Ackerman, Michael J.

Background: LQTS is a genetic heart disease associated with an increased risk of sudden death. Despite advances in genetic testing, a small subset of patients still lacks identifiable genetic markers. Consequently, the true prevalence and clinical phenotype of genotype negative remains to be determined. Objective: To determine the prevalence and clinical characteristics of patients with a clinical diagnosis of LQTS but a negative genetic test. Methods: A retrospective review was conducted on patients evaluated and treated at a tertiary hospital between 2000 and 2024, focusing on those with a clinical diagnosis of LQTS, but a negative genetic test for all LQTS-associated genes, with available follow-up of at least 1 year. Results: After exclusion for follow-up and lack of genetic testing, the study cohort consisted of 1834 patients with LQTS including 1708 (93%) with a (likely) pathogenic (LP/P), LQTS-causative variant. Also, in 95 patients (5%), their variant of uncertain significance was clinically upgraded to a LP/P-variant, leaving only 31 patients classified as phenotype positive but genotype negative (1.6%). Of these, 16/31 underwent next-generation genetic sequencing, revealing the genetic cause in 6/16 cases (37%; 0.3% of all patients). For the remaining 25 genotype negative LQTS patients (1.3%), the mean age at diagnosis was 26 ± 15 years, with 19 (76%) being female, and an average initial QTc of 497 ± 41 ms. In total, 11 patients (44%) experienced a cardiac event before diagnosis [1 sudden cardiac arrest (SCA), 1 Torsades, 1 VT, 8 syncopes] and 1 patient had his first cardiac event during follow-up; 7/12 patients had more than one subsequent event. Twenty patients were proband (80%) and 6 had a family history of SCA. Eleven patients received an ICD (44%), left cardiac sympathetic denervation was performed in 4 (16%), and 2 patients experienced arrhythmia-related deaths (8%). The mean follow-up since diagnosis was 7 ± 5 years. Conclusion: With a prevalence of genotype-negative LQTS of 2%, the number of these patients is much lower than previously suggested, underscoring the advancements in identifying new genetic markers and the role of phenotype-enhanced variant adjudication and next-generation sequencing. Additionally, significant disease severity was observed in the remaining patients, emphasizing the pivotal role of genotype-phenotype correlations and risk stratification in managing and counseling patients lacking identified LQTS-causing mutations.

Background: Arrhythmogenic cardiomyopathy (ACM) is a genetic heart disease characterized by proclivity for ventricular arrhythmias and systolic dysfunction. Rarely, sudden cardiac arrest (SCA) is the presenting event in ACM. These individuals may have concealed disease with no appreciable structural manifestations on imaging. Aims: To determine the prevalence, clinical features, and outcomes of patients with genotype-positive ACM who presented with a sentinel SCA. Methods: In this retrospective study, 445 genotype-positive ACM patients evaluated from 1/2015-4/2024 were analyzed to identify those whose initial presentation was SCA. Pertinent demographic, clinical, genetic, and outcome data were extracted from the electronic medical record. Structural manifestations were defined by having one of the following on baseline TTE: EF < 50%, LVEDV >56 mL (male) or >51 mL (female), or regional RV akinesia, dyskinesia, or aneurysm. Categorical variables are presented as number (%), and continuous variables as median (IQR). Statistical analysis was done using Fisher’s exact test (categorical), t-test (continuous), and Logrank test (survival). Patients were censored at time of transplant, death, or last followup. Results: Overall, 14/445 (3%) ACM patients presented with sentinel SCA [71% male; median age at SCA 39 (IQR 30-46)]. The most common genetic substrates were DSP -encoded desmoplakin (n=4; 29%), LMNA -encoded lamin A/C (n=3; 21%), and PKP2 -encoded plakophilin-2 (n=3; 21%). During a median followup of 8.4 years, 12 (86%) experienced appropriate ICD shocks, 8 (57%) required catheter ablation for ventricular arrhythmias, 6 (42%) underwent transplant, and 2 (14%) died of cardiac causes. Notably, 5 (35%) patients did not have evidence of structural disease during baseline evaluation. Compared to those with structural disease, this group was younger [median age 28 (IQR 21-29) vs 45 (IQR 41-48), p = 0.002] and less likely to undergo transplant [0 (0%) vs 6 (42%), p = 0.03]. Conclusions: Sentinel SCA is a rare presentation in ACM and may precede overt structural cardiac changes in a subset of younger patients. This population remains at increased risk for recurrent ventricular arrhythmias and often require advanced therapies.

