Multiple accessory pathways in the young: the impact of structural heart disease.

BACKGROUND: The presence of multiple accessory pathways (MultAP) is described in structural heart disease (SHD) such as Ebstein's anomaly and cardiomyopathies. Structural defects can impact the tolerability of tachyarrhythmia and can complicate both medical management and ablation. In a large cohort of pediatric patients with and without SHD undergoing invasive electrophysiology study, we examined the prevalence of MultAP and the effect of both MultAP and SHD on ablation outcomes. METHODS: Accessory pathway number and location, presence of SHD, ablation success, and recurrence were analyzed in consecutive patients from our center over a 16-year period. RESULTS: In 1088 patients, 1228 pathways (36% retrograde only) were mapped to the right side (TV) in 18%, septum (S) in 39%, and left side (MV) in 43%. MultAP were present in 111 pts (10%), involving 250 distinct pathways. SHD tripled the risk of MultAP (26% SHD vs 8% no SHD, P < .001). Multivariable adjusted risk factors for MultAP included Ebstein's (OR 8.7[4.4-17.5], P < .001) and cardiomyopathy (OR 13.3[5.1-34.5], P < .001). Of 1306 ablation attempts, 94% were acutely successful with an 8% recurrence rate. Ablation success was affected by SHD (85% vs 95% for no SHD, P < .01) but not by MultAP (91% vs 94% for single, P = .24). Recurrence rate was higher for SHD (17% SHD vs 8% no SHD, P < .05) and MultAP (19% MultAP vs 8% single, P < .001). CONCLUSIONS: MultAP are found in 10% of pediatric patients, and are more common in SHD compared to those with normal hearts. Both the presence of MultAP and SHD negatively influence ablation outcomes.

The Impact of Pre-Exercise Carbohydrate Meal on the Effects of Yerba Mate Drink on Metabolism, Performance, and Antioxidant Status in Trained Male Cyclists.

INTRODUCTION: The consumption of yerba mate (YM), a source of antioxidants, in a fasted state increases fatty acid oxidation (FATox) during low-moderate-intensity exercise and improves performance in high-intensity exercise. However, the impact of a pre-exercise carbohydrate (CHO) meal on YM effects during exercise is unknown. OBJECTIVE: We investigated the effects of yerba mate drink (YMD) consumed in the fasted state (YMD-F) or after a CHO meal (YMD-CHO) on measurements of metabolism, performance, and blood oxidative stress markers in cycling exercise. METHODS: In a randomized, repeated-measures, crossover design, eight trained male cyclists ingested (i) YMD-CHO, (ii) YMD-F, or (iii) control-water and CHO meal (Control-CHO). The YMD (an infusion of 5 g of ultrarefined leaves in 250 mL of water) was taken for 7 days and 40 min before exercise. CHO meal (1 g/kg body mass) was consumed 60 min before exercise. The cycling protocol included a 40-min low-intensity (~ 53% V̇O2peak) constant load test (CLT); a 20-min time trial (TT); and 4 × 10-s all-out sprints. Blood samples and respiratory gases were collected before, during, and/or after tests. RESULTS: During CLT, YMD-CHO increased FATox ~ 13% vs. YMD-F (P = 0.041) and ~ 27% vs. Control-CHO (P < 0.001). During TT, YMD-CHO increased FATox ~ 160% vs. YMD-F (P < 0.001) and ~ 150% vs. Control-CHO (P < 0.001). Power output during TT improved ~ 3% (P = 0.022) in YMD-CHO vs. Control-CHO and was strongly correlated with changes in serum total antioxidant capacity (r = -0.87) and oxidative stress index (r = 0.76) at post-exercise in YMD-CHO. Performance in sprints was not affected by YMD. CONCLUSION: CHO intake did not negate the effect of YMD on FATox or TT performance. Instead, a synergism between the two dietary strategies may be present. Clinical Trial Registration NCT04642144. November 18, 2020. Retrospectively registered.

Adverse event rate during inpatient sotalol initiation for the management of supraventricular and ventricular tachycardia in the pediatric and young adult population.

