Individual Long-Term Mortality Prediction Following Either Coronary Stenting or Bypass Surgery in Patients With Multivessel and/or Unprotected Left Main Disease: An External Validation of the SYNTAX Score II Model in the 1,480 Patients of the BEST and PRECOMBAT Randomized Controlled Trials

Objectives The study sought to validate the SYNTAX (Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery) score II mortality prediction model after percutaneous coronary intervention (PCI) or coronary artery bypass grafting in a large pooled population of patients with multivessel coronary disease (MVD) and/or unprotected left main disease (UPLMD) enrolled in the PRECOMBAT (Bypass Surgery Versus Angioplasty Using Sirolimus-Eluting Stent in Patients With Left Main Coronary Artery Disease) and BEST (Artery Bypass Surgery and Everolimus-Eluting Stent Implantation in the Treatment of Patients with Multivessel Coronary Artery Disease) randomized controlled trials. Background For patients with MVD and/or UPLMD, the choice of the best revascularization strategy remains challenging. Methods Pooled individual patient-level data from PRECOMBAT and BEST were used to assess calibration and discrimination of the SYNTAX score II prediction model for all-cause mortality after PCI and coronary artery bypass grafting at 4-year follow-up. The study population comprised 1,480 patients (600 with UPLMD, 880 with MVD). Results The overall incidence of all-cause mortality was 6.1% after a median follow-up period of 4.9 years. Validation plots showed good model calibration overall and across treatment groups but tended to overestimate all-cause mortality in the highest risk quintiles of patients in the whole population and the PCI arm. The SYNTAX score II showed moderate discrimination ability for the whole population (C index = 0.685) but better for patients receiving PCI than CABG (C index = 0.718 vs. 0.662 in patients with UPLMD, C index = 0.700 vs. 0.661 in those with MVD). Observed all-cause mortality was higher when the treatment received was at variance with that recommended by the model and similar when it was concordant. Conclusions The SYNTAX score II has good calibration but only moderate discrimination ability for long-term mortality prediction in this randomized population. This score provides an important tool to help guide the heart team's decision-making process regarding the selection of the best revascularization strategy for patients with MVD and/or UPLMD.