Which electrolyte disturbance is most likely to provoke ventricular arrhythmias in a patient taking diuretics?

Which electrolyte disturbance is most likely to provoke ventricular arrhythmias in a patient taking diuretics?

• A. Hypokalemia
• B. Hyperkalemia
• C. Hyponatremia
• D. Hypomagnesemia

Answer: (A)

Potassium controls how heart muscle cells repolarize after each beat, so its balance is key to a stable rhythm. Diuretics, especially loop and thiazide types, commonly cause potassium loss, lowering serum potassium. When potassium is low, the ventricles become electrically unstable: repolarization is prolonged, the QT interval can widen, and there’s increased dispersion of repolarization across the ventricular tissue. This creates a substrate for ectopic impulses and dangerous ventricular rhythms, including ventricular tachycardia. Low potassium also promotes afterdepolarizations that can trigger arrhythmias. While other disturbances like low magnesium can contribute, the diuretic-related risk most strongly centers on hypokalemia. Maintaining potassium within the normal range is essential to reduce the likelihood of ventricular arrhythmias in these patients.

Potassium controls how heart muscle cells repolarize after each beat, so its balance is key to a stable rhythm. Diuretics, especially loop and thiazide types, commonly cause potassium loss, lowering serum potassium. When potassium is low, the ventricles become electrically unstable: repolarization is prolonged, the QT interval can widen, and there’s increased dispersion of repolarization across the ventricular tissue. This creates a substrate for ectopic impulses and dangerous ventricular rhythms, including ventricular tachycardia. Low potassium also promotes afterdepolarizations that can trigger arrhythmias. While other disturbances like low magnesium can contribute, the diuretic-related risk most strongly centers on hypokalemia. Maintaining potassium within the normal range is essential to reduce the likelihood of ventricular arrhythmias in these patients.