Background: Although exercise stress testing (EST) has shown to unmask latent electrical substrates in PKP2 -mediated arrhythmogenic cardiomyopathy (ACM), the prognostic role of EST-induced ventricular arrhythmia (VA) patterns in PKP2-ACM patients is unclear. Objective: To examine the exercise-induced VA patterns observed during EST in PKP2-ACM patients and explore their correlation with major VA outcomes. Methods: We retrospectively analyzed 621 patients with either genotype-positive ACM or genotype-positive dilated cardiomyopathy evaluated between 01/2015 and 04/2024 to identify those with a disease-causative variant in PKP2 (N = 108). After exclusion of 38 PKP2-ACM patients without EST data, demographic and electrocardiographic data was extracted from the electronic medical record. The arrhythmic burden [premature ventricular contractions (PVCs), PVCs in bigeminy, PVC couplets, non-sustained VT (NSVT), sustained VT, ventricular fibrillation (VF), and PVCs/minute] during each EST phase (baseline, peak, active and passive recovery) were reviewed and correlated with major VA outcomes [sudden cardiac arrest (SCA), sustained VT, and appropriate implantable cardioverter-defibrillator (ICD) shocks]. Results: A total of 186 exercise tests from 70/108 (65%) PKP2-ACM patients (mean age 36 ± 20 years, 40 % male) were analyzed. The presence and burden of PVCs occurring singly, bigeminy, couplets. and NSVT were more prevalent during the recovery phase, specifically the passive recovery phase ( Table ). PKP2-ACM patients with structural disease (64%) were more likely to have an increased VA burden during recovery than those without structural disease [28/45 (62%) vs 4/25 (16%); p<0.001]. Interestingly, the presence of an increased arrhythmic burden (worsening PVCs/min or complex PVCs) during the recovery was associated with major VA over a median follow-up of 47 months (HR 8.576 [1.015-72.449]; p= 0.019). Conclusion: Increased arrhythmic burden during the recovery phase (late > early) is associated with an increased risk of major VAs in PKP2-ACM. Further studies are needed to understand if this observation extends to other ACM genotypes and whether EST-induced VA patterns can be used to assess therapeutic efficacy in PKP2-ACM.

Background: Long QT syndrome (LQTS) is a potentially lethal cardiac channelopathy. Among women with LQT2, the post-partum period has been considered high risk for cardiac events. However, whether this risk persists after establishing their diagnosis and implementing their LQT2-directed treatment program remains to be determined. Objective: To describe the management and outcomes of LQT2 women during the 9 months post-partum period. Methods: A retrospective analysis of 1869 patients with LQTS treated and evaluated at a tertiary center specializing in Genetic Heart Disease from January 2000 to November 2023 was performed to identify women with diagnosed and treated LQT2 who had a pregnancy during follow-up. Data were abstracted for patient demographics, clinical characteristics, symptomatic status, and treatment plans before and after pregnancy. Results: Overall, 30 pregnancies occurred in 22 women with LQT2. Their average QTc was 489 ± 34 ms with 7 patients (32%) having a resting QTc > 500 ms. Prior to their first post-partum period, 5/22 (23%) were symptomatic with 2 (9%) experiencing a LQT2-triggered sudden cardiac arrest (SCA). Before their post-partum period, their LQT2-directed therapy comprised preventative measures only in 7 (23%), drug therapy in 16 (53%), combination therapy in 7 (23%), and 10 women (43%) had an implantable cardioverter defibrillator (ICD). Pre-emptive treatment intensification was done for 24/30 post-partum periods. Only a single VF-terminating ICD therapy occurred in 1 (3%) of the 30 post-partum periods involving a 21-year-old with p.Lys610Asn-KCNH2 variant, QTc = 490 ms, and a pre-diagnosis presentation of seizures. Conclusion: Although the post-partum period is regarded as a ‘high risk’ window of time for women with LQT2, the risk of a LQT2-triggered cardiac event after diagnosis and implementation of contemporary therapies is very low. This designation of “high risk” among correctly diagnosed and treated women is misleading and generates inappropriate and unnecessary anxiety.

