Bos, J. Martijn

Abstract Background/Introduction Arrhythmogenic mitral valve prolapse syndrome (AMVPS) is a female-predominant sudden cardiac death (SCD)-predisposing disorder characterized clinically by myxomatous mitral valve prolapse (MVP), inferolateral T-wave inversions and complex ventricular ectopy. However, insights into the pathogenesis and potential genetic basis of AMVPS are currently lacking. Purpose Considering recent case reports that suggest a potential role for genetic cardiomyopathies in the pathogenesis of AMVPS, we sought to determine the yield of pathogenic/likely pathogenic (P/LP) genetic variants in strong evidence cardiomyopathy-susceptibility genes amongst AMVPS patients who underwent clinical genetic testing. Methods In this retrospective study, the medical records of 4,907 patients referred to our cardiovascular genetics clinic was used to identify those patients with a clinical phenotype consistent with AMVPS. After exclusion of individuals with severe mitral valve regurgitation, pertinent clinical, electrocardiographic, imaging and genetic testing data was extracted from the electronic record. For those AMVPS that underwent a form of genetic testing that encompassed 23 Clinical Genome Resource-defined strong/definitive evidence cardiomyopathy-susceptibility genes, ultra-rare (minor allele frequency ≤ 0.00005 in the Genome Aggregation Database [n=141,456 individuals]) non-synonymous variants identified within these genes were adjudicated independently as P, LP or variant of uncertain significance with the assistance of Varsome. The frequency of P/LP variants was then compared to a previously published cohort of 973 ostensibly healthy control exomes. Results Overall, 56 unrelated patients with suspected AMVPS were identified (82% female; average age at presentation of 31 ± 13 years; 32% with a family history of MVP and/or SCD). Of these, 24/56 (43%) underwent a form of clinical genetic testing that encompassed the pre-defined panel of cardiomyopathy-susceptibility genes. In comparison to control exomes (n=973), P/LP variants in strong/definitive evidence cardiomyopathy-susceptibility genes were over-represented in AMVPS patients [4/24 (16.7%) vs 20/973 (2.1%); p=0.002]. Interestingly, this enrichment was driven in large part by an excess number of A-band-localizing P/LP truncating variants in TTN-encoded titin in AMVPS cases [3/24 (12.5%) versus 4/973 (0.4%); p=0.0004]. Conclusion This study provides further evidence that a subset of AMVPS may arise secondary to a "two-hit" model whereby an underlying cardiomyopathic genetic substrate is exacerbated by the mechanical force generated by genetically unrelated myxomatous MVP resulting in maladaptive and ventricular arrhythmia-predisposing fibrosis within the inferobasal left ventricle and posteromedial papillary muscles. Larger studies are needed to better understand the potential role of genetic testing in the diagnosis, risk-stratification and management of patients with suspected AMVPS.

BACKGROUND: In severely affected patients with catecholaminergic polymorphic ventricular tachycardia, beta-blockers are often insufficiently protective. The purpose of this study was to evaluate whether flecainide is associated with a lower incidence of arrhythmic events (AEs) when added to beta-blockers in a large cohort of patients with catecholaminergic polymorphic ventricular tachycardia. METHODS: From 2 international registries, this multicenter case cross-over study included patients with a clinical or genetic diagnosis of catecholaminergic polymorphic ventricular tachycardia in whom flecainide was added to beta-blocker therapy. The study period was defined as the period in which background therapy (ie, beta-blocker type [beta1-selective or nonselective]), left cardiac sympathetic denervation, and implantable cardioverter defibrillator treatment status, remained unchanged within individual patients and was divided into pre-flecainide and on-flecainide periods. The primary end point was AEs, defined as sudden cardiac death, sudden cardiac arrest, appropriate implantable cardioverter defibrillator shock, and arrhythmic syncope. The association of flecainide with AE rates was assessed using a generalized linear mixed model assuming negative binomial distribution and random effects for patients. RESULTS: A total of 247 patients (123 [50%] females; median age at start of flecainide, 18 years [interquartile range, 14–29]; median flecainide dose, 2.2 mg/kg per day [interquartile range, 1.7–3.1]) were included. At baseline, all patients used a beta-blocker, 70 (28%) had an implantable cardioverter defibrillator, and 21 (9%) had a left cardiac sympathetic denervation. During a median pre-flecainide follow-up of 2.1 years (interquartile range, 0.4–7.2), 41 patients (17%) experienced 58 AEs (annual event rate, 5.6%). During a median on-flecainide follow-up of 2.9 years (interquartile range, 1.0–6.0), 23 patients (9%) experienced 38 AEs (annual event rate, 4.0%). There were significantly fewer AEs after initiation of flecainide (incidence rate ratio, 0.55 [95% CI, 0.38–0.83]; P =0.007). Among patients who were symptomatic before diagnosis or during the pre-flecainide period (n=167), flecainide was associated with significantly fewer AEs (incidence rate ratio, 0.49 [95% CI, 0.31–0.77]; P =0.002). Among patients with ≥1 AE on beta-blocker therapy (n=41), adding flecainide was also associated with significantly fewer AEs (incidence rate ratio, 0.25 [95% CI, 0.14–0.45]; P <0.001). CONCLUSIONS: For patients with catecholaminergic polymorphic ventricular tachycardia, adding flecainide to beta-blocker therapy was associated with a lower incidence of AEs in the overall cohort, in symptomatic patients, and particularly in patients with breakthrough AEs while on beta-blocker therapy.

