Novel electrocardiographic screening criterion for hypertrophic cardiomyopathy in children.

Electrocardiography is often advocated as a screening tool in children for hypertrophic cardiomyopathy (HC). We sought to establish an electrocardiographic screening tool to identify children with HC. We hypothesized that a pediatric-specific electrocardiographic criterion would perform better than the popular criteria used for screening children for left ventricular hypertrophy and HC. The earliest available electrocardiogram for children (n=108) with HC (ages 7 to 21 yrs) was reviewed. We sought to compare the diagnostic accuracy of 4 screening algorithms: (1) Sokolow-Lyon criterion (SV1+RV5/RV6>35 mm), (2) Cornell criterion (RaVL+SV3>28 mm in men, 20 mm in women), (3) total 12-lead voltage criterion (R wave to the nadir of Q/S wave>175 mm), and (4) pediatric-specific criterion (RaVL+SV2>23 mm). The same criteria were applied to a cohort of age-matched and gender-matched controls without cardiac disease. Statistically significant correlations were found between children with HC and positive screen using all 4 criteria. However, comparison of receiver operating characteristic demonstrated an area under the curve of 0.67 for Sokolow-Lyon criterion, 0.70 for Cornell criterion, 0.83 for total 12-lead criterion, and 0.82 for pediatric-specific criterion. Pediatric-specific criterion had superior sensitivity in gene-positive children and superior overall specificity than total 12-lead criterion. In conclusion, our study demonstrates that the pediatric-specific criterion employing leads RaVL+SV2 is more accurate in identifying children with HC in comparison with other popular screening criteria.

Cryoablation therapy for atrioventricular nodal reentrant tachycardia in children: a multicenter experience of efficacy.

Atrioventricular nodal reentrant tachycardia (AVNRT), a common tachycardia in children, is routinely treated by catheter ablation using radiofrequency or cryothermal energy. Acute success rates of 95-97 % are reported for cryoablation, similar to those achieved with radiofrequency ablation (RFA). However, early studies reported higher recurrence rates after cryoablation for treatment of AVNRT than those reported for RFA. This study evaluated the success and recurrence rates for cryoablation in a current cohort of pediatric patients across several institutions. Patients 21 years old or younger with AVNRT who underwent cryoablation at five participating centers between 2004 and 2009 were retrospectively reviewed. Patient demographics and procedural data were extracted from patient records and analyzed. A total of 434 patients with AVNRT who underwent cryoablation were identified. Cryoablation was used as the exclusive ablation method for 379 patients. For 97 % (368/379) of these patients, cryoablation was acutely successful. A higher acute success rate was found with the 6-mm-tip catheter (99 %) than with the 4-mm-tip catheter (91 %) (p < 0.01). Recurrence was experienced by 7.3 % of the patients. Recurrence was more likely for those treated with the 4-mm-tip catheter (6/42, 14 %) than for those who had the larger catheters (12/204, 6 %) No patient experienced permanent heart block. Success and recurrence rates for this cohort of patients were similar to those reported for RFA used to treat AVNRT in pediatric patients. The findings show a higher success rate and a lower recurrence rate after cryoablation with a 6-mm-tip catheter than after use of the 4-mm-tip catheter, with an associated excellent safety profile.

Catheter ablation of primary supraventricular tachycardia substrate presenting as atrial fibrillation in adolescents.

BACKGROUND: Atrial fibrillation is rarely encountered in children and adolescents, and these cases are usually secondary to myocardial diseases, electrical abnormalities, or scar related in postoperative congenital heart disease patients. Untreated sustained atrial fibrillation may lead to tachycardia-induced cardiomyopathy and/or systemic thromboembolization. OBJECTIVE: The objective here is to describe our findings in four adolescent patients presenting with recurrent atrial fibrillation. DESIGN: We report here the results of the findings in four patients who presented with recurrent clinical atrial fibrillation. RESULTS: Each of the four underwent electrophysiologic study that revealed a primary reentry or automatic supraventricular tachycardia (SVT) substrate, which was able to be treated with radiofrequency ablation. In three of the four cases, elimination of the primary substrate prevented subsequent recurrence of SVT symptoms or documented SVT and/or atrial fibrillation. CONCLUSION: Children and adolescents presenting with atrial fibrillation warrant an exhaustive search for a treatable primary cause of myocardial or electrical disease. If present, a primary SVT substrate may be successfully ablated to prevent recurrence of atrial fibrillation and any associated complications. Pulmonary vein isolation is rarely indicated in adolescents and should be avoided.

