Predictors and Causes of Intraoperative Conversion From Off-Pump to On-Pump Coronary Artery Bypass: A Retrospective Study

Objective: This study evaluated the incidence, causes, and predictors of intraoperative conversion from off-pump coronary artery bypass grafting (OPCAB) to on-pump coronary artery bypass grafting (ONCAB), identifying risk factors to improve surgical planning.

Methods: This retrospective case-control study included patients who underwent OPCAB at the Peshawar Institute of Cardiology, Peshawar, Pakistan, between December 8, 2021, and December 7, 2023. Among 714 patients, 27 (3.78%) required conversion to ONCAB. For comparison, 108 (15.1%) controls were randomly selected from those who completed OPCAB successfully. Preoperative and intraoperative data were analyzed, and logistic regression identified predictors of conversion.

Results: The most frequent cause of conversion was hemodynamic instability, which occurred in 18 (66.67%) cases. Persistent hypotension and ST-segment changes lasting approximately 10-20 minutes were primary indicators before conversion, highlighting the need for close intraoperative monitoring. Left main coronary artery stenosis of 50%-70% emerged as the only independent predictor of conversion (odds ratio (OR) 7.60, 95% CI: 2.91-19.83, p < 0.001). This study emphasizes the importance of robust patient selection criteria, especially for cases with borderline coronary anatomy.

Conclusion: Hemodynamic instability and moderate left main coronary artery stenosis significantly contribute to OPCAB-to-ONCAB conversion. Enhanced preoperative imaging and hemodynamic management protocols can potentially reduce conversion rates, improving surgical outcomes.