Giudicessi, John R.

ABSTRACT Background Ventricular tachycardia (VT) is a life‐threatening arrhythmia frequently observed in structural heart diseases, including LMNA‐related cardiomyopathy, a genetic disorder associated with high risk of sudden cardiac death and progressive systolic dysfunction. While catheter ablation is an established therapeutic option for VT, its efficacy in cardiac laminopathy remains poorly defined. Objectives To synthesize available evidence on the role and outcomes of VT ablation in patients with cardiac laminopathy. Methods A systematic review and single‐arm meta‐analysis was performed in accordance with PRISMA guidelines. PubMed, Embase, and Cochrane databases were searched for studies reporting VT ablation outcomes in LMNA‐related cardiomyopathy. An inverse variance random‐effects model was applied for meta‐analysis of proportions. Results Seven studies (six cohorts, one abstract) comprising 62 patients (mean age 53.2 ± 9.7 years; 85% male; 88% with implantable cardioverter‐defibrillator) were included. An endocardial/endo‐epicardial approach was used in 93% of cases. Acute procedural success was achieved in 37% (95% CI: 14%–63%; I² = 27.4%), and 28% required multiple procedures. Over a median follow‐up of 26 (9–35) months, VT recurrence occurred in 91% (95% CI: 76%–100%; I² = 37.2%). All‐cause mortality was 54% (95% CI: 39%–70%; I² = 28%), predominantly from cardiac causes (51%, 95% CI: 25%–76%; I² = 53%), and 14% (95% CI: 1%–34%; I² = 42%) underwent heart transplantation. Conclusions In LMNA‐related cardiomyopathy, catheter ablation is associated with high VT recurrence, limited long‐term success, and substantial cardiovascular mortality and transplantation rates, underscoring the importance of ICD implantation and the need for alternative strategies, including variant‐specific and molecularly targeted therapies.

Abstract Background and Aims Patients with catecholaminergic polymorphic ventricular tachycardia (CPVT) are at risk for potentially life-threatening arrhythmic events (AEs) even while treated with β-blockers. The aim was to develop a model for individualized prediction of AEs in patients with RYR2-mediated CPVT on β-blocker monotherapy. Methods The derivation and independent validation cohorts included 743 and 129 patients, respectively. AEs were defined as arrhythmic syncope, appropriate implantable cardioverter–defibrillator shock, sudden cardiac arrest (SCA), and sudden cardiac death. Near-fatal or fatal AEs (nf/fAEs) included all AEs except for arrhythmic syncope. Prediction models using Cox regression were developed and internally and externally validated. Results A total of 102 (13.7%) patients in the derivation cohort and 24 (18.6%) patients in the validation cohort experienced ≥1 AE over a median follow-up of 5.1 [interquartile range (IQR), 7.7] and 2.4 (IQR, 4.4) years, respectively. Predictors of AE were arrhythmic syncope or SCA prior to diagnosis and age at β-blocker initiation. In the derivation and validation cohorts, the optimism-corrected C-indices of the models for AE were 0.67 [95% confidence interval (CI) 0.62–0.72] and 0.59 (95% CI 0.48–0.71), respectively. For nf/fAEs, ventricular arrhythmia severity before β-blocker initiation was a fourth independent predictor, and C-indices of the models in the derivation and validation cohorts were 0.74 (95% CI 0.68–0.80) and 0.60 (95% CI 0.47–0.72), respectively. In the derivation cohort, calibration slopes were 1.00 (95% CI 0.59–1.41) for AE and 1.00 (95% CI 0.69–1.32) for nf/fAE. Conclusions These externally validated risk prediction models using clinical parameters accurately distinguished CPVT patients on β-blocker monotherapy at low and high risk for future AEs while treated with β-blockers. These models provide guidance for implementation of clinical management therapies to prevent AEs in patients with CPVT.

Abstract This brief report details the initial findings from a Phase 1b/2 trial of TN-201, an adeno-associated virus serotype 9 (AAV9) gene therapy for MYBPC3-associated hypertrophic cardiomyopathy (HCM), a condition with significant morbidity, increased risk of mortality, and no approved therapy for the majority of patients. TN-201 was well tolerated, and changes to the management of potential immune responses resulted in a shorter period of immunosuppression. These results show consistent transduction and expression of TN-201 in cardiomyocytes, corresponding with increases in MyBP-C levels, reductions or stabilization of cardiac biomarkers, and reductions in key measures of left ventricular (LV) hypertrophy.

