Giudicessi, John R.

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.

Background: Long QT syndrome (LQTS) is a potentially lethal cardiac channelopathy that stems primarily from pathogenic variants in KCNQ1 (LQT1), KCNH2 (LQT2), or SCN5A (LQT3) and is characterized by prolongation of the cardiac action potential duration (APD) at the cellular level. Despite current therapeutic options, there is a pressing need for novel, precision medicine-based, effective pharmacological therapies for LQTS, particularly for LQT2 and LQT3. Goal: To develop a high-throughput drug screening platform to identify novel therapeutics for LQTS using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). Methods: iPSC-CMs were made for patients with LQT2 (p.G604S) or LQT3 (p.P1332L). Voltage dye assays were performed using a kinetic image cytometer (KIC) in a 96 well format. The APD at 90% repolarization (APD90) was measured in treated/untreated iPSC-CMs. Cyteseer image analysis software was used for optical APD analysis. SCN5A-P1332L iPSC-CMs were treated with 10 uM mexiletine (MEX) as a positive control. 114 compounds from a commercially available library of FDA-approved drugs were tested in triplicate to assess their APD shortening efficacy. Whole-cell patch clamp was used to confirm the lead compound’s effect in KCNH2-G604S iPSC-CMs. Results: MEX significantly shortened the APD90 of SCN5A-P1332L iPSC-CMs by 13% (669 ± 5 to 586 ± 10 ms; p<0.0001; n=50). Of the 114 tested compounds, 6 shortened the APD90 of SCN5A-P1332L iPSC-CMs by greater than 20%. The lead compound shortened the APD90 of SCN5A-P1332L iPSC-CMs by 32% (571 ± 2 ms; n=314, to 387 ± 4 ms; n=80; p<0.0001). All 6 candidate compounds also shortened the APD90 of KCNH2-G604S iPSC-CMs by greater than 20% in KIC screening assays. Whole-cell patch clamp confirmed APD shortening by the lead compound in KCNH2-G604S iPSC-CMs (759 ± 35 ms; n=13, to 599 ± 89 ms; n=9; p<0.03). Conclusion: The high-throughput KIC screen confirmed mexiletine’s APD shortening effects in SCN5A-P1332L iPSC-CMs, validating the assay's potential for efficient, large-scale drug screening. In a pilot screen, we identified 6 novel LQTS drug candidates which shortened the APD90 in SCN5A-P1332L (LQT3) and KCNH2-G604S (LQT2) iPSC-CMs more than mexiletine. The lead compound’s APD shortening effects in KCNH2-G604S iPSC-CMs were confirmed with whole cell patch clamp. The KIC platform offers a robust method for identifying novel QT shortening compounds by enabling reproducible APD measurements in a high-throughput format.

Background: Congenital long QT syndrome (LQTS) is characterized by a prolongation of the heart rate-corrected QT interval (QTc) and an increased risk of syncope, seizure and sudden cardiac arrest/death (SCA/SCD). Genome-wide association studies have identified numerous QT interval-influencing loci of small effect sizes. Herein, we sought to investigate whether a polygenic background for the QT interval contributes to the phenotypic heterogeneity in patients with genotype-positive LQTS. Methods: We used summary statistics from a recent genome-wide meta-analysis for QT interval (n = 117,532) to derive 160 different polygenic scores for QT interval (PGS QT ) using LDpred2-grid, each comprising ~1.4 million common variants with varying assumptions of the underlying genetic architecture. Next, we applied these PGS QT to predict the QTc value in a genetically unrelated, European ancestry subset of the ‘All of Us’ cohort with available electrocardiogram and genetic data (n=6,404), where the best performing PGS QT was determined based on explained variance. Next, using 225 patients with genetically confirmed LQTS who were evaluated in the Mayo Clinic Windland Smith Rice Genetic Heart Rhythm Clinic, we tested the effect of the best performing PGS QT on QTc duration and LQTS-associated cardiac events (defined as a composite of syncope, seizures, sustained ventricular arrhythmia, appropriate ICD shocks, and SCA/SCD) using Bayesian regression models. Results: Overall, the best performing PGS QT explained 11.8% of the variance in the QTc in the ‘All of Us’ cohort. Among patients with genotype-positive LQTS (n [%]; KCNQ1 125 [55.6], KCHN2 76 [33.8], SCN5A 21 [9.3], Other 3 [1.3]), those with higher PGS QT had a higher QTc (predicted mean QTc [95% uncertainty interval], 95 th percentile vs 50 th percentile for PGS QT , 478 ms [464-491] vs 459 ms [449-468]). In comparison to the median PGS, those LQTS patients with a PGS QT >95 th percentile were more than twice as likely to have experienced a LQTS-associated cardiac event (Odds ratio [95% UI], 95 th percentile vs 50 th percentile for PGS QT ; 2.16 [1.02-5.41]), ( Figure ). Conclusions: Individuals with genotype-positive LQTS who have high polygenic susceptibility for QTc prolongation are more likely to phenotypically exhibit a higher QTc value and experience potentially life-threatening LQTS-associated cardiac events. Accounting for polygenic background may refine risk stratification strategies for patients with genotype-positive LQTS

