Elizabeth V. Saarel

Safety of Sports for Athletes With Implantable Cardioverter-Defibrillators Results of a Prospective, Multinational Registry

Background— The risks of sports participation for implantable cardioverter-defibrillator (ICD) patients are unknown. Methods and Results— Athletes with ICDs (age, 10–60 years) participating in organized (n=328) or high-risk (n=44) sports were recruited. Sports-related and clinical data were obtained by phone interview and medical records. Follow-up occurred every 6 months. ICD shock data and clinical outcomes were adjudicated by 2 electrophysiologists. Median age was 33 years (89 subjects <20 years of age); 33% were female. Sixty were competitive athletes (varsity/junior varsity/traveling team). A pre-ICD history of ventricular arrhythmia was present in 42%. Running, basketball, and soccer were the most common sports. Over a median 31-month (interquartile range, 21–46 months) follow-up, there were no occurrences of either primary end point—death or resuscitated arrest or arrhythmia- or shock-related injury—during sports. There were 49 shocks in 37 participants (10% of study population) during competition/practice, 39 shocks in 29 participants (8%) during other physical activity, and 33 shocks in 24 participants (6%) at rest. In 8 ventricular arrhythmia episodes (device defined), multiple shocks were received: 1 at rest, 4 during competition/practice, and 3 during other physical activity. Ultimately, the ICD terminated all episodes. Freedom from lead malfunction was 97% at 5 years (from implantation) and 90% at 10 years. Conclusions— Many athletes with ICDs can engage in vigorous and competitive sports without physical injury or failure to terminate the arrhythmia despite the occurrence of both inappropriate and appropriate shocks. These data provide a basis for more informed physician and patient decision making in terms of sports participation for athletes with ICDs.Background— The risks of sports participation for implantable cardioverter-defibrillator (ICD) patients are unknown. Methods and Results— Athletes with ICDs (age, 10–60 years) participating in organized (n=328) or high-risk (n=44) sports were recruited. Sports-related and clinical data were obtained by phone interview and medical records. Follow-up occurred every 6 months. ICD shock data and clinical outcomes were adjudicated by 2 electrophysiologists. Median age was 33 years (89 subjects <20 years of age); 33% were female. Sixty were competitive athletes (varsity/junior varsity/traveling team). A pre-ICD history of ventricular arrhythmia was present in 42%. Running, basketball, and soccer were the most common sports. Over a median 31-month (interquartile range, 21–46 months) follow-up, there were no occurrences of either primary end point—death or resuscitated arrest or arrhythmia- or shock-related injury—during sports. There were 49 shocks in 37 participants (10% of study population) during competition/practice, 39 shocks in 29 participants (8%) during other physical activity, and 33 shocks in 24 participants (6%) at rest. In 8 ventricular arrhythmia episodes (device defined), multiple shocks were received: 1 at rest, 4 during competition/practice, and 3 during other physical activity. Ultimately, the ICD terminated all episodes. Freedom from lead malfunction was 97% at 5 years (from implantation) and 90% at 10 years. Conclusions— Many athletes with ICDs can engage in vigorous and competitive sports without physical injury or failure to terminate the arrhythmia despite the occurrence of both inappropriate and appropriate shocks. These data provide a basis for more informed physician and patient decision making in terms of sports participation for athletes with ICDs. # Clinical Perspective {#article-title-44}

Somatic mosaicism contributes to phenotypic variation in Timothy syndrome

Timothy syndrome type 1 (TS‐1) is a rare disorder that affects multiple organ systems and has a high incidence of sudden death due to profound QT prolongation and resultant ventricular arrhythmias. All previously described cases of TS‐1 are the result of a missense mutation in exon 8A (p.G406R), an alternatively spliced variant of the L‐type calcium channel gene (Cav1.2, CACNA1C). Most patients reported in the literature represent highly affected individuals who present early in life with severe cardiac and neurological manifestations. Here, we describe somatic mosaicism in TS‐1 patients with less severe manifestations than the typical TS‐1 patient. These findings suggest that the TS prognosis may not be as dismal as previously reported. Moreover, our findings have implications for genetic counseling in that previously described de novo TS mutations may represent cases of parental mosaicism and warrant careful genotyping of parental tissue other than peripheral blood lymphocytes.

Fascicular and Nonfascicular Left Ventricular Tachycardias in the Young: An International Multicenter Study

The aim of this study was to evaluate the clinical presentation and outcomes of pediatric patients with ventricular tachycardia (VT) originating from left heart structures.

