The use of off-pump coronary artery bypass graft surgery (OPCAB) has increased considerably in the past decade, however, it is unknown whether it is associated with better outcomes compared to on-pump coronary artery bypass graft (CABG) surgery.
A recently published paper featured in the journal, Circulation (Hannan EL, Wu C, Smith CR, et al. Off-pump versus on-pump coronary artery bypass graft surgery. Differences in short-term outcomes and in long-term mortality and need for subsequent revascularisation. Circulation. 2007;116:1145-1152), has concluded that one-month mortality and rates of perioperative complications are lower with OPCAB surgery than with traditional CABG performed with cardiopulmonary bypass (CPB) support. However, rates of freedom from revascularisation were less in the on-pump CABG patient group and overall three-year mortality outcomes were similar.
Dr Edward L Hannan, State University of New York, and colleagues, assessed the outcomes of 49,830 patients who underwent either OPCAB limited to isolated CABGs involving median sternotomy (13,889 patients) or on-pump CABG surgery (35,941 patients) between 2001 and 2004. The patients were followed-up via New York databases (New York Cardiac Surgery Reporting System database and the New York Percutaneous Coronary Interventions Reporting System database). Therefore, OPCAB accounted for 28% of the CABGs covered study (CPB=72%). For the analysis, the short- and long-term outcomes were compared after adjustment for patient risk factors and after patients were matched on the basis of significant predictors of type of CABG surgery.
Results
OPCAB had a significantly lower inpatient/ 30-day mortality rate (adjusted OR 0.81, 95% confidence interval [CI] 0.68 to 0.97). These patients also reported lower rates for two perioperative complications (stroke: adjusted OR 0.70, 95% CI 0.57 to 0.86; respiratory failure: adjusted OR 0.80, 95% CI 0.68 to 0.93), as well as a higher rate of unplanned operation in the same admission (adjusted OR 1.47, 95% CI 1.01 to 2.15).
In the matched samples, no difference existed in three-year mortality (hazard ratio 1.08, 95% CI 0.96 to 1.22), but OPCAB patients had higher rates of subsequent revascularisation (hazard ratio 1.55, 95% CI 1.33 to 1.80). The three-year OPCAB and on-pump survival rates for matched patients were 89.4% and 90.1%, respectively (P=0.20). For freedom from subsequent revascularisation, the respective rates were 89.9% and 93.6% (P<0.0001).
According to Hannan, the better short outcomes for OPCAB surgery are likely to be a result of the absence of CPB during surgery. He also commented that because OPCAB is more challenging, there is an inclination to revascularise more conservatively, thereby increasing the likelihood of performing incomplete revascularisations reducing the patient risk for short-term adverse events. Also, the higher rates of freedom from revascularisation in the OPCAB patient group are related to the viability of anastomoses performed on a beating heart.
The researchers also compared outcomes in pairs of OPCAB and on-pump-CABG patients matched (matched cases, n=23,530) according to age, gender, race, LVEF, history of MI, >1 prior open-heart surgery, haemodynamic status, ascending- aorta calcification, diabetes, renal failure, emergent CABG after diagnostic catheterisation, history of PCI, stent thrombosis as a risk factor, left main disease, and number of diseased coronary vessels. This allowed the researchers to establish predictors of good OPCAB outcomes, which could improve the selection of candidates for the procedure.
Conclusions
In addition, patient selection and operator experience are crucial factors in determining outcome. Given that OPCAB is the more difficult procedure, a surgeon might prefer to perform OPCAB on patients presenting particular criteria and perform CPB surgery on patients presenting different criteria, and this decision varies by surgeon. In conclusion, the researchers noted that OPCAB remains in its early stages of development with technological and procedural refinements to be made. However, they added that future studies/trials should concentrate on discrepancies in OPCAB outcomes among hospitals and in particularly among surgeons.
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