Abstract： Background Patients presenting with severe left ventricular dysfunction (SLVD) undergoing conventional coronary artery bypass grafting (CCABG) are at an increased risk of perioperative mortality and morbidity.The aim of this study was to assess the risk factors responsible for mortality and morbidity among patients with SLVD by comparing CCABG and off-pump coronary artery bypass surgery (OPCAB).Methods We retrospectively evaluated 186 consecutive patients with SLVD who underwent coronary artery bypass grafting (CABG),including 102 by CCABG and 84 by OPCAB.Registry database,medical notes,and charts were studied for preoperative and postoperative data of the patients.Different variables and risk factors (preoperative,intraoperative,and postoperative) were evaluated and compared.The morbidity and mortality outcomes were compared in the two groups.The follow-up results and quality of life were assessed after surgery.Results The two groups had similar percentage of patients with preoperative high-risk profiles and no significant differences were found between groups in baseline variables such as age or comorbidities.There was a significant difference in the number of grafts used between the two groups.CCABG patients received (3.6±0.5) grafts per patient,while OPCAB patients had (2.7±0.6) grafts (P <0.05).Completeness of revascularization was also significantly different between the two groups (CCABG 91.1% vs OPCAB 73.8%,P <0.05).The hospital mortality was similar in the two groups (4.8% in OPCAB vs 5.9% in CCABG).The risk-adjusted mortality,according to the calculated propensity score,did not reach statistical significance in the two groups.In this study,OPCAB seemed to have a beneficial effect on reducing reoperation for bleeding,blood transfusion requirement,and the length of stay at ICU.But the incidence of perioperative myocardial infarction was more common in the off-pump group (P <0.05).The degree of improvement in angina and quality of life did not differ significantly between the two groups.Conclusions Using cardiopulmonary bypass is not an independent predictor of mortality and morbidity in patients with SLVD.Isolated CABG can be safely performed in SLVD patients with acceptable postoperative morbidity and mortality in addition to encouraging home discharge rates and higher quality of life.Therefore,CCABG remains a viable option in selected patients with SLVD.