How to assess and treat right ventricular electromechanical dyssynchrony in post-repair tetralogy of Fallot: insights from imaging, invasive studies, and computational modelling.

BACKGROUND AND AIMS: Right bundle branch block (RBBB) and resulting right ventricular (RV) electromechanical discoordination are thought to play a role in the disease process of subpulmonary RV dysfunction that frequently occur post-repair tetralogy of Fallot (ToF). We sought to describe this disease entity, the role of pulmonary re-valvulation, and the potential added value of RV cardiac resynchronization therapy (RV-CRT). METHODS: Two patients with repaired ToF, complete RBBB, pulmonary regurgitation, and significantly decreased RV function underwent echocardiography, cardiac magnetic resonance, and an invasive study to evaluate the potential for RV-CRT as part of the management strategy. The data were used to personalize the CircAdapt model of the human heart and circulation. Resulting Digital Twins were analysed to quantify the relative effects of RV pressure and volume overload and to predict the effect of RV-CRT. RESULTS: Echocardiography showed components of a classic RV dyssynchrony pattern which could be reversed by RV-CRT during invasive study and resulted in acute improvement in RV systolic function. The Digital Twins confirmed a contribution of electromechanical RV dyssynchrony to RV dysfunction and suggested improvement of RV contraction efficiency after RV-CRT. The one patient who underwent successful permanent RV-CRT as part of the pulmonary re-valvulation procedure carried improvements that were in line with the predictions based on his Digital Twin. CONCLUSION: An integrative diagnostic approach to RV dysfunction, including the construction of Digital Twins may help to identify candidates for RV-CRT as part of the lifetime management of ToF and similar congenital heart lesions.

Patterns of Electrocardiographic Abnormalities in Children with Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM), a common cardiomyopathy in children, is an important cause of morbidity and mortality. Early recognition and appropriate management are important. An electrocardiogram (ECG) is often used as a screening tool in children to detect heart disease. The ECG patterns in children with HCM are not well described.ECGs collected from an international cohort of children, and adolescents (≤ 21 years) with HCM were reviewed. 482 ECGs met inclusion criteria. Age ranged from 1 day to 21 years, median 13 years. Of the 482 ECGs, 57 (12%) were normal. The most common abnormalities noted were left ventricular hypertrophy (LVH) in 108/482 (22%) and biventricular hypertrophy (BVH) in 116/482 (24%) Of the patients with LVH/BVH (n = 224), 135 (60%) also had a strain pattern (LVH in 83, BVH in 52). Isolated strain pattern (in the absence of criteria for hypertrophy) was seen in 43/482 (9%). Isolated pathologic Q waves were seen in 71/482 (15%). Pediatric HCM, 88% have an abnormal ECG. The most common ECG abnormalities were LVH or BVH with or without strain. Strain pattern without hypertrophy and a pathologic Q wave were present in a significant proportion (24%) of patients. Thus, a significant number of children with HCM have ECG abnormalities that are not typical for "hypertrophy". The presence of the ECG abnormalities described above in a child should prompt further examination with an echocardiogram to rule out HCM.

Pediatric catheter ablation at the beginning of the 21st century: results from the European Multicenter Pediatric Catheter Ablation Registry 'EUROPA'.

