Do we need separate risk stratification models for hospital mortality after heart valve surgery?

The EuroSCORE (European System for Cardiac Operative Risk Evaluation) is often used to benchmark and predict hospital mortality after cardiac surgery. Based mainly upon coronary surgery patients, EuroSCORE may not be optimal for valve surgery patients. We evaluated the New York (NY) State dedicated valve surgery models and compared their performance to the EuroSCORE model.

Required model variables were collected prospectively for all patients, followed by calculation of predictive mortality rates using the logistic and additive EuroSCORE, the logistic and additive NY State models for valve surgery without concomitant coronary surgery (isolated valve surgery) and the logistic and additive NY State models for combined valve and coronary surgery.

Observed mortality was 2.8% (25 of 904) for isolated valve surgery and 6.8% (27 of 395) for valve plus coronary surgery. Logistic NY State and EuroSCORE expected mortality for isolated valve surgery was respectively 3.0% and 6.1%, and for valve plus coronary surgery 5.9% and 7.8%. The logistic NY State model for isolated valve surgery showed better discrimination (c-index 0.86 versus 0.76) and calibration than the logistic EuroSCORE. Discriminatory power for the logistic NY State model for valve plus coronary surgery was comparable to the logistic EuroSCORE (c-index 0.74 versus 0.72), as was calibration.

Our results suggest that dedicated risk models for valve surgery may be useful to provide more valid estimates of hospital mortality after heart valve surgery. Further exploration is needed to demonstrate general applicability of our results and assess the possible additional value of separate models for isolated valve surgery and valve plus coronary artery surgery, or aortic and mitral valve surgery, or both.