Background: Disease-causative variants in LMNA -encoded lamin A/C cause a genetic cardiomyopathy characterized by atrioventricular (AV) block, atrial fibrillation (AF) and ventricular arrhythmias (VA). Whether domain/variant-specific late gadolinium enhancement (LGE) patterns exist and carry prognostic significance is unclear. Objective: To determine if specific LGE patterns correlate with LMNA variant type/missense variant localization and clinical outcomes in a large cohort of cardiac laminopathy patients. Methods: Retrospectively, 621 genotype-positive arrhythmogenic/dilated cardiomyopathy patients were analyzed to identify those with a disease-causative variant in LMNA -encoded lamin A/C. After exclusion of patients without cardiac magnetic resonance data, pertinent demographic/clinical data was extracted from the electronic medical record. LGE distribution (subepicardial, midmyocardial, subendocardial, transmural) and location (septal, free wall, apical) patterns were analyzed by variant type (missense vs truncating) and missense variant localization (central rod domain vs tail domain) and correlated with advanced heart failure (AHF), MVA, AV block, AF and thromboembolic (TE) events. Results: 70 out of 116 (60%) LMNA variant-positive (mean age 39±12, 43% male and 94% Caucasian) were included. Missense variants localizing to the C-terminal tail region showed a higher prevalence of transmural and apical LGE (Table). Amongst the 5 (7%) patients with this distinct apical pseudo-infarct LGE pattern, p.Arg471His-LMNA was identified in all cases. Among the 48/70 (69%) of patients with clinically manifest disease, p.Arg471His-LMNA-positive patients (n=6) were noted to have an increased prevalence of TE events [3 (50%) vs 5 (12%), 0=0.050] despite a reduced prevalence of AF [2 (33%) vs 32 (76%), p= 0.031]. No difference in AHF or MVA were observed, but AV block was less prevalent [1 (20%) vs 29 (74%), p= 0.029]. Conclusion: p.Arg471His-LMNA causes a distinct apical pseudo-infarct LGE pattern associated with an increased risk of TE events and a decreased prevalence of AV block and AF. Future studies are needed to better refine the role of domain/variant-specific risk-stratification/anticoagulation in cardiac laminopathy.

Background: Arrhythmogenic cardiomyopathy (ACM) is a genetic heart disease characterized by fibrofatty replacement of ventricular myocardium. Arrhythmogenic left ventricular (LV) cardiomyopathy (ALVC) is a phenotypic variant of ACM predominantly involving the LV. Mutations in genes encoding for desmosome proteins and filamin C have been implicated in ALVC, especially in the setting of a ring-like late gadolinium enhancement (LGE) imaging pattern. Objective: To identify the underlying genetic substrate responsible for genetically elusive ring-like ALVC in a patient with seemingly sporadic/recessive disease. Methods: A 38-year-old male was referred for genetic investigation to determine the underlying genetic substrate responsible for his ALVC phenotype. The patient fulfilled both electrocardiographic (low voltage in the limb leads and anterolateral T-wave inversions) and imaging (>1 segment of subepicardial LGE) criteria for ALVC. Additionally, the patient experienced unexplained episodes of tachycardia, shakiness, sweating, and nausea prompting concern for an underlying neuromuscular disease. Genome sequencing (GS) was performed on DNA isolated from the affected patient and both of his unaffected parents. Variants were filtered assuming either a sporadic de novo occurrence or an autosomal recessive inheritance pattern. Results: GS identified compound heterozygous GNPTAB variants in the affected patient. A previously reported maternally derived p.Leu257Leu (c.771G>A) variant involving the last nucleotide of exon 7 of the GNPTAB gene and a novel paternally inherited Lys834fs*5 frame-shift variant were identified. The p.Leu257Leu variant has been reported to cause aberrant splicing and exon skipping of the GNPTAB mRNA transcript. Pathogenic variants in the GNPTAB encoded N-acetylglucosamine-1 (GlcNAc)-phosphotransferase subunits alpha/beta cause mucolipidosis type III, a rare recessive lysosomal storage disease characterized by coarse facial features, developmental delay, short stature, skeletal deformities, and cardiac involvement including valvular thickening and cardiomyopathy. Conclusions: Here, using a genome sequencing trio analysis we identified a compound heterozygous GNPTAB pathogenic variants as the underlying genetic substrate in a patient with ring-like ALVC and concomitant neuromuscular disease manifestation. Genome sequencing may identify the genetic etiology responsible for an otherwise undifferentiated diagnosis of cardiomyopathy.