AIMS: Contemporary data from prospective multicentre registries on catheter ablation in pediatric patients are sparse. Aim of the European Pediatric Catheter Ablation Registry EUROPA was to contribute data to fill this gap of knowledge. METHODS AND RESULTS: From July 2012 to June 2017, data on catheter ablation in pediatric patients (≤18 years of age) including a 1-year follow-up from five European pediatric EP centres were collected prospectively. A total of 683 patients (mean age 12.4 ± 3.9 years, mean body weight 50.2 ± 19 kg) were enrolled. Target tachycardia was WPW/atrioventricular-nodal re-entrant tachycardia (AVRT) in 380 (55.7%) patients, AVNRT in 230 (33.8%) patients, ventricular tachycardia (VT) in 24 (3.5) patients, focal atrial tachycardia (FAT) in 20 (2.9%) patients, IART in 14 (2%) patients, and junctional ectopic tachycardia in 3 (0.45) patients. Overall procedural success was 95.6%. Compared with all other substrates, success was significantly lower in FAT patients (80%, n = 16, P = 0.001). Mean procedure duration was 136 ± 67 min and mean fluoroscopy time was 4.9 ± 6.8 min. Major complications occurred in 0.7% of the patients. No persisting AV block requiring permanent pacing was reported. At 1-year follow-up (605/683 patients, 95%), tachycardia recurrence was reported in 7.8% of patients. Recurrence after VT ablation (33%) was significantly higher (P = 0.001) than after ablation of all other substrates. CONCLUSION: The present study proves overall high efficacy and safety of catheter ablation of various tachycardia substrates in pediatric patients. Of note, complication rate was exceptionally low. Long-term success was high except for patients after VT ablation.

2021 PACES expert consensus statement on the indications and management of cardiovascular implantable electronic devices in pediatric patients.

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consensus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology (ACC), and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate CIED follow-up in pediatric patients.

2021 PACES expert consensus statement on the indications and management of cardiovascular implantable electronic devices in pediatric patients: Executive summary.

Guidelines for the implantation of cardiac implantable electronic devices (CIEDs) have evolved since publication of the initial ACC/AHA pacemaker guidelines in 1984 [1]. CIEDs have evolved to include novel forms of cardiac pacing, the development of implantable cardioverter defibrillators (ICDs) and the introduction of devices for long term monitoring of heart rhythm and other physiologic parameters. In view of the increasing complexity of both devices and patients, practice guidelines, by necessity, have become increasingly specific. In 2018, the ACC/AHA/HRS published Guidelines on the Evaluation and Management of Patients with Bradycardia and Cardiac Conduction Delay [2], which were specific recommendations for patients >18 years of age. This age-specific threshold was established in view of the differing indications for CIEDs in young patients as well as size-specific technology factors. Therefore, the following document was developed to update and further delineate indications for the use and management of CIEDs in pediatric patients, defined as ≤21 years of age, with recognition that there is often overlap in the care of patents between 18 and 21 years of age. This document is an abbreviated expert consensus statement (ECS) intended to focus primarily on the indications for CIEDs in the setting of specific disease/diagnostic categories. This document will also provide guidance regarding the management of lead systems and follow-up evaluation for pediatric patients with CIEDs. The recommendations are presented in an abbreviated modular format, with each section including the complete table of recommendations along with a brief synopsis of supportive text and select references to provide some context for the recommendations. This document is not intended to provide an exhaustive discussion of the basis for each of the recommendations, which are further addressed in the comprehensive PACES-CIED document [3], with further data easily accessible in electronic searches or textbooks.

2021 PACES expert consensus statement on the indications and management of cardiovascular implantable electronic devices in pediatric patients.

In view of the increasing complexity of both cardiovascular implantable electronic devices (CIEDs) and patients in the current era, practice guidelines, by necessity, have become increasingly specific. This document is an expert consensus statement that has been developed to update and further delineate indications and management of CIEDs in pediatric patients, defined as ≤21 years of age, and is intended to focus primarily on the indications for CIEDs in the setting of specific disease categories. The document also highlights variations between previously published adult and pediatric CIED recommendations and provides rationale for underlying important differences. The document addresses some of the deterrents to CIED access in low- and middle-income countries and strategies to circumvent them. The document sections were divided up and drafted by the writing committee members according to their expertise. The recommendations represent the consensus opinion of the entire writing committee, graded by class of recommendation and level of evidence. Several questions addressed in this document either do not lend themselves to clinical trials or are rare disease entities, and in these instances recommendations are based on consensus expert opinion. Furthermore, specific recommendations, even when supported by substantial data, do not replace the need for clinical judgment and patient-specific decision-making. The recommendations were opened for public comment to Pediatric and Congenital Electrophysiology Society (PACES) members and underwent external review by the scientific and clinical document committee of the Heart Rhythm Society (HRS), the science advisory and coordinating committee of the American Heart Association (AHA), the American College of Cardiology (ACC), and the Association for European Paediatric and Congenital Cardiology (AEPC). The document received endorsement by all the collaborators and the Asia Pacific Heart Rhythm Society (APHRS), the Indian Heart Rhythm Society (IHRS), and the Latin American Heart Rhythm Society (LAHRS). This document is expected to provide support for clinicians and patients to allow for appropriate CIED use, appropriate CIED management, and appropriate CIED follow-up in pediatric patients.

