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.

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.

Current Management of Focal Atrial Tachycardia in Children

Background—

Focal atrial tachycardia (FAT) is an uncommon cause of supraventricular tachycardia in children. Incessant FAT can lead to tachycardia-induced cardiomyopathy. There is limited information regarding the clinical course and management of FAT. This study characterizes current management strategies for FAT in children including the prevalence of spontaneous resolution and the role of catheter ablation.

Methods and Results—

This is a retrospective chart review of pediatric patients with FAT managed between January 2000 and November 2010 at 10 pediatric centers. There were 249 patients with a median age at diagnosis of 7.2 (95% confidence interval, 5.8–10.4) years. Cardiomyopathy was observed in 28%. Resolution of FAT occurred in 89%, including spontaneous resolution without catheter ablation in 34%. Antiarrhythmic medications were used for initial therapy in 154 patients with control of FAT in 72%. Among first-line medications, β-blockers were the most common (53%) and effective (42%). Catheter ablation was successful in 80% of patients. FAT recurrence was less common with electroanatomic mapping compared with conventional mapping techniques (16% versus 35%; P =0.02). Patients were followed for a median of 2.1 (95% confidence interval, 1.8–2.6) years.

Conclusions—

FAT is managed successfully in most children. Current approaches are variable. Many patients have control of FAT with medications; however, catheter ablation is used for most patients. Spontaneous resolution is common for young children, emphasizing the role for delayed ablation in this group. Ablation is successful for all ages. Lower recurrence occurs when electroanatomic mapping techniques are used.

Dynamic changes of myocardial oxygen consumption at pacing increased heart rate - the first observation by the continuous measurement of systemic oxygen consumption

OBJECTIVES

To assess dynamic changes in myocardial oxygen consumption (myoVO(2)) during atrial pacing increased heart rate by continuous measurement of systemic oxygen consumption (sysVO(2)).

METHODS

Six mechanically ventilated pigs were atrially paced to increase heart rate from baseline 98 ± 9 to 120-140-160-180 bpm for 10 minutes at each stage, with 10 minute intervals without pacing between stages. sysVO(2) was continuously measured with a respiratory mass spectrometer. Left anterior descending coronary arterial flow, aorta and coronary sinus blood gases were measured to calculate index of whole heart myoVO(2).

RESULTS

sysVO(2) peaked at the initiation of pacing in the first two to three minutes, followed by a decrease and subsequent stabilization. As heart rate increased, sysVO(2) increased by 0.08 ± 0.06 ml/kg/min, 0.14 ± 0.05 ml/kg/min and 0.17 ± 0.10 ml/kg/min, representing a 1.2 ± 0.9%, 2.1 ± 0.7% and 3.0 ± 1.8% increase of sysVO(2) respectively; myoVO(2) increased by 0.16 ± 0.12 to 0.31 ± 0.14 to 0.36 ± 0.24 ml/100 g/min, representing a 11 ± 9%, 21 ± 9% and 26 ± 12% increase of myoVO(2), respectively. The absolute and relative increases in sysVO(2) were significantly correlated with the increases in myoVO(2).

CONCLUSIONS

On-line continuous sysVO(2) monitoring by respiratory mass spectrometry allows non-invasive assessments of dynamic changes in myoVO(2) in vivo. The mechanism for the peaked increase in sysVO(2) at the initiation of pacing remains to be explored.

Torsades de Pointes ventricular tachycardia in a pediatric patient treated with fluconazole

Fluconazole is an antifungal medication that has been reported to cause prolongation of the QT interval and Torsades de Pointes (TdP) ventricular tachycardia in adults. We describe the case of an 11-year-old child treated with fluconazole who developed ventricular arrhythmia culminating in TdP. We discuss the possible roles played by genetic and environmental factors in this child's rhythm disturbances. After briefly summarizing similar cases from the adult literature, we outline the putative mechanism by which fluconazole may cause arrhythmia. This case should alert pediatricians to the possible risks of fluconazole use, especially in the presence of electrolyte abnormalities, diuretic use, therapy with other pro-arrhythmic agents, or suspicion of congenital Long-QT Syndrome.

