Clinical significance of serum magnesium levels in patients with heart failure with preserved ejection fraction

Although serum magnesium (Mg) levels are closely associated with the prognosis of heart failure (HF) patients, the clinical significance of sMg levels on the cardiovascular outcomes of HF with preserved ejection fraction (HFpEF) patients is not fully understood. This study was a retrospective, single-center, observational study. We enrolled 452 consecutive HFpEF patients admitted to Kumamoto University Hospital. We defined lower sMg as <2.0 mg/dl (=0.8 mmol/L) based on recent clinical evidence and compared their clinical characteristics and prognosis. There were no significant differences between groups in the use of all medications (loop diuretics, mineralocorticoid receptor antagonists, renin-angiotensin-aldosterone system inhibitors, calcium channel blockers, beta blockers, statins, and Mg preparations). The lower sMg group showed a significantly higher prevalence of diabetes mellitus (DM), uric acid levels, and BNP levels compared with the higher sMg group. Kaplan-Meier curve revealed a significantly higher probability of HF-related events in the lower sMg group compared with the higher sMg group (log-rank test, P = .012). Multivariate Cox-proportional-hazard analysis revealed that the lower sMg group had significantly and independently higher probabilities of HF-related events compared with the higher sMg group (hazard ratio = 2.37, 95% confidence intervals = 1.27-4.41, P = .007). We reclassified the risk of HF-related events after adding the lower sMg to the other prognostic factors (age, previous hospitalization for HF, DM, Ln-BNP); the continuous net reclassification improvement was 29.0% (P = .041). sMg levels might provide important prognostic information in regard to HFpEF.