Left ventricular apical pacing in children: feasibility and long-term effect on ventricular function.

AIMS: Left ventricular apical pacing (LVAP) has been reported to preserve left ventricular (LV) function in chronically paced children with complete atrioventricular block (CAVB). We sought to evaluate long-term feasibility of LVAP and the effect on LV mechanics and exercise capacity as compared to normal controls. METHODS AND RESULTS: Thirty-six consecutive paediatric patients with CAVB and LVAP in the absence (N = 22) or presence of repaired structural heart disease (N = 14, systemic LV in all) and 25 age-matched normal controls were cross-sectionally studied after a median of 3.9 (interquartile range 2.1-6.8) years of pacing using echocardiography and exercise stress testing. Pacemaker implantation was uneventful and there was no death. Probability of the absence of pacemaker-related surgical revision (elective generator replacement excluded) was 89.0% at 5 years after implantation. Left ventricular apical pacing patients had lower maximum oxygen uptake (P = 0.009), no septal to lateral but significant apical to basal LV mechanical delay (P < 0.001) which correlated with decreased LV contraction efficiency (P = 0.001). Left ventricular ejection fraction and global longitudinal LV strain were, however, not different from controls. Results were similar in both the presence and absence of structural heart disease. CONCLUSION: Left ventricular apical pacing is technically feasible with a low reintervention rate. Mechanical synchrony between LV septum and free wall is maintained at the price of an apical to basal mechanical delay associated with LV contraction inefficiency as compared to healthy controls. Global LV systolic function is, however, not negatively affected by LVAP.

Riata lead failure in pediatric and congenital heart disease patients.

BACKGROUND: Implantable cardioverter defibrillator (ICD) lead failures occur at higher rates in pediatric and congenital heart disease (CHD) patients. OBJECTIVE: To determine the rate and timing of Riata lead failure in pediatric and CHD patients. METHODS: This was a retrospective, multicenter cohort study of pediatric patients and adults with CHD with implantation of a Riata or Riata ST lead between 2002 and 2009. The prevalence and timing of electrical failure and conductor coil externalization (CCE) were determined. RESULTS: Fifty-eight patients and 63 leads from seven centers were included. Median (interquartile range [IQR]) age at implant was 14.4 (11.5-18.7) years and median follow-up was 8.7 (7.3-11.1) years. The underlying diagnosis was a primary arrhythmia disorder in 45%, cardiomyopathy in 31%, and CHD in 28% of patients. Electrical failure occurred in 43% and CCE in 16% of leads at median lead ages of 4.7 (3.4-7.5) and 4.3 (3.9-7.0) years, respectively. Median lead survival free from electrical failure or CCE was 7.9 (95% confidence interval, 5.8-10.0) years. Forty-one percent of leads were functional at the end of the follow-up period, and 33% were extracted with a complication rate of 5%. CONCLUSIONS: The rate of Riata lead electrical failure was high in children and patients with CHD, while the rate of CCE was comparable with published data. Counseling on lead management should factor in the high rate of electrical failure with considerations for elective replacement.

Impact of Obesity on Left Ventricular Thickness in Children with Hypertrophic Cardiomyopathy.

