Harinder R. Singh

The Study of Antiarrhythmic Medications in Infancy (SAMIS) A Multicenter, Randomized Controlled Trial Comparing the Efficacy and Safety of Digoxin Versus Propranolol for Prophylaxis of Supraventricular Tachycardia in Infants

Background—Supraventricular tachycardia (SVT) is one of the most common conditions requiring emergent cardiac care in children, yet its management has never been subjected to a randomized controlled clinical trial. The purpose of this study was to compare the efficacy and safety of the 2 most commonly used medications for antiarrhythmic prophylaxis of SVT in infants: digoxin and propranolol. Methods and Results—This was a randomized, double-blind, multicenter study of infants <4 months with SVT (atrioventricular reciprocating tachycardia or atrioventricular nodal reentrant tachycardia), excluding Wolff-Parkinson-White, comparing digoxin with propranolol. The primary end point was recurrence of SVT requiring medical intervention. Time to recurrence and adverse events were secondary outcomes. Sixty-one patients completed the study, 27 randomized to digoxin and 34 to propranolol. SVT recurred in 19% of patients on digoxin and 31% of patients on propranolol (P=0.25). No first recurrence occurred after 110 days of treatment. The 6-month recurrence-free status was 79% for patients on digoxin and 67% for patients on propranolol (P=0.34), and there were no first recurrences in either group between 6 and 12 months. There were no deaths and no serious adverse events related to study medication. Conclusions—There was no difference in SVT recurrence in infants treated with digoxin versus propranolol. The current standard practice may be treating infants longer than required and indicates the need for a placebo-controlled trial. Clinical Trial Registration Information—http://clinicaltrials.gov; NCT-00390546.

Chest Pain in Children and Adolescents

1. Surendranath R. Veeram Reddy, MD* 2. Harinder R. Singh, MD* 1. *Division of Cardiology, The Carman and Ann Adams Department of Pediatrics, Childrens Hospital of Michigan, Wayne State University School of Medicine, Detroit, Mich After completing this article, readers should be able to: 1. Enumerate the most common causes of chest pain in pediatric patients. 2. Differentiate cardiac chest pain from that of noncardiac cause. 3. Describe the detailed evaluation of a pediatric patient who has chest pain. 4. Screen and identify patients who require a referral to a pediatric cardiologist or other specialist. 5. Explain the management of the common causes of pediatric chest pain. ### Case 1 During an annual physical examination, a 12-year-old girl complains of intermittent chest pain for the past 5 days that localizes to the left upper sternal border. The pain is sharp and stabbing, is 5/10 in intensity, increases with deep breathing, and lasts for less than 1 minute. The patient has no history of fever, cough, exercise intolerance, palpitations, dizziness, or syncope. On physical examination, the young girl is in no pain or distress and has normal vital signs for her age. Examination of her chest reveals no signs of inflammation over the sternum or rib cage. Palpation elicits mild-to-moderate tenderness over the left second and third costochondral junctions. The patient reports that the pain during the physical examination is similar to the chest pain she has experienced for the past 5 days. A detailed cardiovascular and other organ system examination yields normal results. What is the most likely cause of this patients chest pain? What will you recommend for this patient? Does she need to see a pediatric cardiologist? ### Case 2 A 17-year-old boy is playing soccer on a Saturday afternoon and has a syncopal event on the field. He regains consciousness within a few seconds, does not require resuscitation, and is taken to the emergency department. The patient informs the physician that he developed sudden midsternal chest pain and lightheadedness prior to passing out. His vital signs are normal for age, and he is …

Remodeling and Thrombosis Following Closure of Coronary Artery Fistula With Review of Management: Large Distal Coronary Artery Fistula—To Close or Not to Close?

To evaluate postdiscovery outcome of coronary artery fistulae (CAF). CAF treatment sequelae and risk factors for coronary thrombosis have not been adequately evaluated.

Congenital Long QT 3 in the Pediatric Population

There is insufficient knowledge concerning long-QT (LQT) 3 in the pediatric population to determine whether recommendations for more aggressive therapy in these patients are appropriate. An international multicenter review of 43 children with cardiac sodium channel (SCN5A) mutations and clinical manifestations of LQT syndrome without overlap of other SCN5A syndromes was undertaken to describe the clinical characteristics of LQT3 in children. Patients were aged 7.6 ± 5.9 years at presentation and were followed for 4.7 ± 3.9 years. There was significant intrasubject corrected QT interval (QTc) variability on serial electrocardiography. Forty-two percent presented with severe symptoms or arrhythmia and exhibited longer QTc intervals compared to asymptomatic patients. None of the 14 patients who underwent primary prevention implantable cardioverter-defibrillator (ICD) implantation received appropriate shocks in 41 patient-years of follow-up, while 2 of 6 patients who underwent secondary prevention ICD implantation received appropriate shocks in 30 patient-years of follow-up. Half of patients who underwent ICD implantation experienced inappropriate shocks or ICD-related complications. Mexiletine significantly shortened the QTc interval, and QTc shortening was greater in patients with longer pretreated QTc intervals. Two ICD patients with frequent appropriate ICD shocks showed immediate clinical improvement, with elimination of appropriate ICD shocks after mexiletine loading. In conclusion, severe symptoms are common in children with LQT3 and are associated with longer QTc intervals. ICD implantation is associated with significant morbidity. Mexiletine shortens the QTc interval, and it may be beneficial.

Radiofrequency and Cryoablation Therapies for Supraventricular Arrhythmias in the Young: Five-Year Review of Efficacies

Background: Cryoablation (Cryo) has augmented radiofrequency (RF) as the ablation energy choice for most supraventricular tachycardias (SVT). Although initial acute results and more recent, but limited, 3–36‐month follow‐up studies have been reported, more longer follow‐up information is required to determine actual efficacy.