Management of infants with idiopathic dilatation of the right atrium and atrial tachycardia

Idiopathic dilatation of the right atrium (IDRA) is a rare anomaly defined as isolated enlargement of the right atrium in the absence of other cardiac lesions known to cause right atrial dilatation. IDRA is a congenital anomaly with unknown pathogenesis and highly variable clinical presentation. Optimal management of severe IDRA is controversial and individualized. Literature reports of long-term follow-up have been limited. We describe a child with IDRA with rapid atrial tachycardia (AT) refractory to both medical and surgical management, and we provide long-term follow-up on our two previously reported cases, both of whom had documented AT. For infants with AT, the clinical course is unpredictable, and medical therapy is the first line of treatment. The decision to proceed with surgical resection of a giant right atrium should be made on an individual basis. Atrial resection along with a modified right atrial MAZE procedure could be considered in infants with life-threatening atrial tachyarrhythmia refractory to medical treatment. Surgical scarring of the right atrium may produce substrate for atrial arrhythmia, which may also be refractory to medical therapy. Histological examination of excised atrial tissue remains inconsistent and not contributory to the determination of the etiology of IDRA. Our three infants with IDRA illustrate unique features of their variable clinical courses, as well as continued difficulties with establishing clear guidelines with regard to surgical management of this unusual disorder.

Direct intracardiac placement of an automatic implantable cardioverter defibrillator coil lead in a small child

A 3.5-year-old child with hypertrophic obstructive cardiomyopathy and recurrent syncope underwent surgical left-ventricular outflow tract myectomy and implantation of a single-chamber automatic cardioverter defibrillator. A single-coil active fixation lead was introduced via a purse-string suture in the right atrial appendage and the lead tip positioned and fixed in the right-ventricular apex under direct visualization via a small right atriotomy incision. Described configuration may be considered in small children undergoing intracardiac surgery at the time of defibrillator implantation.

Right ventricular outflow tract tachycardia in children

OBJECTIVE

To assess the clinical spectrum of right ventricular outflow tract tachycardia and its management in children.

STUDY DESIGN

Five centers identified patients for retrospective review. Patients (age <18 years) demonstrating ventricular tachycardia with an inferior axis and left bundle branch block were included. Patients with structural heart disease, myocarditis, cardiomyopathy, or long QT syndrome were excluded. Demographics, clinical presentation, investigations, and treatment were analyzed. Holter data were used to quantify ectopy.

RESULTS

Patients (n = 48) were referred for evaluation of incidental findings (39/48), near syncope or syncope (7/48), or other (2/48). Investigations included magnetic resonance imaging (51%), endomyocardial biopsy (25%), and angiography (23%). Medical treatment was initiated in 26 of the 48 patients. The most common indications for treatment were frequent ectopy and symptoms. Medical treatment (P <.007) and observation alone (P <.02) were both associated with a reduction in ectopy. Symptoms persisted in 3 of 13 patients who were treated medically and in all untreated patients. At follow-up, there were no deaths and no difference in ectopy (P <.46) between patients who were treated medically and patients who were observed. Ablation was attempted in 6 of the 48 patients (successful in 4/6).

CONCLUSION

The clinical spectrum and management of right ventricular outflow tract tachycardia in children are diverse. Both medical therapy and observation alone were associated with a reduction in ectopy.

Supraventricular tachycardia in children

Several different mechanisms are responsible for paroxysmal supraventricular tachycardia in children. Different forms of tachycardia occur at different age. Atrio-ventricular reentry tachycardia results from the presence of congenital atrio-ventricular bypass tracts and is frequently encountered at all ages. Infants may present with ectopic atrial tachycardia or atrial flutter. Atrio-ventricular node reentry tachycardia becomes more frequent in adolescence. Atrial scarring resulting from open heart surgery predisposes to complex intra-atrial reentry. Certain forms of congenital and acquired heart disease are associated with specific types of arrhythmia. Many children with paroxysmal supraventricular tachycardia do not require any therapy. The decision to proceed with treatment should be based on the frequency and severity of symptoms and on the effect of arrhythmia on the quality of life. Infants require medical treatment because of the difficulty to recognize symptoms of tachycardia and a risk of heart failure. Patients with Wolff-Parkinson-White syndrome as well as those with significant heart disease are at risk of sudden death. Syncope in children with paroxysmal tachycardia may indicate a severe fall in cardiac output from extremely rapid heart rate. Patients with potentially life-threatening arrhythmia should not participate in competitive physical activities. Treatment options have undergone significant evolution over the past decade. Indications for the use of specific antiarrhythmic medications have been refined. Contemporary catheter ablation procedures employ different forms of energy allowing for safe and effective procedures. Catheter ablation is the treatment of choice for symptomatic paroxysmal tachycardia in school children and in some infants who failed medical treatment. Surgery is the preferred treatment in few selected cases. The goal of this review is to present the state of the art approach to the diagnosis and management of paroxysmal supraventricular tachycardia in infants, children and adolescents.

How much do parents know about their children's heart condition and prophylaxis against endocarditis?

BACKGROUND

Caregivers are frequently expected to serve as a conduit for information between heath care providers; however, few previous studies showed inadequate parental knowledge about their children's heart disease.

OBJECTIVES

To assess parental knowledge regarding their children's congenital heart disease, risk of bacterial endocarditis (BE) and requirement for BE prophylaxis.

