1 patient and a persistent increase in mean pulmonary artery wedge pressure in another patient. These hemodynamic changes were not associated with symptomatic deterioration in any of the patients. Both renal blood flow and glomerular filtration rate were impaired at baseline on both days and did not show a significant change 1, 2 and 4 hours after diltiazem administration. Similarly, no significant change was noted after either diltiazem dose in plasma catecholamine levels and renin concentration. In conclusion, administration of 60 to 90 mg of diltiazem in patients with severe chronic LV systolic dysfunction results in only mild and mostly insignificant acute effects on central and renal hemodynamics, plasma hormonal levels and patient clinical status.