Background: Pathogenic/likely pathogenic (P/LP) variants in the RBM20-encoded RNA-binding protein motif 20 splicing factor result in a penetrant form of arrhythmogenic/dilated cardiomyopathy (ACM/DCM) characterized by ventricular arrhythmias (VA) and early-onset heart failure. The role of cardiac magnetic resonance (CMR) imaging in characterizing RBM20 cardiomyopathy and guiding risk stratification remains inadequately defined. Objectives: To characterize CMR phenotypes in patients with RBM20 cardiomyopathy and explore associations between variant type, CMR phenotype, and VA risk. Methods: Retrospective analysis of 1,061 genotype-positive ACM/DCM patients was used to identify individuals with P/LP arginine/serine-rich domain-localizing missense (RBM20msv) or truncating (RBM20tv) variants in RBM20. Clinical outcomes, including major VA (MVA; sudden cardiac arrest, sustained ventricular arrhythmia, or appropriate ICD therapy) events, were compared between RBM20msv and RBM20tv-positive patients. When available, CMR findings were also analyzed by variant type and correlated with MVA events. Results: Overall, 64 of 1,061 (6%) ACM/DCM patients possessed an RBM20msv or RBM20tv. Of those, 35 (mean age 38±16 years, 54% female, 94% Caucasian) underwent CMR. Late gadolinium enhancement (LGE) was present in 9/35 (26%), typically in a mid-myocardial septal or inferolateral pattern. Left ventricular (LV) noncompaction was noted in 9/35 (26%). Within the CMR subgroup, RBM20msv accounted for 29/35 (83%) of cases, while RBM20tv was observed in 6/35 (17%). No significant difference in LV ejection fraction (36±7% vs. 42±13%, p=0.358), LV end-diastolic volume index (100±32 mL/m2 vs. 118±44 mL/m2, p=0.342), or LGE prevalence (1/6 [17%] vs. 8/29 [28%], p=1.000) was observed between RBM20tv- and RBM20msv-positive patients. However, MVA events were more frequent among RBM20tv-positive patients in the CMR subset (3/6 [50%] vs. 2/29 [7%], p=0.026) and the overall cohort (7/15 [47%] vs. 6/49 [12%], p=0.008). Conclusions: RBM20tv-positive patients experienced a higher rate of MVA events despite similar rates of LGE and structural remodeling compared to those with RBM20msv. Future studies are needed to determine whether mechanisms independent of fibrosis/re-entry drive arrhythmogenesis in RBM20tv-positive patients and to establish if RBM20tv represents an independent risk factor for MVA events that merits incorporation into genotype-specific risk stratification strategies.

