High-magnesium exposure to bullfrog heart causes ST segment elevation

Area of Science:

• Cardiology
• Electrophysiology
• Toxicology

Background:

• Hypermagnesemia, often seen in the elderly or those with kidney issues, can result from excessive magnesium-containing laxative use.
• Electrocardiogram (ECG) abnormalities in severe hypermagnesemia include ST segment and T wave changes, similar to acute myocardial infarction.

Purpose of the Study:

• To investigate the direct effects of high magnesium on cardiac electrophysiology.
• To elucidate the underlying mechanism of ECG changes observed in severe hypermagnesemia.

Main Methods:

• Bullfrog hearts were exposed to high-magnesium solutions to observe ECG and cardiac action potential changes.
• Protein abundance of Na+/K+-ATPase was assessed.
• The effect of insulin on Na+/K+-ATPase activity and ECG was evaluated.

Main Results:

• High magnesium exposure reproduced prominent ST segment elevations and T wave changes in ECG.
• Cardiac action potentials showed a depolarized resting membrane potential.
• Na+/K+-ATPase protein levels remained unaffected, but insulin stimulation rapidly reversed ST segment elevations.

Conclusions:

• Magnesium ions functionally block Na+/K+-ATPase activity.
• This blockade disrupts the potassium gradient, leading to ST segment changes in hypermagnesemia.
• Targeting Na+/K+-ATPase activity may offer therapeutic potential for hypermagnesemia-induced ECG changes.