Intermittent anterograde normothermic blood cardioplegia: experimental study in rabbits.

BACKGROUND

We investigated the degree of myocardial protection provided by intermittent anterograde normothermic blood cardioplegia infusion for 60 minutes at 37 degrees C in normal rabbit hearts.

METHODS

Thirty-two New Zealand rabbits were studied and divided into two groups: experimental group and control group. In the experimental group, normothermic blood cardioplegia was infused into the aortic root every 20 minutes over a one-hour period using a two-minute infusion dose. This amounted to an ischemic (unperfused) time of 52 minutes (or 86.6% of the total time). The biochemical investigation was carried out in two phases; Phase I: metabolic study after ischemia with no reperfusion and Phase II: metabolic and functional study after reperfusion. Reperfusion was carried out using a parabiotic perfusion system. Myocardial glycogen and mitochondrial respiration in the ventricular myocardium were established immediately after the end of intermittent cardioplegic solution infusion (Phase I) and after blood reperfusion (Phase II), when left ventricular function (dP/dt max) was also evaluated.

RESULTS

At the end of Phase I, there was a significant decrease in myocardial glycogen levels to 58% compared with the control group. In Phase II, the differences in myocardial glycogen between the experimental and the control group were not significant. Mitochondrial respiration analysis did not show significant differences between the experimental and control groups, either in Phase I or II. In Phase I, dP/dtmax values were 903.39 +/- 113.46 mmHg/sec and 1,043 +/- 256.94 mmHg/sec for the experimental and control group, respectively. These differences were not statistically significant.

CONCLUSIONS

Intermittent anterograde blood cardioplegia infusion every 20 minutes for 60 minutes at 37 degrees C was an effective myocardial protection method in normal rabbit hearts.