C-18 | A NIRS-IVUS Algorithm to Elucidate Culprit Lesion Morphology in Acute Myocardial Infarction

Plaque rupture (PR), plaque erosion (PE), or thrombosis of a calcified nodule (CN) represent the culprit lesion morphologies underlying acute myocardial infarctions (AMI). An algorithm for differentiating PR, PE, and CN using near-infrared spectroscopy and intravascular ultrasound (NIRS-IVUS) was previously published in a Japanese cohort using optical coherence tomography as the reference standard. We sought to apply this NIRS-IVUS algorithm to evaluate AMI culprit lesions in a US cohort. Using data from a single-center NIRS-IVUS registry, images of AMI culprit lesions were analyzed in consecutive registry patients. According to the previously published algorithm, culprit lesions with convex calcium on IVUS were defined as CN. Lesions with a plaque cavity on IVUS or a large LRP (maxLCBI4mm>426) on NIRS were defined as PR. Lesions without convex calcium, plaque cavity, or large LRP were defined as PE. Among 174 AMI patients (male 69.5%; age 59.6 ± 11.9 years), 67% had ST-elevation myocardial infarction and 33% had non-ST-elevation myocardial infarction. AMI culprit lesions were characterized by a maxLCBI4mm of 485±268. After applying the NIRS-IVUS algorithm, 17 (9.8%) culprit lesions met criteria for CN. A plaque cavity was evident in 59 (33.9%) lesions and 53 (30.4%) had a maxLCBI4mm>426. Thus, 112 (64.6%) AMI culprit lesions met criteria for PR. The remaining 45 (25.9%) lesions lacked convex calcium, plaque cavity, or large LRP, and where therefore classified as PE. Application of a NIRS-IVUS algorithm to evaluate AMI culprit lesions in a US cohort classified culprit lesions as PR in 64.6%, PE in 25.9%, and CN in 9.8%. This distribution of lesion phenotypes is consistent with expected rates of PR, PE, and CN in previously published autopsy series and prior intracoronary imaging studies.