Myocardial energy metabolism and functional recovery in coronary bypass surgery: A comparative study between continuous retrograde warm and mild hypothermic blood cardioplegia

Myocardial preservation during coronary surgery with and without cardiopulmonary bypass

BACKGROUND

There is increased interest in coronary artery bypass grafting (CABG) without cardiopulmonary bypass (CPB), although the preservation of the myocardium under such circumstances has not been properly investigated. The aim of this randomized study was to compare the changes in myocardial metabolism during CABG with and without CPB.

METHODS

Myocardial energy metabolism and tissue injury during CABG was monitored in a series of 22 patients (11 with and 11 without CPB).

RESULTS

The maximum myocardial lactate production was significantly higher (p = 0.02) in the group operated with CPB (0.56 mmol/L) than without it (0.17 mmol/L). A similar phenomenon was seen in the transcardiac pH differences (0.085 and 0.034 with and without CPB, p = 0.007). The postoperative peak values of creatine kinase-MB mass (15.1 vs 6.3 microg/L) and troponin I (13.8 vs 5.2 microg/L) were significantly higher (p < 0.001 and p = 0.008) with than without CPB.

CONCLUSIONS

CABG on a beating heart is associated with better myocardial energy preservation and less myocardial damage compared with conventional CABG with CPB and intermittent antegrade mild hypothermic blood cardioplegia.

Myocardial metabolism and hemodynamics during coronary surgery without cardiopulmonary bypass

BACKGROUND

Although renewed interest has recently been shown in coronary artery bypass grafting without cardiopulmonary bypass, no reports are available on myocardial metabolism and hemodynamics during temporary coronary occlusion and rotation of the contracting heart.

METHODS

Changes in myocardial energy metabolism and hemodynamics were monitored in 12 patients undergoing elective coronary artery bypass grafting without cardiopulmonary bypass, and the postoperative efflux of creatine kinase-MB mass and troponin T were also determined.

RESULTS

There was a significant increase in myocardial production of ATP degradation products (p = 0.026) and lactate (p = 0.004) during the operation. Myocardial oxygen extraction decreased (p = 0.012) in correlation with use of the short-acting beta-blocker, esmolol (r = -0.71). Apart from a decrease in mean arterial blood pressure (p = 0.002), there were no significant hemodynamic changes during the operation. The overall postoperative troponin T and creatine kinase-MB mass changes remained nonsignificant during the first two postoperative days. One patient had a myocardial infarction, diagnosed by electrocardiography, on the second postoperative day, but otherwise there were no major complications.

CONCLUSIONS

Coronary artery bypass grafting without cardiopulmonary bypass seems to be well tolerated as only minor changes in myocardial energy metabolism and hemodynamics are observed during the operation.