Quality, Not Volume, Determines Outcome of Coronary Artery Bypass Surgery in a University-Based Community Hospital Network

Study Questions:

What is the relationship between hospital and surgeon coronary artery bypass grafting procedural volume, mortality, morbidity, and National Quality Forum care processes in a university-based community hospital quality improvement program?


The study population consisted of 2,218 consecutive patients undergoing isolated coronary artery bypass grafting from 2007 to 2009 in a university-based quality improvement program that emphasizes involvement of all surgeons in the academic quality endeavor. The endpoints included operative mortality, major morbidity, and National Quality Forum-endorsed process measures, as defined by the Society of Thoracic Surgeons. The procedural volume was analyzed as a categorical and continuous variable using general estimating equations, which accounted for clustering effects and which were adjusted for Society of Thoracic Surgeons risk scores and the propensity for operation in a low- versus high-volume program.


The annual program volume ranged from 67 to 292 (median, 136; interquartile range, 88-224) and surgeon volume from 1 to 124 (median, 58; interquartile range, 30-89). The mortality rate among the hospitals was 0.47% to 2.23% (0.8% overall), and the observed/expected mortality ranged from 0 to 1.20 (0.41 overall). When comparing low-volume (<200 cases/year) and high-volume centers, no difference was found in the mortality (odds ratio [OR], 1.08; 95% confidence interval [CI], 0.46-2.54; p = 0.85), morbidity (OR, 1.34; 95% CI, 0.73-2.43), or any of the medication process measures. No difference was found in mortality (OR, 1.59; 95% CI, 0.81-3.13; p = 0.18), morbidity (OR, 1.20; 95% CI, 0.86-1.66; p = 0.28), or medication failure (OR, 0.57; 95% CI, 0.3-1.10; p = 0.10) between the high- and low-volume surgeons (<87). After adjustment for both the Society of Thoracic Surgeons risk score and the propensity score, no association was found for either hospital or surgeon volume with mortality or morbidity. However, a lack of compliance with National Quality Forum measures was highly predictive of morbidity (OR, 1.51; 95% CI, 1.18-1.93; p = 0.001), regardless of volume, even after adjustment for predicted risk.


The authors concluded that in the setting of a hospital quality improvement program, excellent surgical results can be obtained in relatively low-volume programs.


This study suggests that in the setting of a university-based community hospital quality improvement program, excellent results can consistently be obtained with coronary artery bypass graft surgery in relatively low-volume programs. The surgical outcomes in this context are not associated with program or surgeon volume, but directly correlate with focus on quality, as manifested by compliance with evidence-based quality standards. A notable observation and somewhat unique in the present study is the correlation of process measures with outcomes that are totally unrelated to the specific processes addressed. A meaningful university affiliation might also represent a new quality paradigm for cardiac surgery in the community hospital setting. It is important to note that the authors did not examine effects of very low-volume operators or centers, where the results might be different.

Clinical Topics: Arrhythmias and Clinical EP, Cardiac Surgery, Invasive Cardiovascular Angiography and Intervention, Cardiac Surgery and Arrhythmias

Keywords: Odds Ratio, Quality Improvement, Hospitals, University, Propensity Score, Process Assessment (Health Care), Hospitals, Community, Confidence Intervals, Thoracic Surgery, Coronary Artery Bypass, Cardiac Surgical Procedures

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