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Background: Etripamil nasal spray is a fast-acting, calcium channel blocker in development for the conversion of paroxysmal supraventricular tachycardia (PSVT) outside of a health-care setting. Studies have demonstrated the favorable safety and efficacy of self-administered etripamil in restoring sinus rhythm (SR) and reducing emergency department visits. Purpose: This report analyzes the efficacy, safety, and test-dose tolerability of etripamil across PSVT clinical studies. Methods: We systemically examined randomized, controlled and open-label trials evaluating etripamil in patients with PSVT. Efficacy measures included the proportion of patients converting from PSVT to SR within 30 minutes and the median times to conversion across all Phase 3 studies. Safety data for treatment-emergent adverse events (TEAEs), serious AEs, and test dose tolerability from Phase 2/3 studies were summarized descriptively. Results: NODE-1, NODE-301 Part 1, NODE-301 Part 2 (RAPID, including RAPID Extension, RAPID Open Label, RAPID Open Label Extension periods), NODE-302, and NODE-303 studies were analyzed (Table 1). The Kaplan-Meier estimate of etripamil exposed patients converting to SR within 30 minutes (n= 622) was 59.6% (range, 53.6% to 64.3%) with a median time to conversion of 18.5 minutes (95% CI, 15.7 to 21.0). The proportions of RCT placebo group patients converting from SVT to SR by 30 minutes ranged from 26.7% to 34.7%. Estimates of conversion of SVT to SR with etripamil at 60 minutes for individual studies ranged from 63.2% to 73.5% (Figure). Combined analysis showed mainly the occurrence of mild, transient TEAEs, primarily nasal discomfort, nasal congestion, rhinorrhea, throat irritation, and epistaxis (Table 2). 1,107 patients took at least one etripamil test dose while in SR; no significant change in average baseline heart rate or blood pressure was observed within 45 minutes of administration, and test dose failure occurred in only 16 patients (1.4%). Conclusions: Across multiple clinical studies of acute PSVT management, self-administered etripamil consistently demonstrated robust efficacy and a favorable safety profile for acute PSVT management. Safety data and the low rate of test dose failures indicate favorable tolerability, suggesting no need for a pretreatment test dose. These findings support the potential of etripamil as a patient-administered therapy for PSVT, which may reduce reliance on emergency care.

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.

Introduction: Carotid artery intraplaque hemorrhage (IPH) is increasingly recognized as a predictive marker of cerebrovascular events. Despite widespread utilization of contrast-enhanced CT angiography (CTA) for the evaluation of carotid atherosclerosis, diagnosis of IPH on CTA is challenging, limiting risk stratification capabilities. We evaluated convolutional neural networks (CNN) for detection of histology-proven IPH in carotid CTA. Methods: The study included carotid endarterectomy patients from our center who had preoperative CTA and available plaque specimens from the Mayo Clinic Carotid Artery Atherosclerosis Trial (MCAT) Biobank. A validated segmentation model localized common and internal carotid arteries (CCA/ICA). CCA bifurcation served as landmark after a large language model, Llama3.0-70B, verified culprit plaque proximity to the bifurcation from CTA reports. A 3×3×4cm box around ipsilateral CCA bifurcation was sampled from CTA volumes and images were labeled IPH by histology study of carotid specimen (Fig 1). Given limited cases with concurrent imaging and histology, we employed a robust cross-validation strategy: 22 cases (20%) held-out for testing, with remaining data 86 cases used for 5-fold cross-validation (stratified by IPH presence). The five resulting models independently generated IPH probability scores, and ensembled predictions calculated by three methods to enhance generalizability: Majority and weighted voting based on binary IPH class and soft voting based on IPH probability scores. Results: Of 418 patients with histological analysis, 130 had CTA studies available. After excluding 22 cases lacking histological consensus, 108 cases were analyzed. In the 22 test cases the mean age was 68.1±8.5 years and 59% were male; In the cross-validation folds age ranged from 67.1±6.9 to 75.3±7.6 years 56-82% were male. Individual models' performance on the test set showed mean ROC-AUC of 0.79 (95% CI: ±0.05) and average precision of 0.85 (±0.05) (Fig 2). The ensemble approach achieved superior performance with soft voting demonstrated 82% ROC-AUC, 77% accuracy, 79% precision, 85% sensitivity, and 82% F1-score for IPH detection, outperforming majority voting and weighted voting (Fig 3). Conclusion: Automated IPH detection in widely available CTA imaging can turn it to a powerful stroke risk assessment tool, supporting personalized prevention strategies and surgical decision-making, ultimately reducing cerebrovascular morbidity and mortality.

