Loss-of-function variants in KCNH2, which encodes hERG, are responsible for long QT syndrome type 2 (LQT2), a major cause of sudden cardiac death. Most hERG pore-domain missense variants are associated with severe LQT2. However, functional heterogeneity exists among these variants, with a small subset associated with milder phenotypes. Only a limited number of these atypical variants have been functionally characterized. Caenorhabditis elegans expresses UNC-103, a voltage-gated K