Ackerman, Michael J.

Background: The estimated prevalence of attention-deficit/hyperactivity disorder (ADHD) globally is about 5%. For patients with catecholaminergic polymorphic ventricular tachycardia (CPVT), ADHD-directed stimulant therapy is relatively contraindicated. However, previous studies have shown that use of these treatments is safe for patients with long QT syndrome, a similar genetic heart disease. Whether this is the same for patients with CPVT remains unknown. Objective: To evaluate ADHD-directed treatment, outcome, and frequency of CPVT-triggered events in patients with CPVT and concomitant ADHD. Methods: A retrospective electronic medical record review of 216 patients with CPVT evaluated in Mayo Clinic’s Windland Smith Rice Genetic Heart Rhythm Clinic was performed to determine the prevalence of concomitant ADHD and the incidence of CPVT-triggered events in these patients. Results: Overall, 14 patients (6%) were diagnosed with CPVT and concomitant ADHD (6 female, average age 19 ± 3 years). At the time of first evaluation, ADHD-directed stimulant therapy was stopped or advised against in 8/14 patients (57%). It was (re)started in 11 patients (79%) following comprehensive evaluation and treatment initiation for CPVT with pharmacologic therapy in 14/14 patients (100%), denervation surgery in 12 (86%), and an implantable cardioverter defibrillator in 4 (29%). Prior to Mayo Clinic evaluation, 10 patients (71%) treated for CPVT had a breakthrough cardiac event, without being on stimulant therapy, while 4 patients (29%) had an event while being treated for both CPVT and ADHD for an average time on stimulant therapy of 6 ± 6 years. Following CPVT treatment optimization and ADHD stimulant (re)initiation, patients have remained event-free for a total of 82 patient years (mean follow-up 6 ± 5 years). Conclusion: Among patients with CPVT, the prevalence of ADHD was similar to that in the general population, which can be treated safely and effectively with stimulant therapy. Although the rate of adverse events was low in stimulant-treated patients, physicians should weigh the potential effects of suboptimal treatment of ADHD with the theoretical proarrhythmic risk from stimulant medications on a case-by-case basis.

Background: Type 2 long QT syndrome (LQT2) is an inherited arrhythmia syndrome caused by pathogenic variants in the KCNH2 gene which result in QT prolongation and confers susceptibility to arrhythmic syncope/seizures and sudden cardiac arrest/death. Oral progestin-based contraceptives increase the risk of cardiac events in women with LQT2 and we previously reported the case of a LQT2 woman with recurrent cardiac events attributed to the use of the progestin-based contraceptive, Medroxyprogesterone Acetate (“Depo-Provera”, Depo). Objective: To evaluate the arrhythmic-risk of Depo in a LQT2-specific, induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) model. Methods: An iPSC-CM line was generated from the previously reported woman (KCNH2-G1006A*fs) as well as a control line. Voltage-sensing dye was used to assess the optical action potential duration (APD) with 10 μM Depo. 3-D erratic beating patterns were then assessed using multiple electrode array (MEA) with Depo and isoproterenol (ISO) to mimic an adrenergic surge. Results: Addition of Depo to the G1006A*fs iPSC-CMs decreased the optical APD from baseline 438±14 ms (n=6) to 363±35 ms (n=12; p=0.0001). Despite the APD shortening at baseline, in the setting of ISO, Depo administration induced erratic beating patterns in MEA, characterized as alternating spike amplitudes, alternans, or early after depolarization-like phenomena. Combined Depo and ISO treatment increased the percent of electrodes displaying erratic beating in G1006A*fs [baseline 8%±13 vs. Depo + ISO 38%±40 (p=0.0097)] but not in controls [baseline 2%±5 vs. Depo + ISO 7%±11 (p=0.14)]. Neither Depo nor ISO alone changed beating patterns in G1006A*fs [baseline 8%±13, Depo 30%±41 (p=0.08), ISO 21%±30, (p=0.17)] and controls [baseline 2%±5, Depo 3%±7 (p=0.61), ISO 0%±0 (p=0.4)]. Conclusion: This patient-specific, re-engineered heart cell study provides a potential mechanism for the patient’s clinically documented, Depo-associated episodes of recurrent ventricular fibrillation. This in-vitro data should prompt a large-scale clinical assessment of Depo’s potential pro-arrhythmic effect in women with LQT2.

