KEY TEACHING POINTS

•Andersen-Tawil syndrome type 1 (ATS1) or other genetic arrhythmia syndromes need to be considered in patients with dysmorphic features and/or a high burden of premature ventricular contractions (PVCs), especially polymorphic PVCs, which are unlikely to respond to ablative therapy. •A genetic variant reported as a variant of uncertain significance may be disease-causing and careful clinical evaluation is an important consideration to determine the significance of a gene variant. •Amino acid R218 of Kir2.1 is associated with at least 3 gene variants (R218L, R218Q, R218W) found in ATS1 patients.