In vivo vulnerability grading system of plaques causing acute coronary syndromes: An intravascular imaging study

Background: Autopsy studies shed light on the interplay between fatal acute coronary syndromes (ACS) and features of plaque vulnerability. This is a prospective pilot study designed for generating a new in vivo imaging grading system of plaque vulnerability. Methods: We studied 87 coronary vessels in 63 consecutive patients: 48 with Acute Coronary Syndrome (ACS) and 15 with stable coronary artery disease using IntraVascular-Ultrasound Near-Infrared-Spectroscopy (IVUS-NIRS) and Optical Coherence Tomography (OCT). We identified 99 lesions: 21 were the ACS culprit lesions (18 ulcerations and 3 with intact fibrous cap), 78 were non-culprit lesions including plaques located in the same ACS culprit vessel (N12), plaques located in a non-culprit vessel in patients with ACS (28) and target lesions of stable patients (N 38). A second analysis focused on lipid plaques, comparing the 18 ACS culprit ulcerated lesions and the 55 non-culprit lesions. Results: The co-presence of the following three features of vulnerability [Minimal Luminal Area (MLA) <4 mm2, Fibrous Cap Thickness (FCT) < 75 μm and superficial macrophages] was by far more frequent in ACS culprit lesions than in controls (OR 40.6 for all lesions and OR 45.7 for ulcerated culprit lesions only). The triple-feature OCT grading identified vulnerable plaques with a much higher accuracy than that obtained applying each single feature of vulnerability. Conclusions: The co-presence of the 3 OCT features of vulnerability (MLA < 4 mm2, FCT < 75 μm and superficial macrophages) identifies culprit ACS lesions with a very high odd ratio. This finding could set the basis for a new OCT vulnerability grading system including superficial macrophages.