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.

A 63-year-old female with mixed connective tissue disease on long-term immunosuppression (prednisone, azathioprine, hydroxychloroquine (HCQ)) was referred to a tertiary care center for evaluation of progressive dyspnea and exertional chest discomfort. Cardiac history included transient complete heart block and ventricular tachycardia with dual-chamber AICD, and severe aortic stenosis with bicuspid aortic valve. Laboratory evaluation was notable for NT pro-BNP > 5000 pg/mL and elevated but adynamic troponin (300-500 ng/L). Electrocardiogram revealed atrial pacing with first degree atrioventricular block. Echocardiogram confirmed severe aortic stenosis, elevated filling pressures, abnormal left ventricular longitudinal strain and LV hypertrophy. Cardiac MRI, sarcoid PET, and PYP SPECT/CT were without any evidence of edema, scar, inflammation or amyloid deposition. Catheterization revealed severe pulmonary hypertension and elevated filling pressures, without significant coronary disease. Medical treatment included empagliflozin (discontinued due to urosepsis), bumetanide, spironolactone, and metoprolol succinate. Neither TAVR nor transition to biventricular pacing improved LV function. Ultimately, endomyocardial biopsy was performed, revealing histologic features of HCQ-induced cardiotoxicity, including myocyte hypertrophy and interstitial fibrosis. HCQ was discontinued. She was referred to Rheumatology for alternative treatments. HCQ induced cardiomyopathy represents <2% of adverse events of patients treated with HCQ, presenting as hypertrophic or restrictive cardiomyopathy with conduction abnormalities. Mean treatment duration in HCQ cardiomyopathies is approximately 12.7 years. Confirmation of diagnosis requires endomyocardial biopsy, as imaging findings are often non-specific. Management involves discontinuing the offending agent and optimizing heart failure therapy. Around 45% of patients with HCQ cardiomyopathy exhibit resolution of cardiac function following medication discontinuation. This case emphasizes the importance of a systematic approach to unexplained heart failure, particularly in patients with long-term HCQ use. Infiltrative or toxic cardiomyopathies should be considered when imaging suggests myocardial dysfunction. Multimodal imaging and biopsy are crucial for diagnosis. Early recognition is essential to prevent irreversible myocardial damage and improve long-term outcomes.

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.

