Volume, mortality influence CABG readmission rates

With CABG in the cross hairs for upcoming Medicare penalties, hospitals may want to begin exploring factors that contribute to lower 30-day readmission rates. A study published in the Sept. 19 issue of the New England Journal of Medicine found CABG had the highest 30-day readmission rate of six surgical procedures.

Thomas C. Tsai, MD, of the Harvard School of Public Health in Boston, and colleagues targeted six common and costly surgical procedures for their analysis: CABG, pulmonary lobectomy, endovascular repair of abdominal aortic aneurysm (EVAR), open repair of abdominal aortic aneurysm (AAA), colectomy and hip replacement. Using databases from Medicare files, the American Hospital Association and Hospital Compare, they identified 3,004 hospitals with almost 480,000 discharges for the six procedures in 2009 and 2010.   

Their primary outcome measure was a hospital-level composite of risk-adjusted 30-day readmission rates. Of particular interest was the relationship between 30-day readmission rates for the composite and individual procedures and three quality measures: the Hospital Quality Alliance (HQA) surgical care score, volume and mortality.  

“Cardiovascular procedures such as CABG and open repair of abdominal aortic aneurysm may be included in the CMS [Centers for Medicare & Medicaid Services] Readmissions Reduction Program penalties by 2015, and an understanding of patterns of readmission after these procedures will provide specific insight into the implications of federal policy efforts,” Tsai et al explained.

The median risk-adjusted composite 30-day readmission rate was 13.1 percent. Unadjusted rates by procedure placed CABG at the top of the heap, with a rate of 17.4 percent. Colectomy came in second, at 13.8 percent, followed by AAA (13.4 percent), lobectomy (11.9 percent), EVAR (11 percent) and hip replacement (10.5 percent).

Nonprofit hospitals had a lower composite 30-day readmission rate than for-profits (13.1 percent vs. 13.7 percent) as did nonteaching hospitals vs. major teaching hospital (12.9 percent vs. 13.9 percent). Rates for urban and rural hospitals were similar. Hospitals in the highest quartile for treating patients in high-poverty areas had higher readmission rates than hospitals in the lowest quartile (14 percent vs. 13.1 percent). The trends were similar in procedure-specific analyses.

Procedure volume and mortality were associated with 30-day readmission rates, with high-volume hospitals having lower composite rates compared with low-volume facilities and lowest-mortality hospitals achieving lower readmission rates compared with highest-mortality facilities. HQA score showed a marginal difference. 

“All three quality measures—HQA surgical score, procedure volume, and surgical mortality—were generally associated with the procedure-specific readmission rates, although the differences were not always significant,” they wrote. Adjusted 30-day readmission rates for CABG based on procedure volume were 19.2 percent in the lowest quartile vs. 17.2 percent in the highest quartile, for instance, and for mortality they were 17.3 percent in the lowest quartile vs. 18.1 percent in the highest quartile.

Results showing a modest relationship between surgical quality measures and readmission rates may reassure policy makers and others that these rates provide a measure of performance, they concluded. They added that use of administrative data was a limitation and that results could not be generalized to populations other than the elderly.