BACKGROUND: Sotalol is an important antiarrhythmic drug in the pediatric population. Given the risk of proarrhythmia, sotalol is initiated in inpatient settings, with adult studies as recent as 2015 supporting this practice. OBJECTIVE: The purpose of this study was to determine the frequency of adverse events (AEs) during sotalol initiation for the management of atrial, supraventricular, or ventricular arrhythmias in pediatric patients. METHODS: A retrospective cohort analysis of pediatric patients 21 years or younger initiated on oral sotalol for supraventricular tachycardia or ventricular tachycardia (VT) at Boston Children's Hospital from January 1, 2007, through July 1, 2016, was performed. The primary end point was an AE defined as significant bradycardia, new or increased ventricular arrhythmias, conduction block, or corrected QT interval (QTc) prolongation, resulting in dose reduction or cessation. RESULTS: There were 190 patients who met inclusion criteria, with 110 patients (58%) 6 months or younger. A total of 115 patients (60%) had congenital heart disease. Arrhythmias for which sotalol was initiated included atrioventricular reciprocating tachycardia/atrioventricular nodal reciprocating tachycardia (n = 105 [55%]), atrial flutter (n = 31 [16%]), ectopic atrial tachycardia (n = 26 [14%]), VT (n = 21 [11%]), and atrial fibrillation (n = 7 [4%]). The median pre-sotalol QTc was 438 ms (interquartile range 348-530 ms). Five patients (3%) (aged 0.1-18 years) had AEs including bradycardia <40 beats/min (n = 2) and <100 beats/min (n = 1) and QTc prolongation (n = 2). All 5 patients with AEs had repaired congenital heart disease. CONCLUSION: The incidence of AEs in pediatric patients initiating sotalol for atrial tachycardia, supraventricular tachycardia, or VT is low (3%), with no deaths or malignant rhythms reported in this series.

Influence of patient factors and ablative technologies on outcomes of radiofrequency ablation of intra-atrial re-entrant tachycardia in patients with congenital heart disease.

OBJECTIVES: The goal of this study was to identify factors associated with radiofrequency catheter ablation (RFCA) outcomes of intra-atrial re-entrant tachycardia (IART). BACKGROUND: Radiofrequency catheter ablation of IART is difficult. The influence of patient and procedural factors and novel technologies on outcomes is unknown. METHODS: Acute and chronic RFCA outcomes were studied in patients with congenital heart disease and IART. Clinical status was measured using a multiaxis severity score. Multivariate analyses identified associations of clinical, procedural and technological factors with outcomes. RESULTS: A total of 177 procedures were performed in 134 patients; 139 procedures (79%) resulted in RFCA of > or =1 IART circuit and 117 (66%) in RFCA of all targeted circuits. Multivariate analysis associated acute success with irrigated ablation and absence of atrial fibrillation. Twenty-two complications were noted, nine related to vascular access. Electroanatomic mapping failed to decrease procedure or fluoroscopy time. Improvement in clinical status occurred in most patients (severity score preablation: 6.2 +/- 1.6, postablation: 3.0 +/- 2.3, p < 0.0001). At mean follow-up of 25 +/- 11 months, 42% of patients had IART recurrence and 28% required cardioversion. Six deaths occurred (1.8%/patient-year), and two patients underwent transplant. Chronic outcomes were associated with higher right atrial saturations, use of electroanatomic mapping, fewer IART circuits encountered and acute procedural success. CONCLUSIONS: Improvement of acute RFCA outcomes was contemporaneous with introduction of novel technologies. Intra-atrial re-entrant tachycardia recurrence was common, and no effect on mortality was discerned, but most patients had effective palliation of symptoms. Chronic outcome predictors included the underlying disease severity, application of novel technologies and successful ablation of all targeted arrhythmia circuits.

Pulmonary position cryopreserved homografts: durability in pediatric Ross and non-Ross patients.

