Abstract 3515: Impact of Insulin Resistance on Tissue Characteristics of Non-culprit Plaque in Non-diabetic Patients with Acute Coronary Syndrome
Objectives: Insulin resistance (IR) is associated with elevated risk of acute coronary events even before the onset of diabetes, indicating increased plaque vulnerability in patients with high IR. However, the precise mechanism remains to be elucidated. The aim of this integrated backscatter intravascular ultrasound (IB-IVUS) study was to clarify the association between IR and the tissue characteristics of coronary plaques in non-diabetic patients with acute coronary syndrome (ACS).
Methods: Non-culprit coronary lesions with mild to moderate stenosis in 50 non-diabetic patients with ACS were examined by IB-IVUS using 40-MHz intravascular catheter. Radiofrequency data were captured and IB-IVUS images were constructed. The target plaque had to be an intermediate lesion with angiographically no more than 50% luminal narrowing and had to be at least 5mm apart from the culprit lesion. Measurements of IB-IVUS were made every 1mm for 10mm length in each plaque, and average value of each plaque component (lipid, fibrosis,and calcification) was calculated. All patients underwent 75-g oral glucose tolerance test (OGTT). Homeostatsis model assessment of IR (HOMA-IR) was used as a marker of IR and calculated as follows: fasting glucose (mg/dl) ×fasting insulin (μg/ml) / 405. Patients with previously treated diabetes or newly diagnosed diabetes by 75-g OGTT were excluded.
Results: No significant association was observed between the traditional coronary risk factors and tissue characteristics in this population. In contrast, higher HOMA-IR levels were correlated with greater %lipid area (r=0.28, p<0.05) and lower %fibrous area (r=−0.25, p=0.08), whereas no correlation was observed between HOMA-IR and %calcification area (r =−0.14, p=0.32). Multiple linear regression analysis revealed that HOMA-IR was associated with %lipid area independent of age, gender, and other coronary risk factors including LDL-cholesterol levels (p<0.05).
Conclusions: Higher insulin resistance was associated with elevated lipid content in the non-culprit intermediate lesion in non-diabetic patients with ACS. Pharmacological intervention targeting at insulin resistance may contribute to the stabilization of vulnerable plaque even in patients without diabetes.