Association of Serum Magnesium on Mortality in Patients Admitted to the Intensive Cardiac Care Unit

Niyada Naksuk, Tiffany Hu, Chayakrit Krittanawong, Charat Thongprayoon, Sunita Sharma, Jae Yoon Park, Andrew N. Rosenbaum, Prakriti Gaba, Ammar M. Killu, Alan M. Sugrue, Thoetchai Peeraphatdit, Vitaly Herasevich, Malcolm R. Bell, Peter A. Brady, Suraj Kapa, Samuel J. Asirvatham

Research output: Contribution to journalArticlepeer-review

50 Scopus citations


Background Although electrolyte disturbances may affect cardiac action potential, little is known about the association between serum magnesium and corrected QT (QTc) interval as well as clinical outcomes. Methods A consecutive 8498 patients admitted to the Mayo Clinic Hospital—Rochester cardiac care unit (CCU) from January 1, 2004 through December 31, 2013 with 2 or more documented serum magnesium levels, were studied to test the hypothesis that serum magnesium levels are associated with in-hospital mortality, sudden cardiac death, and QTc interval. Results Patients were 67 ± 15 years; 62.2% were male. The primary diagnoses for CCU admissions were acute myocardial infarction (50.7%) and acute decompensated heart failure (42.5%), respectively. Patients with higher magnesium levels were older, more likely male, and had lower glomerular filtration rates. After multivariate analyses adjusted for clinical characteristics including kidney disease and serum potassium, admission serum magnesium levels were not associated with QTc interval or sudden cardiac death. However, the admission magnesium levels ≥2.4 mg/dL were independently associated with an increase in mortality when compared with the reference level (2.0 to <2.2 mg/dL), having an adjusted odds ratio of 1.80 and a 95% confidence interval of 1.25-2.59. The sensitivity analysis examining the association between postadmission magnesium and analysis that excluded patients with kidney failure and those with abnormal serum potassium yielded similar results. Conclusion This retrospective study unexpectedly observed no association between serum magnesium levels and QTc interval or sudden cardiac death. However, serum magnesium ≥2.4 mg/dL was an independent predictor of increased hospital morality among CCU patients.

Original languageEnglish (US)
Pages (from-to)229.e5-229.e13
JournalAmerican Journal of Medicine
Issue number2
StatePublished - Feb 1 2017
Externally publishedYes


  • Acquired long-QT syndrome
  • Hypermagnesemia
  • Hypomagnesemia
  • Magnesium
  • Mortality
  • QTc interval
  • Sudden cardiac death
  • Ventricular arrhythmias

ASJC Scopus subject areas

  • General Medicine


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