Kir2.1 mutations differentially increase the risk of flecainide proarrhythmia in Andersen Tawil Syndrome

BackgroundFlecainide and other class-Ic antiarrhythmic drugs (AADs) are widely used in Andersen-Tawil syndrome type 1 (ATS1) patients. However, class-Ic drugs might be proarrhythmic in some cases. We investigated the molecular mechanisms of class-I AADs proarrhythmia and whether they might increase the risk of death in ATS1 patients with structurally normal hearts. Methods and ResultsOf 53 ATS1 patients reviewed from the literature, 54% responded partially to flecainide, with ventricular arrhythmia (VA) reduction in only 23%. Of the latter patients, VA persisted in 20-50%. Flecainide was ineffective in 23%, and surprisingly, 13.5% suffered a non-fatal cardiac arrest. In five cardiac-specific ATS1 mouse models (Kir2.1{Delta}314-315, Kir2.1C122Y, Kir2.1G215D and Kir2.1R67W and Kir2.1S136F), flecainide or propafenone (40 mg/Kg i.p.) differentially prolonged the P wave, and the PR, QRS and QTc intervals compared to Kir2.1WT; Kir2.1S136F had milder effects. Flecainide increased VA inducibility in all mutant mice except Kir2.1S136F, which exhibited significant VA reduction. At baseline, Kir2.1G215D cardiomyocytes had the lowest inward rectifier K+ channel (IK1) reduction, followed by Kir2.1C122Y, Kir2.1R67W and Kir2.1S136F. Kir2.1C122Y cardiomyocytes had a significant decrease in sodium inward current (INa). Flecainide (10 {micro}M) slightly increased IK1 density in Kir2.1WT and Kir2.1S136F, while it decreased both IK1 and INa in Kir2.1C122Y and Kir2.1R67W, despite normal trafficking of mutant channels. Optical mapping in ATS1 patient-specific iPSC-CM monolayers expressing Kir2.1C122Y, Kir2.1G215D and Kir2.1R67W showed an increase in rotor incidence at baseline and under flecainide, confirming the dru[g]s proarrhythmic effect. Lastly, in-silico molecular docking predicts that the Kir2.1-Cys311 pharmacophore-binding site is altered in Kir2.1C122Y heterotetramers, reducing flecainide accessibility and leading to channel closure and arrhythmias. ConclusionsClass-Ic AADs are only partially effective and might be proarrhythmic in some ATS1 patients. Kir2.1 mutations impacting the resting membrane potential and cellular excitability create a substrate for life-threatening arrhythmias, raising significant concern about using these drugs in some ATS1 patients. CLINICAL PERSPECTIVE NOVELTY AND SIGNIFICANCEO_ST_ABSWhat is known?C_ST_ABSO_LIAndersen-Tawil syndrome type 1 (ATS1) is a rare autosomal dominant disease caused by loss-of-function mutations in the KCNJ2 gene, which encodes the Kir2.1 channel responsible for the repolarizing, strong inwardly rectifying current IK1. C_LIO_LIATS1 treatment is empirical and subject to clinical judgment. It includes the use of class-Ic antiarrhythmic drugs (AADs), mainly flecainide, alone or in combination with {beta}-adrenergic blocking drugs. However, pharmacological treatment is partial and might fail, leading to life-threatening ventricular arrhythmias (VA) and sudden cardiac death (SCD) in some ATS1 patients. C_LIO_LISome ATS1 mutations are known to disrupt the Kir2.1-Nav1.5 channelosome in mice and human iPSC-CMs, with consequent reductions in cardiac excitability and conduction velocity (CV), leading to VA, which may be exacerbated by flecainide. C_LI What new information does this article contribute?O_LIIn our analysis of 53 ATS1 patients, flecainide showed partial effectiveness. While a few patients experienced complete disappearance of VA, others had persistent arrhythmias and even suffered non-fatal cardiac arrest while on medication. C_LIO_LIIn murine models expressing five relevant ATS1 mutations, flecainide or propafenone produced differential alteration in the P wave, PR, QRS and QTc intervals, and increased VA inducibility compared with Kir2.1WT mice. Additionally, flecainide differentially affected IK1 and the Na+ inward current (INa) current densities despite normal trafficking of mutant channels. C_LIO_LIIn patient-specific induced pluripotent stem cell derived cardiomyocyte (iPSC-CM) monolayers flecainide reduced CV and increased rotor incidence, confirming the drug[s] proarrhythmic effect. C_LIO_LIIn-silico molecular docking studies predicted that the Cys311 pharmacophore binding site and flecainide accessibility are altered in mutated Kir2.1 channels, leading to premature channel closure and arrhythmias. C_LIO_LIWe conclude that class-Ic AADs are only partially effective and might be proarrhythmic in some ATS1 patients. C_LIO_LIThese findings raise concern about the use of class-Ic AADs in ATS1 patients and highlight the need for further studies to guide personalized therapy. C_LI