Background: Arrhythmogenic and dilated cardiomyopathies (ACM/DCM) are associated with adverse cardiovascular outcomes, including sudden death. Artificial intelligence (AI)-enabled electrocardiographic aging algorithms estimate biological age from 12-lead tracings and predict cardiovascular outcomes in the general population. However, their utility in genetic ACM/DCM has not been studied. Methods: Retrospective review of 1,045 genotype-positive ACM/DCM patients was used to identify those with a pathogenic/likely pathogenic variant in ClinGen-classified definitive/strong evidence ACM/DCM-susceptibility genes. Following exclusion of patients without a baseline ECG for analysis (e.g. paced rhythms), the AI-ECG age gap (AI-EAG) was calculated by subtracting chronological from AI-ECG age. Genes were grouped into functional categories: desmosomal ( PKP2, DSP, DSG2, DSC2, JUP ), nuclear envelope ( LMNA ), sarcomeric ( TTN, MYH7, TNNT2 ), cytoskeleton/Z-disc ( FLNC, DES, DMD, BAG3 ), and regulatory/ion channel ( PLN, RBM20, SCN5A ). Cardiac MRI data included left ventricular structure, function, and late gadolinium enhancement (LGE) presence and pattern. Mann-Whitney U was used for group comparisons; results are shown as median (IQR). Results: Overall, 824 patients (52.8% male; median age of 40.7 years, IQR 26.5–53.4; and median AI-EAG of 7.49 years, IQR 0.43–15.26) were included. DES variant-positive patients had the highest (19.98 years, IQR 9.66–23.21) and BAG3 variant-positive patients the lowest (–0.95 years, IQR -6.05–7.61) AI-EAGs. Among gene groups, nuclear envelope had the highest (15.12 years, IQR 6.79–25.17) and sarcomeric the lowest (5.75 years, IQR -0.69-14.01) AI-EAGs. Cardiac MRI was available for 538/824 (65%) of which 233/538 (43.3%) had LGE. No significant difference in AI-EAG was observed between LGE-positive and -negative patients (6.99 vs. 7.94 years; p=0.831). However, several LGE patterns were associated with significantly higher AI-EAGs: subepicardial (9.88 vs. 6.84; p=0.004), transmural (13.83 vs. 7.25; p=0.012), apical (12.89 vs. 7.17; p=0.002), and septal (8.91 vs. 7.19; p=0.016). Conclusion: AI-EAG varies by gene and functional group, possibly reflecting gene-specific myocardial remodeling. While certain LGE patterns were linked to increased biological aging, overall LGE status was not. These findings suggest AI-EAG may capture disease activity that is distinct from LGE and could serve as a complementary, non-invasive biomarker in genetic ACM/DCM.

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%; I 2 = 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%; I 2 = 37.2%). All-cause mortality was 54% (95% CI: 39–70%; I 2 = 28%), predominantly from cardiac causes (51%, 95% CI: 25–76%; I 2 = 53%), and 14% (95% CI: 1–34%; I 2 = 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.

Background Disease‐causative variants in LMNA ‐encoded lamin A/C cause a genetic cardiomyopathy characterized by atrioventricular block, atrial fibrillation, ventricular arrhythmias, and systolic dysfunction. The influence of LMNA variant type/localization on late gadolinium enhancement (LGE) patterns and clinical outcomes remains unclear. Methods Retrospective analysis of 822 genotype‐positive patients with arrhythmogenic/dilated cardiomyopathy was used to identify those with disease‐causative variants in LMNA . Data on LGE distribution and prevalence of advanced heart failure, thromboembolic and sudden cardiac death/major ventricular arrhythmia events were extracted from the electronic record and analyzed by variant type/localization. Results Among the 72/116 (62%) LMNA variant‐positive patients with cardiac magnetic resonance imaging data, LGE was observed in 40/72 (56%) cases. Most exhibited a nonischemic, midmyocardial or subepicardial pattern (73%), and 6/40 (15%) showed a unique “pseudo‐infarct” transmural pattern, predominantly affecting the apical segments. All 6 patients with this distinct LGE pattern harbored C‐terminal IgD (immunoglobulin‐like domain) variants (p.Arg471His or p.Arg541His). In patients with clinically manifest disease (76/116), those with IgD‐localizing variants had a lower prevalence of atrioventricular block (25% versus 72%, P =0.002) and atrial fibrillation (50% versus 81%, P =0.019) but higher rates of thromboembolic events (42% versus 16%, P =0.038). During a median follow‐up of 37 months, IgD variant presence independently predicted sudden cardiac death/major ventricular arrhythmia (hazard ratio, 2.391 [95% CI, 1.046–5.464]; P =0.039). Conclusions LMNA missense variants localizing to IgD present a distinct apical pseudo‐infarct LGE pattern associated with increased risk of ventricular arrhythmias and thromboembolic events but reduced atrioventricular block and atrial fibrillation. Multicenter studies are warranted to develop variant‐specific risk‐stratification strategies in cardiac laminopathy.

