Related Experiment Video
Updated: Oct 18, 2026

Isolation of Human Ventricular Cardiomyocytes from Vibratome-Cut Myocardial Slices
Published on: May 10, 2020
Acute effects of intravenous magnesium on ventricular refractoriness and monophasic action potential duration in
1Department of Medicine, Helsinki University Central Hospital, Finland. hannu.parikka@huch.fi
Abstract:
The objective of this study was to examine the antiarrhythmic mechanisms of magnesium (Mg). The 12 patients who were selected for the study were given 12 mmol Mg sulphate followed by an infusion of 8 mmol/h. Ventricular effective refractory period (VERP). monophasic action potential duration at 50% and 90% repolarization during spontaneous rhythm (MAPD50, MAPD90) and atrial pacing at a cycle length of 600 ms (MAPD(50)600, MAPD(90)600) were measured before and after the intervention. Plasma magnesium concentration rose from 0.83 +/- 0.05 to 1.85 +/- 0.24 mmol/l (p < 0.001). Shortening of MAPD(50) (250 +/- 45 vs 240 +/- 46 ms; p < 0.05), MAPD(90) (294 +/- 42 vs 283 +/- 41 ms; p < 0.05) and shortening of sinus cycle length (SCL) (783 +/- 153 vs 742 +/- 160 ms; p < 0.01) were detected. During controlled cycle length, magnesium decreased MAPD(50)600 (230 +/- 28 vs 221 +/- 28 ms; p < 0.01), MAPD(90)600 (274 +/- 25 vs 261 +/- 29 ms; p < 0.01) and VERP (247 +/- 25 vs 241 +/- 21 ms: p < 0.05). QRS duration, QT interval and blood pressure remained unchanged. The change in SCL correlated with the change in MAPD(50) (r = 0.58; p < 0.05) and MAPD(90) (r = 0.55; p = 0.06 ) but not with MAPD(50)600, MAPD(90)600 or VERP. Magnesium acutely shortens ventricular monophasic action potential duration and refractoriness. This effect is partly mediated by mechanisms that increase heart rate. The reductions might bring salutary effects in arrhythmias evoked by prolonged repolarization.
Related Concept Videos
Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers
Verapamil, a calcium channel blocker, inhibits calcium movement across myocardial cell membranes and vascular smooth muscle. This results in the dilation of coronary and...
Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers
Class 1A Antiarrhythmic Drugs: These drugs work by moderately blocking sodium channels,...
Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers
Cardiac Action Potential
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers
Depolarizing Blockers: Mechanism of Action
Succinylcholine is the most commonly used depolarizing blocker. Chemically, it constitutes two molecules of acetylcholine joined together by an acetate methyl group. They act on the receptors in the same way as acetylcholine. Because succinylcholine...

