AIMS There are limited data on the prognosis of deferred non-culprit lesions in patients with acute coronary syndrome (ACS) based on fractional flow reserve (FFR). We aimed to investigate the prognosis of deferred non-culprit lesions in ACS patients, compared with deferred lesions in patients with stable coronary artery disease (SCAD), on the basis of FFR.

METHODS AND RESULTS The clinical outcomes of 449 non-culprit lesions (301 patients with ACS) were compared with 2,484 lesions (1,295 patients with SCAD) in which revascularisation was deferred on the basis of a high FFR (>0.80). The primary outcome was major adverse cardiac events (MACE), a composite of cardiac death, target vessel-related myocardial infarction (MI) and ischaemia-driven revascularisation. Among the ACS population, 65.8% presented with unstable angina and 34.2% with non-ST-segment elevation MI. Mean angiographic percent diameter stenosis and FFR of the deferred lesions were 39.3±15.0% and 0.92±0.06, respectively. During the median follow-up duration of 722.0 days, the deferred non-culprit lesions of ACS patients showed a significantly higher rate of MACE (3.8% vs. 1.6%, HRadj 2.97, 95% CI: 1.23-7.17, p=0.016), mainly driven by the higher rate of ischaemia-driven revascularisation (2.8% vs. 1.1%, HRadj 3.39, 95% CI: 1.29-8.92, p=0.013) than the deferred lesions in SCAD patients. Regardless of the range of FFR in the deferred lesions (0.81-0.85, 0.86-0.90, 0.91-0.95, and 0.95-1.00), non-culprit lesions of ACS showed a more than twofold higher rate of MACE than that of SCAD. In a multivariable marginal Cox model, ACS was the most powerful independent predictor of MACE (HRadj 2.74, 95% CI: 1.13-6.64, p=0.026).

CONCLUSIONS Compared to the deferred lesions of SCAD patients, deferred non-culprit lesions of ACS on the basis of FFR showed a higher rate of clinical events, regardless of FFR range.