Introduction: Pathogenic variants in PKP2 -encoded plakophilin 2 cause arrhythmogenic right ventricular cardiomyopathy (ARVC). Electrocardiographically, PKP2 -mediated ARVC may mimic RYR2 -mediated catecholaminergic polymorphic ventricular tachycardia (CPVT). We compare the underlying mechanism of arrhythmia in ARVC and CPVT using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). Methods: iPSC-CMs were generated from 2 ARVC patients with different PKP2 variants [E149X (PKP2-1) and c.2146-1G>C (PKP2-2)], 1 patient with a CPVT variant [RyR2-R176Q (CPVT1)], and a wild-type (WT) control. Fluo-4 AM calcium dye was used to assess calcium kinetics in iPSC-CMs before and during treatment with 100 nM isoproterenol (ISO) at 8-10 min. Results: Compared to WT, PKP2 and RYR2 iPSC-CMs had a greater amplitude before (WT: 0.331±0.031, PKP2-1: 1.048±0.074, PKP2-2: 1.076±0.095, CPVT1: 0.966±0.061; P<0.0001) and during ISO (WT: 0.277±0.022, PKP2-1: 0.971±0.069, PKP2-2: 0.622±0.041, CPVT1: 0.756±0.051; P<0.0001). The Ca 2+ transient duration (CTD100) was longer in PKP2 and RYR2 iPSC-CMs compared to WT before (WT: 1.01±0.05 s, PKP2-1: 1.84±0.01 s, PKP2-2: 1.76±0.02 s, CPVT1: 1.81±0.02 s; P<0.0001) and during ISO (WT: 1.38±0.05 s, PKP2-1: 1.65±0.03 s, PKP2-2: 1.71±0.03 s, CPVT1: 1.61±0.05 s; P<0.001). Before (WT: 259±13 ms, PKP2-1: 538±23 ms, PKP2-2: 493±28 ms, CPVT1: 586±24 ms; P<0.0001) and during ISO (WT: 311±19 ms, PKP2-1: 406±21 ms, P=0.0172, PKP2-2: 487±28 ms, P<0.0001, CPVT1: 453±21 ms, P=0.0001), peak to 50% decay time was slower in PKP2 and RYR2 iPSC-CMs compared with WT. Upstroke time was longer in PKP2 and RYR2 iPSC-CMs compared to WT before (WT: 205±5 ms, PKP2-1: 539±13 ms, PKP2-2: 429±19 ms, CPVT1: 455±12 ms; P<0.0001) and during ISO (WT: 213±7 ms, PKP2-1: 375±16 ms, PKP2-2: 416±20 ms, CPVT1: 389±10 ms; P<0.0001). Conclusion: Here, iPSC-CMs, derived from patients with either PKP2 -mediated ARVC or RYR2 -mediated CPVT, display similar abnormal calcium handling properties such as greater amplitude, longer CTD100, and slower peak to 50% decay time and upstroke time compared to WT iPSC-CMs before and during ISO treatment. This may explain why patients with PKP2 -mediated ARVC often mimic the treadmill stress test seen in patients with CPVT1.

Background: Long QT syndrome (LQTS) stems from cardiac action potential duration (APD) prolonging pathogenic variants in KCNQ1 (LQT1), KCNH2 (LQT2), or SCN5A (LQT3). Sodium/glucose co-transporter 2 inhibitor (SGLT2i), a class of drugs used to treat type II diabetes and all forms of heart failure, reduces cardiac late sodium channel current. Objective: To test the ability of three commercially available SGLT2i to reduce APD in patient-specific induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) models of LQT1, LQT2, and LQT3. Method: Patient-specific iPSC-CMs and a CRISPR/Cas9 gene-edited variant corrected, isogenic control (IC) iPSC-CMs were generated. The variant-corrected IC was used to determine the curative APD in order to establish the degree of APD attenuation. The SCN5A-P1332L (LQT3) and IC iPSC-CMs were tested with 10 μM of either canagliflozin (CANA), dapagliflozin (DAPA), or empagliflozin (EMPA). An ATXII (5μM)-induced APD prolongation iPSC-CM model, mimicking drug-induced LQT3, was also treated. The APD was measured 30 minutes, 1 hour, and 2 hours after treatment using local extracellular action potential recordings on multielectrode array. The efficacy of these SGLT2i were also tested in KCNQ1-V254M (LQT1) and KCNH2-G604S (LQT2) iPSC-CMs. Results: The APD90 was prolonged in SCN5A-P1332L iPSC-CMs compared to its IC (469 ± 4 ms vs 305 ± 2 ms, p<0.0001). While 10 μM of SGLT2i had no APD shortening effect on the KCNQ1-V254M or KCNH2-G604S iPSC-CMs, all three SGLT2i compounds shortened the APD90 of the SCN5A-P1332L iPSC-CMs after 1 hour of treatment from 463±5 ms to 432±6 ms (EMPA, 18.8% attenuation, p=0.0002), 459±8 ms to 430±5 ms (CANA, 17.5%, p=0.004), and 453±6 ms to 434±4 ms (DAPA, 11.4%, p=0.01). Additionally, IC iPSC-CMs treated with 5 μM of ATXII induced significant APD prolongation from 318±9 ms to 379±12 ms (p=0.0003) after 30 min incubation. However, co-incubation of ATXII and SGLT2i abolished the APD prolonging effect of ATXII. Conclusions: Therapeutically inhibiting SGLT2 effectively shortens the cardiomyocyte APD in human heart cell models of the LQT3, but not LQT1 or LQT2. This pre-clinical data compels further assessment of SGLT2i as a novel therapy for patients with congenital LQT3.

