Not all plaque ruptures are born equal: an optical coherence tomography study

Plaque rupture (PR) represents the most common substrate of coronary thrombosis, in at least 50% of cases. Chronic low grade inflammation is a common background for atherosclerosis development; however, increased plaque inflammation may predispose by itself to PR. In the last decade, studies performed by optical coherence tomography (OCT) have allowed to establish the severity of plaque inflammation by assessing macrophage infiltration (MØI). Our retrospective study aimed at assessing the role of plaque inflammation in PR among patients with acute coronary syndrome (ACS) using OCT.

We enrolled 56 patients with ACS exhibiting PR at the site of the culprit stenosis identified by OCT. Patients were divided into two cohorts according to the presence of MØI at OCT analysis, defined as signal-rich, distinct, or confluent punctate regions that exceed the intensity of background speckle noise. Serum high-sensitivity C-reactive protein (CRP) was measured on admission by latex-enhanced immunophelometric assay. Thirty-seven (66%) patients had MØI at the site of PR, whereas 19 (34%) patients had no evidence of MØI. Patients with MØI showed a higher rate of CRP values >3 mg/dL as compared with those without MØI (92% vs. 47%, P = 0.004). In contrast, patients without MØI had a higher prevalence of hypertension compared with those with MØI (89% vs. 59%, P = 0.021). Furthermore, the group with MØI exhibited a significantly higher rate of lipid-rich plaques (86% vs. 50%, P = 0.008), a higher rate of multifocal disease (59% vs. 10%, P < 0.001), and an MØI in both culprit and remote lesions (97% vs. 0%, P < 0.001) compared with those without MØI. At multivariate analysis, CRP value >3 mg/dL was the only independent predictor of MØI in the culprit plaque (OR 8.72, 95% CI 1.78-41.67, P= 0.007).

In conclusion, PR can be caused by predominant inflammatory or non-inflammatory mechanisms, over a common low-grade chronic inflammatory background well known from pathology observations.