Mexiletine prevents transient heart failure in a polymicrogyria child with an ATP1A3 variant: a case report

Loss of function of the Na-K-ATPase caused high concentrations of intracellular Na⁺ and subsequent increments in Ca²⁺ via the Na⁺/Ca²⁺ exchanger in the steady state. An augmentation of the late Na⁺ current (I_{Na, L}) due to bradycardia may have led to further increments of intracellular Na⁺ and Ca²⁺, causing myocardial stunning. Based on the proposed pathophysiological mechanism, we selected mexiletine, which blocks Na⁺ channels particularly in the inactivated state, reducing I_{Na, L} and the subsequent Ca²⁺ overload. Mexiletine was administered safely, successfully preventing transient HF.