OBJECTIVE: The purpose of this study was to evaluate the outcome and risk factors for implant failure in pediatric patients who underwent pulmonary position homograft placement for right ventricular outflow tract obstruction compared with conduit placement as a component of the Ross operation. Actuarial 5-year survivals for cryopreserved right ventricle-to-pulmonary artery homografts range from 55% to 94% at all ages. It is not known whether there is a difference in homograft durability when utilized for right ventricular outflow tract obstruction or as part of the Ross operation. METHODS: The records of all pediatric patients receiving a right ventricle-to-pulmonary artery homograft from July 1989 through October 2003 were reviewed. Ninety-eight consecutive patients were studied (26 Ross, 72 non-Ross). In addition to Ross versus non-Ross comparisons, other potential risk factors for homograft failure analyzed included age at operation, follow-up time, type of surgery, and homograft type and size. RESULTS: Ross and non-Ross patients were comparable in age at the time of the operation and follow-up time. Homograft failure rates were 12% and 51% for Ross and non-Ross patients, respectively. Freedom from reintervention was 93% in the Ross and 66% in the non-Ross group at 5 years (P = .019). On multivariate analysis, non-Ross operation and age less than 2 years were significant predictors of homograft failure. CONCLUSIONS: 1. Pediatric patients undergoing the Ross operation have longer homograft survival than pediatric patients treated for right ventricular outflow tract obstruction, independent of age. 2. Homografts placed in patients less than 2 years of age have shorter homograft survival.

Modification to the Fontan procedure for the prophylaxis of intra-atrial reentrant tachycardia: short-term results of a prospective randomized blinded trial.

OBJECTIVES: We evaluated the feasibility, safety, and short-term efficacy of an interventional atrial incision placed at the time of the Fontan operation to reduce the development of intra-atrial reentrant tachycardia. METHODS: This prospective randomized blinded trial was conducted in patients with congenital heart disease undergoing an initial lateral tunnel Fontan. Intervention patients underwent a lateral tunnel Fontan with an interventional atrial incision/cryoablation from the atriotomy to the right atrioventricular annulus. Controls underwent a standard lateral tunnel Fontan. Safety of the intervention was monitored. Short-term efficacy was determined by comparisons of conduction block across the incision area and spontaneous or inducible atrial arrhythmias. RESULTS: There were no significant differences between intervention (n = 21, median 2.4 years, range 0.8-3.9) and controls (n = 21, median 2.7 years, range 1.5-13.9) in age, type of heart disease, surgical parameters, or postoperative outcomes. Safety parameters showed no difference between groups in number or severity of adverse events. Short-term efficacy included evidence of conduction block with a longer conduction time across the incision area in intervention patients (median 97 ms, range 35-160) compared with controls (median 40 ms, range 8-77, P =.0001). No intervention patients had spontaneous or inducible intra-atrial reentrant tachycardia versus 2 controls (0/21 versus 2/21, P = NS). CONCLUSIONS: An interventional atrial incision to reduce intra-atrial reentrant tachycardia in the Fontan operation was feasible and safe. The intervention changed the atrial substrate as shown by an increase in conduction time. Short-term results showed a low incidence of intra-atrial reentrant tachycardia in all patients. Longer follow-up is necessary to assess clinical efficacy.

Discovery and management of diaphragmatic hernia related to abandoned epicardial pacemaker wires in a pregnant woman with {S,L,L} transposition of the great arteries.

Epicardial pacemaker leads placed during childhood are often not removed when transvenous systems are placed later in life. The risk of complications related to retained pacemaker leads and generators is not clear but is generally considered low. We report the case of a 23-year-old pregnant woman who presented with left upper quadrant pain at 20 weeks gestation. The patient was born with {S,L,L} transposition of the great arteries and had high-grade conduction disease in infancy compelling epicardial pacemaker placement. A standard transvenous pacemaker was placed at age 9 years, without removal of the epicardial system. The patient's abdominal pain was attributed to herniation of abdominal contents through a diaphragmatic defect at the site of the abandoned epicardial pacing wire. Her pain improved spontaneously but worsened later in pregnancy leading to repair of the diaphragmatic hernia via anterolateral thoracotomy at 30 weeks gestation. The procedure was well tolerated by mother and fetus. At 38 3/7 weeks gestation, the patient underwent uneventful delivery by cesarean section for breech presentation. This case illustrates the importance of multidisciplinary collaboration in the care of women with congenital heart disease.