Background: Drug-induced QT prolongation (DI-QTP) is a clinical entity in which administration of a HERG/I Kr blocker such as dofetilide prolongs the cardiac action potential duration (APD) at the cellular level and the QT interval clinically, and increases the risk for a potentially lethal, QT-triggered ventricular arrhythmia. There may be a role for inhibition of I NaL to counter DI-QTP. Recently, we have shown that inhibition of serum and glucocorticoid regulated kinase-1 (SGK1) reduces the APD90 in induced pluripotent stem cell derived cardiomyocytes (iPSC-CM) from patients with LQT3 and ameliorates increases in I NaL . Objective: To test the efficacy of novel SGK1 inhibitors (SGK-I) in re-engineered cardiomyocyte models of dofetilide-induced APD prolongation. Methods: Normal iPSC-CMs were treated with dofetilide [5 nM] to produce a DI-QTP iPSC-CM model. The SGK1-I’s therapeutic efficacy for shortening the dofetilide-induced APD90 prolongation was compared to mexiletine. The APD90 values were recorded 4 hours after treatment using FluoVolt, a voltage-sensitive fluorescent dye. Results: The APD90 was significantly prolonged in normal iPSC-CMs treated with dofetilide (673 ± 8 ms with dofetilide vs 436 ± 4 ms with DMSO, p<0.0001). While 10 μM mexiletine shortened the average APD90 of dofetilide-treated normal iPSC-CMs from 673 ± 4 ms to 563 ± 8 ms (46% attenuation, p<0.0001), 30 nM of SGK-I shortened the APD90 from 673 ± 4 ms to 478 ± 10 ms (82% attenuation, p<0.0001). Conclusions: Therapeutically inhibiting SGK1 effectively shortens the cardiomyocyte APD in a human heart cell model of DI-QTP. The novel SGK1 inhibitor normalized the pathological APD prolongation almost fully (> 80%) in the iPSC-CM model treated with dofetilide. This pre-clinical data supports further development of this therapeutic strategy to counter and neutralize the threat of DI-QTP.

Background: Long QT syndrome (LQTS) often stems from pathogenic variants in KCNQ1 (LQT1), KCNH2 (LQT2), or SCN5A (LQT3) and is characterized cellularly by prolongation of the cardiac action potential duration (APD). We have shown that inhibition of serum and glucocorticoid regulated kinase-1 (SGK1) reduces I NaL and is proposed as a novel therapeutic strategy for LQT3. Objective: To test the efficacy of a potent and selective SGK1 inhibitor (SGK1-I) in human cardiomyocyte models of LQT1, LQT2, and LQT3. Methods: Induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) were generated from patients with either LQT1, LQT2, or LQT3. The mexiletine (MEX)-sensitive SCN5A-P1332L iPSC-CMs were tested initially. A CRISPR/Cas9 P1332L variant-corrected isogenic control (IC) was used as a control. The SGK1-I’s therapeutic efficacy was compared to MEX and to a commercially available SGK1 inhibitor (EMD638683). The novel SGK-I was then tested for APD shortening in SCN5A-R1623Q, KCNH2-G604S and KCNQ1-V254M iPSC-CMs. The APD90 values were recorded 4 hours after treatment using FluoVolt. Results: The APD90 was significantly prolonged in SCN5A-P1332L iPSC-CMs compared to its IC (646 ± 7 ms vs 482 ± 23 ms, p<0.0001). MEX shortened the average APD90 to 560 ± 7 ms (52% attenuation). Interestingly, SGK1-I significantly shortened the APD to 518 ± 5 ms (78% attenuation) but did not further shorten the APD in the IC. SGK1-I also shortened the APD90 of the SCN5A-R1623Q iPSC-CMs from 753 ± 8 ms to 475 ± 19 ms compared to 558 ± 19 ms with MEX. The SGK1-I shortened the APD90 in KCNH2-G604S (666 ± 10ms to 574 ± 18ms for SGK1-I versus 538 ± 15 ms after MEX). EMD had limited APD shortening effects in SCN5A and KCNH2 iPSC-CMs. Interestingly, while neither MEX nor EMD reduced the APD90 in the KCNQ1-V254M iPSC-CMs, the novel SGK1-I reduced the APD90 from 544 ± 10 ms to 475 ± 11ms (p=0.0004). Conclusions: Therapeutically inhibiting SGK1 effectively shortens the cardiomyocyte APD in human heart cell models of the 3 major LQTS genotypes. The novel SGK1-I normalized the pathological APD prolongation almost fully (> 70%) in the patient-derived SCN5A-P1332L iPSC-CM model. These pre-clinical data support further development of SGK1-I as a novel, first-in-class therapy for patients with congenital LQTS.