Introduction: Long QT syndrome (LQTS) is a potentially life-threatening genetic heart disease. Patients with LQTS may also have co-existent mental health illnesses that may benefit from psychiatric medications. However, because many of these medications have QT-prolonging potential (www.crediblemeds.org), many of these patients receive suboptimal mental health care. Objective: To evaluate the frequency, management, and incidence of breakthrough cardiac events (BCEs) in patients with LQTS and concomitant mental health issues treated with psychiatric medications. Methods: A retrospective review was conducted on patients cared for in Mayo Clinic's Windland Smith Rice Genetic Heart Rhythm Clinic between 2000 and 2024 focusing on patients with LQTS and a concomitant psychiatric diagnosis requiring medication with known, possible or conditional risk of torsades de pointes (TdP). Electronic medical records were reviewed for data. BCEs were defined as LQTS-triggered syncope, seizures, appropriate ICD therapy, sudden cardiac arrest (SCA), or sudden cardiac death (SCD). Patients with missing information were excluded. Results: Overall, 195 /1899 LQTS patients [10%, 86 (43%) with LQT1, 83 (42%) with LQT2, and 16 (8%) with LQT3] had a concomitant psychiatric diagnosis requiring medication [150 female (76%), mean age at diagnosis 27 ± 18 years, median follow-up time 6.6 years (IQR 2.9-13)]. The most common psychiatric conditions were depression (71%), anxiety (62%), and ADHD (9%). The mean duration of therapy was 3.36 +/- 3.48 years and the most common medications used were fluoxetine (26%), sertraline (14%), and escitalopram (11%). There was no significant difference in QTc after starting the first psychiatric medication when compared to baseline (473 ± 33 vs 474 ± 35 ms, p=0.6). Prior to their LQTS diagnosis and while therefore untreated, 61/195 (31%) had at least 1 LQTS-associated cardiac event. This occurred in the setting of a psychiatric drug in 7 patients (11%). Following LQTS diagnosis and treatment, 14/195 patients (7%) have experienced a non-lethal BCE of which only 3/14 (21%) while on psychiatric medications. Conclusions: Although avoidance of medications with known QT-prolonging potential is prudent, attention to patient’s overall well-being besides just their LQTS must be given. After correct diagnosis and treatment, LQTS patients with concomitant mental health issues may be safely and effectively treated with medications known to prolong QTc.

