Background Myocardial infarction with nonobstructive coronary arteries (MINOCA) is heterogeneous and increasingly recognized. Myocardial bridging (MB) may predispose to nonobstructive ischemia, yet the clinical relevance of serum magnesium in this phenotype is unclear. Objectives To evaluate whether lower serum magnesium is independently associated with MINOCA among patients with angiographically confirmed MB without significant coronary atherosclerosis. Methods We conducted a single‐center, retrospective study of consecutive adults undergoing coronary angiography (April 2020–June 2024). Among 25, 240 angiograms, MB was identified in 2592 patients; after excluding obstructive stenosis and major comorbidities, 337 MB patients without significant atherosclerosis were included: 44 with MINOCA and 293 controls. Serum magnesium (first value within 24 h) was the exposure. Associations were estimated using Firth’s penalized logistic regression. Dose–response was examined with restricted cubic splines (RCSs) ; discrimination was assessed by receiver operating characteristic (ROC) analysis. Prespecified subgroup analyses tested for effect modification. Results Patients with MINOCA had lower magnesium than controls (0. 77 ± 0. 07 vs. 0. 92 ± 0. 10 mmol/L). Each 0. 1 mmol/L decrease in magnesium was associated with higher odds of MINOCA (adjusted odds ratios ORs ≈ 7. 1, 95% confidence interval CI ≈ 4. 0–14. 3). RCS showed a near‐linear inverse relationship (Pₒverall < 0. 001; Pₙonlinear = 0. 434), with risk increasing below ∼0. 89 mmol/L (reference). Magnesium alone demonstrated excellent discrimination (area under the curve AUC 0. 901) ; the Youden‐optimal threshold (0. 855 mmol/L) yielded sensitivity of 88. 6% and specificity of 74. 4%. Findings were broadly consistent across subgroups (no significant interactions). Conclusions In MB patients without significant atherosclerosis, lower serum magnesium is independently associated with MINOCA, with an approximately linear dose–response and strong discriminative performance.
Xiong et al. (Thu,) studied this question.