Risk factors for atrioventricular tachycardia degenerating to atrial flutter/fibrillation in the young with Wolff-Parkinson-White.

Background: Atrioventricular reciprocating tachycardia (AVRT) is common in patients (pts) with Wolff‐Parkinson‐White (WPW) syndrome but atrial flutter/fibrillation (AF) with rapid ventricular response (RVR) is rare. Although AF occurs in 18% of adult WPW pts, its incidence in children is unknown. We sought to determine risk factors for AVRT spontaneously degenerating to AF during electrophysiologic studies (EPS) in children with WPW.

A novel Alu-mediated Xq28 microdeletion ablates TAZ and partially deletes DNL1L in a patient with Barth syndrome.

A Novel Alu-Mediated Xq28 Microdeletion Ablates TAZ and Partially Deletes DNL1L in a Patient With Barth Syndrome Harinder R. Singh, Zhao Yang, Saad Siddiqui, Liana S. Pe~na, Brandy H. Westerfield, Yuxin Fan, Jeffrey A. Towbin, and Matteo Vatta* Children’s Hospital of Michigan, Division of Cardiology, The Carman and Ann Adams, Department of Pediatrics, Wayne State University School of Medicine, Detroit, Michigan Department of Pediatrics (Cardiology) and John Welsh Cardiovascular Diagnostic Laboratory, Baylor College of Medicine, Texas Children’s Hospital, Houston, Texas

Catheterization-Based Intervention in Low Birth Weight Infants Less than 2.5 kg with Acute and Long-Term Outcome

The number of low birth weight infants with congenital heart disease is increasing and catheterizations may have an increased risk for mortality and morbidity.

Optimizing paced ventricular function in patients with and without repaired congenital heart disease by contractility-guided lead implant.

This study evaluates the concept of optimizing ventricular pacing in regard to functional cardiac response. Lead implant based on physiologic variables of contractility at various sites was performed in patients with and without congenital heart disease (CHD). Since right ventricular apical pacing may adversely alter contractility and myocellular function, septal and outflow tract pacing have been advocated. However, there are few studies in the young and essentially none in those with CHD.

CT Artifact Mimicking Pulmonary Embolism in a Patient with Single Ventricle

A 16-year-old male with known tricuspid atresia-type IB, who had previously undergone a lateral tunnel Fontan palliation presenting with chest pain, was referred to our hospital with massive pulmonary embolism (PE) based on computed tomography (CT) scan findings of a filling defect in the area of the superior vena cava (SVC) and pulmonary arteries with a SVC clot (Fig. 1). The CT scan was performed on a two-slice Siemens/Emotion Duo Isovue 300 scanner with standard protocol for PE with deep vein thrombosis. At our hospital, the patient’s CT scan was reviewed by experienced pediatric radiologists who concurred with the findings. He underwent a cardiac catheterization that revealed normal Fontan hemodynamics. The angiograms revealed a widely patent lateral tunnel and SVC communication to the pulmonary arteries, with no filling defects within the SVC, lateral tunnel, or branch pulmonary arteries (Fig. 2). The distal pulmonary arteries and pulmonary venous return appeared normal. The patient was discharged the next day in stable clinical condition with a diagnosis of noncardiac chest pain. Fontan palliation is a multiple-stage surgical reconstruction culminating in diversion of systemic venous return to the pulmonary arteries, which is performed in the setting of single ventricle physiology. Central venous (3%– 16%) and intracardiac (17%–20%) thromboses are a major cause of morbidity and mortality after Fontan palliation (both early and late) [1]. Low-velocity and nonlaminar flow patterns in the Fontan circuit, atrial arrhythmias, abnormal liver functions, protein-losing enteropathy, and coagulation abnormalities have been described as etiologic factors causing thromboembolism [2]. Until recently pulmonary angiography has been the ‘‘gold standard’’ for diagnosing PE, but it is not readily available, is invasive, and delivers a high radiation dose. CT is evolving as the test of choice for diagnosing PE. Single-slice CT exceeds 95% sensitivity and specificity for detection of emboli in the main, lobar, and segmental pulmonary arteries; however, it is unable to reliably detect emboli limited to subsegmental or smaller vessels [3]. Multidetector (MD) CT has improved the sensitivity and specificity of detection not only of PE, but also of indirect signs of detection of PE and alternative diagnoses; MDCT has also reduced acquisition times, reduced respiratory and cardiac motion artifacts, and is noninvasive. In one study MDCT had an accuracy of 91% in the depiction of suspected acute PE when conventional pulmonary angiography was used as the reference standard [4]. The factors leading to misdiagnosis of PE on a CT scan include patientrelated, technical, anatomical, and pathologic factors [5]. Gadolium-enhanced magnetic resonance angiography is a noninvasive technique that involves no ionizing or iodinated contrast agent and has a good sensitivity and specificity to provide the correct diagnosis [3]. This case illustrates that the sluggish, nonpulsatile, lowvelocity blood flow seen in the Fontan circuit can cause misdiagnosis of PE on a CT scan. In the setting of a single ventricle physiology, MDCT, with particular attention to optimizing scanning technique, contrast injections, and understanding the physiology and anatomy, can be diagnostic. However, there have been no data available suggesting that MDCT protocols need to be revised for patients with sluggish, low-velocity blood flow as seen in the Fontan circuit. If these modalities are unavailable, H. R. Singh (&) T. J. Forbes R. A. Humes Division of Cardiology, The Carman and Ann Adams Department of Pediatrics, Children’s Hospital of Michigan, Wayne State University School of Medicine, 3901 Beaubien Street, Detroit, MI 48201, USA e-mail: hsingh6@dmc.org