Which electrolyte abnormality is commonly linked to dangerous cardiac arrhythmias?

• A. Hypercalcemia
• B. Hypophosphatemia
• C. Hyperkalemia
• D. Hypernatremia

Answer: (C)

Potassium balance drives the heart’s electrical activity. The resting membrane potential and the way cardiomyocytes repolarize depend heavily on extracellular potassium levels. When potassium in the blood rises, the gradient across the cell membrane decreases, cells become less polarized, and conduction is altered. This produces early signs on the ECG—tall, peaked T waves—and can progress to PR prolongation, QRS widening, and eventually a dangerous, life-threatening rhythm as the cells fail to coordinate properly.

Because these changes directly affect cardiac rhythm and can escalate to fatal arrhythmias, the electrolyte abnormality most commonly linked to dangerous cardiac arrhythmias is high potassium.

Other abnormalities can influence the heart as well, but they do not produce malignant arrhythmias with the same frequency or immediacy as hyperkalemia.