Obesity is associated with additional left ventricular hypertrophy (LVH) in adults with hypertrophic cardiomyopathy (HCM). It is not known whether obesity can lead to further LVH in children with HCM. Echocardiographic LV dimensions were determined in 504 children with HCM. Measurements of interventricular septal thickness (IVST) and posterior wall thickness (PWT), and patients' weight and height were recorded. Obesity was defined as a body mass index (BMI) ≥ 99th percentile for age and sex. IVST data was available for 498 and PWT data for 484 patients. Patient age ranged from 2 to 20 years (mean ± SD, 12.5 ± 3.9) and 340 (68%) were males. Overall, patient BMI ranged from 7 to 50 (22.7 ± 6.1). Obesity (BMI 18-50, mean 29.1) was present in 140 children aged 2-19.6 (11.3 ± 4.1). The overall mean IVST was 20.5 ± 9.6 mm and the overall mean PWT was 11.0 ± 8.4 mm. The mean IVST in the obese patients was 21.6 ± 10.0 mm and mean PWT was 13.3 ± 14.7 mm. The mean IVST in the non-obese patients was 20.1 ± 9.5 mm and mean PWT was 10.4 ± 4.3 mm. Obesity was not significantly associated with IVST (p = 0.12), but was associated with increased PWT (0.0011). Obesity is associated with increased PWT but not IVST in children with HCM. Whether obesity and its impact on LVH influences clinical outcomes in children with HCM needs to be studied.

Acute right ventricular resynchronization improves haemodynamics in children after surgical repair of tetralogy of Fallot.

Aims: Right bundle branch block is associated with right ventricular (RV) electromechanical dyssynchrony, which may contribute to acute haemodynamic impairment after repair of tetralogy of Fallot (ToF). We sought to evaluate the effects of RV resynchronization on haemodynamics and tissue oxygenation during the first 24 h after surgery. Methods and results: Arterial pressures, cardiac output, and tissue oxygenation were measured in 28 consecutive patients (median age 10.1 months) during baseline sinus rhythm with right bundle branch block and after RV resynchronization by atrial-triggered RV free wall pacing in complete fusion with spontaneous activation. Studied variables were compared in a crossover design in four 5-min intervals (baseline rhythm and stimulation, 2x each). Resynchronization reduced the QRS complex duration from median 110 to 70 ms (P < 0.001), increased significantly median arterial systolic, mean and pulse pressure, cardiac index, left ventricular maximum +dP/dT and decreased central venous pressure (P < 0.001 for all). Both cerebral and renal oxygenation improved (P < 0.001). Eleven of the 28 patients showed a clinically highly significant resynchronization effect defined as an increase in arterial pulse pressure of ≥ 10%. The q-RV interval (expressed as % of QRS duration) at the RV pacing site during baseline rhythm was the only predictor of resynchronization effect. Conclusions: RV resynchronization carried short-term improvement of haemodynamics in children early after surgery for ToF and might be a useful non-pharmacologic adjunct to the management of haemodynamically compromised patients. Resynchronization effect was maximized when pacing from area of the latest RV activation.

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.

Permanent cardiac pacing in children: choosing the optimal pacing site: a multicenter study.

BACKGROUND: We evaluated the effects of the site of ventricular pacing on left ventricular (LV) synchrony and function in children requiring permanent pacing. METHODS AND RESULTS: One hundred seventy-eight children (aged <18 years) from 21 centers with atrioventricular block and a structurally normal heart undergoing permanent pacing were studied cross-sectionally. Median age at evaluation was 11.2 (interquartile range, 6.3-15.0) years. Median pacing duration was 5.4 (interquartile range, 3.1-8.8) years. Pacing sites were the free wall of the right ventricular (RV) outflow tract (n=8), lateral RV (n=44), RV apex (n=61), RV septum (n=29), LV apex (n=12), LV midlateral wall (n=17), and LV base (n=7). LV synchrony, pump function, and contraction efficiency were significantly affected by pacing site and were superior in children paced at the LV apex/LV midlateral wall. LV dyssynchrony correlated inversely with LV ejection fraction (R=0.80, P=0.031). Pacing from the RV outflow tract/lateral RV predicted significantly decreased LV function (LV ejection fraction <45%; odds ratio, 10.72; confidence interval, 2.07-55.60; P=0.005), whereas LV apex/LV midlateral wall pacing was associated with preserved LV function (LV ejection fraction ≥55%; odds ratio, 8.26; confidence interval, 1.46-47.62; P=0.018). Presence of maternal autoantibodies, gender, age at implantation, duration of pacing, DDD mode, and QRS duration had no significant impact on LV ejection fraction. CONCLUSIONS: The site of ventricular pacing has a major impact on LV mechanical synchrony, efficiency, and pump function in children who require lifelong pacing. Of the sites studied, LV apex/LV midlateral wall pacing has the greatest potential to prevent pacing-induced reduction of cardiac pump function.

