Volume of frail patients predicts outcome in frail patients after cardiac surgery.

OBJECTIVE:Recent data from major noncardiac surgery suggest that outcomes in frail patients are better predicted by a hospital's volume of frail patients specifically, rather than overall surgical volume. We sought to evaluate this "frailty volume-frailty outcome relationship" in patients undergoing cardiac surgery. METHODS:We studied 72,818 frail patients undergoing coronary artery bypass grafting or valve replacement surgery from 2010 to 2014 using the Nationwide Readmissions Database. Frailty was defined using the Johns Hopkins Adjusted Clinical Groups frailty-defining diagnoses indicator. Multilevel logistic regression was used to assess the independent effect of frailty volume by quartile on mortality, surgical complications, failure to rescue, nonhome discharge, 30-day readmissions, length of stay, and hospital costs in frail patients. RESULTS:In comparing the highest volume quartiles with the lowest, both overall cardiac surgical volume and volume for frail patients were significantly associated with shorter length of stay and reduced costs. However, frailty volume was also independently associated with significantly reduced in-hospital mortality (odds ratio, 0.79; 95% confidence interval, 0.67-0.94; P = .006) and failure to rescue (odds ratio, 0.83; 95% confidence interval, 0.70-0.98; P = .03), whereas no such association was seen between overall volume and either mortality (odds ratio, 0.94; 95% confidence interval, 0.74-1.10; P = .43) or failure to rescue (odds ratio, 0.98; 95% confidence interval, 0.83-1.17; P = .85). Neither frailty volume nor overall volume showed any significant relationship with the rate of 30-day readmissions. CONCLUSIONS:In frail patients undergoing cardiac surgery, surgical volume of frail patients was a significant independent of predictor of in-hospital mortality and failure to rescue, whereas overall surgical volume was not. Thus, the "frailty volume-outcome relationship" superseded the traditional "volume-outcome relationship" in frail patients with cardiac disease.