Clinical outcomes and programming strategies of implantable cardioverter-defibrillator devices in paediatric hypertrophic cardiomyopathy: a UK National Cohort Study.

AIMS: Sudden cardiac death (SCD) is the most common mode of death in paediatric hypertrophic cardiomyopathy (HCM). This study describes the implant and programming strategies with clinical outcomes following implantable cardioverter-defibrillator (ICD) insertion in a well-characterized national paediatric HCM cohort. METHODS AND RESULTS: Data from 90 patients undergoing ICD insertion at a median age 13 (±3.5) for primary (n = 67, 74%) or secondary prevention (n = 23, 26%) were collected from a retrospective, longitudinal multi-centre cohort of children (<16 years) with HCM from the UK. Seventy-six (84%) had an endovascular system [14 (18%) dual coil], 3 (3%) epicardial, and 11 (12%) subcutaneous system. Defibrillation threshold (DFT) testing was performed at implant in 68 (76%). Inadequate DFT in four led to implant adjustment in three patients. Over a median follow-up of 54 months (interquartile range 28-111), 25 (28%) patients had 53 appropriate therapies [ICD shock n = 45, anti-tachycardia pacing (ATP) n = 8], incidence rate 4.7 per 100 patient years (95% CI 2.9-7.6). Eight inappropriate therapies occurred in 7 (8%) patients (ICD shock n = 4, ATP n = 4), incidence rate 1.1/100 patient years (95% CI 0.4-2.5). Three patients (3%) died following arrhythmic events, despite a functioning device. Other device complications were seen in 28 patients (31%), including lead-related complications (n = 15) and infection (n = 10). No clinical, device, or programming characteristics predicted time to inappropriate therapy or lead complication. CONCLUSION: In a large national cohort of paediatric HCM patients with an ICD, device and programming strategies varied widely. No particular strategy was associated with inappropriate therapies, missed/delayed therapies, or lead complications.

Permanent pacemaker implantation after pediatric heart transplantation: Risk factors, indications, and outcomes.

BACKGROUND: Permanent pacemaker (PPM) placement in adults following orthotopic heart transplantation (OHT) has been well documented. However, studies concerning the need for PPM implantation in pediatric heart transplant recipients are less common. METHODS: Institutional transplant and pacing databases as well as patient medical records were reviewed for all pediatric patients undergoing OHT (n = 314; all with bicaval connection) at our institution between January 2000 and March 2018. RESULTS: A total of 16 patients (5.1%) were implanted with a pacemaker after transplantation. Donor age was the only significant risk factor for post-transplant PPM implantation, with a median age of 28.5 years (7.0-49.0) in the pacing group vs 15.5 years (0.4-56.0) in the non-pacing group (P = 0.009). Indication for pacemaker insertion was more often complete heart block (CHB) (12/16, 75%) than sinus node dysfunction (SND) (4/16, 25%). There was no significant difference in mortality between recipients who received a PPM and those who did not (log-rank test; P = 0.345). CONCLUSIONS: Increasing donor age is associated with increased PPM placement following pediatric heart transplantation. Interestingly, a high proportion of CHB patients recovered sinus rhythm, and long-term outcomes for paced patients are similar to other heart transplant recipients.

Impact and Modifiers of Ventricular Pacing in Patients With Single Ventricle Circulation.