Background: Ventricular tachycardia (VT) is a potentially life-threatening arrhythmia frequently observed in structural heart diseases, including cardiac laminopathy, a genetic cardiomyopathy associated with a high risk of sudden cardiac death (SCD) and progressive systolic dysfunction caused by pathogenic variants in LMNA -encoded lamin A/C. While catheter ablation is a key therapeutic strategy for VT management, its efficacy in cardiac laminopathy remains poorly defined. Objective: This systematic review and single-arm meta-analysis aims to synthesize the available evidence in the literature on the role of VT ablation for patients with cardiac laminopathy. Methods: A single-arm meta-analysis was conducted following PRISMA guidelines, systematically searching PubMed, Embase, and Cochrane databases for studies investigating VT ablation outcomes in patients with cardiac laminopathy. We applied an inverse variance random-effects model for a meta-analysis of proportions. Results: We included 6 cohort studies and 1 abstract comprising 62 patients with LMNA-related cardiomyopathy (mean age at 53.2 ± 9.7 years, 85% males, and 88% with an ICD). The predominant ablation strategy was endocardial/endo-epicardial in 93% of cases. Acute success rate following VT ablation was 37% (95% CI: 14 to 63%) and 28% of the patients required multiple procedures. Over a median follow-up of 26 (9-35) months, VT recurrence rate after ablation was 91% (95% CI: 76 to 100%; Figure A ). The all-cause mortality rate was 54% (95% CI: 39% to 70%; Figure B ), primarily driven by cardiac causes 51% (95% CI: 25 to 76%; Figure C ). There was an elevated rate of heart transplantation 14% (95% CI: 1 to 34%), highlighting overall poor outcomes in this patient population. Conclusion: Catheter ablation in cardiac laminopathy is associated with limited long-term efficacy, with high rates of VT recurrence, cardiovascular mortality and heart transplantation. These findings underscore the importance of ICD implantation for primary prevention and the pressing need to develop alternative treatment strategies. Further research is necessary to determine whether specific LMNA variants influence ablation outcomes and to explore emerging therapies targeting the underlying molecular mechanisms of cardiac laminopathy.

Background: Current guidelines recommend prophylactic beta-blocker therapy for all genotype-positive newborns with long QT syndrome (LQTS), despite the potential for QT normalization in the first few weeks of life and the rarity of cardiac events during infancy. We previously reported our early experience with intentional non-therapy (INT) for low-risk adolescents and adults. Objective: To evaluate our single-center experience regarding INT for infants with genotype-positive LQTS identified following family screening/cascade testing. Methods: We retrospectively reviewed all infants diagnosed with genotype-positive LQTS between 2015 and 2024. Only LQTS patients with clinical and ECG data within the first 2 years of life and follow-up were included. INT was defined as adherence to precautionary QT-preventative measures and structured periodic follow-up rather than treating with prophylactic drugs, devices, or denervation. Candidacy for INT was based on absence of symptoms, down-trending QT during first few weeks of life, family agreement with the strategy, and frequent surveillance (e.g., ECG and Holter every 6 months). Prophylactic drug therapy was initiated if a surveillance QTc exceeded 470ms on 2 consecutive ECGs or at family request. Results: Of 94 infants, 38 [40%; 19 females (50%), mean age at diagnosis 0.3±0.4 years] were managed with INT (14 LQT1 (36%), 15 LQT2 (39%), 8 LQT3 (21%)). Genetic testing and ECG screening were performed because of a family history in all 38 infants including 11 (29%) with a family history of SCA/SCD. None had fetal bradycardia reported or any cardiac symptoms prior to diagnosis. Mean neonatal QTc during the first week of life was 477±41ms and 442±6ms at 3 months of age. No cardiac events were reported during a mean follow-up of 3.9±2.3 years. Management was escalated from INT to prophylactic pharmacologic therapy in 8 infants (21%) with nadolol in 4, propranolol in 3, and LQT3 mutation-specific therapy with flecainide in 1 based on 2 consecutive QTc values>470ms, at a mean age of 4.3±2 years (mean QTc at treatment initiation 485±13ms). Conclusions: In selected LQTS infants with favorable down-trending QT and access to close follow-up, INT rather than universal prophylactic drug therapy can be considered. This approach may offer an alternative strategy in infancy, avoiding unnecessary early exposure to medication-related side effects and reinforcing individualized genotype- and phenotype-directed tailoring of therapeutic options.

