"Optimal" left ventricular filling pressure during nitroprusside infusion for congestive heart failure

On the basis of preload manipulations, an optimal left ventricular filling pressure of 14 to 18 mm Hg has been suggested for patients with left ventricular failure. Since afterload reduction results in increased cardiac output in heart failure, the hypothesis that left ventricular filling pressure could be reduced to normal by nitroprusside without compromising cardiac output was tested in 15 patients with acutely decompensated chronic congestive heart failure. Cardiac index was measured after each 4 to 6 mm Hg decrease in pulmonary wedge pressure until the latter fell below 14 mm Hg (Group I, nine patients) or until systolic arterial pressure reached 90 mm Hg during nitroprusside infusion (Group II, six patients). In Group I, pulmonary wedge pressure fell in significant decrements (p < 0.001) from 28 ± 4 (SD) to 24 ± 3, 17 ± 2, and 11 ± 2 mm Hg during nitroprusside infusion. Cardiac index rose in significant increments (p < 0.05) from 2.5 ± 0.8 to 2.8 ± 0.6, 3.3 ± 0.7, and 3.7 ± 1.1 liter/minute/m² with each increase in nitroprusside dosage. Mean arterial pressure fell during nitroprusside infusion from 97 ± 16 to 70 ± 8 mm Hg (p < 0.001) without any change in heart rate. In Group II, directionally identical changes in hemodynamics were observed during nitroprusside infusion; the highest cardiac index occurred at the lowest pulmonary wedge pressure attained, and no side effects were observed despite the fall in systolic arterial pressure to 90 mm Hg. Thus, reduction of left ventricular filling pressure to within the normal range by nitroprusside infusion in patients with chronic left ventricular failure can raise cardiac output beyond levels observed at left ventricular filling pressures of 14 to 18 mm Hg. Normalization of filling pressure may improve subendocardial coronary perfusion, and invasive monitoring of filling pressure during nitroprusside infusion may not be routinely required.