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Tissue magnesium levels and the arrhythmic substrate in humans
M C Haigney1, R Berger, S Schulman
1Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA. MCPH@AOL.com
Journal of Cardiovascular Electrophysiology
|September 23, 1997
Summary
Low tissue magnesium levels are linked to abnormal heart repolarization and arrhythmias, especially in patients with reduced heart function. This finding may not apply to certain types of ventricular tachycardia.
Area of Science:
- Cardiology
- Electrophysiology
- Biochemistry
Background:
- Magnesium deficiency is a suspected factor in sudden cardiac death.
- Measuring cellular magnesium stores for arrhythmia research has been challenging.
Purpose of the Study:
- To investigate the association between tissue magnesium levels and triggered arrhythmias.
- To assess if magnesium deficiency correlates with QT interval dispersion, an indicator of repolarization abnormalities.
Main Methods:
- Tissue magnesium was measured in the sublingual epithelium of 40 patients with arrhythmic complaints using X-ray dispersive analysis.
- QT interval dispersion was assessed via 12-lead surface ECGs.
- Programmed electrical stimulation was performed in a subset of patients.
Main Results:
- Sublingual epithelial magnesium levels, not serum levels, inversely correlated with QT interval dispersion (r = 0.58, P < 0.005).
- Patients with reduced left ventricular ejection fraction (<40%) had significantly lower tissue magnesium and higher QT dispersion.
- No significant difference in tissue magnesium or QT dispersion was observed between patients with inducible and non-inducible monomorphic ventricular tachycardia.
Conclusions:
- Reduced tissue magnesium stores are a potential risk factor for arrhythmias linked to abnormal repolarization, particularly in patients with impaired left ventricular systolic function.
- Magnesium deficiency may not be a risk factor for excitable gap arrhythmias like monomorphic ventricular tachycardia, which have a fixed anatomic substrate.