Off-pump versus on-pump coronary artery bypass grafting: A systematic review and meta-analysis of propensity score analyses

Aims: After numerous observational studies (OS) and randomized studies (RS), neither off- nor on-pump revascularization comes out superior. Patient selection and small sample size limit the compilation of clinically relevant outcomes in RS; lack of randomization limits OS. Propensity score analyses (PSA) are expected to improve on at least some of these problems. Methods: PSA on off- vs. on-pump surgery were identified from eight bibliographic data bases, citation tracking, and a free web search. Two independent reviewers abstracted data on eleven binary short-term outcomes. We used the odds ratio (OR) to describe the treatment effect. To combine ORs from different studies, the random effects inverse-variance method was applied. Results: 35 of 58 initially retrieved PSA were included, accounting for a total of 123,137 patients. The estimated odds ratio was <1 for all outcomes in favour of off-pump surgery. This was significant for mortality, stroke, renal failure, RBC transfusion (p<0.0001), wound infection (p<0.001), prolonged ventilation (p<0.01), inotropic (p=0.02) and IABP support (p=0.05). The odds ratios for myocardial infarction and atrial fibrillation remained nonsignificant. Conclusions: Like OS, but unlike RS, PSA find significant advantages for relevant outcomes with off-pump surgery. Study populations need to be compared to clarify if different results of PSA and RS are related to patient selection (limited external validity).