Cardiac phenotype in adolescents and young adults with long-chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) deficiency.

PURPOSE: Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency (LCHADD) is a rare fatty acid oxidation disorder characterized by recurrent episodes of metabolic decompensation and rhabdomyolysis, as well as retinopathy, peripheral neuropathy, and cardiac involvement, such as infantile dilated cardiomyopathy. Because LCHADD patients are surviving longer, we sought to characterize LCHADD-associated major cardiac involvement in adolescence and young adulthood. METHODS: A retrospective cohort of 16 adolescent and young adult participants with LCHADD was reviewed for cardiac phenotype. RESULTS: Major cardiac involvement occurred in 9 of 16 participants, including sudden death, out-of-hospital cardiac arrest, acute cardiac decompensations with heart failure and/or in-hospital cardiac arrest, end-stage dilated cardiomyopathy, and moderate restrictive cardiomyopathy. Sudden cardiac arrest was more common in males and those with a history of infant cardiomyopathy. CONCLUSION: The cardiac manifestations of LCHADD in adolescence and early adulthood are complex and distinct from the phenotype seen in infancy. Life-threatening arrhythmia occurs at substantial rates in LCHADD, often in the absence of metabolic decompensation or rhabdomyolysis. The potential risk factors identified here-male sex and history of infant cardiomyopathy-may hint at strategies for risk stratification and possibly the prevention of these events.

Reduced kinase function in two ultra-rare TNNI3K variants in families with congenital junctional ectopic tachycardia.

Genetic missense variants in TNNI3K, encoding troponin-I interacting kinase, have been associated with dilated cardiomyopathy (DCM) and observed in families with supraventricular tachycardias (SVT). Previously, a family harboring the TNNI3K-c.1615A > G (p.Thr539Ala) variant presented with congenital junctional ectopic tachycardia (CJET), an arrhythmia that arises from the atrioventricular (AV) node and His bundle. However, this was a relatively small four-generational family with limited genetic testing (N = 3). We here describe a multigenerational family with CJET harboring a novel ultra-rare TNNI3K variant: TNNI3K-c.1729C > T (p.Leu577Phe). Of all 18 variant carriers, 13 individuals presented with CJET, resulting in a genetic penetrance of 72%. In addition, CJET is reported in another small family harboring TNNI3K-c.2225C > T (p.Pro742Leu). Similar to the previously published CJET family, both TNNI3K variants demonstrate a substantial reduction of kinase activity. Our study contributes novel evidence supporting the involvement of TNNI3K genetic variants as significant contributors to CJET, shedding light on potential mechanisms underlying this cardiac arrhythmia.

Translation of Tools and Techniques from the Adult Electrophysiology World to Pediatric Cardiac Implantable Electronic Devices.

This article reviews various opportunities to translate established and novel tools and techniques used in adult electrophysiology to pediatrics and the adult congenital heart disease population. There is a specific focus on preoperative management of special population, implantation techniques, and postoperative programming of devices.

Clinical presentation of calmodulin mutations: the International Calmodulinopathy Registry.

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.

An unusual cause of repolarization abnormality after congenital heart surgery: A case report.

We present a case of a young boy who developed persistent tachycardia despite fluid resuscitation, antipyretics, and analgesia after a Fontan procedure. Review of telemetry and ECGs revealed repolarization abnormalities, including the appearance of T-wave alternans, for which an uncommon cause was ultimately identified.

Life-threatening cardiac arrhythmia and sudden death during electronic gaming: An international case series and systematic review.

BACKGROUND: Electronic gaming has recently been reported as a precipitant of life-threatening cardiac arrhythmia in susceptible individuals. OBJECTIVE: The purpose of this study was to describe the population at risk, the nature of cardiac events, and the type of game linked to cardiac arrhythmia associated with electronic gaming. METHODS: A multisite international case series of suspected or proven cardiac arrhythmia during electronic gaming in children and a systematic review of the literature were performed. RESULTS: Twenty-two patients (18 in the case series and 4 via systematic review; aged 7-16 years; 19 males [86%]) were identified as having experienced suspected or proven ventricular arrhythmia during electronic gaming; 6 (27%) had experienced cardiac arrest, and 4 (18%) died suddenly. A proarrhythmic cardiac diagnosis was known in 7 (31%) patients before their gaming event and was established afterward in 12 (54%). Ten patients (45%) had catecholaminergic polymorphic ventricular tachycardia, 4 (18%) had long QT syndrome, 2 (9%) were post-congenital cardiac surgery, 2 (9%) had "idiopathic" ventricular fibrillation, and 1 (after Kawasaki disease) had coronary ischemia. In 3 patients (14%), including 2 who died, the diagnosis remains unknown. In 13 (59%) patients for whom the electronic game details were known, 8 (62%) were war games. CONCLUSION: Electronic gaming can precipitate lethal cardiac arrhythmias in susceptible children. The incidence appears to be low, but syncope in this setting should be investigated thoroughly. In children with proarrhythmic cardiac conditions, electronic war games in particular are a potent arrhythmic trigger.

