Impact of off-pump to on-pump conversion rate on post-operative results in patients undergoing off-pump coronary artery bypass

Abstract

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was: In patients undergoing off-pump coronary artery bypass (OPCAB) surgery, does the off-pump to on-pump conversion rate have an impact on post-operative results? Altogether more than 420 papers were found using the reported search, of which 14 randomized controlled trials (RCTs) represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated and ordered according to the sample size. In the 14 RCTs reviewed, the off-pump to on-pump conversion rate incidence ranged from 0 to 13.3%. The most frequent causes of conversion were haemodynamic instability and intramyocardial-coronary target. A low conversion rate (<2%) was reported by five studies. Three of them did not show any difference in terms of mortality between the OPCAB and on-pump groups, one showed better survival of the OPCAB group at 5 years, and one reported better early survival of the OPCAB group. Three of these trials describe a high OPCAB experience and reported that patients undergoing OPCAB had a shorter post-operative stay and lower morbidity compared with patients undergoing on-pump coronary artery bypass grafting. Five RCTs showed a high conversion rate (>9%), and among them, one reported lower morbidity of the OPCAB patients, three were not able to show any benefit in terms of morbidity of the OPCAB, and one reported worse survival and patency graft rate of the OPCAB group. Four RCTs reported conversion rates ranging from 3.7 to 7.0%, describing a wide spectrum of results. We conclude that RCTs with a high off-pump to on-pump conversion rate were often associated with a lower experience in OPCAB of the surgeons participating in the trials. These studies were also mostly unable to show any benefit in terms of mortality or morbidity of OPCAB over the on-pump strategy. On the contrary, a low conversion rate is mostly reported by RCTs with a high structured experience in OPCAB. These trials were mostly able to show a benefit, in terms of morbidity and survival, of the OPCAB over the on-pump strategy.