Comparative Analysis of Lipid Indices in Predicting Residual SYNTAX Score After Primary PCI in Patients with Acute Coronary Syndrome

Background: Atherosclerotic cardiovascular disease remains the leading cause of ischemic heart disease, with dyslipidemia representing one of its principal modifiable risk factors. This study sought to evaluate the association between residual coronary artery disease burden and contemporary lipid indices in patients presenting with a first episode of acute coronary syndrome. Methods: A total of 317 patients were retrospectively evaluated between January 2022 and June 2023. Demographic features, comorbid conditions, laboratory measurements, conventional lipid parameters, contemporary lipid ratios, SYNTAX scores (SS), and residual SYNTAX scores (rSS) were recorded. Following primary percutaneous coronary intervention (PCI), patients were categorized by residual SYNTAX score (rSS) as rSS-negative (score = 0) or rSS-positive (score ≥ 1). Results: Of the 317 patients, 174 had an rSS > 0, with a median rSS of 6 (IQR, 3–10). Patients with rSS > 0 had lower HDL-C and higher LDL-C/HDL-C and non-HDL-C/HDL-C ratios than those with rSS = 0. In adjusted models, HDL-C was inversely associated with rSS positivity (OR per 1-mg/dL increase, 0.965; 95% CI, 0.932–0.999), whereas the LDL-C/HDL-C ratio (OR per 1-unit increase, 1.337; 95% CI, 1.021–1.752) and the non-HDL-C/HDL-C ratio (OR per 1-unit increase, 1.257; 95% CI, 1.017–1.553) were positively associated. Baseline SYNTAX score was the dominant predictor, and none of the lipid-extended models significantly improved discrimination over the reference model. Conclusions: HDL-C, the LDL-C/HDL-C ratio, and the non-HDL-C/HDL-C ratio were independently associated with residual SYNTAX score positivity following primary PCI in patients presenting with a first ACS. These routinely available lipid indices may provide complementary information regarding the presence of residual coronary disease in this specific patient population.