Inappropriate ICD shocks in pediatrics and congenital heart disease patients: Risk factors and programming strategies

BACKGROUND Inappropriate implantable cardioverter-defibrillator (ICD) shocks are a common and significant problem in pediatric patients and patients with congenital heart disease (CHD). OBJECTIVE The purpose of this study was to evaluate the effect of programming high detection rates and long detection duration on inappropriate shocks in this population. METHODS We performed a retrospective review of all patients with ICDs at a single pediatric center. Inappropriate shocks were defined as a shock for any rhythm except ventricular tachycardia or fibrillation. RESULTS A total of 144 patients were included, 63 (44%) with CHD. At implant, mean age and weight were 17 ± 10 years and 57 ± 23 kg. ICDs were single chamber in 35 (24%), dual chamber in 97 (67%), and biventricular in 12 (8%). The mean follow-up duration was 42 ± 39 months. Appropriate shocks occurred in 29 (20.1%) and inappropriate shocks in 14 (9.7%). Causes of inappropriate shocks were supraventricular tachycardia (n = 6), lead malfunction (n = 4), sinus tachycardia (n = 3), and T-wave oversensing (n = 1). The mean ventricular fibrillation detection rate was 222 ± 15 beats/min, and the detection duration was 18 ± 12 beats. Patients with shocks programmed in the ventricular tachycardia zone were more likely to receive an inappropriate shock (P = .03). There were no associations between inappropriate shocks and age or weight at implant, presence of CHD, dual-chamber vs single-chamber device, history of supraventricular tachycardia, or antiarrhythmic use. There were no adverse events as a result of programming. CONCLUSION Programming high detection rates and long detection duration resulted in a low rate of inappropriate shocks without associated adverse events in this large cohort of pediatric and CHD patients with ICDs.

Failure to impact prevalence of arterial ischemic stroke in pediatric cardiac patients over three decades.

INTRODUCTION Over the past three decades, significant advances in treatment have improved the mortality of children with cardiac disease. The effect of these advances on the prevalence of arterial ischemic stroke (AIS) is unknown. We describe AIS in children with cardiac disease in the modern era. DESIGN The prospectively enrolled Intermountain Pediatric Stroke Database (including Utah, Wyoming, Idaho, and Nevada) was queried for all patients less than 18 years old with new-onset AIS between January 1, 2003 and August 31, 2009. Medical records of patients with AIS and cardiac disease were reviewed for cardiac diagnosis, age at AIS, anticoagulant therapy, diuretics, hematocrit, bolus fluids, and ongoing morbidity. Data were analyzed using chi-square test and a mixed-effects Poisson regression growth curve model. RESULTS AIS incidence in our catchment area was 0.01% (10.7/100,000; N = 97). The incidence of AIS in patients with cardiac disease was higher compared with AIS in the total population (incidence 0.13% [132/100,000], odds ratio [OR] 16.1, 95% confidence interval [CI; 9.7--25.9], P < 0.001). Of the 97 patients with AIS, 24 had cardiac disease (25%). The most common cardiac diagnosis was single ventricle (SV; 8/24, 33%). The incidence of AIS in patients with SV cardiac disease was higher compared with those with other cardiac diagnoses (incidence 1.38% [1380/100,000], OR 15.3, 95% CI [5.7--38.2], P < 0.001). Modeling the prevalence estimates reported since 1978, the prevalence of cardiac disease in AIS patients has remained unchanged across time (prevalence increase per each additional year, 0.5%, 95% CI [--2.1%, 3.1%], P = 0.71). CONCLUSION Children with cardiac disease (particularly those with SV) have increased risk for AIS. The prevalence is unchanged from reports over previous decades. AIS occurred in SV patients despite compliance with current anticoagulation recommendations. Future efforts should focus on best practices to prevent AIS in cardiac patients.

Phenotype of a patient with contiguous deletion of TBX5 and TBX3: Expanding the disease spectrum

The important roles that T‐box genes play in the morphogenesis of the heart and its conduction system has long been established, and a number of disorders are linked to mutations in these T‐box genes. Holt–Oram syndrome (HOS), the classic heart and hand syndrome, is clinically typified by radial ray upper limb abnormalities and cardiac malformations, and is caused by mutations involving TBX5. Another member of the T‐box gene family, TBX3, is found in close proximity to TBX5 on chromosome 12q24. Mutations in TBX3 cause ulnar–mammary syndrome (UMS), which is distinguished by upper limb malformations affecting the ulnar ray, apocrine, and mammary gland hypoplasia, and genital defects. While disorders involving isolated mutations of TBX5 and TBX3 have been well described, contiguous deletions of these T‐box genes remain exceptional. We report on a patient with features of both HOS and UMS consisting of bilateral symmetric limb malformations, congenital cardiac defects, and rapidly progressive cardiac conduction disease.