ImportanceSyncope is the most powerful predictor for subsequent life-threatening events (LTEs) in patients with congenital long QT syndrome (LQTS). Whether distinct syncope triggers are associated with differential subsequent risk of LTEs is unknown.ObjectiveTo evaluate the association between adrenergic (AD)– and nonadrenergic (non–AD)-triggered syncopal events and the risk of subsequent LTEs in patients with LQT types 1 to 3 (LQT1-3).Design, Setting, and ParticipantsThis retrospective cohort study included data from 5 international LQTS registries (Rochester, New York; the Mayo Clinic, Rochester, Minnesota; Israel, the Netherlands, and Japan). The study population comprised 2938 patients with genetically confirmed LQT1, LQT2, or LQT3 stemming from a single LQTS-causative variant. Patients were enrolled from July 1979 to July 2021.ExposuresSyncope by AD and non-AD triggers.Main Outcomes and MeasuresThe primary end point was the first occurrence of an LTE. Multivariate Cox regression was used to determine the association of AD- or non–AD-triggered syncope on the risk of subsequent LTE by genotype. Separate analysis was performed in patients with β-blockers.ResultsA total of 2938 patients were included (mean [SD] age at enrollment, 29 [7] years; 1645 [56%] female). In 1331 patients with LQT1, a first syncope occurred in 365 (27%) and was induced mostly with AD triggers (243 [67%]). Syncope preceded 43 subsequent LTEs (68%). Syncopal episodes associated with AD triggers were associated with the highest risk of subsequent LTE (hazard ratio [HR], 7.61; 95% CI, 4.18-14.20; P &amp;lt; .001), whereas the risk associated with syncopal events due to non-AD triggers was statistically nonsignificant (HR, 1.50; 95% CI, 0.21-4.77; P = .97). In 1106 patients with LQT2, a first syncope occurred in 283 (26%) and was associated with AD and non-AD triggers in 106 (37%) and 177 (63%), respectively. Syncope preceded 55 LTEs (56%). Both AD- and non–AD-triggered syncope were associated with a greater than 3-fold increased risk of subsequent LTE (HR, 3.07; 95% CI, 1.66-5.67; P ≤ .001 and HR, 3.45, 95% CI, 1.96-6.06; P ≤ .001, respectively). In contrast, in 501 patients with LQT3, LTE was preceded by a syncopal episode in 7 (12%). In patients with LQT1 and LQT2, treatment with β-blockers following a syncopal event was associated with a significant reduction in the risk of subsequent LTEs. The rate of breakthrough events during treatment with β-blockers was significantly higher among those treated with selective agents vs nonselective agents.Conclusion and RelevanceIn this study, trigger-specific syncope in LQTS patients was associated with differential risk of subsequent LTE and response to β-blocker therapy.

