The study was performed as per the Helsinki Declaration. After approval from the institutional research ethics committee, data prospectively collected during cardiac surgery at our center from January 2006 to December 2011 were used. In-hospital mortality was defined as death occurring at any time after surgery during the primary hospital stay. In total, 1,833 patients aged 19–95 years with complete data were included. Patients who underwent the maze procedure or cardiac tumor resection were excluded because of too few cases. The ejection fraction was not available in 35 patients, so the ACEF score could not be calculated in those patients. The EuroSCORE II and ACEF score were calculated according to the original publications,[2 (link)12 (link)] but the variable “poor mobility” was missing in our database and could not be included. Receiver operating characteristic curves (ROC) producing an area under the curve (AUC) with 95% confidence intervals (CIs) were used to assess discrimination. Differences of AUC between the two scores were assessed with DeLong's method. Calibration was evaluated using the Hosmer–Lemeshow test (HL test), which differentiates between expected and observed mortality at each decile of risk. For the HL test, significant results indicate poor calibration.
Due to small numbers, thoracic surgery was excluded. Several variables were recoded before recalibration of the EuroSCORE II. New York Heart Association (NYHA) groups were recoded into two groups: NYHA I and II patients versus NYHA III and IV patients. For renal impairment, patients on dialysis were grouped with those with severe renal impairment. For pulmonary hypertension, patients with severe and moderate forms were placed in the same group. The weight of intervention was reduced to three categories, placing “two procedures” and “three procedures” in the same group. The urgency of the procedure was reduced to two categories, combining patients with “urgent”, “emergency”, and “salvage” surgery. Very severely reduced LVEF was merged with poor LVEF, resulting in three LVEF categories.
SPSS (version 20.0 SPSS Inc., Chicago, IL, USA) was used for descriptive statistics. Continuous data are presented as mean ± standard deviation (SD) and categorical data as numbers with percentages. Multivariable logistic regression including the EuroSCORE II variables was used to generate new odds ratios (ORs) for a recalibrated EuroSCORE II in our population. Variables with Pvalue < 0.2 were included to achieve a simplified, recalibrated model. This threshold was chosen in order not to omit clinically important variables that were non-significant in the present study because of the study size. Logistic regression and AUC comparison were performed in STATA (version 13, StataCorp LLC, Texas, USA). P values < 0.05 were considered statistically significant.
Due to small numbers, thoracic surgery was excluded. Several variables were recoded before recalibration of the EuroSCORE II. New York Heart Association (NYHA) groups were recoded into two groups: NYHA I and II patients versus NYHA III and IV patients. For renal impairment, patients on dialysis were grouped with those with severe renal impairment. For pulmonary hypertension, patients with severe and moderate forms were placed in the same group. The weight of intervention was reduced to three categories, placing “two procedures” and “three procedures” in the same group. The urgency of the procedure was reduced to two categories, combining patients with “urgent”, “emergency”, and “salvage” surgery. Very severely reduced LVEF was merged with poor LVEF, resulting in three LVEF categories.
SPSS (version 20.0 SPSS Inc., Chicago, IL, USA) was used for descriptive statistics. Continuous data are presented as mean ± standard deviation (SD) and categorical data as numbers with percentages. Multivariable logistic regression including the EuroSCORE II variables was used to generate new odds ratios (ORs) for a recalibrated EuroSCORE II in our population. Variables with Pvalue < 0.2 were included to achieve a simplified, recalibrated model. This threshold was chosen in order not to omit clinically important variables that were non-significant in the present study because of the study size. Logistic regression and AUC comparison were performed in STATA (version 13, StataCorp LLC, Texas, USA). P values < 0.05 were considered statistically significant.
