Higher Anatomical Syntax Score is Associated With Lower Survival After CABG in the REGROUP Trial

Introduction: The SYNergy between Percutaneous Coronary Intervention with TAXus and Cardiac Surgery (SYNTAX) score quantifies complexity of coronary artery disease (CAD) using angiographic data to objectively guide mode of revascularization. Recent studies evaluating complexity of CAD by the anatomical SYNTAX score (SS1) and impact on clinical outcomes following CABG have been inconclusive. Hypothesis: We sought to investigate the prognostic value of SS1 in predicting survival and incidence of major adverse cardiac events (MACE) following CABG in the REGROUP trial (ClinicalTrials.gov number NCT01850082.) Methods: This was a pre-planned sub-analysis of the REGROUP trial which randomized patients undergoing isolated CABG to endoscopic versus open vein harvest at 16 U. S. Veterans Affairs Medical Centers between 2014-2017; The median follow-up was 4.7 years (interquartile range 3.84-5.45). SS1 was extracted for all patients and stratified by terciles. Time-to-event survival analysis was performed for MACE defined as death from any cause, nonfatal myocardial infarction, or repeat revascularization over the study follow-up. Results: The mean SS1 for this cohort (N=1,145) was 28.5±11.5 (median 27). Mean age was 66.4±6.90 years, 50.2% were diabetics and 99.5% were males reflecting the Veterans population. According to SS1 terciles, low (<23), intermediate (23-32) and high (>32) SS1 groups comprised 383, 393 and 369 patients, respectively. Over study follow-up, SS1 terciles were associated with all-cause death (log-rank, p=0.012), which occurred in 8.6%, 14.2% and 15.2% of patients respectively (p=0.013). However, SS1 was not associated with higher rates of the composite MACE which occurred in 20.4%, 22.6% and 25.5% of patients (p=0.247). Conclusions: Over the REGROUP study follow-up, complexity of CAD evaluated by the SS1 is significantly associated with all-cause death, but not MACE.