Ascending aortic dilation in patients with congenital complete heart block.

BACKGROUND: The clinical spectrum and underlying pathophysiology of isolated congenital complete heart block (CCHB) remain incompletely understood. Aortic dilation has been anecdotally observed in some children with CCHB, but detailed reports are lacking. OBJECTIVE: This study sought to systematically describe aortic size in children with CCHB and to investigate predictor variables associated with aortic dilation. METHODS: A retrospective review of clinical features and echocardiograms was performed for all patients with CCHB and a structurally normal heart or simple anatomic lesions seen at our center over 22 years. Echocardiographic measurements were assigned z-scores using validated norms. RESULTS: Sixty subjects met inclusion criteria. The median ascending aorta (AsAo) z-score was 2.2 (range -0.6 to 7.2) at first echocardiogram, with 30 of 58 (52%) having a z-score >2 (P <.0001) and 11 of 58 (19%) having a z-score >4. The distribution of aortic root dimensions was nearly normal with a median z-score of 0.4 (range -1.3 to 3.2). Although the AsAo remained dilated at the last echocardiogram (median z = 1.7, range -0.9 to 6.3), the trend toward normalization was significant (P = .002). Maternal autoantibody seropositivity and decreased left ventricular function were associated with AsAo dilation at initial echocardiogram in a multiple logistic regression model controlling for heart rate and indexed stroke volume (odds ratio 15, P = .03, and odds ratio 0.8, P = .02, respectively). CONCLUSION: Potentially clinically significant AsAo dilation, but not aortic root dilation, is present in a large proportion of pediatric patients with isolated CCHB. Maternal autoantibody seropositivity and decreased left ventricular function at initial echocardiogram correlate with this previously unreported finding. This observation may indicate a previously unrecognized consequence of fetal exposure to these autoantibodies.

Advances in pediatric electrophysiology.

PURPOSE OF REVIEW: The pediatric electrophysiology literature during the past year has addressed several topics that are particularly relevant for children and other patients with congenital heart disease. This paper reviews selected studies germane to physicians and health care personnel who treat pediatric and adult congenital heart patients with arrhythmias and electrophysiologic disorders. RECENT FINDINGS: Advances in arrhythmia diagnostics have been reported in pediatrics using loop monitoring, both external and implanted. Diagnostic criteria and risk stratification strategies have been refined for the congenital and inherited rhythm disorders such as cardiomyopathies and long QT syndrome. The use of therapeutic procedures such as catheter ablation for complex arrhythmias in congenital heart disease is discussed. Finally, a summary of articles on implanted devices in pediatrics and congenital heart disease is reviewed, including implantable defibrillators, atrial antitachycardia pacemakers, and cardiac resynchronization therapy in pediatrics. SUMMARY: Pediatric electrophysiology is a rapidly changing field, with advances seen in diagnostic evaluation of arrhythmia, refinement of risk-stratification testing, and therapeutic options such as catheter ablation and cardiac rhythm management devices. The evolution of pediatric electrophysiology from a diagnostic specialty into a therapeutic and interventional subspecialty has advanced the treatment options for children with cardiac arrhythmias and conduction disorders.

Molecular biological and genetic approaches to the evaluation of inherited electrophysiologic disorders.

Although previously thought of as sporadic errors in development, some arrhythmias are now established to have a hereditary basis. The genetic and molecular bases of inherited cardiac arrhythmias are being recognized with increased frequency. Environmental and somatic influences may complicate classical identification of the patterns of inheritance. In several examples of inherited heart disease with a distinct molecular and genetic foundation, multiple gene defects appear to be responsible for similar phenotypes. In addition, specific genotypes may lead to differing severity of phenotype and differential prognostic risks. There is also variability in phenotypic expression, even among identical genotypes within a family, complicating risk stratification. Improved understanding of rare familial arrhythmia disorders may increase our overall comprehension of the pathophysiology of rhythm disturbances in general. The inherited arrhythmia disorders can be classified under three broad headings -- those familial arrhythmias that originate above the ventricles, familial arrhythmias originating within the ventricles and familial disorders affecting impulse propagation and cardiac conduction. Familial occurrences of tachyarrhythmias and bradyarrhythmias have been reported for each of these types of disorders. Recent discoveries of genetic etiologies have shed new light on the mechanisms underlying arrhythmogenesis and molecular genetics of cardiac electrophysiology.

