Sodium nitroprusside infused in 18 patients with intractable heart failure (nine with ischemic heart disease and nine with cardiomyopathy) produced a prompt reduction of left ventricular filling pressure (pulmonary wedge or left ventricular end-diastolic pressure) from an average of 32.2 to 17.2 mm Hg and a rise in cardiac output from an average of 2.98 to 5.2 liters per minute. Mean arterial pressure fell by 15 mm Hg, and heart rate was slightly but significantly slowed. Stroke volume and forward ejection fraction were nearly doubled. Responses were similar in ischemic heart disease and cardiomyopathy. A diuresis and natriuresis accompanied the infusion, and the clinical response was sustained in five patients in whom the drug was continued for 24 to 72 hours. These results suggest that intractable heart failure may be effectively treated by reduction in impedance to left ventricular ejection. (N Engl J Med 291:587–592, 1974), CONGESTIVE heart failure refractory to conventional therapy with digitalis and diuretics is a common clinical problem in patients with advanced cardiomyopathy or severe ischemic heart disease. Such patients often require frequent and prolonged hospitalizations during which rigid control of fluid intake and aggressive diuresis may produce modest relief of congestion but often at the expense of electrolyte imbalance and continued weakness indicative of a low cardiac output. Prolonged bed rest.