Quantification of Incomplete Revascularization and its Association With Five-Year Mortality in the Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery (SYNTAX) Trial Validation of the Residual SYNTAX Score

Background The residual Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery (SYNTAX) Score is an objective measure of the degree and complexity of residual stenosis after percutaneous coronary intervention (PCI). Methods and Results In the randomized PCI cohort of the SYNTAX Trial (n=903), the baseline and residual SYNTAX Scores were calculated. Subjects with a residual SYNTAX Score of 0 were defined as having undergone complete revascularization (CR), and a residual SYNTAX Score >0 as incomplete revascularization (ICR). Five-year clinical outcomes were stratified by CR and ICR (tertiles of the residual SYNTAX Score: >0-4, >4-8, and >8). In the PCI cohort, the mean baseline and residual SYNTAX Scores were 28.4 +/- 11.5 and 4.5 +/- 6.9, respectively. The mean SYNTAX Score (representative of the burden of disease removed by PCI) was 23.8 +/- 10.9. The residual SYNTAX Score was distributed as follows: CR, 0 (n=386, 42.7%); ICR, >0 to 4 (n=184, 20.4%), >4 to 8 (n=167, 18.5%), >8 (n=153, 16.9%). A progressively higher residual SYNTAX Score was shown to be a surrogate marker of increasing clinical comorbidity and anatomic complexity. Subjects with CR or residual SYNTAX Scores 8 had comparable 5-year mortality (CR, 8.5%; residual SYNTAX Score >0-4, 8.7%; >4-8, 11.4%; P=0.60). A residual SYNTAX Score >8 was associated with 35.3% all-cause mortality at 5-years (P<0.001). Stratified analyses in the predefined medical treated diabetic and left main subgroups yielded similar results. Conclusions The residual SYNTAX Score was shown to be a powerful indicator of 5-year mortality in the SYNTAX Trial. The residual SYNTAX Score may aid in determining a reasonable level of revascularization.