On-pump Versus Off-Pump Coronary Artery Bypass Grafting: A Comparison Study

Background and objectivesConventional coronary artery bypass grafting (CCABG) must depend on cardiopulmonary bypass (CPB) and cardiac arrest, and it has been classic operative method in recent 30 years. The systemic inflammatory reaction caused by CPB and the myocardial ischemic- reperfusion would lead to myocardial injury, and the myocardial injury might be related to postoperative complications, such as, arrhythmia, low cardiac output syndrome(LCOS), etc. As a result, people improved CCABG and made myocardial protection better. In recent years, continuous warm blood cardioplegia applied in CCABG reduced the myocardial injury, and made better myocardial protection effects.Thanks to the improvement of modern surgical instruments, off-pump coronary artery bypass grafting (OPCAB) had become popular and been widely accepted in recent years. Because of avoiding CPB and the myocardial ischemic- reperfusion, OPCAB had less postoperative complications than CCABG and was welcomed by many doctors. However, myocardial injury existed in OPCAB, too, and some postoperative complications appeared in patients accepted OPCAB. Therefore, we investigate the mechanism of myocardial injury of OPCAB, and take corresponding myocardial protection measure.In recent years, the myocardial injury had been compared between OPCAB and CCABG (cold crystalloid cardioplegia was used for myocardial protection). However, the comparison between OPCAB and CCABG (continuous warm blood cardioplegia was applied in CCABG) has not been reported. The present research aim to evaluate the myocardial protective effect of OPCAB and CCABG (continuous warm blood cardiopegia is applied for myocardial protection) by monitoring serum level of cardiac tropnin I (cTnI)/ CK-MB, which are the more sensitive and specific marker of myocardial injury, and by observing recent clinical outcomes. Methods22 patients with coronary heart disease received CABG for the first time were randomly divided into two groups: group CCABG (8 cases) and group OPCAB (14 cases). The continuous warm blood cardioplegia was used for myocardial protection in the group CCABG① Clinical outcomes were observed during and after operation, including vasoactive drugs applications, the length of stay in ICU(h), the length of ventilation(h), the length of stay in hospital and postoperative complications. ② Serum CK-MB and cTnI: 10 ml venous blood samples were taken before operation and after operation 8/ 24/ 72 hours, then the blood samples were separated by 1500 g centrifugal force for 15 min. 4 milliliter serum were conserved in -20℃ refrigerator for measuring together in the future. cTnI were measured by double with filling ELISA method and CK-MB were measured by immunosuppressive method. Results1. General patient dataThe two groups were well matched for most preoperative situation, such as, sex/ age/ unstable angina/ cardiac function (EF/ FS)/ number of grafts, etc. No significant differences were found between two groups (p>0.05).2. Changes in the serum level of CK-MBThere were no significant differences in CK-MB level between two groups before operation. But there were significant differences between two groups afteroperation 8/ 24/ 72hours, and the CK-MB level of group CCABG was higher than that of group OPCAB. The CK-MB level of two groups after operation was higher than that before operation.3. Changes in the serum level of cTnIThe mean serum level of cTnI in the group CCABG was significant higher than that in group OPCAB 8/ 24/ 72hours after operation(8.85±2.24 vs 4.00±1.60, 6.54±1.51 vs 2.63±0.80, 3.82+1.15 vs 1.96±0.72, p<0.01), but they were similar between two groups before operation (0.52±0.21 vs 0.41±0.27, p>0.05). In addition, cTnI still had a increase course in two groups. The serum level of cTnI 8/ 24/ 72hours after operation was significant higher than that before operation,4. Clinical outcomesThe dosage of vasoactive drug in group CCABG were significantly higher than that in group OPCAB (p<0.05). The mean time of mechanical ventilation was (11.75±3.64) hours in group CCABG and (12.39±6.39) hours in group OPCAB (p>0.05), and the mean period of stay in ICU was (62.07±13.67) hours in group OPCAB and (62.50±8.85) hours in group CCABG (p>0.05). Postoperative arrhythmia was 6 cases in group CCABG and 3 cases in group OPCAB (p<0.05). No significant differences were found about the postoperative myocardial infarction, angina and mortality between group CCABG and group OPCAB (3 months after operation). Conclusions1. Both OPCAB and CCABG (continuous warm blood cardioplegia is applied for myocardial protection) result in myocardial injury, but comparing with CCABG, OPCAB may create less perioperative myocardial injury.2. Comparing with CCABG (continuous warm blood cardioplegia is applied for myocardial protection), OPCAB has a low arrhythmia rate, and cardiac function in OPACB resumes earlier than that in CCABG. OPCAB has a better perioperative clinical outcome.