The influence of elevated Mg2+ concentrations on cardiac electrophysiologic parameters

This study was performed to evaluate the direct effects of magnesium ions on cardiac conduction velocities and on refractoriness using a modified Langendorff perfusion system and a special ECG recording and stimulation technique. An increase of the MG2+ concentration to 2.3 mM had no detectable effe...

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Bibliographic Details
Published in:Cardiovascular drugs and therapy 1989-04, Vol.3 (2), p.183-189
Main Authors: Stark, G, Stark, U, Pilger, E, Hönigl, K, Bertuch, H, Tritthart, H A
Format: Article
Language:English
Subjects:
Animals
Atrioventricular Node - drug effects
Bundle of His - drug effects
Cardiac Complexes, Premature - physiopathology
Electric Stimulation
Electrocardiography
Electrophysiology
Female
Guinea Pigs
Heart - drug effects
Heart Conduction System - drug effects
In Vitro Techniques
Magnesium - pharmacology
Male
Refractory Period, Electrophysiological - drug effects
Sinoatrial Node - drug effects
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Summary:This study was performed to evaluate the direct effects of magnesium ions on cardiac conduction velocities and on refractoriness using a modified Langendorff perfusion system and a special ECG recording and stimulation technique. An increase of the MG2+ concentration to 2.3 mM had no detectable effects. Higher concentrations of up to 4.6 mM decreased the spontaneous sinus rate and the conduction velocity through the AV node and the His bundle in a concentration-dependent manner. During stimulation with premature beats, in the presence of 4.6 mM of Mg2+, the effective and relative refractory periods (ERP, RRP) of sinoatrial, AV nodal, and His bundle conduction and the ERP of the ventricular myocardium were significantly prolonged, whereas the ERP of the atrial myocardium remained unaffected. The refractoriness of sinoatrial, AV nodal, and His bundle conduction, and of the ventricular myocardium, were also prolonged during pacing with a stepwise increased pacing rate. These observations suggest a marked rate-dependent inhibitory effect of magnesium on the refractoriness of the His-bundle conduction and of the ventricular myocardium, which might be an important factor in the antiarrhythmic effectiveness of magnesium in ventricular tachyarrhythmias.
ISSN:0920-3206
1573-7241
DOI:10.1007/bf01883863