Residual SYNTAX score and optical coherence tomography–derived thin-cap fibroatheroma in patients with ST-elevation myocardial infarction undergoing percutaneous coronary intervention: an exploratory descriptive pilot study

Abstract Background ST-elevation myocardial infarction (STEMI) remains a leading cause of global morbidity and mortality. While percutaneous coronary intervention (PCI) is the definitive reperfusion strategy, residual disease burden and plaque vulnerability both influence clinical recovery. The residual SYNTAX score (rSS) quantifies untreated macroscopic coronary artery disease, whereas optical coherence tomography (OCT) resolves microscopic plaque architecture, notably thin-cap fibroatheroma (TCFA). This pilot study explored the descriptive characteristics and short-term outcomes associated with combining rSS and OCT-derived TCFA in a highly selected STEMI cohort. Methods This retrospective observational pilot study included 30 patients with STEMI who underwent primary PCI and culprit lesion OCT evaluation at a tertiary care center. Patients were stratified into four groups according to the presence of culprit TCFA and the post-PCI rSS threshold ( $$\le$$ ≤ 4 vs. > 4): group 0 (TCFA absent, rSS > 4), group 1 (TCFA absent, rSS $$\le$$ ≤ 4), group 2 (TCFA present, rSS > 4), and group 3 (TCFA present, rSS $$\le$$ ≤ 4). The primary clinical endpoint was major adverse cardiac events (MACE)—a composite of all-cause death, recurrent myocardial infarction, target lesion revascularization, heart failure hospitalisation, and ischemic stroke—assessed over 3 months. Results The cohort (mean age, 54.5 ± 10.1 years; 83.3% male, 40% with diabetes mellitus) had a 53.3% prevalence (16 of 30) of culprit lesion TCFA. Complete or reasonable revascularization (rSS ≤ 4) was achieved in 12 patients (40.0%). The overall cumulative 3-month MACE rate was 30.0% (9 of 30). MACE occurred in 1 of 7 patients (14.3%) in group 0, 1 of 7 (14.3%) in group 1, 4 of 11 (36.4%) in group 2, and 3 of 5 (60.0%) in group 3 (Fisher exact test, P = 0.23; log-rank P = 0.38). Patients with TCFA accounted for 7 of 9 clinical events (77.8%). Given the small subgroup sizes ( n < 12), multivariable predictive risk modeling was not performed. Conclusions In this exploratory pilot cohort of STEMI patients undergoing PCI, the presence of OCT-derived TCFA was descriptively associated with higher short-term adverse event rates across both complete and incomplete revascularization strata. Given the small sample size and clear indication bias, these findings are strictly hypothesis-generating and support the need for adequately powered prospective registries to evaluate dual anatomical-biological risk stratification.