Conduction disturbances in coronary artery bypass surgery

Conduction disturbances are very common after coronary artery bypass grafting (18-45%). Long cross-clamp time, method of cardioplegia, depth of hypothermia, and patient age are some of the risk factors. We planned this study to ascertain the effect of crystalloid or tepid blood cardioplegia (CP) on conduction disturbances.

One hundred patients were randomly divided into two groups. The first group received tepid blood CP and the second received cold crystalloid CP. St. Thomas II CP was used as CCP and the same CP was mixed with blood with a ratio of 4:1 in the tepid CP group. In both groups as an initial bolus, a 10 to 15 ml/kg CP was infused with a pressure of 75 mmHg. Additionally, 400 ml of CP were given every 20 min during the cross clamping period in addition to infusion of 50-100 ml of CP after each distal anastomosis. Blood samples for CK, CK-MB, LDH and Troponin T measurements were obtained at induction, before bypass, after cross clamping, before de-clamping, after de-clamping and after bypass. Postoperative ECGs were analyzed by a cardiologist.

There were no deaths in both groups but the mean hospitalization was 8.4 +/- 1.7 days in group I, and 14.4 +/- 3.1 days in group II (P=0.004). Although there were significant rises in CK, CK-MB, LDH and Troponin T levels in both groups after CPB or de-clamping, the difference in increment between the two groups was not significant. Twelve patients in group II (24%) developed new fascicular blocks, four of these caused hemodynamic instability and needed inotropic treatment but only one was discharged with LAHB. Four patients in group I (8%) also developed new conduction disturbances within the first hour, but all completely resolved. Incidence of conduction disturbances was significantly increased in the crystalloid CP group (P=0.019).

There were no significant differences in cardiac enzyme measurements between cold crystalloid and tepid blood CP, but crystalloid CP caused more fascicular blocks. We conclude that myocardial protection was equal in both cardioplegia methods whereas conduction disturbances have been assumed to be caused by cold injury to the conduction tissues.