What's new in cardiac pacing in children?

PURPOSE OF REVIEW: To review and prioritize data on pediatric cardiac pacing published during the period of the last 18 months. RECENT FINDINGS: New approaches to preservation of ventricular function in pediatric pacing are based on recent publications confirming major influence of the ventricular pacing site on left ventricular (LV) function and synchrony. Current studies on epicardial vs. transvenous pacing continue to show survival superiority of endocardial leads. Long-term outcome of epicardial pacing may, however, be positively influenced by technical refinements. Recent amendments of the guidelines for cardiac resynchronization therapy (CRT) in adult idiopathic and ischemic cardiomyopathy are likely to influence CRT indications in children. Novel data give interesting insights into implantable cardioverter-defibrillator (ICD) lead survival as well as the use of ICDs in young patients with hypertrophic cardiomyopathy. SUMMARY: Pediatric cardiac pacing and ICD therapy is still a developing field likely to improve with technical refinements, proper lead placement and more specific therapy indications. The current review will give the reader information about recent developments and directions for the future.

Long-term results of paediatric radiofrequency catheter ablation: a population-based study.

AIMS: We aimed to evaluate long-term utilization and results of paediatric radiofrequency catheter ablation (RFCA) in a population-based study. METHODS AND RESULTS: Data from all three centres performing paediatric RFCA for the whole population of the Czech Republic between 1993 and 2010 were retrospectively reviewed. A total of 708 ablation procedures in 633 consecutive patients <18 years for 716 different substrates were tracked, with accessory pathways = 439 (61.3%) and atrioventricular nodal reentry tachycardia (AVNRT) = 205 (28.6%) being most frequent. Incidence of RFCA reached 0.049 per 1000 children <18 years of age in the recent era (2006-10). Indications included patient preference (68.0%), drug refractoriness (15.5%), asymptomatic Wolff-Parkinson-White pre-excitation (8.4%), and malignant arrhythmia (6.1%). Median follow-up was 13.7 (interquartile range 5.7-21.5) months. Overall acute/long-term success of the primary procedure was 89.1/77.2% (accessory pathways 87.2/77.7%, AVNRT 98.5/84.4%). Re-ablation was performed in 73 of 163 substrates after a primary unsuccessful ablation resulting in a long-term cumulative efficacy of 96.3%. Between 1993-2005 and 2006-10, procedure/fluoroscopy time decreased from median 154/24 to 105/14 min. (P < 0.001 for both). Serious complications occurred in nine patients (1.4%). CONCLUSION: This population-based study could replicate data from previous single- or multi-centre reports confirming RFCA as a safe method of arrhythmia treatment in children with long-term cumulative efficacy exceeding 90% and significant decrease in the procedure and fluoroscopy time during the study period. The need for RFCA can be estimated at ∼0.05/1000 children <18 years using current indication criteria.

Sudden cardiac arrest in a child with Gitelman syndrome: a case report and literature review.