Clinical and Functional Characterization of Ryanodine Receptor 2 Variants Implicated in Calcium-Release Deficiency Syndrome.

Importance: Calcium-release deficiency syndrome (CRDS), which is caused by loss-of-function variants in cardiac ryanodine receptor 2 (RyR2), is an emerging cause of ventricular fibrillation. However, the lack of complex polymorphic/bidirectional ventricular tachyarrhythmias during exercise stress testing (EST) may distinguish it from catecholaminergic polymorphic ventricular tachycardia (CPVT). Recently, in the first clinical series describing the condition, mouse and human studies showed that the long-burst, long-pause, short-coupled ventricular extra stimulus (LBLPS) electrophysiology protocol reliably induced CRDS ventricular arrhythmias. Data from larger populations with CRDS and its associated spectrum of disease are lacking. Objective: To further insight into CRDS through international collaboration. Design, Setting, and Participants: In this multicenter observational cohort study, probands with unexplained life-threatening arrhythmic events and an ultrarare RyR2 variant were identified. Variants were expressed in HEK293 cells and subjected to caffeine stimulation to determine their functional impact. Data were collected from September 1, 2012, to March 6, 2021, and analyzed from August 9, 2015, to March 6, 2021. Main Outcomes and Measures: The functional association of RyR2 variants found in putative cases of CRDS and the associated clinical phenotype(s). Results: Of 10 RyR2 variants found in 10 probands, 6 were loss-of-function, consistent with CRDS (p.E4451del, p.F4499C, p.V4606E, p.R4608Q, p.R4608W, and p.Q2275H) (in 4 [67%] male and 2 [33%] female probands; median age at presentation, 22 [IQR, 8-34] years). In 5 probands with a documented trigger, 3 were catecholamine driven. During EST, 3 probands with CRDS had no arrhythmias, 1 had a monomorphic couplet, and 2 could not undergo EST (deceased). Relatives of the decedents carrying the RyR2 variant did not have EST results consistent with CPVT. After screening 3 families, 13 relatives were diagnosed with CRDS, including 3 with previous arrhythmic events (23%). None had complex ventricular tachyarrhythmias during EST. Among the 19 confirmed cases with CRDS, 10 had at least 1 life-threatening event at presentation and/or during a median follow-up of 7 (IQR, 6-18) years. Two of the 3 device-detected ventricular fibrillation episodes were induced by a spontaneous LBLPS-like sequence. ß-Blockers were used in 16 of 17 surviving patients (94%). Three of 16 individuals who were reportedly adherent to ß-blocker therapy (19%) had breakthrough events. Conclusions and Relevance: The results of this study suggest that calcium-release deficiency syndrome due to RyR2 loss-of-function variants mechanistically and phenotypically differs from CPVT. Ventricular fibrillation may be precipitated by a spontaneous LBLPS-like sequence of ectopy; however, CRDS remains difficult to recognize clinically. These data highlight the need for better diagnostic tools and treatments for this emerging condition.

Long-term Outcomes of Children Operated on for Anomalous Left Coronary Artery From the Pulmonary Artery.

BACKGROUND: We examined the outcomes of children (<18 years) operated on for anomalous left coronary artery from the pulmonary artery (ALCAPA). METHODS: We linked patients undergoing ALCAPA repair between 1982 and 2003 in the Pediatric Cardiac Care Consortium with the National Death Index and the Organ Procurement and Transplantation Network to examine their outcomes through 2019. RESULTS: We identified 228 children (median age, 6.0 months) operated on for ALCAPA. At the time of repair, 38.6% had severe mitral regurgitation (MR), and 71.4% had severe left ventricular (LV) dysfunction. Repair included primarily coronary reimplantation in 173 and the Takeuchi procedure in 34; concurrently, 18 underwent mitral valve (MV) operation. In-hospital death occurred in 31 (13.6%) and was not associated with MR severity (P = .846); however, among patients with moderate or severe MR, risk of death was 28% lower when undergoing MV operation (P = .033). After adjustment for other risk factors, only infant operation reached statistical significance for in-hospital death (adjusted odds ratio, 12.99; 95% CI, 1.61-104.59; P = .016). Among those discharged alive with long-term data available (n = 155), the 30-year transplant-free survival reached 95.5% (95% CI, 92.3%-98.8%) and was not associated with the degree of preoperative MR or LV dysfunction. Coronary reimplantation was associated with better long-term survival compared with other surgical techniques (adjusted odds ratio, 0.11; 95% CI, 0.02-0.74; P = .023). CONCLUSIONS: Favorable long-term outcomes can be expected after coronary artery reimplantation for ALCAPA, even in patients with severe LV dysfunction at presentation. MV operation predicted decreased risk for in-hospital mortality in patients with moderate/severe MR, but MR severity predicted neither in-hospital nor longer-term outcomes.