Introduction: Cardiopulmonary bypass time (CPBT) and aortic cross-clamp time (AXCT) are independently associated with postoperative morbidity and mortality. However, no universally accepted “optimal” duration exists, as these times are influenced by the complexity of cardiac surgery. ECMO is being increasingly used for cardiogenic shock in patients undergoing cardiotomy, but the impact of CPBT and AXCT on outcomes in this specific population remains unexplored. This study investigates how CPBT and AXCT influence outcomes in cardiotomy patients on ECMO support. Research Question: Do CPBT and AXCT influence mortality and complication rates in cardiotomy patients receiving ECMO support? Methods: We conducted a retrospective chart review (Jan 2020–Dec 2024) across a multidisciplinary North American practice, identifying 623 patients who required ECMO. Of these, 236 (37.8%) received ECMO in the preoperative, intraoperative, or postoperative period of cardiotomy. Patients were grouped by prolonged CPBT (>150 min) vs standard (≤150 min) and prolonged AXCT (>90 min) vs standard (≤90 min). We analyzed outcomes including 30-day mortality, ECMO characteristics, and postoperative complications. Results: Among the 236 patients, the average age was 60.8 years, BMI 37.43 kg/m 2 ; 63% were male, 85% White. Prolonged CPBT and AXCT were associated with higher BMI (p=0.02, 0.03), prior cardiac surgery (p<0.001, 0.006), and combined CABG+AVR procedures (p=0.01, 0.001). Patients with prolonged durations were more likely to require postoperative ECMO (p=0.001, 0.03). Complications such as mediastinal bleeding, AKI requiring CRRT, mediastinitis, bacteremia, and pneumonia, showed significant association with increased CPBT whereas prolonged AXCT was only linked with mediastinal bleeding. CPBT and AXCT durations did not significantly affect 30-day mortality, ICU/hospital stay, ECMO duration, or ventilation duration. Independent predictors of 30-day mortality included pre-/intraoperative IABP use (OR 2.19, 95% CI 1.11–4.30, p=0.023), Impella use (OR 0.20, 95% CI 0.03–0.75, p=0.040), post-op intracranial bleeding (OR 5.46, 95% CI 1.43–23.9, p=0.016), and CRRT-requiring AKI (OR 3.24, 95% CI 1.63–6.57, p<0.001). Conclusion: Prolonged CPBT and AXCT were significantly linked to higher rates of postoperative complications such as mediastinal bleeding, CRRT requiring AKI, mediastinitis, and pneumonia along with increased need for postoperative ECMO support, without significantly affecting mortality.

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.

Background: Disease-causative variants in LMNA -encoded lamin A/C cause the laminopathies, a heterogeneous group of diseases variably resulting in arrhythmogenic/dilated cardiomyopathy (ACM/DCM), lipodystrophy, muscular dystrophy, and progeria. The artificial intelligence (AI)-derived electrocardiographic age gap (AI-EAG), determined by the discrepancy between a patient’s artificial AI-enabled electrocardiogram (ECG) predicted biological age versus their chronological age, is accelerated in laminopathy. Thus, we sought to determine if the AI-EAG serves as a prognostic marker in patients with cardiac laminopathy. Methods: Retrospective analysis of 1,049 genotype-positive patients with genetic ACM/DCM was used to identify those with pathogenic/likely pathogenic (P/LP) variants in LMNA . After the exclusion of those who lacked a 12-lead ECG while in sinus rhythm, a previously trained AI-ECG age algorithm was used to determine the AI-EAG by subtracting the patient’s chronological age from the AI-ECG derived biological age. The AI-EAG was then correlated with a combined outcome of major ventricular arrhythmia [sudden cardiac arrest, sustained ventricular tachycardia, and appropriate implantable cardioverter-defibrillator shocks], heart transplantation, and cardiovascular death. Results: Overall, 147/1,049 (14%) patients with genetically-mediated ACM/DCM had a P/LP variant in LMNA . Of these, 80/147 (54%) LMNA variant-positive patients (52% female, mean chronological age 36 ± 15 years) had ECGs suitable for AI-EAG analysis. Most (52/80; 65%) had an AI-EAG >10 years with a mean AI-EAG of 17 ± 13 years. Of note, the AI-EAG was greater in those with a clinical cardiac phenotype (20 ± 14 vs. 13 ± 10 years; p = 0.011). As a continuous variable, an increased AI-EAG was associated with increased risk of the composite outcome at a median follow-up of 20 months (HR 1.036; 95% CI 1.004–1.068; p = 0.026) and AI-EAG > 10 and > 20 years were both associated with elevated risk (HR 4.272; 95% CI 1.388–13.147; p = 0.011 and HR 3.732; 95% CI 1.505–9.255; p = 0.004, respectively). Conclusion: In cardiac laminopathy, an increased AI-EAG was common and correlated with adverse cardiovascular outcomes. Non-invasive ascertainment of electrocardiographic aging by AI may provide a novel prognostic marker in cardiac laminopathy. Future studies are needed to validate this finding and further define the role of the AI-EAG in the risk-stratification of patients with cardiac laminopathy.