Lipid Profiles, Angiographic Characteristics, and in-Hospital Outcomes in Adults Younger Than 45 Years with Myocardial Infarction.

OBJECTIVE: To characterize adults younger than 45 years with myocardial infarction (MI) and examine factors associated with multivessel disease. METHOD: This single-center retrospective study included patients aged 18-44 years who were hospitalized between January 2024 and January 2026 with STEMI, NSTEMI, or a working diagnosis of MI with nonobstructive coronary arteries (MINOCA). Patients with alternative diagnoses or type 2 MI were excluded. Logistic regression analysis was performed among patients with obstructive coronary disease. RESULTS: Among 180 patients, the mean age was 39.0+-4.1 years, and 160 (88.9%) were male. Low sex-specific HDL-C levels were present in 78.9%, triglyceride levels ≥150 mg/dL in 56.4%, LDL-C levels ≥130 mg/dL in 44.5%, and LDL-C levels ≥160 mg/dL in 22.0%. Multivessel disease was present in 65 of 164 patients with obstructive disease (39.6%). In the exploratory primary model, each 5-mg/dL decrease in HDL-C was associated with multivessel disease (adjusted odds ratio, 1.35; 95% confidence interval, 1.02-1.77; P = 0.034). In a separately specified alternative model using non-HDL-C as the sole lipid covariate, the adjusted association estimate for non-HDL-C did not reach statistical significance (adjusted odds ratio, 1.13 per 25-mg/dL increase; 95% confidence interval, 0.95-1.35; P = 0.175). The composite in-hospital adverse event occurred in 14 patients (7.8%), and mortality was 1.1%. CONCLUSION: In the exploratory primary model, lower HDL-C levels were associated with multivessel disease. In a separately specified alternative model, the adjusted association estimate for non-HDL-C did not reach statistical significance. Because the models differed in covariate composition and complete-case populations and were not designed for direct comparison, these findings do not establish the relative importance of HDL-C and non-HDL-C.