Salt-losing tubulopathies are well-recognised diseases predisposing to metabolic disturbances in affected patients. One of the most severe complications can be life-threatening arrhythmias causing sudden cardiac arrest. We present here the first case of a pediatric patient with Gitelman syndrome associated sudden cardiac arrest without precipitating event. A 10-year-old boy collapsed due to ventricular fibrillation in the Prague tram. Lay cardiopulmonary resuscitation was initiated and external defibrillation restored sinus rhythm within minutes. Initial laboratory examination revealed severe hypokalemia requiring large amounts of electrolyte supplementation. Genetic testing focused to tubulopathies was performed and the diagnosis of Gitelman syndrome was made following the identification of two pathogenic variants in SLC12A3 gene (c.2633 + 1G>A and c.2221G>A). Implantable cardioverter-defibrillator was implanted to prevent sudden cardiac death. The patient was in a good clinical condition with satisfactory electrolyte serum levels at the last follow-up. Causes of electrolyte abnormalities in children should be identified early to prevent the development of rare but potentially fatal complications.

Natural History of Nonsurgical Complete Atrioventricular Block in Children and Predictors of Pacemaker Implantation.

BACKGROUND: Data on the natural history of complete atrioventricular block (CAVB) in children are scarce, and criteria for pacemaker (PM) implantation are based on low levels of evidence. OBJECTIVES: This study aimed to evaluate the natural course and predictors of PM implantation in a nationwide cohort of pediatric patients with nonsurgical CAVB. METHODS: All children with CAVB in the absence of structural heart disease presenting from 1977 to 2016 were retrospectively identified, yielding 95 subjects with a mean age of 4.05 years at the first presentation with a follow-up median of 0.80 years (IQR: 0.02-6.82 years). PM implantation was performed according to the available guidelines. Serial 24-hour Holter recordings and echocardiograms were reviewed. Predictors of PM implantation performed >1 month after the first presentation were evaluated. RESULTS: The minimum and mean 24-hour heart rates and maximum RR intervals had a nonlinear correlation with age (P < 0.0001 for all). The left ventricular (LV) size was moderately increased, and the shortening fraction was normal in the majority throughout follow-up. PM implantation was performed in 62 patients (65.3%) reaching guideline criteria. The mean 24-hour heart rate at presentation was a predictor of subsequent PM implantation (HR: 0.938; 95% CI: 0.894-0.983; P = 0.003 per unit increase) regardless of age at presentation. Patients presenting with a mean 24-hour heart rate >58 beats/min (>75th percentile) had a high probability of freedom from PM within the subsequent 5 years (91.7% vs 44.4%; P < 0.001). CONCLUSIONS: Pediatric patients with CAVB showed an age-dependent decrease in heart rate, moderate LV dilation, and preserved LV function. The probability of subsequent PM implantation could be predicted by the heart rate profile at presentation, defining a low-risk group and allowing for individualized follow-up.

Clinical characteristics and mutational analysis of the RyR2 gene in seven Czech families with catecholaminergic polymorphic ventricular tachycardia.

BACKGROUND: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare hereditary arrhythmia. The onset of clinical symptoms usually occurs during childhood, and is typically related to exercise. The aim of our study was to describe the clinical characteristics of seven Czech families with CPVT and the results of mutational analysis of the RyR2 gene in these families. METHODS: The subjects and their relatives were investigated at the participating departments. They underwent basic clinical investigation, and history was focused on possible CPVT symptoms, that is, syncopes during exercise. Bicycle ergometry was performed to obtain electrocardiogram recording during adrenergic stimulation. In all the investigated individuals, blood samples were taken for mutation analysis of the RyR2 gene. RESULTS: To date, seven families have been investigated, comprising 11 adults and 13 children. In seven CPVT patients, the indication for examination was syncope during exercise. Diagnosis was confirmed by bicycle ergometry-induced polymorphic ventricular tachycardia. In one relative, polymorphic ventricular tachycardia was also induced. All eight affected individuals were treated with ß-blockers and in two, a cardioverter-defibrillator was implanted due to recurrent syncopi. Coding variants of the RyR2 gene were found in four probands. CONCLUSIONS: This is a systematic description of CPVT families in the Czech Republic. Our data support the importance of exercise testing for the diagnosis of CPVT. In addition, RyR2 gene coding variants were found in 50% of affected individuals.

