HDL Cholesterol and the Triglyceride-to-HDL Cholesterol Ratio in Relation to Coronary Artery Disease Complexity in Patients with Type 2 Diabetes Mellitus

Background/Objectives: Patients with type 2 diabetes mellitus (T2DM) frequently develop diffuse and anatomically complex coronary artery disease (CAD), resulting in a substantially increased cardiovascular risk. Although both HDL-C and the triglyceride-to-high-density lipoprotein cholesterol (TG/HDL-C) ratio have been associated with cardiovascular risk, their relative associations with and discriminatory performance for angiographic CAD complexity remain uncertain. This study aimed to evaluate and compare these two lipid parameters in relation to CAD complexity as assessed by the SYNTAX score. Methods: A retrospective, observational, single-center study was conducted involving 167 consecutive T2DM patients who underwent diagnostic coronary angiography. CAD complexity was quantified using the SYNTAX score, with patients categorized into low (≤22) and higher (>22) complexity groups. Statistical evaluation included correlation analyses, univariable and multivariable logistic regression, and receiver operating characteristic (ROC) curve analysis. Results: Of the 167 patients, 48 (28.7%) were classified with higher SYNTAX scores. HDL-C showed a significant inverse correlation with the SYNTAX score (r = −0.339, p < 0.001), whereas the TG/HDL-C ratio showed a weak positive correlation (r = 0.159, p = 0.040). In separate multivariable models adjusted for sex, both HDL-C (OR 0.944, 95% CI 0.908–0.980; p = 0.003) and the TG/HDL-C ratio (OR 1.085, 95% CI 1.003–1.175; p = 0.041) remained associated with a higher SYNTAX score. HDL-C showed a numerically higher AUC than the TG/HDL-C ratio (0.659 vs. 0.621); however, the difference between the AUCs was not statistically significant (DeLong p = 0.268). Conclusions: Lower HDL-C and a higher TG/HDL-C ratio remained associated with a higher SYNTAX score after adjustment for sex. Although HDL-C showed numerically better discrimination, no statistically significant difference in discriminatory performance was demonstrated between the two markers.