Electrocardiographic screening in children with attention-deficit hyperactivity disorder.

Some investigators have suggested that children receiving stimulant medications to manage attention-deficit hyperactivity disorder should undergo screening electrocardiography to identify asymptomatic cardiac disease. However, no study to date has examined the efficacy and costs of this strategy. In the present study we sought to determine the utility of electrocardiographic screening in children with attention-deficit hyperactivity disorder. We reviewed the clinical experience of electrocardiographic screening of subjects with attention-deficit hyperactivity disorder <21 years of age from April to September 2008. Additional cardiac care and testing that resulted from an abnormal initial electrocardiogram were recorded. Screening electrocardiograms were obtained in 1,470 children with attention-deficit hyperactivity disorder and were interpreted as abnormal in 119 subjects (8.1%). Further evaluation of these 119 subjects included 63 transthoracic echocardiograms, 5 stress tests, and 9 Holter monitor studies. Cardiac disease was identified in 5 subjects (0.3% of entire cohort), yielding a positive predictive value of 4.2%. Cardiac diagnoses included ventricular pre-excitation syndrome (n = 2), bicuspid aortic valve (n = 2), and moderate secundum atrial septal defect (n = 1). The mean cost of electrocardiographic screening including further testing for subjects with abnormal initial screen results was $58 per child. The mean cost to identify a true-positive result was $17,162. In conclusion, electrocardiographic screening for children with attention-deficit hyperactivity disorder can successfully identify cardiac disease in otherwise asymptomatic subjects, although the positive predictive value is low. Ongoing studies are needed to know what role electrocardiographic screening should play in the management of children with attention-deficit hyperactivity disorder.

Acute pacing-induced dyssynchronous activation of the left ventricle creates systolic dyssynchrony with preserved diastolic synchrony.

INTRODUCTION: Patients with heart block have conventionally received a pacemaker that stimulates the right ventricular apex (RVA) to restore heart rate control. While RVA pacing has been shown to create systolic dyssynchrony acutely, dyssynchrony can also occur in diastole. The effects of acute RVA pacing on diastolic synchrony have not been investigated. RVA pacing acutely impairs diastolic function by increasing the time constant of relaxation, decreasing the peak lengthening rate and decreasing peak negative dP/dt. We therefore hypothesized that acute RVA pacing would cause diastolic dyssynchrony in addition to creating systolic dyssynchrony. METHODS AND RESULTS: Fourteen patients (13 +/- 4 years old) with non-preexcited supraventricular tachycardia underwent ablation therapy with subsequent testing to confirm elimination of the tachycardia substrate. Normal cardiac structure and function were then documented on two-dimensional echocardiography and 12-lead electrocardiography prior to enrollment. Tissue Doppler images were collected during normal sinus rhythm (NSR), right atrial appendage pacing (AAI), and VVI-RVA pacing during the postablation waiting interval. Systolic and diastolic dyssynchrony were quantified using cross-correlation analysis of tissue Doppler velocity curves. Systolic dyssynchrony increased 81% during RVA pacing relative to AAI and NSR (P < 0.01). Diastolic synchrony was not affected by the different pacing modes (P = 0.375). CONCLUSION: Acute dyssynchronous activation of the LV created by RVA pacing resulted in systolic dyssynchrony with preserved diastolic synchrony in pediatric patients following catheter ablation for treatment of supraventricular tachycardia. Our results suggest that systolic and diastolic dyssynchrony are not tightly coupled and may develop through separate mechanisms.

