Influence of intraoperative conversion from off-pump to on-pump coronary artery bypass grafting on costs and quality of life: a cost-effectiveness analysis

OBJECTIVE: Off-pump coronary artery bypass (OPCAB) surgery has become a widely accepted alternative to standard coronary artery bypass graft (CABG) surgery using cardiopulmonary bypass; however, the influence of intraoperative conversion from OPCAB to standard CABG on costs and quality of life is unclear. The objective of this study was to determine whether intraoperative conversion affects costs and quality of life. DESIGN: A decision-analysis model and Monte Carlo simulation. SETTING: The US healthcare system over a maximum 10-year lifetime horizon. PARTICIPANTS: A hypothetical cohort of 60-year-old male patients undergoing elective OPCAB surgery or standard CABG surgery. INTERVENTIONS: Each patient was entered into the decision tree with varying transition probabilities. Outcome measures included quality-adjusted life-years (QALYs) and costs in US dollars. MEASUREMENTS AND MAIN RESULTS: In base-case analysis, OPCAB surgery led to a discounted lifetime cost of $91,282 and 7.64 discounted QALYs, and standard CABG surgery led to $91,685 and 7.52 QALYs. Patients who required conversion from off-pump to on-pump surgery incurred a cost of $103,909 and gained 6.63 QALYs. OPCAB is dominant (less costly and more effective) if the conversion rate is below 8.5%, whereas costs increase exponentially if the probability of conversion exceeds 15%. Sixty-one percent of the Monte Carlo simulations favored cost-effectiveness of the OPCAB strategy. CONCLUSION: In low-risk patients, OPCAB surgery, in comparison to standard CABG surgery, would increase QALYs by reducing complications related to cardiopulmonary bypass, but it would result in lifetime costs similar to those of standard CABG surgery. The benefit of OPCAB may be offset by the risk of intraoperative conversion.