Influence of Coronary Artery Obstruction on Cardiac Prostaglandin Metabolism during Experimental Cardioplegic Arrest

Summary

In order to test the influence of coronary artery obstruction on cardiac prostaglandin metabolism during surgically induced cardioplegia (CP), we have measured transcardiac venoarterial gradients of prostacyclin and thromboxane A₂ (TXA A₂) during experimental canine cardiopulmonary bypass. Cardiac arrest was induced by infusion of 500 ml of hypothermic (8°C), hyperkalemic (25 meq) crystalloid CP solution into the aortic root with (group I) and without (group II) occlusion of the left anterior descending artery (LAD). After 30 minutes of cardioplegic arrest the LAD occlusion in group I was released and a second set of CP infusion was applied in both groups. Transcardiac gradients were obtained 5 seconds after onset of the first and second CP washouts. Significant prostacyclin and TXA A₂ gradients were observed at both times. Prostacyclin gradients did not differ between group I and group II. In contrast, TXA A₂ gradients were significantly higher during the second CP washout in group I as compared to the unoccluded group (group I 918 + 221, group II 244 ± 144 pg/ml, p < 0.05). The results of our study suggest that cardiac TXA A₂ metabolism during cardioplegic arrest is increased distal to a coronary artery obstruction. Cardiac TXA A₂ production might contribute to the increased ischemic myocardial injury observed in this setting.

Key words

Prostaglandins - Prostacyclin - Thromboxane A₂ - Cardioplegic arrest - Cardiopulmonary bypass - Coronary artery obstruction