Techniques for Cardiac Resynchronization Therapy in Patients with Congenital Heart Disease.

Cardiac resynchronization therapy (CRT) for congenital heart disease has shown promising suucess as an adjunct to medical therapy for heart failure. While cardiac conduction defects and need for ventricular pacing are common in congential heart disease, CRT indications, techniques and long term outcomes have not been well establaished. This is a review of the techniques nad short term outcomes of CRT for the following complex congenital heart disease conditions: single ventricle physiology, systemic right ventricle, and the subpulmonic right ventricle.

Sudden Death in the Young: Information for the Primary Care Provider.

There are multiple conditions that can make children prone to having a sudden cardiac arrest (SCA) or sudden cardiac death (SCD). Efforts have been made by multiple organizations to screen children for cardiac conditions, but the emphasis has been on screening before athletic competition. This article is an update of the previous American Academy of Pediatrics policy statement of 2012 that addresses prevention of SCA and SCD. This update includes a comprehensive review of conditions that should prompt more attention and cardiology evaluation. The role of the primary care provider is of paramount importance in the evaluation of children, particularly as they enter middle school or junior high. There is discussion about whether screening should find any cardiac condition or just those that are associated with SCA and SCD. This update reviews the 4 main screening questions that are recommended, not just for athletes, but for all children. There is also discussion about how to handle post-SCA and SCD situations as well as discussion about genetic testing. It is the goal of this policy statement update to provide the primary care provider more assistance in how to screen for life-threatening conditions, regardless of athletic status.

Belhassen Ventricular Tachycardia in a Child.

First reported in 1981, idiopathic left ventricular tachycardia (VT) of the Belhassen type is characterized during electrocardiography (ECG) by a right bundle branch pattern and left axis deviation. We report the case of a 15-year-old Hispanic male who, during a routine evaluation ECG to support sports participation, was found to have nonsustained monomorphic VT. Prior to his exercise treadmill test, his physical examination and echocardiogram were normal. Then, during preparation for the exercise treadmill test, the ECG showed sustained monomorphic VT with a right bundle branch block pattern and superior QRS axis, suggesting a diagnosis of Belhassen VT.

False Asystole Alarms Post-Temporary Pacemaker Placement Due to Pseudo-fusion.

An infant with congenital heart block and hemodynamically significant bradycardia underwent therapeutic temporary pacing wires placement. Post-operatively, frequent "asystole" alarms were observed on telemetry causing distress to both the family and the nursing staff. Investigation of these alarms showed that pacemaker malfunction led to monitor pseudo-malfunction. The alarms were alleviated with mindful setting of the pacemaker and telemetry monitor parameters. This case highlights the challenges of pacemaker placement and monitoring of very small infants in the intensive care setting. Awareness of these challenges would help in troubleshooting pacemaker and telemetry monitor issues.

Loss of ventricular preexcitation during noninvasive testing does not exclude high-risk accessory pathways: A multicenter study of WPW in children.

BACKGROUND: Abrupt loss of ventricular preexcitation on noninvasive evaluation, or nonpersistent preexcitation, in Wolff-Parkinson-White syndrome (WPW) is thought to indicate a low risk of life-threatening events. OBJECTIVE: The purpose of this study was to compare accessory pathway (AP) characteristics and occurrences of sudden cardiac arrest (SCA) and rapidly conducted preexcited atrial fibrillation (RC-AF) in patients with nonpersistent and persistent preexcitation. METHODS: Patients 21 years or younger with WPW and invasive electrophysiology study (EPS) data, SCA, or RC-AF were identified from multicenter databases. Nonpersistent preexcitation was defined as absence/sudden loss of preexcitation on electrocardiogram, Holter monitoring, or exercise stress test. RC-AF was defined as clinical preexcited atrial fibrillation with shortest preexcited R-R interval (SPERRI) ≤ 250 ms. AP effective refractory period (APERP), SPERRI at EPS , and shortest preexcited paced cycle length (SPPCL) were collected. High-risk APs were defined as APERP, SPERRI, or SPPCL ≤ 250 ms. RESULTS: Of 1589 patients, 244 (15%) had nonpersistent preexcitation and 1345 (85%) had persistent preexcitation. There were no differences in sex (58% vs 60% male; P=.49) or age (13.3±3.6 years vs 13.1±3.9 years; P=.43) between groups. Although APERP (344±76 ms vs 312±61 ms; P<.001) and SPPCL (394±123 ms vs 317±82 ms; P<.001) were longer in nonpersistent vs persistent preexcitation, there was no difference in SPERRI at EPS (331±71 ms vs 316±73 ms; P=.15). Nonpersistent preexcitation was associated with fewer high-risk APs (13% vs 23%; P<.001) than persistent preexcitation. Of 61 patients with SCA or RC-AF, 6 (10%) had nonpersistent preexcitation (3 SCA, 3 RC-AF). CONCLUSION: Nonpersistent preexcitation was associated with fewer high-risk APs, though it did not exclude the risk of SCA or RC-AF in children with WPW.

