Elevated homocysteine (Hcy) levels have been linked to poorer outcomes in acute coronary syndrome. This study aimed to assess the predictive value of elevated Hcy levels for major adverse cardiac events (MACE) in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).

This retrospective cohort study included 183 STEMI patients who underwent primary PCI at a tertiary university hospital in southern China from January 2020 to December 2021. Laboratory values, including Hcy levels, were obtained within 24 hours of admission. Patients were categorized into elevated and normal Hcy groups using a threshold of 12 μmol/L. The study outcome was the occurrence of 6-point MACE, defined as cardiac death, nonfatal myocardial infarction, stroke, ischemia-driven revascularization (PCI or coronary artery bypass grafting), heart failure and all-cause death. Survival analyses were conducted using Kaplan-Meier and Cox proportional hazard methods. Propensity score matching (PSM) and inverse probability of treatment weighting (IPTW) approaches were employed to minimize bias.

The mean age of the patients was 64.8 years, with 76.0% being male. After adjusting with PSM or IPTW, covariate imbalances between the two groups were corrected. Over a median follow-up period of 25.8 months, 55 MACE events occurred, resulting in an event rate of 30.1%. Patients with elevated Hcy levels had a higher incidence of MACE in both unadjusted (hazard ratio [HR] = 2.778; 95% confidence interval [CI]: 1.591–4.850; p < 0.001) and adjusted analyses (PSM: HR = 2.995; 95% CI: 1.397–6.423, p = 0.005; IPTW: HR = 3.2; 95% CI: 1.631–6.280, p < 0.001). Multivariate Cox regression further confirmed that elevated Hcy levels were associated with a worse prognosis across the entire cohort (HR = 1.062, 95% CI: 1.029–1.097, p < 0.001), PSM cohort (HR = 1.089, 95% CI: 1.036–1.145, p < 0.001), and IPTW cohort (HR = 1.052, 95% CI: 1.020–1.086, p = 0.001).

Elevated plasma levels of Hcy (≥12 μmol/L) are associated with worse outcomes in STEMI patients undergoing primary PCI, highlighting the potential role of Hcy as a prognostic marker in this population.