Longitudinal Distribution of Plaque Burden and Necrotic Core–Rich Plaques in Nonculprit Lesions of Patients Presenting With Acute Coronary Syndromes

Objectives In this substudy of the PROSPECT (Providing Regional Observations to Study Predictors of Events in the Coronary Tree) study, we examined the longitudinal distribution of atherosclerotic plaque burden, virtual histology–intravascular ultrasound (VH-IVUS) characterized necrotic core (NC) content and VH–thin-cap fibroatheroma (TCFA) distribution in nonculprit lesions of patients presenting with acute coronary syndromes. Background Previous analyses suggested that vulnerable plaques and acute myocardial infarction may occur more frequently in the proximal than the distal coronary tree. Methods A total of 4,234 proximal, mid, and distal 30-mm-long segments of each epicardial coronary artery were compared with each other and to the left main coronary artery (LMCA). Results Combining IVUS data from all 3 arteries, there was a gradient in plaque burden from the proximal (42.4%) to mid (37.6%) to distal (32.6%) 30-mm-long segments (p < 0.0001). Overall, 67.4% of proximal, 41.0% of mid, and 29.7% of distal 30-mm-long segments contained at least 1 lesion (plaque burden >40%). Proportion of NC, however, was similar in the proximal and mid 30-mm-long segments of all arteries (10.3% [interquartile range (IQR): 4.8% to 16.7%] vs. 10.6% [IQR: 5.0% to 18.1%], p = 0.25), but less in the distal 30-mm-long segment (9.1% [IQR: 3.7% to 17.8%], p = 0.03 compared with the proximal segment and p = 0.003 compared with the mid segment). Overall, 17.3% of proximal, 11.5% of mid, and 9.1% of distal 30-mm-long segments had at least 1 lesion that was classified as VH-TCFA (p < 0.0001). Comparing the LMCA with the combined cohort of proximal left anterior descending, left circumflex, and right coronary artery 30-mm-long segments: 1) plaque burden was less (35.4% [IQR: 28.8% to 43.5%] vs. 40.9% [IQR: 33.3% to 48.0%], p < 0.0001); 2) fewer LMCAs contained at least 1 lesion (17.5%, p < 0.0001); 3) there was less NC (6.5% [IQR: 2.9% to 12.2%] vs. 9.3% [IQR: 4.3% to 15.9%], p < 0.0001); and 4) LMCAs rarely contained a VH-TCFA (1.8%, p < 0.0001). Conclusions The current analysis appears to confirm that lesions that are responsible for acute coronary events (large, plaque burden–rich in NC) are somewhat more likely to be present in the proximal than the distal coronary tree, except for the LMCA.