Fortuitous Left Bundle Branch Area Pacing in a Small Child.

Deep septal pacing is an emerging technique for physiologic pacing in adults. We report a case where left bundle capture was inadvertently achieved in a small child with routine lead deployment into a thin septum and discuss the potential feasibility of this technique for future study. (Level of Difficulty: Advanced.).

An interesting response to adenosine during right ventricular pacing. What is the mechanism?

We describe an interesting case in which single dose of adenosine during RV pacing elicited a series of abrupt transitions in the retrograde activation behaviour in an 11-year-old child undergoing electrophysiology study for Wolff-Parkinson-White syndrome.

Permanent conduction system pacing for congenitally corrected transposition of the great arteries: A Pediatric and Congenital Electrophysiology Society (PACES)/International Society for Adult Congenital Heart Disease (ISACHD) Collaborative Study.

BACKGROUND: Congenitally corrected transposition of the great arteries (CCTGA) is associated with spontaneous atrioventricular block and pacing-induced cardiomyopathy. Conduction system pacing is a potential alternative to conventional cardiac resynchronization therapy (CRT). OBJECTIVE: The purpose of this study was to determine the outcomes of conduction system pacing for CCTGA. METHODS: Retrospective data were collected from 10 international centers. RESULTS: His bundle (HBP) or left bundle branch pacing (LBBP) was attempted in 15 CCTGA patients (median age 23 years; 87% male). Previous surgery had been performed in 8 and chronic ventricular pacing in 7. Conduction system pacing (11 HBP, 2 LBBP 2; nonselective in 10, selective in 3) was acutely successful in 13 (86%) without complication. In 9 cases, electroanatomic mapping was available and identified the distal His bundle and proximal left bundle branches within the morphologic left ventricle below the pulmonary valve separate from the mitral annulus. Median implant HV interval was 42 ms (interquartile range [IQR] 35-48), R wave 6 mV (IQR 5-18), and threshold 0.5 V (IQR 0.5-1.2) at median 0.5 ms. QRSd was unchanged compared to junctional escape rhythm (124 vs 110 ms; P = .17) and decreased significantly compared to baseline ventricular pacing (112 vs 164 ms; P <.01). At a median of 8 months, all patients were alive without significant change in pacing threshold or lead dysfunction. New York Heart Association functional class improved in 5 patients. CONCLUSION: Permanent conduction system pacing is feasible in CCTGA by either HBP or proximal LBBP. Narrow paced QRS and stable lead thresholds were observed at intermediate follow-up. Unique anatomic characteristics may favor this approach over conventional CRT.

Mortality Following Pediatric Congenital Heart Surgery: An Analysis of the Causes of Death Derived From the National Death Index.

Background Prior research has focused on early outcomes after congenital heart surgery, but less is known about later risks. We aimed to determine the late causes of death among children (<21 years of age) surviving their initial congenital heart surgery. Methods and Results This is a retrospective cohort study from the Pediatric Cardiac Care Consortium, a US-based registry of interventions for congenital heart defects (CHD). Excluding patients with chromosomal anomalies or inadequate identifiers, we matched those surviving their first congenital heart surgery (1982-2003) against the National Death Index through 2014. Causes of death were obtained from the National Death Index to calculate cause-specific standardized mortality ratios (SMRs). Among 31 132 patients, 2527 deaths (8.1%) occurred over a median follow-up period of 18 years. Causes of death varied by time after surgery and severity of CHD but, overall, 69.9% of deaths were attributed to the CHD or another cardiovascular disorder, with a SMR for CHD/cardiovascular disorder of 67.7 (95% confidence interval: 64.5-70.8). Adjusted odds ratios revealed increased risk of death from CHD/cardiovascular disorder in females [odds ratio=1.28; 95% confidence interval (1.04-1.58); P=0.018] with leading cardiovascular disorder contributing to death being cardiac arrest (16.8%), heart failure (14.8%), and arrhythmias (9.1%). Other major causes of death included coexisting congenital malformations (4.7%, SMR: 7.0), respiratory diseases (3.6%, SMR: 8.2), infections (3.4%, SMR: 8.2), and neoplasms (2.1%, SMR: 1.9). Conclusions Survivors of congenital heart surgery face long-term risks of premature mortality mostly related to residual CHD pathology, heart failure, and arrhythmias, but also to other noncardiac conditions. Ongoing monitoring is warranted to identify target factors to address residual morbidities and improve long-term outcomes.

Trends in Long-Term Mortality After Congenital Heart Surgery.