Use of the wearable external cardiac defibrillator in children.

Background: The wearable cardiac defibrillator (WCD) is an alternative to the implantation of cardioverter defibrillator (ICD) for patients at risk for sudden death who do not fulfill standard criteria for ICD implantation or in whom the risk:benefit ratio is equivocal. Published data pertaining to the WCD in children is sparse. We describe the utility of the WCD in children at a single tertiary care center.

Congenital Long QT Syndrome in Children Identified by Family Screening

The diagnosis of congenital long-QT syndrome (LQTS) in the relatives (nonprobands) of index patients (probands) is increasing because of screening. This report documents the clinical courses and outcomes of nonproband pediatric patients with LQTS. All patients aged <18 years with LQTS were identified at 3 pediatric centers. Demographic data, personal and family histories, electrocardiographic data, and genetic diagnoses (if available) were obtained. Probands were defined as the first patients in their families diagnosed with LQTS and nonprobands as those diagnosed by screening. Of 144 patients with LQTS, 84 (58%) were nonprobands aged 6.5+/-5.4 years with QTc intervals of 479+/-34 ms. No nonproband presented with resuscitated sudden death, atrioventricular block, or ventricular arrhythmia, but 7 (8.3%) had histories of syncope at presentation. All nonproband patients were treated. During a follow-up period of 4.7+/-3.9 years, there were no deaths in the nonproband group, but device implantation was performed in 13 (15%), 4 of whom had appropriate shocks. As expected, compared with probands, nonprobands were less symptomatic. Additionally, nonprobands were younger and had shorter QTc intervals. Although device implantation was more common in probands, there was no difference in appropriate implantable cardioverter-defibrillator shocks or mortality between the probands and their affected relatives. In conclusion, children are increasingly identified with LQTS as a result of family screening. Although phenotypic differences exist between probands and nonprobands, survival is excellent in the 2 groups with therapy. Appropriate implantable cardioverter-defibrillator discharges in the nonproband group underscore the importance of follow-up in this relatively asymptomatic population.

The multicenter pediatric and adult congenital EP quality (MAP-IT) initiative-rationale and design: Report from the pediatric and congenital electrophysiology society's MAP-IT taskforce

Multicenter clinical registries are increasingly recognized as valuable tools for establishing benchmarks, facilitating patient-centered quality improvement and research. In 2010, the Pediatric and Congenital Electrophysiology Society convened a taskforce of its members to design, construct, and implement a clinical registry known as the Multicenter Pediatric and Adult Congenital EP Quality (MAP-IT) Initiative. The present aim of the MAP-IT Initiative is to create an infrastructure by which we can measurably improve patient-centered outcomes and reduce complications associated with electrophysiology studies and catheter ablation in pediatric and congenital heart disease patients. The purpose of this writing is to report the progress to date from three of the four subcommittees of the MAP-IT taskforce. Specifically, we present our initial set of key data elements and definitions, recommended database table structure, and considerations regarding wide-scale implementation of the registry. Development of a risk/complexity score for use in the MAP-IT registry is presented in a separate companion manuscript. It is our intent that these manuscripts will serve to introduce the electrophysiology and pediatric cardiology community to the MAP-IT initiative and provide a rationale for its design and recommended implementation strategy.

The application of root mean square electrocardiography (RMS ECG) for the detection of acquired and congenital long QT syndrome.

Background Precise measurement of the QT interval is often hampered by difficulty determining the end of the low amplitude T wave. Root mean square electrocardiography (RMS ECG) provides a novel alternative measure of ventricular repolarization. Experimental data have shown that the interval between the RMS ECG QRS and T wave peaks (RTPK) closely reflects the mean ventricular action potential duration while the RMS T wave width (TW) tracks the dispersion of repolarization timing. Here, we tested the precision of RMS ECG to assess ventricular repolarization in humans in the setting of drug-induced and congenital Long QT Syndrome (LQTS). Methods RMS ECG signals were derived from high-resolution 24 hour Holter monitor recordings from 68 subjects after receiving placebo and moxifloxacin and from standard 12 lead ECGs obtained in 97 subjects with LQTS and 97 age- and sex-matched controls. RTPK, QTRMS and RMS TW intervals were automatically measured using custom software and compared to traditional QT measures using lead II. Results All measures of repolarization were prolonged during moxifloxacin administration and in LQTS subjects, but the variance of RMS intervals was significantly smaller than traditional lead II measurements. TW was prolonged during moxifloxacin and in subjects with LQT-2, but not LQT-1 or LQT-3. Conclusion These data validate the application of RMS ECG for the detection of drug-induced and congenital LQTS. RMS ECG measurements are more precise than the current standard of care lead II measurements.