Introduction: Gain-of-function mutations in SCN5A- encoded cardiac sodium channel (Na V 1.5) cause type 3 long QT syndrome (LQT3). Patients with SCN5A variants localizing to the local anesthetic binding domain might not be sensitive to lidocaine or mexiletine treatment. Hypothesis: Phenytoin, a sodium channel blocker used to treat epilepsy, may be a novel LQT3-directed therapy for a variant involving a critical residue of the Nav1.5’s local anesthetic binding domain. Methods: SCN5A-F1760C was identified in a now deceased infant with severe LQT3 (QTc of 680-1200 ms) who was refractory to left cardiac sympathetic denervation and pharmacological treatments with either lidocaine or mexiletine. SCN5A-F1760C was engineered by site directed mutagenesis and expressed in TSA201 cells. Patient-specific pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from the SCN5A-F1760C-positive infant and gene-edited/variant-corrected isogenic control (IC) iPSC-CMs were generated. Na V 1.5 currents were recorded in TSA201 cells transfected with SCN5A-WT/ F1760C and action potentials (APs) from iPSC-CMs were recorded before and after treatment with 5μM Phenytoin using the whole cell patch-clamp technique. Results: SCN5A-F1760C did not change the NaV1.5 current density. However, the V1/2 of inactivation was right-shifted significantly by +14.1 mV from -86.3±0.9 mV (WT) to -72.2±0.7 mV (F1760C, p<0.0001) resulting in a marked increase in window current. F1760C increased sodium late current 2-fold from 0.18±0.04% in WT to 0.49±0.07% in F1760C (p=0.0005). Baseline APD to 90% repolarization (APD90) was prolonged significantly in F1760C-derived iPSC-CMs (641±40 ms) compared to IC iPSC-CMs (412±22 ms, p<0.0001). Treatment with 5μM phenytoin normalized the APD90 in F1760C-derived iPSC-CMs to 423+34 ms (p<0.0001), values approximating the ‘gene/variant-edited’ cure. Conclusions: Na V 1.5 gain-of-function caused by a novel SCN5A-F1760C variant results in marked APD90 prolongation which were rescued by phenytoin indicating the antiepileptic drug, phenytoin, may be a mutation-specific, LQT3-directed therapy for those LQT3-causative variants that disrupt the local anesthetic/lidocaine-binding domain.

Abstract Hypertrophic Cardiomyopathy (HCM) is an inheritable heart disease with the highest rate of sudden cardiac death (SCD) in young adults. Implantable Cardioverter Defibrillator (ICD) therapy is recommended for HCM patients at high risk for SCD. Reviewing the recent clinical literature revealed the potential to improve the selection of candidates for ICD implantation. The current study uses information extracted from echocardiography reports to evaluate HCM patients with ICD and aims to provide a comparative insight into patients who benefited the most from the device therapy, including shock and anti-tachycardia pacing (ATP). The proposed interpretable machine learning approach has used the XGboost algorithm. The model’s performance was considered satisfactory, as evidenced by an accuracy score of 81% and an area under the receiver operating characteristic curve (AUC) value of 69% and SHapley Additive exPlanations (SHAP) identified common properties of HCM patients in each category and provided high-level reasoning and foundation for a clinical decision support tool.