Background: Pathogenic variants in LMNA -encoded lamin A/C cause a genetic cardiomyopathy marked by conduction disease, atrial and ventricular arrhythmias, and systolic dysfunction. The mechanisms underlying phenotypic differences between Ig-like and coiled-coil domain missense variants remains unclear. Here, we developed a novel suppression-and-replacement disease modeling (SupRep-DM) platform to screen LMNA missense variant function and prioritize mechanistically informative phenotypes. Methods: LMNA-SupRep-DM is a dual-component lentiviral system that enables simultaneous knockdown of endogenous LMNA via an LMNA -targeted shRNA and replacement with an shRNA-immune mutant lamin A cDNA encoding the pathogenic variant of interest with HA-tag. HEK293T cells and iPSC-derived cardiomyocytes (iPSC-CMs) were transduced with 9 unique SupRep-DM constructs harboring variants in either the coiled-coil (E82K, K97E, R216C, H222P, T224I, R335W) or Ig-like (R471H, R541C, R541H) domains. Cells were stained using HA-specific antibodies, imaged by confocal microscopy, and analyzed for nuclear morphology, aggregate burden, and fluorescence intensity. Statistics: Dunnett’s test and one-way ANOVA. Results: In HEK293T cells, 8/9 LMNA variants significantly reduced nuclear circularity (p< 0.05), most notably in K97E (-11%, n=89), R471H (-12%, n=62), and R541C (-9%, n=104). Additionally, K97E increased nuclear area (+24%) and R541C decreased it (−29%) vs wild-type (WT, p<0.0001). Lamin A intensity was significantly reduced in K97E, R471H, and R541C, but increased in T224I and R335W vs WT. In iPSC-CMs, Ig-fold variants R541C and R541H significantly reduced nuclear circularity (−28%, –34%), increased elongation (+42%, +49%), and elevated lamin A aggregates ~4–5-fold vs WT (p≤0.0005). R471H and the coiled-coil variant E82K also increased aggregate burden, while the remaining variants (K97E, R216C, H222P, T224I, R335W) showed no significant effects in iPSC-CMs. Conclusions: LMNA missense variants cause domain-specific nuclear disruptions, with variants localizing to the Ig-like domain inducing nuclear deformities and consistent aggregation across both cellular models. Coiled-coil variants showed more variable, context-dependent effects. The more pronounced phenotypes in iPSC-CMs may reflect contraction-mediated stress absent in HEK293T cells. The SupRep-DM platform sensitively detects these structural changes, demonstrating its utility for mechanistic prioritization of LMNA variants.

Background: An increased burden of premature ventricular contractions (PVCs)/non-sustained ventricular tachycardia (NSVT) during the recovery phase of exercise stress testing (EST) appears to be a distinctive feature of PKP2-related arrhythmogenic cardiomyopathy (ACM) associated with an increased risk of major ventricular arrhythmia (VA) events. While flecainide may help manage VA, its impact on post-exercise VA burden and the role of EST in guiding its use remain unclear. Objective: To examine the effect of flecainide on EST-VA burden in PKP2-related ACM. Methods: A retrospective analysis of 1,049 genotype-positive ACM patients identified those with PKP2 variants who underwent ESTs on and off flecainide. Clinical data were collected and the arrhythmic burden—measured as PVCs, couplets, bigeminy, NSVT, sustained VT, ventricular fibrillation, and PVCs per minute—during each EST phase (baseline, peak, active recovery, and passive recovery) was assessed and compared between the EST performed pre- and post-initiation of flecainide. Results: Of 147 PKP2-ACM patients, 11 (35 ESTs) had at least one EST on flecainide. Eight patients (mean age 31 ± 13 years, 50% male) underwent both on and off flecainide for a total of 29 ESTs [on beta-blockers (80%), flecainide (52%), amiodarone (3%), or sotalol (3%)]. When comparing EST performed pre- and post-initiation of flecainide, the frequency of PVCs per minute was significantly lower both during exercise (3 ± 3 vs 1 ± 2, p=0.023) and during the recovery phase (12 ± 13 vs 2 ± 4, p=0.010). Similarly, the presence of PVCs during exercise (85% vs 47%, p=0.026) and recovery (85% vs 47%, p=0.027), couplets during exercise (27% vs 0%, p=0.026) and recovery (85% vs 20%, p<0.001), and bigeminy during exercise (36% vs 7%, p=0.054) and recovery (72% vs 13%, p=0.002) was significantly reduced following the initiation of flecainide. No significant differences were observed in the prevalence of NSVT or sustained VT. Five patients (63%) had prior sustained VT without breakthrough events post-flecainide. One patient without prior VT had an early event but remained event-free after dose up titration. Conclusion: Flecainide significantly reduces the EST arrhythmic burden in patients with PKP2-ACM, particularly in the recovery phase. Future studies are needed to determine if the EST can be used to guide flecainide dosing and efficacy in PKP2-ACM akin to current strategies employed for catecholaminergic polymorphic ventricular tachycardia.

