Comparison Between Different Insulin Resistance Markers and Their Correlation With Severity of Coronary Artery Disease in Non-diabetic Patients.

evaluates the predictive value of multiple insulin resistance indices - specifically, the homeostatic model assessment for insulin resistance (HOMA-IR), Metabolic score for insulin resistance (METS-IR), Triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio, and triglyceride and glucose (TyG) index, as non-invasive markers of coronary artery disease severity.

Insulin resistance will be assessed using the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), calculated as fasting plasma glucose and fasting insulin levels according to the following formula: HOMA-IR = [FPG (mg/dL) x fasting insulin (microU/mL)] / 405.

Results will be reported as a continuous, dimensionless index; higher values indicate greater insulin resistance.

The association between HOMA-IR and coronary artery disease severity will be evaluated using coronary angiographic findings, including SYNTAX score and TIMI flow grade.

METS-IR will be calculated according to the following formula: Ln[(2 × fasting plasma glucose (mg/dL)) + fasting triglycerides (mg/dL)] × body mass index (kg/m²) ÷ Ln[HDL-cholesterol (mg/dL)]. Biochemical parameters will be derived from fasting venous blood collected before coronary angiography. Higher scores indicate greater insulin resistance.

The association between METS-IR and coronary artery disease severity will be evaluated using coronary angiographic findings, including SYNTAX score and TIMI flow grade.

The TyG index will be calculated according to the following formula: Ln[fasting triglycerides (mg/dL) × fasting plasma glucose (mg/dL) ÷ 2], using blood samples collected before coronary angiography. The index is dimensionless and serves as a surrogate marker of insulin resistance, with higher values indicating greater resistance.

The association between TyG index and coronary artery disease severity will be evaluated using coronary angiographic findings, including SYNTAX score and TIMI flow grade.

The TG/HDL-C ratio will be calculated according to the following formula: fasting serum triglycerides (mg/dL) divided by fasting serum HDL-cholesterol (mg/dL), using blood samples collected before coronary angiography. The ratio is dimensionless and serves as a surrogate marker of insulin resistance, with higher values indicating greater resistance.

The association between TG/HDL-C ratio and coronary artery disease severity will be evaluated using coronary angiographic findings, including SYNTAX score and TIMI flow grade.

The anatomical complexity and severity of coronary artery disease will be assessed using the SYNTAX score calculated from coronary angiographic images. The SYNTAX score will be calculated based on the number, location, and anatomical characteristics of coronary lesions with diameter stenosis of at least 50% in coronary vessels with a reference diameter of at least 1.5 mm. The total numerical score will be reported; higher scores indicate greater anatomical complexity. Categories are low (≤22), intermediate (23-32), and high (≥33).

The relationship between SYNTAX score and the four insulin resistance markers (HOMA-IR, METS-IR, TyG index, and TG/HDL-C ratio) will be evaluated.

Coronary blood flow in all major coronary arteries will be assessed during coronary angiography using the Thrombolysis in Myocardial Infarction (TIMI) flow grading system. Coronary blood flow will be classified into four grades:

• TIMI Grade 0: No antegrade flow.
• TIMI Grade 1: Penetration without distal perfusion.
• TIMI Grade 2: Partial perfusion with delayed flow.
• TIMI Grade 3: Complete perfusion. The association between insulin resistance markers and TIMI flow grade will be evaluated