Evaluation of the quality of cardiovascular surgery care using risk stratification analysis according to the EuroSCORE additive model

Risk stratification according to the EuroSCORE additive model of 803 consecutive patients undergoing heart and thoracic aorta surgery using cardiopulmonary bypass from August 1994 to December 2000 was performed. The population was divided into 5 clinically relevant risk categories: 0-2% risk, 3-5% risk, 6-8% risk, 9-11% risk, and 12+% risk. Observed and predicted mortalities were compared within 3 groups of patients divided by year of operation (early: August 1994 to September 1996, n=260; middle: October 1996 to September 1998, n=259; late: October 1998 to December 2000, n=284). Overall hospital mortality was 4.5%; predicted mortality was 5.3% in the early, 5.1% in the middle, and 5.4% in the late period; observed mortality was 6.5%, 3.9%, and 3.2%, respectively (p=0.0024 in early vs late). In the early period, observed mortality was lower than predicted mortality in the 0-2% and 3-5% risk categories, but higher in the other categories. Moreover, observed mortality increased markedly with the increase in predicted mortality. In the late period, observed mortality was lower than predicted mortality in all 5 risk categories. The EuroSCORE is clinically relevant index for constructing a risk stratification scoring system for Japanese cardiovascular patients as well and shows that the quality of surgical care has improved gradually over the years.