Is it Worth Performing off--‐Pump Coronary Bypass Surgery on High Risk patients? EuroSCORE Adjusted Mortality according to the revascularization Technique

Background: Even though OPCAB (off--‐pump coronary artery bypass) surgery has proved to reduce the incidence of postoperative adverse events, such as stroke or need for blood transfusion, a significant reduction in global mortality hasn’t been observed yet.
Methods: We analysed all patients who underwent CABG (coronary artery bypass graft) surgery in our Department since 2010. 411 patients were included in the study; on 301 of them surgery was performed under cardiopulmonary bypass(CPB), while 110 of them were done OPCAB. Preoperative mortality estimation was done with logistic EuroSCORE I. We created different stratified groups according to the estimated preoperative risk, analyzing the association between the postoperative observed mortality and the estimated one, depending on the revascularization technique (CBP vs OPCAB).
Results: Preoperative estimated risk was significantly higher in the OPCAB group (Logistic EuroSCORE I: 8,63% vs 5,93%; p=0,038). Nevertheless, despite this, the observed mortality was lower (2,73% vs 6,98%), although this difference was not significant. Mortality was similar in low risk patients, but in those with an EuroSCORE higher than 3%, a significant difference was observed (mortality in OPCAB: 4,41%, vs 12,57% in CPB; Unilateral exact Fisher test: p = 0,045). This difference was notoriously higher as the preoperative estimated risk increased, therefore, OPCAB surgery proved to be more beneficial in this group of patients. Risk--‐adjusted mortality rate (RAMR) was calculated, observing that RAMR in CPB patients was 1,17, while in the OPCAB group was 0,31 (the observed mortality was one third of the estimated one).
Conclusion: EuroSCORE is an excellent tool for mortality prediction in coronary revascularization surgery, although it overestimates mortality in high risk patients undergoing OPCAB surgery. Off--‐pump surgery reduces mortality in high risk patients, with an increasing difference between the observed mortality and estimated one in patients with a logistic EuroSCORE I higher than 3%.