Silent plaque ruptures in non-obstructive lesions of non-infarct-related arteries: a multimodality, serial intracoronary imaging study.

Background And Aims Plaque rupture can occur at non-obstructive lesions in non-infarct-related coronary arteries (non-IRAs) without inducing ischaemia. This study aimed to: (1) assess the frequency and lesion characteristics of plaque rupture in non-IRAs of acute myocardial infarction (AMI) patients, (2) evaluate morphological changes in rupture sites over 52 weeks, and (3) investigate the baseline morphology of new-onset ruptures.Methods This study analysed pooled data from the IBIS-4 and PACMAN-AMI trials. Patients presenting with AMI underwent multimodality intracoronary imaging of non-IRAs at baseline and after 52 weeks.Results Among 783 lesions from 336 patients evaluated at baseline, plaque rupture was observed in 41 lesions of 40 patients (12%). Biomarkers including lipid and inflammation markers were comparable between patients with and without rupture in non-IRAs. Lesions with rupture showed larger percent atheroma volume (53.3 ± 6.4 vs. 49.5 ± 5.8%, estimated difference 3.6[1.9 to 5.4]), larger external elastic membrane area (20.5 ± 4.8 vs. 15.7 ± 5.6 mm2, 4.1[2.5 to 5.7]), and smaller minimum fibrous cap thickness (69 ± 49 vs. 116 ± 84 μm, -43[-75 to -11]) compared to those without. Among 41 rupture sites assessed serially, 21 (51%) healed by 52 weeks. At follow-up, 10 rupture sites were newly identified, and thin-cap fibroatheroma was the most frequent baseline morphology of those.Conclusions Plaque rupture in non-obstructive lesions of non-IRAs was present in 12% of AMI patients. Larger plaque volume, positive remodeling, and thinner fibrous cap were associated with rupture. More than half of untreated ruptures transitioned into stable morphologies. Thin-cap fibroatheroma was the most frequent underlying morphology of new-onset rupture.