Case Volume Deemed Not a Significant Factor in CABG Outcomes



PHILADELPHIA – Outcomes following isolated coronary artery bypass surgery did not differ significantly based on the volume of such procedures that were performed by individual surgeons or at particular institutions in a study of more than 2,000 patients.

In the setting of a university-based, community-hospital, quality-improvement program, excellent surgical results can consistently be obtained even in relatively low-volume programs. Surgical outcomes are not associated with program or surgeon volume, but are directly correlated with focus on quality as manifested by compliance with evidence-based quality standards, according to the study’s lead investigator, Dr. Paul Kurlansky.

He and his colleagues from the Florida Heart Research Institute, Miami, conducted a study of 2,218 consecutive patients undergoing isolated CABG from 2007 to 2009 in a university-based quality-improvement program that emphasized involvement of all surgeons in the academic quality endeavor. End points included operative mortality, major morbidity, and National Quality Forum (NQF)–endorsed process measures as defined by the Society of Thoracic Surgeons (STS).

Procedural volume was analyzed as a categorical and a continuous variable using general estimating equations that accounted for clustering effects and were adjusted for STS risk scores, as well as for propensity for operation in a low- vs. high-volume program, Dr. Kurlansky reported at the annual meeting of the American Association for Thoracic Surgery.

The annual program volume ranged from 67 to 292 procedures (median 136), and surgeon volume ranged from 1 to 124 procedures (median 58). Mortality among all hospitals was 0.8% (ranging from 0% to 2.23%); annual observed/expected mortality was 0.41% overall, ranging from 0% to 1.20%.

A comparison of low-volume (less than 200 cases/year) with high-volume centers (at least 200 cases/year) showed no significant difference in mortality (odds ratio 1.08), morbidity (OR 1.34), or any of the medication process measures.

In addition, there was no difference in mortality (OR 1.59), morbidity (OR 1.20), or medication failure (OR 0.57) between high- (at least 87 cases/year) and low-volume surgeons (less than 87 cases), according to Dr. Kurlansky.

After adjusting for both STS risk score and for propensity score, the researchers found no association between either hospital or surgeon volume with regard to mortality or morbidity.

Lack of compliance with NQF measures, however, was significantly and highly predictive of morbidity (OR 1.51), regardless of volume, even after adjustment for predicted risk.

The findings indicate that outcome rather than volume is the metric by which cardiac surgical programs should be evaluated, according to Dr. Kurlansky. In addition, meaningful and active academic involvement may represent a new paradigm for the delivery of quality care at the community hospital level, he said.

"The quality process measures, I believe, are only a surrogate of the entire environment created by the academic affiliation, ones that shift the entire focus of the program toward accountability, education, and excellence: open disclosure, discussion of problems, awareness of advances, and striving toward excellence," he said in an interview.

The public policy implications of this study are considerable. "The simple administrative approach of a volume threshold (such as that adopted by the Leapfrog group) may be completely inappropriate. Merely adding volume to a mediocre or poor program will only compound the problem, while potentially removing the excellent service provided to the patients of a high-performing, smaller program," he said.

Dr. Kurlansky pointed out that CABG surgery is unique in that it is a very mature, highly practiced, complex surgical procedure. The information gathered from a better understanding of quality outcomes in this study, he said, may help inform efforts to improve other complex procedures.

Dr. Kurlansky reported that he had no disclosures relevant to this presentation.

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