BACKGROUND: Palliation of the single ventricle (SV) circulation is associated with a burden of lifelong complications. Previous studies have identified that the need for a permanent ventricular pacing system (PPMv) may be associated with additional adverse long-term outcomes. OBJECTIVES: The goal of this study was to quantify the attributable risk of PPMv in patients with SV, and to identify modifiable risk factors. METHODS: This international study was sponsored by the Pediatric and Congenital Electrophysiology Society. Centers contributed baseline and longitudinal data for functionally SV patients with PPMv. Enrollment was at implantation. Controls were matched 1:1 to PPMv subjects by ventricular morphology and sex, identified within center, and enrolled at matched age. Primary outcome was transplantation or death. RESULTS: In total, 236 PPMv subjects and 213 matched controls were identified (22 centers, 9 countries). Median age at enrollment was 5.3 years (quartiles: 1.5-13.2 years), follow-up 6.9 years (3.4-11.6 years). Median percent ventricular pacing (Vp) was 90.8% (25th-75th percentile: 4.3%-100%) in the PPMv cohort. Across 213 matched pairs, multivariable HR for death/transplant associated with PPMv was 3.8 (95% CI 1.9-7.6; P < 0.001). Within the PPMv population, higher Vp (HR: 1.009 per %; P = 0.009), higher QRS z-score (HR: 1.19; P = 0.009) and nonapical lead position (HR: 2.17; P = 0.042) were all associated with death/transplantation. CONCLUSIONS: PPMv in patients with SV is associated with increased risk of heart transplantation and death, despite controlling for increased associated morbidity of the PPMv cohort. Increased Vp, higher QRS z-score, and nonapical ventricular lead position are all associated with higher risk of adverse outcome and may be modifiable risk factors.

Outcomes From Pediatric Ablation: A Review of 20 Years of National Data.

OBJECTIVES: This study set out to examine outcomes from pediatric supraventricular tachycardia ablations over a 20-year period. This study sought to examine success rates and repeat ablations over time and to evaluate whether modalities such as 3-dimensional (3D) mapping, contact force, and cryotherapy have improved outcomes. BACKGROUND: Ablation of supraventricular tachycardia in pediatric patients is commonly performed in most congenital heart centers with excellent long-term results. METHODS: Data were retrieved from the NICOR (National Institute of Clinical Outcomes Research) database in the United Kingdom. Outcomes over time were evaluated, and procedure-related details were compared. RESULTS: There were 7,069 ablations performed from January 1, 1999, to December 31, 2018, at 10 centers. Overall, ablation success rates were 92% for accessory pathways, 97% for atrioventricular node re-entry tachycardia, and 89% for atrial tachycardia. There was an improvement in procedural success rates over time (p < 0.01). The use of 3D mapping did not alter success or need for repeat ablation but was associated with a higher proportion of lower fluoroscopy cases; 55% of 3D mapping cases used <5 min of fluoroscopy (p < 0.01). Patients needing a repeat ablation were 341 (12%) for accessory pathways, 128 (7%) for atrioventricular node re-entry tachycardia, and 35 (7%) for atrial tachycardia. Overall, the risk of complete heart block was low (n = 12, <0.01%). The use of cryotherapy was associated with an increased risk of needing a repeat ablation. CONCLUSIONS: Overall success rates from pediatric ablations are excellent and compare favorably to other registries. Introduction of newer technologies have likely made procedures safer and reduced radiation exposure, but they have not changed success rates or the need for a repeat procedure.

The clinical utility of brain natriuretic peptide in paediatric left ventricular failure.

AIMS: To assess the role of brain natriuretic peptide (BNP) in both the acute and chronic settings in children with left ventricular (LV) failure. METHODS AND RESULTS: We undertook a retrospective review of all BNP levels taken over a 2-year period in our institution. Minimum follow-up was 90 days. Ninety-two BNP samples from 48 patients were reviewed. Twenty patients (42%) reached the combined endpoint of death, transplantation, or listing for transplantation. Median age was 3 years and 3 months. Mean BNP levels in NYHA or Ross classes I-IV were 29, 239, 744, and 1593 pg/mL, respectively, with significant differences between mean logBNP in classes I-III (P < 0.001). LogBNP levels correlated with fractional shortening (P < 0.001), LVEDd z-score (P < 0.001), and tissue Doppler velocities (P < 0.02). From serial data there was a strong correlation between change in BNP and change in clinical status (F 9.5, P < 0.001). Receiver-operator curve (ROC) demonstrated that BNP > 290 pg/mL predicts poor outcome with sensitivity of 0.80, specificity of 0.87, and likelihood ratio of 6.4 in paediatric patients with chronic LV dysfunction. A separate ROC from acute presentations did not demonstrate superiority of BNP over other assessments. CONCLUSION: BNP levels in paediatric heart failure (HF) patients show a strong correlation to both impaired heart function on echocardiogram and clinical status. Serial BNP levels follow the clinical course. In chronic HF, a BNP level of >290 pg/mL is predictive of an adverse outcome.