Outcomes following electroanatomic mapping and ablation for the treatment of ectopic atrial tachycardia in the pediatric population.

Ectopic atrial tachycardia (EAT) is often resistant to medical therapy, with radiofrequency ablation (RFA) being a preferred treatment option. Three-dimensional (3-D) electroanatomic mapping was introduced as a tool for improved substrate localization, although there are no published data with this technology in pediatric patients with EAT. The objective of this study was to examine our experience with 3-D mapping and standard mapping in this patient population. We used retrospective chart review of pediatric patients with EAT requiring RFA from 1993 to 2004. We analyzed the method of ablation, acute success and recurrence rates, procedure and fluoroscopy times, and cardiac function. Twenty-five patients underwent 31 RFA procedures. All patients had been followed for >6 months (6 months to 7 years). Standard mapping (Group 1) was used in 11 patients (5F/6M, 1.4-11.8 years) who underwent 13 RFA procedures; 3-D mapping (Group 2, October 2000-2004) was used in 16 patients (8 F/8M, 2.7-17 years) who underwent 18 RFA procedures. Left-sided focus was present in 6/13 in Group 1 and 7/18 in Group 2 (all transeptal, NS). There was a trend toward fewer lesions with 3-D mapping (15 +/- 14, median 9.5 in Group 1; 8 +/- 6, median 6.5 in Group 2, NS). Acute success was more likely for patients in which 3-D mapping was utilized (10/13 Group 1 vs. 18/18 Group 2, p < 0.04). Recurrence or persistence of tachycardia at follow-up (2 weeks to 1 year) was documented in 7/13 cases in Group 1, compared to only 2/18 cases in Group 2 (p = 0.01). Six patients underwent repeat RFA: two patients using standard mapping (one failure, one success) and four patients using 3-D mapping [all acute and long-term (>1 year) success]. Procedure times (232 +/- 84 vs. 268 +/- 72 min, skin-to-skin) and fluoroscopy times (47 +/- 24 vs. 40 +/- 20 min) were similar (NS). Of the 25 pts, 17 (7 in Group 1, 10 in Group 2, NS) presented with cardiomyopathy [Ejection fraction (EF), 38.6 +/- 12.1%]. Successful RFA resulted in improved EF (61.1 +/- 11.6%, p < 0.0001) in the 14 patients in whom pre-RFA and post-RFA echocardiograms were available. Compared to standard techniques, 3-D electroanatomic mapping has resulted in no acute failures, statistically reduced recurrence rates, and improved overall success in the management of EAT.

Natural history and current therapy for complete heart block in children and patients with congenital heart disease.

Complete heart block, either congenital or acquired, in children and patients with congenital heart disease is a relatively frequent occurrence requiring therapy. The natural history of this condition has been distorted by the advent of new diagnostic and therapeutic modalities. The therapy of complete heart block is evolving with new data suggesting that traditional treatment strategies utilizing right ventricular apical pacing may have inadvertent deleterious effects on cardiac function. In the following manuscript, the natural history of complete heart block is reviewed and the current therapy examined.

Effects of single-site versus biventricular epicardial pacing on myocardial performance in an immature animal model of atrioventricular block.