Anchored Transponder Guided Lung Radiation Therapy.

PURPOSE: The Calypso Beacon transponder has been modified by the addition of a nitinol anchor feature to allow for positional stability when implanted bronchoscopically into the lung. The purpose of this study was to confirm the feasibility and safety of anchored transponder placement and feasibility of lung target localization and tracking. METHODS AND MATERIALS: This study enrolled patients with histologically confirmed cancer in the lung (primary or metastatic) who were scheduled to receive external beam radiation therapy. Three anchored transponders were implanted via flexible bronchoscopy into small (approximately 2- to 2.5-mm diameter) airways. Patient alignment at each radiation fraction was performed with the Calypso system, and anchored transponder position was tracked during radiation delivery. The primary endpoint was defined as the ability to localize at least 85% of the patients during the first week of treatment. Four follow-up visits were specified including a posttreatment assessment and every 3 months up to 1 year. RESULTS: A total of 69 patients underwent anchored transponder placement, and all 207 implanted anchored transponders were visible on the treatment-planning simulation computed tomography scan. Sixty-seven patients underwent radiation therapy, and localization was successful in 66 cases (98.5%). With 1 failure in 67 cases, the P value for rejecting the null hypothesis was <.001 and the primary objective of the study met. Five adverse events in 5 patients were potentially attributed to the study device or implantation procedure, consisting of pneumonia (2 cases), pleural abscess (1 case), and pneumothorax (2 cases). Two serious events (cardiac arrest and acute hypotension) were attributed to anesthesia during the implantation procedure. CONCLUSIONS: This study strongly supports that anchored transponders are safe, positionally stable, and useful for lung tumor localization and monitoring.

The Progress and Significance of QRS Duration by Electrocardiography in Hypoplastic Left Heart Syndrome.

Patients with hypoplastic left heart syndrome (HLHS) are now surviving through to Fontan palliation and beyond, however, with increased morbidity and mortality. Prolonged QRSd has become one of the predictors of morbidity and mortality in certain congenital heart diseases. There is limited data characterizing the QRSd in patients with HLHS. We aimed to describe the changes in QRSd at various times during the lifetime and to evaluate whether QRSd correlates with a higher risk of developing a composite endpoint of heart failure, heart transplant, or death. We conducted a retrospective chart review of patients with HLHS who survived Fontan palliation. QRSd was measured on ECGs at various stages pre- and postsurgical palliations and subsequently at 5 year intervals. Patients with a composite endpoint were compared to those without. A total of 89 patients were included in the final analysis. The QRSd increased significantly with time from 68.7 ± 9.0 ms prior to Norwood to 91.0 ± 14.0 ms immediately following Fontan and 104.7 ± 13.6 ms 15 years after Fontan (p < 0.001). The composite endpoint was observed in 28 patients (31.4%). The time trends of QRSd differ so that the patients having the composite endpoint experienced a greater increase in QRSd over time (p = 0.009). Ever having a QRSd of 120 ms or more predicted the composite endpoint with 93% specificity. The area under the curve of the receiver operator curve analysis was 0.596. A Cox regression analysis demonstrated that QRS duration > 120 ms was independently related to a greater frequency of composite endpoint and this was confirmed by a Kaplan-Meier analysis (p = 0.011). This study unveils a novel relationship between QRSd of 120 ms or more with the composite endpoint. Despite the low sensitivity, this finding on a routine surveillance ECG could help identify HLHS Fontan patients at risk for heart failure, heart transplant, or death.

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.

Risk factors for lethal arrhythmic events in children and adolescents with hypertrophic cardiomyopathy and an implantable defibrillator: An international multicenter study.

