Short-term biventricular circulatory support in the regionally stunned pig myocardium

Mechanical circulatory support is only meaningful when reversible myocardial damage exists. Prompt biventricular assistance during reperfusion for six hours was tried in the regionally sublethally injured pig myocardium which has perspective for recovery. Postmortem tissue was examined with a quickly performed histochemical technique for tissue viability. Animals underwent five coronary occlusions (5 min occlusion/10 min reperfusion). Postischemic systolic wall thickening, observed by direct echocardiography, fell about 50% (p < 0.05 vs base line) before treatment which paralleled cardiac inosine and lactate efflux. Biventricular unloading (n = 5) resulted in contractile recovery to 94 +/- 19% (p < 0.05 vs stunning), untreated pigs remained depressed (33 +/- 12%, n = 5). During circulatory support the arterial lactate levels rose three-fold, concomitant with a drop in pH of 0.2 units (p < 0.05). Post-mortem histochemistry showed scattered areas with decreased activities of cytoplasmic lactate dehydrogenase and mitochondrial beta-hydroxybutyrate dehydrogenase, irrespective of treatment. Transmission electron microscopy revealed irreversible damage to mitochondria in depleted areas in contrast to areas where enzyme activity was present. We conclude that prompt volume unloading during reperfusion accelerated contractile recovery of sublethally postischemic myocardium.