Myocardial catecholamines following cold cardioplegic arrest during open-heart surgery

Preservation of both right and left ventricular subendocardial and subepicardial muscle was assessed using quantitative polarization microscopy (birefringence measurements) with preservation of myocardial catecholamines measured by fluorescence microscopy in biopsies from 20 consecutive patients who underwent open heart surgery with cold cardioplegic arrest (St. Thomas' Solution). Six of the 7 patients with clinical complications were predicted from the birefringence results. One developed left ventricular deterioration during bypass, two patients right ventricular deterioration, one patient both left and right ventricular deterioration and two patients had poor left ventricular function before bypass. Birefringence measurements were thus reliable in predicting post-operative cardiac outcome. There were no significant changes during the bypass period in the catecholamine scores, even in those patients who had clinical complications. Fluorescence microscopy showed that the "free" myocardial nerve net and the pericoronary nerve plexuses retained their catecholamine stores equally well. This indicated that St. Thomas' cardioplegia preserves myocardial catecholamine stores, depletion of which would remove a potentially important compensatory mechanism in cardiac pump failure. There may however be a temporary blockade in the release of endogenous cardiac catecholamine (noradrenaline) stores from the adrenergic nerve terminals following cold cardioplegic arrest despite myocardial pump failure.