Thin-Cap Fibroatheroma as High-Risk Plaque for Microvascular Obstruction in Patients With Acute Coronary Syndrome

BACKGROUND: Plaque contents can cause microvascular impairment, which is an important determinant of clinical outcomes in patients with acute coronary syndrome (ACS). We hypothesized that percutaneous coronary intervention (PCI) for thin-cap fibroatheroma (TCFA) could easily disrupt the fibrous cap and expose the contents of plaque to coronary flow, possibly resulting in microvascular obstruction (MVO). The purpose of this study was to investigate whether TCFA was associated with MVO after PCI in patients with ACS. METHODS AND RESULTS: We enrolled 115 patients with ACS who were successfully recanalized with PCI. The patients were divided into a ruptured plaque group (n=59), a nonrupture with TCFA group (n=21), and a nonrupture and non-TCFA group (n=35), according to optical coherence tomography findings of the culprit lesion. Using contrast-enhanced MRI, we assessed MVO. There were no statistically significant differences in patient characteristics. The nonrupture with TCFA group more frequently presented MVO (ruptured plaque, 27%; versus nonrupture with TCFA, 43%; versus non-TCFA and nonrupture, 9%; P=0.012). The prevalence of MVO increases as cap thickness decreases. CONCLUSIONS: TCFA is more frequently associated with MVO after PCI. TCFA is a high-risk plaque for MVO after PCI in patients with ACS.