Original Article

Crystalloid Cardioplegia Versus Oxygenated Crystalloid Cardioplegia in the Isolated Rat Heart

Cardiac Research Laboratories, Killingbeck Hospital, York Road, Leeds, England

^* Direct communications to: S. Whittaker, Cardiac Research, Killingbeck Hospital, Leeds LS14 6UQ England.

Abstract

To determine if the protection afforded by a crystalloid cardioplegic solution could be enhanced by the addition of oxygen, 12 rat hearts were studied using an isolated perfused heart model, with a 2-hour ischemic arrest at 20°C.

Group 1 hearts (n = 6) received a crystalloid cardioplegic solution every 30 minutes of the arrest. Group 2 (n = 6) was treated identically except that the cardioplegic solution was oxygenated. Pre-arrest (control) and post-arrest coronary effluent enzyme levels, heart rate and coronary vascular resistance were determined. In addition time to spontaneous defibrillation was measured.

Control coronary effluent lactate dehydrogenase was elevated in group 2 (p<0.05). There was no significant difference in the other control parameters.

Post-arrest coronary effluent creatine kinase in group 1 and group 2 hearts was 640.67 ± 263.23 and 62.9 ± 43.83 (± SEM) (p<0.05 t-test). The post-arrest heart rate was 200.6 ± 13.8 and 245.5 ± 13.5 (p<0.05). One heart failed to spontaneously defibrillate and one had an irregular rhythm, both were in group 1. Time to spontaneous defibrillation was 58.4 ± 5.71 for group 1 and 44.67 ± 2.7 for group 2 (p<0.05). Post-arrest coronary effluent lactate dehydrogenase was 442.32 ± 180.74 and 100.07 ± 32.08 and showed no significant difference (p = 0.06).

This study demonstrates that at 20°C, markers of ischemic injury are significantly improved, leading us to conclude that the addition of oxygen to the cardioplegic solution may enhance its myocardial protective effect.