BACKGROUND: Congenital heart surgery has improved the survival of patients with even the most complex defects, but the long-term survival after these procedures has not been fully described. OBJECTIVES: The purpose of this study was to evaluate the long-term survival of patients (age <21 years) who were operated on for congenital heart defects (CHDs). METHODS: This study used the Pediatric Cardiac Care Consortium data, a U.S.-based, multicenter registry of pediatric cardiac surgery. Survival analysis included 35,998 patients who survived their first congenital heart surgery at <21 years of age and had adequate identifiers for linkage with the National Death Index through 2014. Survival was compared to that in the general population using standardized mortality ratios (SMRs). RESULTS: After a median follow-up of 18 years (645,806 person-years), 3,191 deaths occurred with an overall SMR of 8.3 (95% confidence interval [CI]: 8.0 to 8.7). The 15-year SMR decreased from 12.7 (95% CI: 11.9 to 13.6) in the early era (1982 to 1992) to 10.0 (95% CI: 9.3 to 10.8) in the late era (1998 to 2003). The SMR remained elevated even for mild forms of CHD such as patent ductus arteriosus (SMR 4.5) and atrial septal defects (SMR 4.9). The largest decreases in SMR occurred for patients with transposition of great arteries (early: 11.0 vs. late: 3.8; p < 0.05), complete atrioventricular canal (31.3 vs. 15.3; p < 0.05), and single ventricle (53.7 vs. 31.3; p < 0.05). CONCLUSIONS: In this large U.S. cohort, long-term mortality after congenital heart surgery was elevated across all forms of CHD. Survival has improved over time, particularly for severe defects with significant changes in their management strategy, but still lags behind the general population.

Outcomes after surgical coronary artery revascularisation in children with congenital heart disease.

OBJECTIVE: Surgical coronary revascularisation in children with congenital heart disease (CHD) is a rare event for which limited information is available. In this study, we review the indications and outcomes of surgical coronary revascularisation from the Pediatric Cardiac Care Consortium, a large US-based multicentre registry of interventions for CHD. METHODS: This is a retrospective cohort study of children (<18 years old) with CHD who underwent surgical coronary revascularisation between 1982 and 2011. In-hospital mortality and graft patency data were obtained from the registry. Long-term transplant-free survival through 2014 was achieved for patients with adequate identifiers via linkage with the US National Death Index and the Organ Procurement and Transplantation Network. RESULTS: Coronary revascularisation was accomplished by bypass grafting (n=72, median age 6.8 years, range 3 days-17.4 years) or other operations (n=65, median age 2.6 years, range 5 days-16.7 years) in 137 patients. Most revascularisations were related to the aortic root (61.3%) or coronary anomalies (27.7%), but 10.9% of them were unrelated to either of them. Twenty in-hospital deaths occurred, 70% of them after urgent 'rescue' revascularisation in association with another operation. Long-term outcomes were available by external linkage for 54 patients surviving to hospital discharge (median follow-up time 15.0 years, max follow-up 29.8 years) with a 15-year transplant-free survival of 91% (95% CI 83% to 99%). CONCLUSIONS: Surgical coronary revascularisation can be performed in children with CHD with acceptable immediate and long-term survival. Outcomes are dependent on indication, with the highest mortality in rescue procedures.

The clinical and genetic spectrum of catecholaminergic polymorphic ventricular tachycardia: findings from an international multicentre registry.

Aims: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an ion channelopathy characterized by ventricular arrhythmia during exertion or stress. Mutations in RYR2-coded Ryanodine Receptor-2 (RyR2) and CASQ2-coded Calsequestrin-2 (CASQ2) genes underlie CPVT1 and CPVT2, respectively. However, prognostic markers are scarce. We sought to better characterize the phenotypic and genotypic spectrum of CPVT, and utilize molecular modelling to help account for clinical phenotypes. Methods and results: This is a Pediatric and Congenital Electrophysiology Society multicentre, retrospective cohort study of CPVT patients diagnosed at <19 years of age and their first-degree relatives. Genetic testing was undertaken in 194 of 236 subjects (82%) during 3.5 (1.4-5.3) years of follow-up. The majority (60%) had RyR2-associated CPVT1. Variant locations were predicted based on a 3D structural model of RyR2. Specific residues appear to have key structural importance, supported by an association between cardiac arrest and mutations in the intersubunit interface of the N-terminus, and the S4-S5 linker and helices S5 and S6 of the RyR2 C-terminus. In approximately one quarter of symptomatic patients, cardiac events were precipitated by only normal wakeful activities. Conclusion: This large, multicentre study identifies contemporary challenges related to the diagnosis and prognostication of CPVT patients. Structural modelling of RyR2 can improve our understanding severe CPVT phenotypes. Wakeful rest, rather than exertion, often precipitated life-threatening cardiac events.