Hypocalcaemia mimicking long QT syndrome: case report.

We describe a teenage girl who presented with syncope on exertion and prolonged QT on electrocardiogram (ECG). She was found to be hypocalcaemic due to hypoparathyroidism. Following oral calcium and vitamin D supplementation, there were no further episodes of syncope with normalization of the QT segment. This case highlights the need to consider all causes of a long QT segment.

Feasibility and outcomes of ajmaline provocation testing for Brugada syndrome in children in a specialist paediatric inherited cardiovascular diseases centre.

OBJECTIVES: Brugada syndrome (BrS) is an inherited arrhythmia syndrome that causes sudden cardiac death in the young. The class Ia antiarrhythmic ajmaline can be used to provoke the diagnostic ECG pattern. Its use has been established in adults, but little data exist on the ajmaline provocation test in children. This study aims to determine the safety and feasibility of ajmaline provocation testing in a large paediatric cohort in a specialist paediatric inherited cardiac diseases centre. METHODS: 98 consecutive ajmaline tests were performed in 95 children between September 2004 and July 2012 for family history of BrS (n=46 (48%)); family history of unexplained sudden cardiac death (n=39 (41%); symptoms with suspicious ECG abnormalities (n=9 (10%)). Three patients were retested with age, due to the possibility of age-related penetrance. ECG parameters were measured at baseline and during maximal ajmaline effect. RESULTS: The mean patient age was 12.55 years, 43% were female. Nineteen patients (20%) had a positive ajmaline test. There were no arrhythmias or adverse events during testing. Ajmaline provoked significant prolongation of the PR, QRS and QTc in all patients. Mean follow-up was 3.62 years with no adverse outcomes reported in any patients with BrS. There were no predictors of a positive ajmaline provocation test on multivariable analysis. One patient who tested negative at 12 years of age, subsequently tested positive at 15 years of age. CONCLUSIONS: Ajmaline testing appears safe and feasible in children when performed in an appropriate setting by an experienced team. Test positivity may change with age in individuals, suggesting that the test should be repeated in the late teenage years or early adulthood.

Decreased milk drinking causing flecainide toxicity in an older child.

Flecainide is a class IC antiarrhythmic agent, used frequently in all age groups for the treatment of tachyarrhythmias. Flecainide blocks the voltage-gated sodium channel in the myocardium, leading to prolongation of depolarisation resulting in slowed conduction velocity. Within a paediatric population, flecainide is indicated primarily for supraventricular tachycardia resulting from atrioventricular nodal re-entry and accessory pathway mediated re-entry. It can be considered for use in patients with atrial tachycardia, fascicular ventricular tachycardia, benign right ventricular outflow tract tachycardia and paroxysmal atrial fibrillation. It is well documented to cause paradoxical proarryhthmia in children, with evidence that milk can reduce absorption in infants. The authors present the case of an older child whose flecainide levels were persistently subtherapeutic until he reduced his milk intake. At this time he developed symptoms of severe flecainide toxicity associated with increased levels.

Early pediatric anthracycline cardiotoxicity: managed by serial heart and bone marrow transplantation.

We report a favorable outcome in a child who underwent cardiac transplantation for severe early post-anthracycline-induced cardiomyopathy, 9 months after completion of treatment for acute myeloid leukemia (AML). The child suffered a relapse of AML 2 months after cardiac transplantation and then underwent a successful bone marrow transplant. This case is unique in the literature. We believe it offers an alternative strategy for children with hematologic malignancies, where severe early post-anthracycline cardiotoxicity might preclude bone marrow transplantation.

Successful cardiac transplantation in Barth syndrome--single-centre experience of four patients.

We describe four patients with Barth syndrome who have undergone successful orthotopic heart transplantation. Patients are one, seven, 12.5 and 14.7 yr post-transplantation. One episode of severe infection occurred. Renal dysfunction and coronary allograft vasculopathy do not appear accelerated over non-Barth patients. Despite withholding purine synthesis inhibitors, these patients have not demonstrated an increased rate of rejection.