Performance of contemporary surgical risk scores for mitral valve surgery

Risk stratification for mitral valve repair or replacement (MVR) is important in the decision-making for treating several mitral valve disease but is rarely studied. We compared the prognostic utility of EuroSCORE, EuroSCORE II, and Society of Thoracic Surgeons (STS) Score for MVR.

The three scores were retrospectively calculated for consecutive patients undergoing isolated MVR at Auckland City Hospital during 2005-2012 and their discrimination and calibration for mortality and morbidities assessed.

There were 408 patients (mitral valve repair 48.1% and replacement 51.9%) followed-up for 6.0 ± 2.6 years. The operative mortality was 2.5%. Mean EuroSCORE, EuroSCORE II, and STS Score were 7.6%, 3.4%, and 3.5%. C-statistics were 0.844, 0.817, and 0.850 for operative mortality. Hosmer-Lemeshow test p values were 0.076, 0.541, and 0.306, and Brier scores 0.0246, 0.0035, and 0.0075, respectively, for operative mortality. The numerically highest c-statistic for predicting complications include EuroSCORE for return to the operating room (c = 0.673); EuroSCORE II for stroke (c = 0.669) and mediastinitis (c = 0.801); and STS for renal failure (c = 0.828), ventilation >24 hours (c = 0.789), and composite morbidity (c = 0.732). The individual STS complication models for MVR had a numerically higher c-statistic only for stroke (c = 0.737).

All scores discriminated mortality and most morbidities after MVR, although EuroSCORE over-estimated operative mortality. The STS Score was the best overall predictor of mortality and morbidity in the MVR cohort.