BACKGROUND: Predictors of risk of lethal arrhythmic events (LAE) is poorly understood and may differ from adults in children with hypertrophic cardiomyopathy (HCM). OBJECTIVE: The purpose of this study was to determine predictors of LAE in children with HCM. METHODS: A retrospective data collection was performed on 446 children and teenagers 20 years and younger (290 [65%] male; mean age 10.1 ± 5.7 years) with idiopathic HCM from 35 centers. Patients were classified as group 1 (HCM with LAE) if having a secondary prevention implantable cardioverter-defibrillator (ICD) or primary prevention ICD with appropriate interventions or group 2 (HCM without LAE) if having a primary prevention ICD without appropriate interventions. RESULTS: There were 152 children (34%) in group 1 and 294 (66%) in group 2. Risk factors for group 1 by univariate analysis were septal thickness, posterior left ventricular (LV) wall thickness, lower LV outflow gradient, and Q wave > 3 mm in inferior electrocardiographic leads. Factors not associated with LAE were family history of SCD, abnormal blood pressure response to exercise, and ventricular tachycardia on ambulatory electrocardiographic monitoring. Risk factors for SCD by multivariate analysis were age at ICD placement (hazard ratio [HR] 0.9; P = .0025), LV posterior wall thickness z score (HR 1.02; P < .005), and LV outflow gradient < 30 mm Hg (HR 2.0; P < .006). LV posterior wall thickness z score ≥ 5 was associated with LAE. CONCLUSION: Risk factors for LAE appear different in children compared to adults. Conventional adult risk factors were not significant in children. Further prospective studies are needed to improve risk stratification for LAE in children with HCM.

Ventricular pacing in single ventricles-A bad combination.

BACKGROUND: Chronic ventricular pacing (VP) is associated with systolic dysfunction in a subset of pediatric patients with heart block and structurally normal hearts. The effect of chronic VP in congenital heart disease is less well understood, specifically in the single-ventricle (SV) population. OBJECTIVE: To determine the longitudinal effect of VP in SV patients. METHODS: SV patients with heart block and dual-chamber pacemakers requiring >50% VP were compared with nonpaced (controls) SV patients matched for age, sex, and SV morphology. Patients were excluded if a prepacing echocardiogram was not available. Echocardiogram and clinical parameters were compared at baseline (prepacing) and at last follow-up in the paced group, and in controls when they were at ages similar to those of their paced-group matches. RESULTS: Twenty-two paced and 53 control patients from 2 institutions were followed for similar durations (6.6±5 years vs 7.6±7.6 years; P = .59). There was no difference between groups regarding baseline ventricular function or the presence of moderate-to-severe atrioventricular valvar regurgitation (AVVR). Paced patients were more likely to develop moderate-to-severe systolic dysfunction (68% vs 15%; P < .01) and AVVR (55% vs 8%; P < .001) and require heart failure medications (65% vs 21%; P < .001). Chronic VP was also associated with a higher risk of transplantation or death (odds ratio, 4.9; 95% confidence interval, 1.05-22.7; P = .04). CONCLUSIONS: SV patients requiring chronic VP are at higher risk of developing moderate-to-severe ventricular dysfunction and AVVR with an increased risk of death or transplantation compared with controls. New strategies to either limit VP or improve synchronization in this vulnerable population is imperative.

ECG screening for SCD in young adults: community volunteers can acquire higher quality ECGs than health professionals.

BACKGROUND AND PURPOSE: ECG screening of young athletes for risk of sudden cardiac death has grown in popularity throughout the world. The purpose of this study is to assess the technical error rate of ECGs acquired by appropriately trained community volunteers compared to that reported in the literature utilizing trained medical personnel. METHODS: This is a retrospective study analyzing consecutive ECGs acquired during 5 successive high school screenings at 3 separate schools in 2011. RESULTS: A total of 4477 consecutive ECGs were acquired and assessed for technical quality. The total rate of technically inadequate tracings was 0.34%. This is lower than that reported in outpatient clinics acquired by medically trained technicians (0.4%) and in ICUs acquired by nurses (4.8%). CONCLUSIONS: This study demonstrates that the ECG training program utilized by the YH4L program for community volunteers results in a technical error rate that is lower than reported in the literature.

Success rates in pediatric WPW ablation are improved with 3-dimensional mapping systems compared with fluoroscopy alone: a multicenter study.