INTRODUCTION: Single-site ventricular pacing results in dyssynchronous ventricular activation and may contribute to ventricular dysfunction. We evaluated epicardial biventricular (BiV) pacing as a means of maintaining synchronous ventricular activation in an acute piglet model of AV block with normal ventricular anatomy and function. METHODS AND RESULTS: We used left ventricular (LV) impedance catheters and tissue Doppler imaging to assess the cardiodynamics of immature piglets (n = 6, 33-78 days, 9.35 +/- 0.85 kg). Following catheter ablation of the AV node, a pacemaker was programmed 20 beats per minute above the intrinsic atrial rate. The animals were paced at 5-minute intervals via the following AV sequential configurations: Right atrial appendage (RA)-RV apex (RVA), RA-LV apex (LVA), and RA-biventricular (RVA/LVA). RA-RVA was the experimental control. LV systolic mechanics, measured by the slope of the end-systolic pressure-volume relationship (E(es)), increased with BiV pacing (12.8 +/- 3.4 mmHg/mL, P < 0.02) or single-site LVA pacing (10.6 +/- 3.4 mmHg/mL, P < 0.05) compared with single-site RVA pacing (8.3 +/- 1.4 mmHg/mL). QRS duration lengthened compared with sinus rhythm (42 +/- 8 msec) with either RVA (56 +/- 9 msec, P < 0.02) or LVA (54 +/- 7 msec, P < 0.03), but not with BiV (48 +/- 7 msec, P = 0.08) pacing. Tissue Doppler imaging showed LV dyssynchrony with RVA (septal-to-lateral delay 46.0 +/- 51.7 msec), with return toward normal with LVA (-9.6 +/- 33.6 msec, P < 0.04) or BiV (-4.1 +/- 33.8 msec, P < 0.04) pacing. CONCLUSIONS: In this acute immature piglet model of AV block, LV performance improved with single-site pacing from the LVA and BiV pacing (RVA/LVA), as compared with single-site pacing from the RVA. These changes correlated with tissue Doppler indices of mechanical synchrony, though not necessarily with QRS duration.

Resynchronization therapy in pediatric and congenital heart disease patients: an international multicenter study.

OBJECTIVES: Our objective was to evaluate the short-term safety and efficacy of cardiac resynchronization therapy (CRT) in children. BACKGROUND: Cardiac resynchronization therapy has been beneficial for adult patients with poor left ventricular function and intraventricular conduction delay. The efficacy of this therapy in the young and in those with congenital heart disease (CHD) has not yet been established. METHODS: This is a multi-center, retrospective evaluation of CRT in 103 patients from 22 institutions. RESULTS: Median age at time of implantation was 12.8 years (3 months to 55.4 years). Median duration of follow-up was four months (22 days to 1 year). The diagnosis was CHD in 73 patients (71%), cardiomyopathy in 16 (16%), and congenital complete atrioventricular block in 14 (13%). The QRS duration before pacing was 166.1 +/- 33.3 ms, which decreased after CRT by 37.7 +/- 30.7 ms (p < 0.01). Pre-CRT systemic ventricular ejection fraction (EF) was 26.2 +/- 11.6%. The EF increased by 12.8 +/- 12.7 EF units with a mean EF after CRT of 39.9 +/- 14.8% (p < 0.05). Of 18 patients who underwent CRT while listed for heart transplantation, 3 improved sufficiently to allow removal from the transplant waiting list, 5 underwent transplant, 2 died, and 8 others are currently awaiting transplant. CONCLUSIONS: Cardiac resynchronization therapy appears to offer benefit in pediatric and CHD patients who differ substantially from the adult populations in whom this therapy has been most thoroughly evaluated to date. Further studies looking at the long-term benefit of this therapy in this population are needed.

Radiofrequency modification for inducible and suspected pediatric atrioventricular nodal reentry tachycardia.

INTRODUCTION: AV Node Reentry Tachycardia (AVNRT) is the second most common supraventricular tachycardia (SVT) undergoing pediatric radiofrequency ablation behind accessory pathway reentry tachycardias. AVNRT can be difficult to induce during electrophysiology study (EPS) and dual atrioventricular nodal (AVN) pathways physiology may not be demonstrated in young patients. PURPOSE: This report is the largest single center long term pediatric experience of radiofrequency modification of slow AVN input fibers for inducible or suspected (non-inducible) AVNRT. RESULTS: One hundred thirty-two patients underwent slow input AVN modification from 1993 to 2002. The mean patient age was 13.7 years (4-20 yrs) with 62M/70F. Outpatient tachycardia was documented by ambulatory monitoring in all patients. AVNRT was induced in 98/132 patients during EPS (group A) with mean SVT cycle length of 324 msec (230-570 msec). Initial AVN modification (group A) was successful in 97/98 patients (99%). During 34/132 EPS, AVNRT was non-inducible; dual AVN physiology was present in 19/34 (group B), and 15/34 did not show evidence for dual AVN physiology (group C). These 34 patients underwent empiric AVN modification following discussion with patients' families. Freedom of recurrence from SVT at 1 year was 96% for group A (94/98), 89% (17/19) for group B and 93% (14/15) for group C. 1 major and 6 minor complications occurred. CONCLUSIONS: AVN modification for AVNRT can be performed safely and effectively in pediatric patients with good long-term results. Empiric slow pathway AVN modification for non-inducible SVT results in a high rate of freedom from recurrence of tachycardia.

