To compare the hemodynamic effect of volume loading with that of dobutamine infusion in severe ischemic right ventricular (RV) dysfunction, 11 patients with inferior and RV infarction complicated by low cardiac output syndrome and important hemodynamic derangement (systolic blood pressure < 100 mm Hg, cardiac index < 2.0 liters/min/m2, right atrial pressure > 10 mm Hg) were prospectively studied within 48 hours of symptom onset. After right heart catheterization, volume loading (mean 400 ml saline solution) and dobutamine infusion (5 and 10 micrograms/kg/min over 10 minutes) were performed according to a randomized, crossover design. Volume loading resulted in increased right atrial (from 15 +/- 2 to 19 +/- 3 mm Hg, p < 0.05) and pulmonary capillary (from 15 +/- 2 to 19 +/- 3 mm Hg, p < 0.05) pressures, without increasing cardiac index, heart rate, aortic pressure, or right and left ventricular stroke work index. Dobutamine (5 micrograms/kg/min) increased cardiac index (from 1.5 +/- 0.3 to 1.9 +/- 0.5 liters/min/m2, p < 0.05), incrementing both heart rate (from 61 +/- 12 to 70 +/- 13 beats/min, p < 0.05) and stroke volume index (from 25 +/- 6 to 27 +/- 5 ml/beat/m2, p < 0.05), as well as right (from 1.4 +/- 1.6 to 2.3 +/- 2.2 g.m/m2, p < 0.05) and left (from 21 +/- 7 to 27 +/- 10 g.m/m2, p < 0.05) stroke work indexes; right and left ventricular filling pressures did not decrease. Dobutamine (10 micrograms/kg/min) significantly improved myocardial performance.(ABSTRACT TRUNCATED AT 250 WORDS)