INTRODUCTION: Three-dimensional mapping (3-D) systems are frequently used for ablation of supraventricular tachycardia. Prior studies have demonstrated radiation dosage reduction with 3-D, but there are no data on whether 3-D improves the efficacy of ablation of Wolff-Parkinson-White syndrome (WPW). We sought to determine if 3-D improves the success rate for ablation of WPW in children. METHODS: Multicenter retrospective study including patients ≤21 years of age with WPW undergoing ablation from 2008 to 2012. Success rates using the 2 techniques (3-D vs. fluoroscopy alone [FLUORO]) were compared. RESULTS: Six hundred and fifty-one cases were included (58% male, mean age 13 ± 4 years, 366 [56%] 3-D). Baseline characteristics including gender, weight, accessory pathway (AP) location, number of APs, and repeat ablation attempts were similar between the 2 groups (3-D and FLUORO) The 3-D group was slightly younger (12.7 ± 4.0 vs. 13.3 ± 4.0 years; P = 0.04) and less likely to undergo ablation utilizing cryoenergy (38 [10%] vs. 56 [20%]; P < 0.01). The 3-D group had a higher acute success rate of ablation (355 [97%] vs. 260 [91%]; P < 0.01). No differences were seen in recurrence (16 [5%] vs. 26 [9%]; P = 0.09) or complication rates (1 [0.3%] vs. 1 [0.4%]; P = 0.86) between the groups. On multivariable analysis, 3-D was shown to significantly improve success at ablation with an odds ratio of 3.1 (95% CI 1.44-6.72; P < 0.01). CONCLUSIONS: Use of 3-D significantly improved success rates for ablation of WPW in children. The increase in acute success associated with 3-D suggests it is an important adjunct for catheter ablation of WPW in children.

Isolated left bundle branch block in a toddler.

Left bundle branch block (LBBB) usually occurs as a postoperative complication from surgical correction of congenital heart disease and can be associated with hypertensive heart disease, coronary artery disease, myocarditis, and aortic valvular disease. Although isolated LBBB is a conduction abnormality found in some healthy adults, it has not been reported in pediatric population. We report a 2-year-old, healthy African American female who was incidentally discovered to have isolated LBBB that has persisted in a follow-up of 3 years.

Transesophageal echocardiography of intracardiac thrombus in congenital heart disease and atrial flutter: the importance of thorough examination of the Fontan.

Transesophageal echocardiography (TEE) is used in atrial flutter or fibrillation (AFF) before electric cardioversion to detect intracardiac thrombi. Previous studies have described the use of TEE to diagnose intracardiac thrombi in the left atrium and left atrial appendage, which has an incidence of 8 % among patients without congenital heart disease (CHD). In their practice the authors have noted a significant incidence of intracardiac thrombi in other structures of patients with CHD and AFF. This study aimed to determine the incidence and location of intracardiac thrombi using TEE in patients with CHD requiring electric cardioversion of AFF and to compare the use of TEE and transthoracic echo (TTE) to detect intracardiac thrombus in this population. A retrospective chart review of TEE and TTE findings for all patients with CHD who had electric cardioversion of AFF at our institution from 2005 to 2013 was conducted. The diagnosis, presence, and location of intracardiac thrombus were determined. The TEE and TTE results were compared. The study identified 27 patients with CHD who met the study entry criteria at our institution between 2005 and 2013. Seven of these patients had a single ventricle with Fontan palliation. All the patients presented with AFF and had TEE before electric cardioversion. No patients were excluded from the study. The patients ranged in age from 2 to 72 years (median, 21 years) and weighed 17-100 kg (median, 65 kg). The duration of AFF before TEE and attempted cardioversion ranged from 1 day to 3 weeks (median, 3.5 days). Intracardiac thrombus was present in 18 % (5/27) of the patients and in 57 % (4/7) of the Fontan patients with AFF. No embolic events were reported acutely or during a 6-month follow-up period. Among patients with CHD who present with AFF, a particularly high incidence of intracardiac thrombi is present in the Fontan patients that may be difficult to detect by TTE. Thorough TEE examination of the Fontan and related structures is indicated before electric cardioversion of AFF. The incidence of intracardiac thrombus in CHD patients is more than double that reported in non-CHD patients.

Feasibility and findings of large-scale electrocardiographic screening in young adults: data from 32,561 subjects.

