The STS AVR + CABG Composite Score: A Report of the STS Quality Measurement Task Force

Background The Society of Thoracic Surgeons (STS) is developing a portfolio of composite performance measures for the most commonly performed adult cardiac procedures. This manuscript describes the third composite measure in this series, aortic valve replacement (AVR) combined with coronary artery bypass grafting surgery (CABG). Methods We identified all patients in the STS Adult Cardiac Surgery Database who underwent AVR + CABG during recent 3-year (July 1, 2009, through June 30, 2012) and 5-year (July 1, 2007, through June 30, 2012) periods. Variables from the STS risk model for AVR + CABG were used to adjust morbidity and mortality outcomes. Evidence for internal mammary artery use in AVR + CABG was examined. We compared composite measures constructed using 3 or 5 years of outcomes with Bayesian credible intervals of 90%, 95%, or 98%. The final STS AVR + CABG composite performance measure is based on 3 years of data and 95% credible intervals. It includes risk-adjusted mortality and morbidity but not internal mammary artery use. Results Median composite score is 91.0% (interquartile range, 89.5% to 92.2%). There were 2.6% (24 of 915) one-star (lower performing) and 6.5% (59 of 915) three-star (higher performing) programs. Morbidity and mortality decrease monotonically as star ratings increase. The percentage of three-star programs increased substantially among programs that performed more than 150 procedures over 3 years compared with those performing 25 to 50 procedures (32.8% versus 1.6 %). Measure reliability was 0.51. Conclusions The STS has developed a composite performance measure for AVR + CABG based on 3-year data samples and 95% credible intervals. This composite measure identified 9.1% of STS participants as having higher or lower than expected performance.