METHODS

Parents of 65 consecutive children with heart disease, aged from two months to 16 years, were asked to complete a survey while awaiting their ambulatory appointment.

RESULTS

On average, patients had been seen by 1.7 cardiologists and had attended 7.8 clinic appointments before the study, with 55% having undergone heart surgery and 18% currently taking cardiac medications. In general, caregivers felt they had received full explanation of their child's condition (89%) and were informed sufficiently about ongoing care (91%), yet only 71% knew the specific name of their child's heart defect, with 65% being able to correctly explain the condition in layman's terms. Of the 55 children whose heart defects fulfilled risk criteria for BE, only 47% of their parents declared to have ever heard of the disease, with just 25% able to correctly define it. Although 71% of the children's parents knew that special medication was required when seeing a dentist, only 29% were aware of any other situations when they would also require it. As many as 27% of the children who required BE prophylaxis had had significant dental problems in the past, including root canals, extracted teeth, braces, caps and gingivitis.

CONCLUSION

Many parents are not familiar with their child's heart disease and do not understand the risks of BE or the need for BE prophylaxis. Results of this study and several other queries published over the past 20 years point to the need for continuous education of patients and their parents by physicians, nurses and allied health care providers.

A pacemaker for asystole in breath-holding spells

Two cases of young children with frequent severe breath-holding spells complicated by prolonged asystole and seizures are reported. A ventricular pacemaker was implanted in each child, and both have subsequently remained free of syncope, although they continue to exhibit breath-holding behaviour.

The long QT syndrome with impaired atrioventricular conduction: a malignant variant in infants

INTRODUCTION

The long QT syndrome (LQTS) is occasionally complicated by impaired AV conduction, mostly 2:1 AV block. This form of LQTS can manifest before birth or during neonatal life, and it is more sporadic than familial. It is usually an isolated disorder, although it can be accompanied by a variety of cardiovascular and other anomalies. In spite of different treatment modes, mortality is high.

METHODS AND RESULTS

The reported case presented not only with 2:1 AV conduction, but also with Wenckebach episodes with impaired right and left bundle branch conduction, and decremental conduction in the His-Purkinje axis. We also observed sinus pauses and accelerated AV junctional escape beats.

CONCLUSION

Our findings, and similar observations by others, suggest involvement of the sinus node and the distal conduction system in this form of the LQTS. Several histologic studies have documented abnormalities within the conduction system, including apoptosis. Because of the rare occurrence and poor prognosis of the LQTS with impaired AV conduction, international guidelines for diagnosis and treatment are needed. Development of an internal cardiac defibrillator for this young age group is necessary.

Risks of intravenous amiodarone in neonates

The courses of two neonates treated with intravenous amiodarone for supraventricular tachyarrhythmia, both of whom developed significant adverse effects, are reported. A 13-day-old term newborn developed hypothyroidism after 27 days of mostly intravenous amiodarone for atrioventricular reciprocating tachycardia and severe heart failure. A one-day-old, 36 weeks' gestation newborn developed electromechanical dissociation after receiving an intravenous bolus of amiodarone for rapid atrial flutter. Judicious use of amiodarone is recommended.

Use of transesophageal echocardiography in radiofrequency catheter ablation in children and adolescents

OBJECTIVE

To assess the utility of transesophageal echocardiography (TEE) in radiofrequency (RF) catheter ablation of left-sided atrioventricular bypass tracts.

PATIENTS

RF catheter ablation was assisted with TEE in 13 children and adolescents aged 9.9 to 16.3 years (mean 13.3). Results were compared with 21 procedures done in 19 patients (age 8.8 to 18 years, mean 14.5) without TEE assistance.

MAIN RESULTS

RF ablation success rate was similar in both groups (90% to 92%). Successful RF ablation required 6 +/- 8 RF pulses in the TEE group and 10 +/- 7 RF pulses in the non-TEE group (nonsignificant). Fluoroscopy time was 36 +/- 17 mins and 54 +/- 28 mins, respectively (P = 0.03). Characteristic tenting of the fossa ovalis by a transseptal needle was easily visualized with TEE. TEE allowed for precise positioning of the ablation electrode on the mitral valve ring. At the successful site, the ventriculoatrial (VA) time was 42 +/- 10 ms in the TEE group and 52 +/- 16 ms in the non-TEE group (P = 0.05). The atrioventricular (A:V) ratio was 1.1 +/- 1.1 and 1.2 +/- 0.7, respectively (nonsignificant) with a large scatter of individual values. Electrogram amplitudes and VA conduction times that are desirable for RF ablation were also recorded on the mitral valve leaflets and over the coronary sinus. TEE visualized thrombus formation in the right atrium (three patients) and in the left atrium (two patients).

