Effect of ouabain on O2 supply/demand in normal and ischemic heart.

The effect of ouabain (15 microgram/kg) on subepicardial and sub-endocardial blood flow, oxygenation, and small-vessel blood content was studied in anesthetized open chest rabbits with hearts subjected to acute coronary occlusion. 10 minutes after occlusion, blood flow was 48% lower than in the control region. Ouabain lowered blood flow significantly in the non-occluded region and insignificantly in the occluded area. Small-vessel blood content, a measure of open capillary density, was unaffected by occlusion or ouabain. After occlusion, relative tissue PO2 fell to a greater extent in the affected subendocardium than the affected subepicardium. Ouabain, therefore, appears to be well tolerated in both the control and ischemic regions in terms of oxygen supply and consumption.