(STS) has published two risk models that can be used to

adjust the results of valve surgery combined with coronary

artery bypass graft surgery (CABG). The most recent was

developed from data for patients who had surgery between

1994 and 1997 using operative mortality as the only endpoint.

Furthermore, this model did not specifically consider mitral

valve repair plus CABG, an increasingly common procedure.

Consistent with STS policy of periodically updating and

improving its risk models, new models for valve surgery

combined with CABG have been developed. These models

specifically address both perioperative morbidity and mitral

valve repair, and they are based on contemporary data.

procedures, including aortic valve replacement (AVR) plus

CABG, mitral valve replacement (MVR) plus CABG, or mitral

valve repair (MVRepair) plus CABG between January 1, 2002,

and December 31, 2006. Model outcomes included operative

mortality, stroke, deep sternal wound infection, reoperation,

prolonged ventilation, renal failure, composite major morbidity

or mortality, prolonged postoperative length of stay, and

short postoperative length of stay. Candidate variables were

screened for frequency of missing data, and imputation techniques

were used where appropriate. Stepwise variable selection

was employed, supplemented by advice from an expert

panel of cardiac surgeons and biostatisticians. Several variables

were forced into models to insure face validity (eg, atrial

fibrillation for the permanent stroke model, sex for all models).

Based on preliminary analyses of the data, a single model

was employed for valve plus CABG, with indicator variables

for the specific type of procedure. Interaction terms were

included to allow for differential impact of predictor variables

depending on procedure type. After validating the model in

the 40% validation sample, the development and validation

samples were then combined, and the final model coefficients

were estimated using the overall 100% combined sample. The

final logistic regression model was estimated using generalized

estimating equations to account for clustering of patients

within institutions.

valve plus CABG population was 0.75. Morbidity model

c-indices for specific complications (permanent stroke, renal

infection, reoperation for any reason, major morbidity or

mortality composite, and prolonged postoperative length of

stay) for the overall group of valve plus CABG procedures

ranged from 0.622 to 0.724, and calibration was excellent.

for heart valve surgery combined with CABG. These are the

first valve plusCABGmodels that also include risk prediction

for individual major morbidities, composite major morbidity

or mortality, and short and prolonged length of stay.

(Ann Thorac Surg 2009;88:S43–62)

© 2009 by The Society of Thoracic Surgeons