Angiographic SYNTAX score was widely used to assist clinical decision between percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG) by scoring coronary artery disease burden.1,2 While the burden of coronary artery disease (CAD), assessed by the angiographic SYNTAX score, was reported to be associated with greater mortality at 5 years,3-6 the predictive ability of the SYNTAX score on long-term outcomes (>5 years) has not been established. The authors extended the clinical follow-up to 10 years in patients enrolled in the SIRTAX study7 and evaluated the impact of SYNTAX score on long-term outcomes at 10 years.
The SYNTAX score was retrospectively calculated in 858 patients enrolled in the SIRTAX trial (median: 11, interquartile range [IQR]: 7–17). Since patients were included in the randomised controlled trial, SYNTAX score was relatively low compared with the all-comer population. Patients with previous CABG (n=92), those without suitable angiography (n=47), and those without creatinine clearance data available (n=15) were excluded. The follow-up rate was high but not complete (763 patients, 88.9%) at 10 years.
During the 10-year follow-up, 174 (21.9%) patients died, myocardial infarction (MI) occurred in 76 (9.8%) patients, target lesion revascularisation (TLR) in 157 (19.7%) patients, target vessel revascularisation (TVR) in 202 (25.4%) patients, and non-TVR in 153 (19.9%) patients, respectively. Rates of clinical events between 5 and 10 years were lower than those within 5 years, except for all-cause death (9% at 5 years and 22% at 10 years).
The SYNTAX score emerged as an independent predictor for all-cause mortality (adjusted hazard ratio [HR] [per 10]: 1.23; 95% confidence interval [CI]: 1.004–1.50; p=0.046), TLR (adjusted HR: 1.37; 95% CI: 1.12–1.68; p=0.003), and TVR (adjusted HR: 1.37; 95% CI: 1.14–1.64; p<0.001), and was associated with a trend toward greater adjusted risks for MI (adjusted HR: 1.30; 95% CI: 0.97–1.74; p=0.08) and non-TVR (adjusted HR: 1.22; 95% CI: 0.98–1.52; p=0.08), respectively.
The authors performed stratified analyses according to the median patient age of 62 years (≥62 years: 435 patients; <62 years: 423 patients). The SYNTAX score was higher in older patients compared to younger patients (11 [7–17.75] versus 9 [5.75–15.0]; p<0.001). The SYNTAX score independently predicted non-TVR in the younger group (adjusted HR [per 10]: 1.67; 95% CI: 1.20–2.32, p=0.002) but not in the older patient group (adjusted HR: 1.04; 95% CI: 0.75–1.44; p=0.82; p interaction=0.049) with significant interaction. Conversely, there was no significant interaction between SYNTAX score and age category for all-cause mortality, MI, TLR, and TVR.
The study has important limitations. The follow-up rate of 88.9% at 10 years was not complete. The majority of events, except for all-cause mortality, were observed within 5 years. Thus, the reported association of SYNTAX score on clinical outcomes might be mainly driven by earlier events, although it was notable that all-cause mortality rate increased from 9% at 5 years to 22% at 10 years.
The authors concluded that the SYNTAX score was independently associated with 10-year risks of all-cause mortality, TLR, and TVR. Among young, but not elderly patients, the SYNTAX score independently predicted non-TVR.