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): National Institute of Health Research St George's, University of London Background SCN5A-E1784K (c.5350G&gt;A) is the most common variant associated with the LQT3 long QT syndrome (LQTS) and Brugada syndrome (BrS). It exhibits incomplete penetrance and can manifest variably as a mixed clinical phenotype of LQTS, BrS and/or conduction disorders (1-4). This presents a challenge for risk stratification and optimal management. We aimed to describe the clinical characteristics and risk markers in a large, well characterised international cohort of SCN5A-E1784K subjects and identify demographic and/or ECG parameters associated with event free survival. Methods Comprehensive clinical data, including initial presentation and follow-up data, were collected from SCN5A-E1784K subjects. Outcome ‘events’ included sudden death, aborted cardiac arrest, and documented VF or VT or arrhythmic syncope. ‘Lethal events’ included sudden death, aborted cardiac arrest or documented VF or VT. Associations between clinical characteristics and event free survival were investigated using Cox proportional hazard regression models. Results SCN5A-E1784K subjects (n=231) were recruited from 16 centres. Median follow up was 24.9 years (15.2 - 43.3) and 45 individuals (19%) experienced an event. Lethal events were observed in 14 subjects (6%). Figure 1 shows event (A) and lethal event (B) free survival in SCN5A-E1784K subjects. Higher QRS duration (corrected for age) was associated with shorter event-free interval. QRS duration was the only characteristic associated with increased risk with a hazard ratio (HR) of 1.04 or 1.05 per ms for events and lethal events, respectively. The observed survival for events and lethal events for QRS tertiles are shown in Figure 2. Discussion Ventricular myocardial conduction, as evidenced by QRS duration, appears to play a role in the risk of arrhythmic events in patients with SCN5A-E1784K. Corrected QT interval and BrS phenotype were, however, not associated with risk. This provides an important opportunity for the personalisation of risk stratification of these patients, whose management can otherwise be very challenging. Figures

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by the ZonMW Priority Medicines for Rare Diseases and Orphan Drugs (grant 113304045 to Dr Van der Werf) and the Netherlands CardioVascular Research Initiative: the Dutch Heart Foundation, Dutch Federation of University Medical Centres, the Netherlands Organisation for Health Research and Development and the Royal Netherlands Academy of Sciences (PREDICT2 to Dr. Wilde). Background In patients with catecholaminergic polymorphic ventricular tachycardia (CPVT), β-blocker may be insufficiently protective. A randomized clinical trial showed that flecainide reduces ventricular arrhythmias (VAs) in CPVT and small retrospective cohort studies suggest that this translates into a reduction of arrhythmic events. Objective To evaluate the efficacy of flecainide when added to β-blockers for the prevention of arrhythmic events (AE) in a large cohort of patients with CPVT using paired analysis. Methods From two international registries, this multicentre retrospective cohort study included patients with a clinical and/or genetic diagnosis of CPVT using flecainide as an adjunct to β-blockers. The study period, which comprised a pre- and on-flecianide period, was defined as the period in which background therapy, i.e. β-blocker type (β1-selective or nonselective), left cardiac sympathetic denervation (LCSD), and implantable cardioverter-defibrillator (ICD) treatment status, remained unchanged within individual patients. The primary endpoint was AEs, defined as SCD, sudden cardiac arrest (SCA), appropriate ICD shock, and arrhythmic syncope. The effect of flecainide on AE rates was assessed using a generalized linear mixed model assuming Poisson distribution and random effects for patients. Results Two-hundred forty-seven patients (median age at start of flecainide 18 years [IQR 14-29], 123 [50%] female, median flecainide dose 2.2 mg/kg/day [IQR 1.7-3.1]) were included. At baseline, 70 (28%) patients had an ICD and 21 (9%) had a LCSD performed. Nonselective β-blockers were used by 133 (54%) patients. During a median pre-flecainide follow-up of 2.1 years (IQR 0.4-7.2), 41 patients experienced 58 AEs. During a median on-flecainide follow-up of 2.9 years (IQR 1.0-6.0), 23 patients experienced 38 AEs. There was a significant reduction in AEs after initiation of flecainide (OR 0.55 [0.38-0.83]; p=0.007). Among patients who were symptomatic before diagnosis or before the initiation of flecainide (n=167), flecainide was associated with a significant reduction in AEs (OR 0.49 [0.31-0.77]; p=0.002). Among patients with ≥1 AE on β-blocker therapy (n=41), adding flecainide was associated with a significant reduction in AEs (OR 0.25 [0.14-0.45]; p&lt;0.001). Conclusion Flecainide was associated with a reduction in AEs when added to β-blockers in patients with CPVT in the overall cohort, symptomatic patients, and particularly in patients with breakthrough AEs on β-blocker therapy.