Abstract Aims Calmodulinopathy due to mutations in any of the three CALM genes (CALM1–3) causes life-threatening arrhythmia syndromes, especially in young individuals. The International Calmodulinopathy Registry (ICalmR) aims to define and link the increasing complexity of the clinical presentation to the underlying molecular mechanisms. Methods and results The ICalmR is an international, collaborative, observational study, assembling and analysing clinical and genetic data on CALM-positive patients. The ICalmR has enrolled 140 subjects (median age 10.8 years [interquartile range 5–19]), 97 index cases and 43 family members. CALM-LQTS and CALM-CPVT are the prevalent phenotypes. Primary neurological manifestations, unrelated to post-anoxic sequelae, manifested in 20 patients. Calmodulinopathy remains associated with a high arrhythmic event rate (symptomatic patients, n = 103, 74%). However, compared with the original 2019 cohort, there was a reduced frequency and severity of all cardiac events (61% vs. 85%; P = .001) and sudden death (9% vs. 27%; P = .008). Data on therapy do not allow definitive recommendations. Cardiac structural abnormalities, either cardiomyopathy or congenital heart defects, are present in 30% of patients, mainly CALM-LQTS, and lethal cases of heart failure have occurred. The number of familial cases and of families with strikingly different phenotypes is increasing. Conclusion Calmodulinopathy has pleiotropic presentations, from channelopathy to syndromic forms. Clinical severity ranges from the early onset of life-threatening arrhythmias to the absence of symptoms, and the percentage of milder and familial forms is increasing. There are no hard data to guide therapy, and current management includes pharmacological and surgical antiadrenergic interventions with sodium channel blockers often accompanied by an implantable cardioverter–defibrillator.

Introduction: Over 100 FDA-approved medications, electrolyte perturbations, and many disease states can prolong the QTc beyond its 99 th percentile value resulting in acquired QT prolongation. In contrast, approximately 1 in 2000 people have congenital long QT syndrome (LQTS) hallmarked by pathological QT prolongation secondary to genetic defects in the heart. Hypothesis: An artificial intelligence (AI) deep neural network (DNN) can distinguish patients with LQTS from those with acquired QT prolongation. Methods: The study cohort included all patients with LQTS evaluated in the Windland Smith Rice Genetic Heart Rhythm Clinic and controls from Mayo Clinic’s ECG data vault comprising over 2.5 million patients. For the AI-DNN model, every patient/control with ≥ 1 ECG above age- and sex- specific 99 th percentile values for QTc [> 460 ms for all patients (male/female) < 13 years of age, or > 470 ms for men and > 480 ms for women above this age] was included. An AI-DNN involving a multi-layer c onvolutional n eural n etwork (CNN) was developed to classify patients. LQTS patients were age- and sex- matched to controls at 1:5 ratio. Results: Among the 1,599 patients with genetically confirmed LQTS, 808 had ≥ 1 ECG with QTc above the threshold (2,987 ECGs) compared to 361,069/2.5M controls (14% of Mayo Clinic patients getting an ECG, ‘presumed negative’; 989,313 ECGs). Following age- and sex- matching and splitting, 3,309 (training), 411 (validation) and 887 (testing) control ECGs were used. This model distinguished LQTS from those with acquired QT prolongation with an AUC of 0.896 (accuracy 85%, sensitivity 77%, specificity 88%, PPV 0.58, NPV 0.94). After exclusion of patients with a wide QRS (>150 ms) or pacemaker, the model remained successful in distinguishing the two groups (AUC 0.85, accuracy 78%, sensitivity 78%, specificity 87%, PPV 59%, NPV 94%). Conclusions: For patients with a QTc exceeding its 99 th percentile values, this novel AI-DNN functions as a LQTS mutation detector being able to identify patients with abnormal QT prolongation secondary to a LQTS-causative mutation rather than acquired QT prolongation with a >50% positive predictive value. This algorithm may facilitate screening for this potentially lethal, yet highly treatable, genetic heart disease.

