Impact of low-density lipoprotein cholesterol-lowering therapy on intermediate stenosis in non- culprit vessels of acute coronary syndrome

Background Associations between optimal low-density lipoprotein cholesterol (LDL-C) level and changes in coronary flow and plaque characteristics are unclear. Therefore, we examine the impact of LDL-C-lowering therapy changes lipid-rich coronary plaques and flow using near-infrared spectroscopy-intravascular ultrasound (NIRS-IVUS) and quantitative flow ratio (QFR) in non-culprit vessels of patients with acute coronary syndrome (ACS). Methods We prospectively examined 70 patients with ACS who underwent NIRS-IVUS for intermediate stenosis in non-culprit vessels at baseline and at follow-up. According to patients’ LDL-C levels at follow-up, they were divided into two groups: VL group (LDL-C levels < 55 mg/dl) and L group (LDL-C levels ≥ 55 mg/dl). Changes in the lesion lipid core burden index (LCBI) and maximum 4-mm lipid core burden index (maxLCBI _4mm ) were assessed using NIRS-IVUS. Coronary flow was assessed using the QFR. The differences (Δ) between each value at follow-up and at baseline were determined. Results The median LDL-C level at follow-up was 48 (42–53) mg/dl in the VL group and 64 (60–68) mg/dl in the L group. There was a strong correlation between reduction of maxLCBI _4mm and improvement of QFR (R ²  = 0.58). The proportion of plaques with a maxLCBI _4mm  ≥ 400 (P = 0.002) and the lesion LCBI (P = 0.03) at follow-up was lower in the VL group than in the L group (P = 0.002). Plaques with a maxLCBI _4mm  ≥ 400 at baseline changed more frequently to a maxLCBI _4mm  < 400 at follow-up in the VL group than in the L group (P < 0.05). Conclusion Aggressive LDL-C-lowering therapy for non-culprit intermediate stenosis in ACS appears to promote plaque stabilization and improve coronary flow.