Background: Calcium release channel deficiency syndrome (CRCDS) is caused by biogenic or biophysical loss-of-function (LOF) pathogenic variants in the RYR2 -encoded ryanodine receptor (RyR2), a key intracellular Ca 2+ release channel. Previously, we identified a novel homozygous duplication involving the promoter and exons 1-4 of RYR2 , leading to 80% RyR2 protein loss and exertion-related sudden death in the young. Here, we generated a RYR2 knockout (RYR2-KO) induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) model to explore intracellular and electrophysiological compensatory mechanisms that overcome this extreme loss of RyR2 protein. Methods: Using CRISPR/Cas9 gene editing, a homozygous c.163delT variant (p.S55Pfs*46) was inserted into a normal iPSC line (isogenic control) to create a homozygous RYR2-KO iPSC line. After re-engineering the lines into ventricular-like cardiomyocytes (iPSC-CMs), intracellular Ca 2+ handling was assessed by Fluo-4 AM cell imaging (0.5 Hz stimulation). Electrical remodeling in the L-type Ca 2+ current (I CaL ) was assessed using the whole-cell patch clamp technique. Results: Significant differences were observed in Ca 2+ transient parameters between RYR2-KO and isogenic control iPSC-CMs. Biogenic RyR2 loss significantly reduced Ca 2+ transient peak amplitude (CTA: 0.16 ± 0.01 ΔF/F0, p<0.0001) and upstroke velocity (CTV: 0.42 ± 0.06 (ΔF/F0)/t, p<0.0001), and prolonged Ca 2+ transient duration (CTD 90 : 1.59 ± 0.03 s, p=0.01) as compared to isogenic control (CTA: 0.48 ± 0.04 ΔF/F0; CTV: 1.30 ± 0.15 (ΔF/F0)/t; CTD 90 : 1.46 ± 0.05 s). Additionally, RyR2 loss abolished SR Ca 2+ leak (0.9 ± 0.9 % versus 35.1 ± 15.5 %, p=0.03). Lastly, a significant reduction in I CaL density was observed in RYR2-KO iPSC-CMs as compared to isogenic control iPSC-CMs (at 0 mV, RYR2-KO: -8.54 ± 1.60 pA/pF, control: -17.45 ± 3.69 pA/pF, p=0.0004). These data indicate that I CaL reduction may contribute to the reduced Ca 2+ transient peak. Conclusions: Complete loss of RyR2 in iPSC-CMs profoundly disrupts intracellular Ca 2+ handling, abolishes Ca 2+ sparks frequency, and secondarily down-regulates the sarcolemmal L-type Ca 2+ channel.

Background: Previously, we discovered that DENND3, a guanine nucleotide exchange factor regulating Rab GTPases, influences cardiac ion channel trafficking. Both electrophysiological dysfunction and arrhythmic events were identified in variant inserted inducible pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) expressing DENND3-p.R534S. This was a novel missense variant identified in a patient with familial idiopathic ventricular fibrillation (IVF). Notably, augmented membrane retention of key cardiac ion channels was observed in both DENND3-p.R534S expressing TSA201 cells and variant inserted iPSC-CMs. To further study the mechanisms underlying arrhythmogenesis associated with IVF, intracellular calcium handling was characterized in these re-engineered heart cells with DENND3-p.R534S. Methods: Here, iPSC-CMs expressing DENND3-p.R534S and isogenic controls (IC) were studied. Optical action potentials were recorded using the FluoVolt voltage-sensitive dye at a constant pacing rate of 1 Hz. Multi-electrode array (MEA) recordings assessed beat period and conduction dynamics. Intracellular calcium dynamics were analyzed using Fluo-4 calcium imaging. Results: DENND3-p.R534S iPSC-CMs exhibited frequent arrhythmic activity, including irregular beating patterns (78%, n=28/36), alternans (25%), early afterdepolarizations (EADs, 8%), and delayed afterdepolarizations (DADs, 8%) versus 0% in IC lines (n=0/36, p<0.05). MEA recordings revealed significantly prolonged and irregular beat periods (2.59±0.26s vs. 1.37±0.10s, p<0.05), indicating electrical instability. Calcium imaging further showed significantly reduced calcium transient amplitude in DENND3-p.R534S iPSC-CMs compared to ICs (0.035±0.039ΔF/F 0 vs. 0.302±0.099ΔF/F 0 , p<0.05), and slowed upstroke velocity (0.170±0.212 ΔF/F 0 ●s -1 vs. 1.340±0.463ΔF/F 0 ●s -1 ) suggesting impaired intracellular calcium release. Conclusion: The DENND3-p.R534S variant not only disrupts ion channel distribution as shown previously but also markedly perturbs intracellular calcium handling, contributing to electrophysiological instability and arrhythmogenic cellular phenotypes. These findings highlight DENND3’s novel and emerging role in maintaining cardiac cellular homeostasis and rhythm stability.