MedWire News: Off-pump coronary artery bypass grafting (OPCAB) is associated with lower operative mortality than coronary artery bypass grafting (CABG) on cardiopulmonary bypass (CPB) in the highest risk patients, concludes a study published in the Annals of Thoracic Surgery.

In an effort to avoid morbidity and mortality that may be attributable to aortic manipulation, global myocardial ischemia, and systemic inflammatory response associated with CPB, some surgeons have embraced OPCAB.

Yet, to date, the criteria regarding selection for OPCAB have been highly variable. In this study, John Puskas (Rollins School of Public Health, Emory University, Atlanta, Georgia, USA) and co-workers analyzed mortality risk associated with each procedure in patients with different levels of risk over a 10-year period (1997—2007).

The Society of Thoracic Surgeons Predicted Risk of Mortality (PROM) was calculated for 14,766 patients from the three Emory University Hospitals, using a formula based on 30 pre-operative risk factors. Patients were divided into quartiles based on their PROM, and 30-day operative mortality was compared between patients treated with OPCABG or CPB.

Puskas et al report that 48% of patients had OPCABG, and 52% underwent CPB.

There was no difference in operative mortality between OPCAB and CPB for patients in the lowest two risk quartiles. In the higher two quartiles there was a mortality benefit associated with OPCAB versus CPB, at odds ratios of 0.62 and 0.45 in the second-highest and highest risk quartiles, respectively, a finding which was statistically significant. The benefit was most significant for patients with PROM values above 3%, where mortality curves sharply diverged.

The Society of Thoracic Surgeons National Adult Cardiac Database confirms that coronary patients undergoing OPCAB tend to be older and sicker than those undergoing CABG on CPB, and exhibit a significantly higher predicted mortality risk and numerous morbidities. Puskas and co-workers believe the findings of the present study indicate that this unspoken consensus of North American surgeons is well founded, because it is precisely those patients with highest risk for mortality with conventional CABG who are found to benefit most from OPCAB.

They add: “The finding that OPCAB and CABG on CPB mortality curves diverge sharply for patients with PROM in excess of 2.5% to 3.0% should guide surgeons to perform OPCAB in this patient population or alternatively to refer such patients to a surgeon experienced in OPCAB.”

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