Genotype-Specific Electrophysiological Remodeling in PLN R14del Cardiomyopathy: Implications for Precision Antiarrhythmic Therapy

BACKGROUND: Inherited PLN (phospholamban) R14del variants cause dilated cardiomyopathy with a high burden of malignant ventricular arrhythmias. However, the single-cell electrophysiological substrate underlying arrhythmogenicity is incompletely characterized, and it is unclear whether antiarrhythmic agents validated in wild-type (WT) or long QT models retain efficacy in this genotype. We sought to define the genotype-specific electrophysiological phenotype of PLN R14del cardiomyocytes and evaluate how modulation of the transient outward potassium current and late sodium current alters arrhythmic risk. METHODS: Isogenic WT (HD.15S1) and CRISPR (clustered regularly interspaced short palindromic repeats)-edited PLN R14del human induced pluripotent stem cell-derived cardiomyocytes were studied using high-throughput optical action potential (AP) recordings. A deep learning framework classified AP morphology to quantify normal versus aberrant AP types, AP duration, and early afterdepolarization incidence at baseline and under graded concentrations of the transient outward potassium current activator NS-5806, the transient outward potassium current inhibitor acacetin, and the selective late sodium current blocker GS-967 (eleclazine). RESULTS: At baseline, PLN R14del human induced pluripotent stem cell-derived cardiomyocytes exhibited a subtle but significant arrhythmogenic phenotype, with a reduced proportion of normal APs, prolonged AP duration, and increased early afterdepolarizations compared with isogenic WT, consistent with impaired calcium handling and diminished repolarization reserve. In WT cells, NS-5806 produced a biphasic, dose-dependent response, transiently destabilizing and then restoring normal AP morphology; in PLN R14del cells, NS-5806 induced marked proarrhythmic remodeling and near-complete loss of normal APs at higher doses. GS-967 paradoxically exacerbated arrhythmic features in the mutant line, including AP duration prolongation and suppression of normal APs. Acacetin preserved stability in WT cells but failed to rescue normal AP morphology in PLN R14del cardiomyocytes. CONCLUSIONS: PLN R14del cardiomyopathy creates a distinct electrophysiological substrate that fundamentally alters antiarrhythmic drug responsiveness, such that agents beneficial in WT contexts may be ineffective or proarrhythmic in this genotype. Preclinical antiarrhythmic evaluation should incorporate genotype-specific, patient-derived human induced pluripotent stem cell models to enable precision medicine strategies in inherited cardiomyopathies.