Non-flow limiting non-culprit plaque characteristics in patients presenting with STEMI versus NSTEMI

Abstract Background Non-ST-elevation myocardial infarction (NSTEMI) and ST-elevation myocardial infarction (STEMI) are often considered distinct clinical entities. Although differences in culprit plaque characteristics have been described extensively, less is known about differences in non-culprit (NC) plaque characteristics. Purpose To compare plaque characteristics of fractional flow reserve (FFR)-negative NC lesions as assessed by optical coherence tomography (OCT) in STEMI and NSTEMI patients. Methods PECTUS-obs is a prospective, observational study in which 438 patients presenting with STEMI or NSTEMI underwent OCT of any intermediate FFR-negative NC lesion (defined as a FFR >0.80) after treatment of the infarct related artery. Quantitative and qualitative OCT analyses were performed by an independent core laboratory. A high risk plaque (HRP) was defined as the presence of ≥2 of the following prespecified criteria: 1) a lipid arc ≥90°, 2) a minimal fibrous cap thickness <65 µm, or 3) either cap rupture or thrombus presence. In the present sub-analysis, lesion-level plaque characteristics were compared between patients presenting with STEMI versus NSTEMI while accounting for within-patient clustering and correcting for prespecified clinical variables (age, history of myocardial infarction, diabetes, and estimated glomerular filtration rate (eGFR)). Results Among 420 patients with at least one analyzable OCT, 217 (51.7%) presented with STEMI and 203 (48.3%) with NSTEMI. Patients with STEMI were younger (mean age 62±10 vs 65±11 years, p=0.004) and less frequently had diabetes (11.1% vs 18.2%, p=0.037) and hypercholesterolemia (31.8% vs 41.6%, p=0.038). Baseline mean eGFR (84±19 vs 75±19 ml/min, p<0.001) and low density lipoprotein-cholesterol levels (3.2±1.2 vs 2.9±1.2, p=0.010) were higher in STEMI patients with fewer of these patients using lipid lowering therapy (18.9% vs 33.0%, p<0.001) before enrollment. A total of 494 NC lesions were analyzed, which were equally distributed in number and location between groups. The mean fractional flow reserve was 0.89±0.05 and was comparable between groups (p=0.26). Patients with STEMI had a smaller minimal lumen area (2.56±1.48 vs 2.84±1.58 mm2, p=0.031) and minimal lumen diameter (1.47±0.44 vs 1.55±0.45 mm, p=0.026) with a subsequent larger percentage area stenosis (64±15 vs 61±17%, p=0.022). Lipid plaques were more common in STEMI patients (81.7% vs 70.7%, p=0.006) and the maximal lipid arc more frequently was ≥90º (79.0% vs 69.0%, p=0.018). There was no difference in the presence of plaque ruptures (8.3% vs 11.2%, p=0.31) or HRP (32.9% vs 29.3%, p=0.40), whereas macrophage accumulation was more prevalent in STEMI patients (27.8% vs 18.2%, p=0.040). Conclusions FFR-negative NC lesions in patients with STEMI have smaller luminal dimensions, and more frequently harbor lipid plaques and macrophage accumulation. No difference was observed in the prevalence of HRP or plaque rupture.