BACKGROUND: Large-scale electrocardiographic (ECG) screening of young athletes has been shown to reduce the incidence of sudden cardiac death in Italy. Debate exists regarding the feasibility and benefits of such a program in the United States. OBJECTIVE: The purpose of this study was to describe implementation and results of a large-scale high school ECG screening program (Young Hearts for Life [YH4L]) developed in the Chicago area. METHODS: A retrospective cohort study of 32,561 high school students from 38 ECG screenings was performed between September 2006 and May 2009. Screenings were performed by the YH4L program, which consisted of a core group of administrators, cardiologists, and community volunteers who underwent specialized training and quality review. The rates of abnormal ECGs requiring further evaluation and unacceptable ECGs due to poor quality were determined. RESULTS: Of the 32,561 students screened, 817 (2.5%) had abnormal ECGs requiring further evaluation. The majority of abnormal ECGs occurred in males (66%). Only 0.81% of ECGs were determined to be technically inadequate, requiring repeat ECGs on the same day of the screening. The prevalence of left ventricular hypertrophy and abnormal ST-T wave changes was lower in our study than in the rates reported in an Italian registry, possibly due to the lower frequency of men and highly trained athletes in our study. CONCLUSION: Large-scale ECG screening of U.S. high school students is feasible and identifies ECGs requiring further evaluation in 2.5% of individuals. These findings have implications for implementing screening and preventing sudden cardiac death in U.S. youth.

Real-time three-dimensional echocardiographic assessment of left ventricular systolic dyssynchrony in healthy children.

BACKGROUND: The use of resynchronization therapy for the treatment of left ventricular (LV) systolic dysfunction in children has been expanding. Because QRS duration is not a reliable indicator of the presence or severity of dyssynchrony in every case, additional methods of quantitation of dyssynchrony are needed. The purpose of this study was threefold: (1) to define normal values for LV real-time quantitative three-dimensional echocardiographic (3DE) dyssynchrony indices (DIs), (2) to analyze the feasibility and observer variability of 3DE DIs in a wide range of children, and (3) to determine the effects of age, heart rate, body surface area, and LV end-diastolic volume on these parameters. METHODS: The two specific parameters studied were the standard deviation of the time to minimum systolic volume for the number of segments analyzed and the time difference between the earliest and latest contracting segments. Both parameters were expressed as a percentage of the cardiac cycle length. RESULTS: In 125 normal children aged 1 day to 19 years, adequate dyssynchrony studies were obtained in 102 (81.8%). The mean LV 3DE DIs expressed as the standard deviation of the time to minimum systolic volume for the number of segments analyzed were 1.16 ± 0.58 for 16 segments, 1.01 ± 0.60 for 12 segments, and 0.93 ± 0.68 for 6 segments. The mean LV 3DE DIs expressed as the time difference between the earliest and latest contracting segments were 3.80 ± 1.57 for 16 segments, 2.99 ± 1.42 for 12 segments, and 2.27 ± 1.35 for 6 segments. There were no effects of age, heart rate, body surface area, or LV end-diastolic volume on 3DE DIs. Intraobserver variability was 5.1%, and interobserver variability was 7.6%. CONCLUSION: Three-dimensional echocardiographic DI analysis is reproducible and feasible in most children. Three-dimensional echocardiographic DIs are not affected by growth-related parameters in children but are lower than previously reported adult values.

Chiari drop attacks: surgical decompression and the role of tilt table testing.

BACKGROUND: Chiari I malformation (CM1) is characterized by impaired CSF flow through the foramen magnum. Dysfunctional autonomic cardiovascular regulation may result in syncope. Syncope may be the primary presenting symptom of CM1: a syndrome termed Chiari drop attack. It has been postulated that Chiari drop attack is secondary to dysautonomia caused by hindbrain compression. There has been recent debate regarding the association between CM1, dysautonomia and Chiari drop attack. METHODS: We selected patients with Chiari drop attacks who had negative workups for cardiac syncope, followed by tilt table testing and subsequent surgical decompression. We report test results and clinical outcomes following CM1 decompression. RESULTS: Ten patients met the inclusion criteria: 5 patients had positive and 5 negative tilt table tests. Following decompression, 7 had symptomatic improvement or resolution and 3 failed to improve. The sensitivity and specificity of the tilt table test for detecting clinical improvement with surgical decompression was 43 and 33%, respectively. Tilt table testing had 40% accuracy in predicting clinical response to decompression. CONCLUSIONS: In this short series, surgical decompression of CM1 has a high success rate (70%) for patients with Chiari drop attacks. Tilt table testing has poor predictive value in judging the clinical response to surgical decompression and is not a useful test to guide surgical decision- making.