Clinical Features and Natural History of Preadolescent Nonsyndromic Hypertrophic Cardiomyopathy.

BACKGROUND: Up to one-half of childhood sarcomeric hypertrophic cardiomyopathy (HCM) presents before the age of 12 years, but this patient group has not been systematically characterized. OBJECTIVES: The aim of this study was to describe the clinical presentation and natural history of patients presenting with nonsyndromic HCM before the age of 12 years. METHODS: Data from the International Paediatric Hypertrophic Cardiomyopathy Consortium on 639 children diagnosed with HCM younger than 12 years were collected and compared with those from 568 children diagnosed between 12 and 16 years. RESULTS: At baseline, 339 patients (53.6%) had family histories of HCM, 132 (20.9%) had heart failure symptoms, and 250 (39.2%) were prescribed cardiac medications. The median maximal left ventricular wall thickness z-score was 8.7 (IQR: 5.3-14.4), and 145 patients (27.2%) had left ventricular outflow tract obstruction. Over a median follow-up period of 5.6 years (IQR: 2.3-10.0 years), 42 patients (6.6%) died, 21 (3.3%) underwent cardiac transplantation, and 69 (10.8%) had life-threatening arrhythmic events. Compared with those presenting after 12 years, a higher proportion of younger patients underwent myectomy (10.5% vs 7.2%; P = 0.045), but fewer received primary prevention implantable cardioverter-defibrillators (18.9% vs 30.1%; P = 0.041). The incidence of mortality or life-threatening arrhythmic events did not differ, but events occurred at a younger age. CONCLUSIONS: Early-onset childhood HCM is associated with a comparable symptom burden and cardiac phenotype as in patients presenting later in childhood. Long-term outcomes including mortality did not differ by age of presentation, but patients presenting at younger than 12 years experienced adverse events at younger ages.

Relationship Between Maximal Left Ventricular Wall Thickness and Sudden Cardiac Death in Childhood Onset Hypertrophic Cardiomyopathy.

BACKGROUND: Maximal left ventricular wall thickness (MLVWT) is a risk factor for sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM). In adults, the severity of left ventricular hypertrophy has a nonlinear relationship with SCD, but it is not known whether the same complex relationship is seen in childhood. The aim of this study was to describe the relationship between left ventricular hypertrophy and SCD risk in a large international pediatric HCM cohort. METHODS: The study cohort comprised 1075 children (mean age, 10.2 years [±4.4]) diagnosed with HCM (1-16 years) from the International Paediatric Hypertrophic Cardiomyopathy Consortium. Anonymized, noninvasive clinical data were collected from baseline evaluation and follow-up, and 5-year estimated SCD risk was calculated (HCM Risk-Kids). RESULTS: MLVWT Z score was <10 in 598 (58.1%), ≥10 to <20 in 334 (31.1%), and ≥20 in 143 (13.3%). Higher MLVWT Z scores were associated with heart failure symptoms, unexplained syncope, left ventricular outflow tract obstruction, left atrial dilatation, and nonsustained ventricular tachycardia. One hundred twenty-two patients (71.3%) with MLVWT Z score ≥20 had coexisting risk factors for SCD. Over a median follow-up of 4.9 years (interquartile range, 2.3-9.3), 115 (10.7%) had an SCD event. Freedom from SCD event at 5 years for those with MLVWT Z scores <10, ≥10 to <20, and ≥20 was 95.6%, 87.4%, and 86.0, respectively. The estimated SCD risk at 5 years had a nonlinear, inverted U-shaped relationship with MLVWT Z score, peaking at Z score +23. The presence of coexisting risk factors had a summative effect on risk. CONCLUSIONS: In children with HCM, an inverted U-shaped relationship exists between left ventricular hypertrophy and estimated SCD risk. The presence of additional risk factors has a summative effect on risk. While MLVWT is important for risk stratification, it should not be used either as a binary variable or in isolation to guide implantable cardioverter defibrillator implantation decisions in children with HCM.