Effects of Ouabain on the Left Ventricular Response to Exercise in Patients with Angina Pectoris

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Abstract
The response of the left ventricle to a level of supine bicycle exercise that induced angina, and the effects of ouabain (0.01 mg/kg) on this response were evaluated in 14 patients with coronary arterial disease. Before administration of ouabain, exercise was associated with depressed pumping performance of the left ventricle in four patients: stroke work fell with exercise while left ventricular end-diastolic pressure (LVEDP) increased. In five patients left ventricular (LV) performance was not frankly depressed, but nevertheless was abnormal: stroke work increased, but was accompanied by an inordinately large rise in LVEDP. In the remaining five patients LV function was essentially normal. Ouabain improved LV performance at rest in only a minority of patients, but during the stress of exercise, LV hemodynamics were improved by ouabain in 12 of the 14 patients. Five patients, however, continued to show either depressed or abnormal function with exercise after they were given ouabain. As judged by the relationship of LVEDP to LV peak dp/dt, left ventricular contractility was increased by ouabain in most patients both at rest and during exercise. Despite its beneficial effects on left ventricular performance, ouabain did not consistently alter either exercise tolerance or the LV tension-time index and pressure-rate product at which angina occurred.