Introduction: Sudden cardiac arrest (SCA) and death (SCD) are the most serious sequelae of many genetic heart diseases (GHDs). Increased awareness of this has led to increased detection in employment screenings. For patients in high-risk jobs, premature and potentially unnecessary termination from their profession, rather than “Return-to-Work (RTW),” has become an undesired consequence of this awareness. The objective of this study is to evaluate the outcomes of patients with GHDs in high-risk professions who were allowed to RTW. Methods: We performed a retrospective review of 3,641 working-age patients referred for evaluation of a potential GHD between 6/2000-12/2021 to identify those either in or being recruited into a high-risk profession. A profession was defined as “high-risk” if it is safety-sensitive or required regular medical evaluations. Charts were reviewed for medical history, RTW decision making, and breakthrough cardiac events (BCEs). Results: Overall, 33 patients [(0.9%); 3 females (9%); mean age at diagnosis 25 ± 15 years] had been either put on hold from their high-risk job (n = 15; 45%) or disqualified as a recruit (18; 55%) prior to our evaluation due to their GHD diagnosis. This included 15 military, 10 pilots, 6 law enforcement and first responders, and 2 commercial driver license professionals and recruits. Most patients were diagnosed with Long QT syndrome (n = 23; 70%). After treatment initiation, 14 (93%) professionals and 16 (89%) recruits received physician RTW approval while 3 (9%) patients did not receive RTW approval due to disease severity and/or unwillingness to initiate treatment. Of the remaining 14 professionals that received physician RTW approval, 4 (29%) were not allowed to return to their jobs, while 14/16 recruits (88%) were not permitted to start their career. None of the RTW-approved patients had a BCE after evaluation (160.7 follow-up years). Conclusions: Patients with GHDs in high-risk professions are often terminated due to perceived SCA/SCD risk. However, within our small cohort, the risk of BCEs in optimally treated patients was low. This data suggests that the certification process of individuals in these high-risk and safety-sensitive occupations should be further examined and potentially modified.

Introduction: Hypertrophic cardiomyopathy (HCM) is a disease characterized by genotypic and phenotypic heterogeneity. Correct classification of genetic variation is critical for clinical interpretation. Herein, variants of uncertain significance (VUS) pose a dilemma in clinical practice, limiting physicians’ decision making and causing anguish to patients and family members. Furthermore, with increasing knowledge and changing guidelines, continuous reassessment is crucial to maintain usefulness in practice. This study sought to assess contemporary variant classification in a large cohort of patients with HCM. Methods: Retrospective analysis of all patients with HCM seen at Mayo Clinic and all patients with a variant in one of 8 genes with strong disease association for HCM were included. Genetic test reports were obtained from electronic health records along with their original variant classification assigned by either a commercial or research laboratory. Reassessment of variant pathogenicity was performed using the 2015 ACMG guideline criteria. Population frequency was obtained using Gnomad. Co-segregation presence or absence was determined by family history and co-segregation studies. Combined Annotation Dependent Depletion (CADD) was used as computational evidence of genetic deleterious effects for single nucleotide variants. Results: Between 2003 to 2019, a total of 1,782 patients underwent laboratory or commercial HCM genetic testing. Of these, 787 (44%) had positive genetic test with a variant at least 1 of the 8 genes. The original pathogenic classification was obtained for 754 patients. Of those, 430 (57%) variants where within the gene MYBPC3, 244 (32%) within MYH7 and 80 (11%) within either ACTC1, MYL2, MYL3, TINNI3, TNNT2 or TPM1. Overall, 222 patients (29%) originally had one or more variants classified as a VUS. Upon reassessment, 120 (54%) were reclassified as either pathogenic (33%), likely pathogenic (58%), benign (5%) or likely benign (3%). Conclusion: Periodic reassessment for HCM genetic variants, especially VUS, is critical for adequate patient care and management. Cascade screening could decrease patients’ uncertainty regarding their prognosis and management.