Abstract Background and Aims Truncating variants in the TTN gene (TTNtv) are the most common genetic cause of dilated cardiomyopathy (DCM) but also occur as incidental findings in the general population. This study investigated factors associated with the clinical manifestation of TTNtv. Methods An international multicentre retrospective observational study was performed in families with TTNtv-related DCM. Shared frailty models were used to estimate associations of variant characteristics with lifetime risk of DCM, and logistic regression to estimate odds ratios (ORs) for individual-level clinical risk factor profiles (cardiac conditions, cardiovascular comorbidities, lifestyle) and DCM. Results A total of 3158 subjects in 1043 families with TTNtv-related DCM were studied. TTNtv-positive subjects were 21-fold more likely to develop DCM [OR, 21.21; 95% confidence interval (CI), 14.80–30.39]. Disease onset was earlier in males, but was similar for TTNtv of different types and locations. The presence of clinical risk factors was associated with earlier DCM onset (OR, 3.41; 95% CI, 2.06–5.64), with a prior history of atrial fibrillation having a two-fold increased odds of DCM (OR, 2.05; 95% CI, 1.27–3.32). The prevalence of clinical risk factors increased with age; however, the strength of the DCM association was greatest for young-onset (&lt;30 years) disease (OR, 4.75; 95% CI, 2.35–9.60). Administration of beta-adrenergic receptor or renin-angiotensin system-blocking drugs prior to overt DCM was associated with 87% reduced odds of DCM (OR, .13; 95% CI, .08–.23). Conclusions Disease onset in TTNtv-associated familial DCM is dependent on individual patient context and is potentially modifiable by risk factor management and prophylactic therapeutic intervention.

Abstract Aims Catheter ablation is commonly performed in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) for management of ventricular arrhythmias (VAs). The impact of catheter ablation on cardiac function is unknown. The aim is to assess the impact of catheter ablation for VAs on cardiac function in patients with ARVC. Methods and results This retrospective study included consecutive patients with ARVC who underwent catheter ablation for VAs. Cardiac and valvular functions were assessed on pre- and post-procedure cardiac imaging. The severities of tricuspid regurgitation, pulmonic regurgitation, right ventricular (RV) enlargement, and RV systolic dysfunction was graded as absent (=0), mild (=1), mild-moderate (=2), moderate (=3), moderate-severe (=4), or severe (=5). Thirty-four patients were included. Median age at the time of ablation was 49 [inter-quartile range (IQR), 23] years, and 10 (29%) patients were female. After a median follow-up of 1 (IQR, 0) day, 11 (34%) patients had worsening RV function, and 4 (12%) patients had worsening left ventricular ejection fraction (LVEF) &gt;5%. Five (15%) patients required inotropic support. After a median follow-up of 6.5 (IQR, 6.4) months, 20 (59%) patients had repeat transthoracic echocardiograms. Among patients with worsening RV function post-ablation, one-sixth (17%) had improvement in the RV function at follow-up. In contrast, among patients who had an acute drop in LVEF post-ablation, two-thirds (67%) had improvement at follow-up. Conclusion Right ventricular dysfunction following catheter ablation in patients with ARVC is common, affecting one-third of patients. Patients undergoing catheter ablation of VAs should be counselled on the potential negative impact of ablation on cardiac function.