CONCLUSIONS

TEE should be strongly considered as supplemental imaging for RF ablation of left-sided bypass tracts performed under general anesthesia in children and adolescents. TEE renders transseptal puncture safe. TEE may decrease fluoroscopic exposure. TEE confirmation of the ablation catheter tip in the angle between the coronary sinus and the mitral valve ring may allow limitation of unnecessary RF lesions and injury to the mitral valve. The demonstration of early intracardiac thrombus formation argues for prompt and full heparinization after transseptal puncture.

Adult patients' knowledge about their congenital heart disease

OBJECTIVE

To assess patient knowledge about their congenital cardiovascular disease.

DESIGN

Fifty consecutive patients (25 women) attending the Adult Congenital Heart Disease Clinic, University of Alberta, Edmonton, Alberta, filled out a questionnaire that tested knowledge about their heart defect and endocarditis prophylaxis. The patients ranged in age from 18 to 60 years (mean 25). The most frequent cardiovascular anomalies were obstruction of the left ventricular outflow tract (13), coarctation of the aorta (10), tetralogy of Fallot (six), transposition of the great arteries (five) and Marfan syndrome (four). Patients had been seen on average by three cardiologists (range one to six) and had made an average of seven clinic visits (range one to 22) since the age of 17 years. Eight patients had been followed at other clinics in the past.

MAIN RESULTS

Fifty-four per cent of patients knew their diagnosis. Forty-four per cent could explain the defect in lay language, and another 48% made an attempt. When given a heart diagram, 26% marked their defect correctly and 28% made an attempt. Terms 'endocarditis' and 'antibiotic prophylaxis' were known to 16% and 22% of patients, respectively. Fifty-eight per cent could name at least one situation that carries a risk of 'infection in the heart'.

CONCLUSION

Adults with congenital heart disease have poor knowledge of their heart defects and the importance of endocarditis and antibiotic prophylaxis. Although time consuming, patient education should be a part of every clinic visit. Repetitive and structured patient education may improve patients' knowledge and, hence, participation in their health care.

Left ventricular transvenous electrode dislodgement after Mustard repair for transposition of the great arteries

An 11-year-old girl who underwent Mustard's operation for complete transposition of the great arteries in infancy, developed Mobitz type II second-degree AV block 8 1/2 years later. A transvenous, active fixation left ventricular lead was inserted and connected to a rate responsive pacemaker. Two years later the lead dislodged due to the child's growth. A new active fixation electrode was positioned in the left ventricle below the pulmonary valve, leaving an electrode loop in the ventricle. Such an approach may prevent lead dislodgement due to growth after intraatrial repair for transposition of the great arteries, but regular radiological or echocardiographic follow-up of lead position is recommended in these patients.

Randomized cross-over evaluation of two adaptive pacing algorithms for the termination of ventricular tachycardia

OBJECTIVE

In a randomized, cross-over study we evaluated the efficacy of rate adaptive constant cycle length (BURST) and autodecremental (RAMP) pacing for termination of sustained monomorphic ventricular tachycardia.

METHODS

An external device capable of delivering the same types of antitachycardia pacing as the newer generation implantable cardioverter defibrillators was used. Thirty-one patients with ischemic and nonischemic cardiomyopathy and documented clinical ventricular tachycardia or ventricular fibrillation were examined during routine invasive electrophysiological studies. RAMP and BURST pacing were each attempted in 54 matched pairs of induced ventricular tachycardia. After a therapy was applied, the tachycardia was reinitiated and the other therapy applied during the second episode so that a total of 108 ventricular tachycardia episodes were studied.

RESULTS

Overall efficacy of ventricular tachycardia pace termination was 69% and the time required to stop ventricular tachycardia was 14.1 +/- 11.3 seconds. The ability to terminate ventricular tachycardia by RAMP (72%) or BURST (65%) pacing was not significantly different. However, time to terminate ventricular tachycardia by RAMP (11.8 +/- 8.5 sec) was significantly shorter than by BURST (16.4 +/- 13.5), P < .001. Acceleration of ventricular tachycardia was uncommon with both pacing modes, 7/108 (7%). The ability to pace terminate ventricular tachycardia was cycle length dependent. The highest success was with ventricular tachycardia cycle length between 300 and 350 msec. The success rate decreased with faster and also slower ventricular tachycardia.

CONCLUSIONS

1. Rate adaptive pacing methods for ventricular tachycardia termination are effective and safe. 2. Autodecremental RAMP pacing afford quicker ventricular tachycardia termination than constant cycle length BURST pacing. 3. The ability to terminate ventricular tachycardia is cycle length dependent with cycle length range of 300-350 msec being most responsive to pace termination.