Incidence of Atrial Fibrillation in Hypokalemic Periodic Paralysis
Atrial fibrillation is not a documented complication of hypokalemic periodic paralysis (HPP); instead, ventricular arrhythmias—including ventricular fibrillation and ventricular tachycardia—are the primary cardiac rhythm disturbances reported in this condition.
Cardiac Arrhythmias in HPP: The Evidence
The available literature on HPP focuses exclusively on ventricular arrhythmias rather than atrial fibrillation:
Ventricular fibrillation has been documented in at least one case of thyrotoxic hypokalemic periodic paralysis, representing a life-threatening complication during severe hypokalemic episodes 1.
A systematic review of 27 HPP patients with cardiac arrhythmias found no cases of atrial fibrillation; instead, ventricular arrhythmias predominated, with 9 patients dying from these arrhythmias 2.
The arrhythmias in HPP occur primarily during severe hypokalemia (11 patients), though some occurred at normokalemia between attacks (4 patients) or were treatment-dependent (2 patients) 2.
Why Ventricular Rather Than Atrial Arrhythmias?
The pathophysiology explains this pattern:
Hypokalemia induces atrial ectopic activity and shortens atrial action potential duration, which theoretically could facilitate AF through re-entry mechanisms 3.
However, in HPP, the severe and acute nature of hypokalemia (often <2.0 mmol/L) creates a more immediate threat to ventricular myocardium, leading to ventricular rather than atrial arrhythmias 4, 5.
Genetic mutations in calcium (CACNA1S) or sodium (SCN4A) channels affect skeletal muscle primarily, and while cardiac expression of these defective channels remains unclear, the clinical manifestation is ventricular dysrhythmia 2.
Clinical Implications and Monitoring
Close cardiac monitoring is essential during HPP attacks, but the focus should be on preventing ventricular arrhythmias:
ECG changes during hypokalemic episodes include U-waves, QRS widening, and ventricular ectopy—not atrial fibrillation 4.
Severe cases require electrophysiology evaluation and possible implantable cardioverter-defibrillator placement to prevent sudden cardiac death from ventricular fibrillation 6.
Treatment-induced arrhythmias can occur during aggressive potassium repletion, requiring careful monitoring to avoid iatrogenic hyperkalemia 4, 2.
Critical Pitfall
Do not confuse HPP with conditions that cause both hypokalemia and atrial fibrillation (such as thyrotoxicosis alone, diuretic use, or primary hyperaldosteronism). In HPP, hypokalemia results from intracellular potassium sequestration rather than total body depletion, and the cardiac manifestation is distinctly ventricular 4, 5.