Background: Long QT syndrome (LQTS) is a genetic heart disease affecting about 1 in 2000 persons. Around 40% of patients with LQTS can have a nondiagnostic, normal QTc at rest. The treadmill exercise stress test (TEST) can help unmask patients with concealed LQTS with a characteristic maladaptive, paradoxical increase in QTc ( 460 ms) during the recovery phase. In fact, the recovery phase QTc value has been added to the latest diagnostic score for LQTS. Objective: To characterize the TEST-derived QTc profile of untreated patients with LQTS and determine its diagnostic and prognostic utility. Methods: Retrospective analysis was performed on TEST data derived from 249 patients with LQTS (129 LQT1, 64 LQT2 and 56 LQT3) untreated at the time of their TEST compared with 236 controls. The Bazett’s corrected QTc was calculated at rest (sitting, supine, and standing), during exercise at 1 min, 3 mins, and peak exercise, and during recovery phase at 1, 3 and 5 mins. Results: The mean resting QTc was significantly higher in LQTS patients (457 ± 30 ms) compared to controls (420 ± 24 ms; p<0.0001) as well as at every stage during the TEST (p<0.001). For LQT1 patients, highest QTc was observed at peak exercise (mean 496 ± 38 ms) and during the third minute of recovery phase (mean 500 ± 40 ms). In contrast, LQT2 patients showed the lowest QTc (mean 452 ± 48 ms) during peak exercise but the greatest QTc latency (QTc at 5 min - QTc at 1 min recovery; mean QTc latency 33 ± 77 ms; p=0.005) compared to controls. For LQT3, the mean QTc was greatest at rest compared to controls (p<0.001), and there was no difference during exercise and recovery phases. Among 162 LQT1 and LQT2 patients that presented with concealed LQTS, 119 (73%) showed a maladaptive QT response. ROC analysis showed that in patients with LQT1, a maladaptive QTc > 523 ms at 3 min of recovery was highly predictive of breakthrough cardiac events (AUC 0.84; sensitivity 100%, specificity 72%); no such association was identified for LQT2 or 3. Conclusions: This comprehensive characterization of the QTc response before, during, and after a TEST in the largest untreated cohort of patients with LQTS provides important genotype-specific characteristics and can be used as a predictor for potential LQT1-triggered cardiac events after diagnosis and treatment.

Introduction: Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy. Approximately 40-50% of HCM is caused by pathogenic variants in genes encoding proteins of the cardiac sarcomere. Patients with sarcomeric HCM have earlier expression and more severe disease progression. Herein, we evaluated the proteomic differences between patients with sarcomeric HCM and genotype negative HCM. Methods: Mass-spectrometry was performed on cardiac tissue from genotyped patients with HCM obtained after surgical myectomy, followed by differential proteomics (log2fc ≥

Background: Sex hormones influence the arrhythmogenic risk for various genetic heart diseases (GHDs) including long QT syndrome (LQTS), Brugada syndrome (BrS), catecholaminergic polymorphic ventricular tachycardia (CPVT), and idiopathic ventricular fibrillation (IVF). Although exogenous hormones are used frequently in transgender medicine for gender-affirming hormone therapy (GAHT), the effect of such treatments on sudden cardiac death (SCD) risk in transgender patients with a GHD is unknown. Objective: To describe the prevalence and spectrum of transgender patients with GHD and to evaluate the impact of GAHT on the treatment and outcomes of their underlying GHD. Methods: We performed a retrospective review of all patients seen and evaluated in Mayo Clinic’s Windland Smith Rice Genetic Heart Rhythm Clinic from January 1999-2022 to identify transgender patients. Clinical notes were reviewed for sex, gender identity, GAHT, and details of their GHD, therapy, and outcomes. Results: Among 1990 patients with a GHD, we found 7 patients (0.35%) who self-identify as a gender different from their chromosomal sex (transgender). Specifically, there were 4 patients who identified as transgender women (XY males at birth) and 3 as transgender men (XX females at birth). Five of seven patients (71%) have used forms of GAHT, with 2 patients on estradiol and 3 patients on testosterone. GHDs identified include LQT1 (2 transgender women), LQT3 (1 transgender man), LQT3/BrS overlap syndrome (1 transgender woman), genotype negative LQTS (1 transgender man), CPVT (1 transgender woman), and IVF (1 transgender man). Guideline-directed GHD therapy was optimized, not altered nor escalated, for all patients and no patients were advised against initiating GAHT due to perceived interactions. One of seven patients (transgender man with IVF) experienced a breakthrough cardiac event (BCE) while on GAHT, while the other 6 patients have had no BCEs. Conclusion: Although less than 0.5% of patients seen over 20+ years self-identified as transgender, their holistic care must include a careful discussion of the possible cardiac risks associated with GAHT. Additional studies are needed to determine the potential pro-arrhythmic risk of GAHT.