Abstract Introduction Hypertrophic cardiomyopathy (HCM) is the most prevalent heritable cardiomyopathy typically transmitted in an autosomal dominant fashion. There is growing importance in identifying genetic test positive patients given its prognostic value. The Mayo HCM Genotype Predictor Score has been extensively validated for assessment of patient’s pre-test probability for genotype positive HCM and helps guide clinical decision-making based on clinical and echocardiographic variables. Herein, we evaluated the role of cardiac magnetic resonance (CMR) to enhance the genotype predictor score. Purpose Evaluate performance of the Mayo Clinic HCM Genotype Predictor Score using CMR variables, and develop an updated, CMR incorporated score. Methods Retrospective analysis was conducted on 175 unrelated HCM patients with at least 1 MRI and a HCM genetic testing seen at the Mayo Clinic between April 2004 and April 2018. Phenotyping information was obtained through review of electronic medical records. The original Mayo HCM Genotype Predictor Score was calculated using both echocardiography and clinical variables. An updated score was created incorporating CMR-specific variables. Diagnostic accuracy of the models was assessed thought Receiver Operating Characteristic (ROC) curves. Results Overall, 108 (62%) were males with a mean age at CMR of 51 ± 18 years. The yield of positive genetic test for the echocardiogram-derived Mayo HCM Genotype Predictor Score ranged from 38% for patients with -1 point to 100% for patients with 4 or 5 points. There was a significant incremental increase in diagnostic yield between score subgroups (p &lt; 0.01) with an AUC of 0.659 (Figure 1A). Similar findings were observed using CMR variables (AUC of 0.697; Figure 1B). Univariate and multivariate analysis identified late gadolinium enhancement (LGE) as a strong predictor of a positive genetic test (OR 3.72; p=0.002), and it was added to the original score to create a new version. The Updated Mayo HCM Genotype Predictor Score predicted a positive genetic test ranging from 25% for patients with -1 point to 100% for patients with 5 or 6 points (p &lt; 0.01). There was a significant increase in diagnostic accuracy when compared to the original score (AUC 0.724 vs 0.679; p=0.03; Figure 1C). Conclusion Using LGE, the updated CMR-based Mayo HCM Genotype Predictor score provides a simple and improved tool to aid in genetic counseling for HCM patients.

AbstractIntroductionLong QT syndrome (LQTS) is a cardiac channelopathy characterized by QT prolongation and a potential for arrhythmic syncope, sudden cardiac arrest or deaths (SCA/SCD). It has been speculated that patients with LQTS might have a primary sinoatrial node (SAN) phenotype of chronotropic insufficiency (CI). This has not been demonstrated convincingly before because of the potentially confounding effects of beta blocker (BB) therapy. Herein, we set out to determine whether untreated patients with LQTS demonstrate intrinsic CI.Methods and ResultsA retrospective review of all treadmill exercise stress tests (TEST) was performed on patients with one of the three most common LQTS genotypes: LQT1, LQT2, and LQT3. For each patient, the first TEST completed while off BB was analyzed. Patients with prior left cardiac sympathetic denervation (LCSD) therapy were excluded. CI was defined as having an age‐ and gender‐predicted peak heart rate (HR) < 85% and/or a predicted HR reserve (HRR) < 80%. Overall, 463 LQTS patients (245 LQT1, 125 LQT2, and 93 LQT3) were included (267 female [58%]; mean age at time of TEST [29 ± 17 years]). Mean % predicted peak HR for all LQTS patients was 87.6% (range 42.9% ‐ 119.1%) and mean % predicted HRR was 80% (range 19.1% ‐ 153%). Overall, half of all LQTS patients (n = 234; 51%) displayed CI; 64% of patients with LQT1 (n = 157), 37% with LQT2 (n = 46), and 33% with LQT3 (n = 31). Patients with LQT1 were most likely to exhibit CI compared to patients with LQT2 (p < .0001) and LQT3 (p < .0001). CI was significantly more common in LQT1 compared to controls (p < .0001), while there was no difference between LQT2 (p = .5) or LQT3 and controls (p > .9). Presence of CI was not a predictor of LQTS‐associated symptoms, BB side effects or likelihood of future breakthrough cardiac events (BCE).ConclusionsPatients with LQTS, particularly LQT1, demonstrate a SAN phenotype of CI. If assessing BB therapy effect by impact on peak HR, the patient's pretreatment peak HR, rather than an age‐ and gender‐predicted maximum HR, should be used.