Combined Assessment of Immunonutritional Indices and the Triglyceride-Glucose Index in Coronary Slow Flow Phenomenon in a Non-Elderly Population

Background/Objectives: Coronary slow flow phenomenon (CSFP) is considered a condition identified during coronary angiography (CAG), associated with recurrent ischemic symptoms and adverse cardiovascular outcomes while no significant epicardial coronary obstruction is present. The combined predictive role of metabolic and nutritional indices in CSFP has not been fully elucidated. Methods: This analysis, based on a retrospective observational design at a single center, included 214 patients aged < 65 years undergoing CAG who had either normal coronary arteries (NCA) (n = 100) or CSFP (n = 114). CSFP was defined using the TIMI frame count criteria. The triglyceride-glucose (TyG) index, Prognostic Nutritional Index (PNI), Controlling Nutritional Status (CONUT) score, Naples prognostic score (NPS), and C-reactive protein–albumin–lymphocyte (CALLY) index were calculated. Logistic regression was employed to assess independent contributors to CSFP. Results: In comparison with the NCA group, patients with CSFP were more frequently male (73.7% vs. 43.0%, p < 0.001) and active smokers (33.3% vs. 19.0%, p = 0.018). Among these calculated indices, higher TyG index values were observed; in contrast, the CSFP group exhibited lower PNI and CALLY index values. In multivariable analysis, male sex (OR = 5.187, 95% CI: 2.520–10.674, p < 0.001), the TyG index (OR = 1.811, 95% confidence interval [CI]: 1.251–2.622, p = 0.002), and PNI (OR = 0.544, 95% CI: 0.362–0.817, p = 0.003) retained their predictive value for CSFP. Conclusions: Coronary slow flow phenomenon in a non-elderly cohort appears to be linked to metabolic dysfunction, immunonutritional imbalance, and sex-specific differences, with the combined evaluation of the TyG index, PNI, and male sex potentially enhancing risk stratification.