Implications of implantable cardioverter defibrillator therapy in congenital heart disease and pediatrics.

INTRODUCTION: The incidence of appropriate and inappropriate discharges, indicators of system failure, and clinical implications of implantable cardioverter defibrillator (ICD) therapy in children and young adults with heart disease is poorly defined. METHODS AND RESULTS: In a retrospective study at a single medical center, a total of 90 ICD procedures were performed in 76 patients younger than age 30 years (median 16 years, range 1-30): 42% with congenital heart disease, 33% with primary electrical disease, 17% with hypertrophic cardiomyopathy, and 8% with idiopathic dilated cardiomyopathy. Indications for ICD included arrest or sustained ventricular tachycardia (n = 27), and combinations of syncope (n = 32), palpitations (n = 17), spontaneous ventricular arrhythmia (n = 40), inducible ventricular tachycardia (n = 36), or severe hypertrophic cardiomyopathy. Transvenous dual-chamber ICDs were implanted in 29 patients. Subcutaneous arrays or epicardial patches were used in 9 patients. Over a median 2-year follow-up, 28% of patients received appropriate shocks for ventricular tachycardia (median 13 months to first shock) and 25% experienced inappropriate shocks for multiple causes (median 16 months). With multivariate analysis, growth strongly correlated with lead failure (odds ratio 73, 3.5-1530, P = 0.006). Complications occurred in 29 patients, including lead failure in 16 (21%), ICD "storm" with sequential shocks in 5, and infection in 2 patients. No deaths were attributable to ICD placement or subsequent device failure. CONCLUSION: ICD therapy can effectively manage malignant arrhythmias in selected pediatric and congenital heart patients. Spurious shocks or ICD storm may increase morbidity and emphasize the need for concomitant medical and ablative therapy. ICD lead failure was relatively frequent in this population.

The use of implantable cardioverter-defibrillators in pediatric patients awaiting heart transplantation.

BACKGROUND: This multicenter study evaluated experience with implantable cardioverter defibrillators (ICD) as a bridge to orthotopic heart transplantation (OHT) in children. METHODS: The application of ICD therapy continues to expand in pediatric populations, due in part to improved technology and new indications, including the prevention of sudden death while awaiting OHT. METHODS: We performed a retrospective review of ICD databases at 9 pediatric transplant centers. RESULTS: Twenty-eight patients (16 males) underwent implantation or had a preexisting ICD while awaiting OHT between 1990 and 2002. The median age at implant was 14.3 years (11 months to 21 years) with a median weight of 49 kg (11.7-88 kg). Diagnoses included cardiomyopathy (n=22), and congenital heart disease (n=6). Indications for ICD implantation included ventricular tachycardia/fibrillation (n=23), syncope (n=5), aborted sudden death with no documentation of rhythm disturbance (n=5), ventricular ectopy (n=1), and poor function (n=5). Of the 28 ICDs, 23 were implanted by a transvenous approach and 5 by epicardial route. There were 55 defibrillator discharges in 17 patients, 47 (85%) of which (in 13 patients) were appropriate. The 8 inappropriate discharges (in 6 patients) were triggered by sinus tachycardia, inappropriate sensing, and atrial flutter. The mean time from implantation to first appropriate shock was 6.9 months (1 day to 2.6 years). Twenty-one patients underwent transplantation during the study period, whereas 2 died while awaiting a donor. Morbidity included a lead fracture, 3 episodes of electromechanical dissociation, and 1 episode of electrical storm. CONCLUSIONS: ICD implantation represents an effective bridge to transplantation in pediatric patients. The complication rate is low, with inappropriate device discharge due primarily to sinus tachycardia or atrial flutter. There is a high incidence of appropriate ICD therapy for malignant ventricular arrhythmias in this highly selected group of patients.