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.