Distinguishing benign syncope from life-threatening cardiac causes of syncope.

Syncope, defined as the temporary loss of consiousness and postural tone resulting from an abrupt transient decrease in cerebral blood flow, is a common usually benign self-limiting event. However, rarely, it may be the first warning sign of a serious condition including arrhythmias, structural heart disease, or non-cardiac disease. This article presents a differential diagnosis of syncope in children with an emphasis on neurocardiogenic syncope, details important positives and negatives in the history and physical exam that would suggest cardiac syncope and gives recommendations on when to refer a child for syncope to a pediatric cardiologist.

Congenital sick sinus syndrome caused by recessive mutations in the cardiac sodium channel gene (SCN5A).

Sick sinus syndrome (SSS) describes an arrhythmia phenotype attributed to sinus node dysfunction and diagnosed by electrocardiographic demonstration of sinus bradycardia or sinus arrest. Although frequently associated with underlying heart disease and seen most often in the elderly, SSS may occur in the fetus, infant, and child without apparent cause. In this setting, SSS is presumed to be congenital. Based on prior associations with disorders of cardiac rhythm and conduction, we screened the alpha subunit of the cardiac sodium channel (SCN5A) as a candidate gene in ten pediatric patients from seven families who were diagnosed with congenital SSS during the first decade of life. Probands from three kindreds exhibited compound heterozygosity for six distinct SCN5A alleles, including two mutations previously associated with dominant disorders of cardiac excitability. Biophysical characterization of the mutants using heterologously expressed recombinant human heart sodium channels demonstrate loss of function or significant impairments in channel gating (inactivation) that predict reduced myocardial excitability. Our findings reveal a molecular basis for some forms of congenital SSS and define a recessive disorder of a human heart voltage-gated sodium channel.

Survey of current practice of pediatric electrophysiologists for asymptomatic Wolff-Parkinson-White syndrome.

OBJECTIVE: To determine the approach that pediatric electrophysiologists use as they evaluate asymptomatic patients with Wolff-Parkinson-White (WPW) syndrome regarding electrophysiologic testing and radio frequency ablation. METHODS: A 21-question survey was mailed to 66 pediatric electrophysiologists who had voluntarily submitted patient data at any time to the Pediatric Radio Frequency Ablation Registry since its inception in 1990. The survey addressed issues regarding physician experience with electrophysiologic testing and radio frequency ablation, risk assessment, electrophysiology study, and factors that influence the decision to perform radio frequency ablation in asymptomatic patients. RESULTS: Returned surveys (43 of 66 [65%]) were analyzed blindly. The 43 physicians who responded were experienced, with 37 reporting >5 years of performing radio frequency ablation and 30 having performed >200 radio frequency ablation procedures. Thirty-six of the 43 electrophysiologists used invasive electrophysiologic study for risk stratification in asymptomatic patients with WPW. Electrophysiologic findings guided selection of patients for radio frequency ablation procedures. Expected radio frequency ablation outcome quotes to the family were consistent with recently published data from the Electrophysiology Society regarding current-era experience with radio frequency ablation. CONCLUSION: The majority of responding electrophysiologists use invasive electrophysiologic study both to stratify risk for asymptomatic WPW and to select appropriate patients for radio frequency ablation. This current practice should be communicated to other pediatric cardiologists and pediatricians.