Comparison of high-risk characteristics of non-culprit plaques in relation to plaque severity in acute coronary syndrome

Introduction: Patients with acute coronary syndrome (ACS) have high event rates related to non-culprit (NC) lesions, therefore plaque composition of these lesions is of great interest. Although marginal atherosclerotic lesions were studied extensively, more significant lesions might have more high-risk characteristics.

Aim: To compare differences in high-risk lesion characteristics between significant versus non-stenotic NC plaques in ACS and the discrepancies with chronic coronary syndrome (CCS) patients.

Methods: Non-culprit vessels of 26 ACS patients with 26 angiographically significant lesions and 37 patients (17 ACS and 20 CCS) with 48 non-stenotic lesions were investigated with intravascular ultrasound (IVUS) and near-infrared spectroscopy (NIRS). Overall, 74 segments of 30 mm length were analyzed in 1 mm intervals. External elastic lamina (EEM), plaque burden (PB), minimal luminal area (MLA), percent atheroma volume (PAV) and lipid core burden index maximum 4 mm (maxLCBI_4mm) were determined for each segment.

Results: Cardiovascular risk factors were similar in all groups. PB was higher and MLA smaller in significant non-culprit ACS lesions vs non-stenotic lesions: PB 73.5% (IQR 68.7-78.5) vs 59.2 (IQR 49.6-71.5), p = 0.003, MLA 3.0 mm² (IQR 2.3-3.9) vs 4.0 mm² (IQR 2.8-4.7). MaxLCBI_4mm was similar 308.1 (±155.4) vs 287.8 (±165.7), p = 0.67. Among non-stenotic plaques, MaxLCBI_4mm was comparable between ACS and CCS patients, 275.7 (±151.5) in CCS patients vs 287.8 (±165.7) in ACS patients, p = 0.79.

Conclusion: Although visually significant non-culprit lesions had a higher plaque burden compared to non-stenotic lesions, a significant relation between MaxLCBI_4mm and hemodynamic significance of the plaques couldn't be established.