Pamela S. Ro

A multicenter experience with novel implantable cardioverter defibrillator configurations in the pediatric and congenital heart disease population.

Both slowed and regularized ventricular rate provide hemodynamic benefits to patients with atrial fibrillation and thus constitute a primary therapeutic goal. The return to sinus rhythm obviously reaches this goal and has been the preferred strategy over several decades. Given that recurrence of atrial fibrillation is frequent in the face of both pharmacological and ablation-based invasive therapy, and that side effects may limit their use, rhythm control approaches may frequently fall short of expected clinical benefits. In that situation, rate control becomes the alternate strategy. In fact, a number of recent clinical trials comparing rhythm and rate control strategies consistently reported net benefits of rate control therapy (see1,2 for review). Accordingly, for many patients rate control is becoming the preferred strategy while rhythm control is being targeted when needed and/or possible.1 Rate control is primarily achieved by drug-induced conduction impairment of the AV node. When this approach fails, ablation-induced third-degree AV block coupled with ventricular pacing may be considered.3,4 Several other approaches are currently under scrutiny: ventricular pacing without AV block, slow pathway ablation, gene therapy, and selective ganglionic parasympathetic stimulation.3 The modulation of AV nodal function by cardiac ganglionic stimulation may prove to be of significant value in heart failure patients in whom antiarrhythmic drug-induced depression of ventricular function must be avoided.5-8 An added benefit is that a normal ventricular activation sequence is maintained. Selective ganglionic stimulation combined with ventricular pacing may provide further benefits by achieving a slowed and regularized ventricular rate in spite of persistent atrial fibrillation.9 The Soos et al. study in the current issue10 raises the possibility that ganglionic stimulation may be feasible with currently available pacemaker technology. The concept of rate control through parasympathetic stimulation is derived from pioneering experimental work showing that selective AV node conduction slowing can be achieved through local cardiac nerve stimulation.11-15 Effective parasympathetic ventricular rate slowing during atrial fibrillation has been reached in animals with nerve stimulation applied endocardially in the vicinity of AV node,16 transvenous catheter stimulation from the coronary sinus,5 and local electrical stimulation of inferior interatrial parasympathetic ganglionated plexus.7-10 In humans, transvenous

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.

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.

Rate of inducible ventricular arrhythmia in adults with congenital heart disease

Patients with adult congenital heart disease are at increased risk of ventricular arrhythmia (VA) and sudden cardiac death, although no clear predictors have been found. Ventricular programmed stimulation has been shown to predict clinical ventricular tachycardia and sudden death events, but the role of screening electrophysiology studies (S-EPSs) in this population remains poorly defined. Therefore, we sought to determine the prevalence of inducible VA and to evaluate the clinical predictors in a heterogeneous group of patients with adult congenital heart disease (> or =18 years old) undergoing S-EPSs at preoperative or interventional cardiac catheterization. Studies for the primary evaluation of clinical VA were excluded. The demographic, clinical, and diagnostic findings were compared between the patients with positive and negative findings. From 2005 to 2009, 80 patients (mean age 30 +/- 9 years) underwent S-EPSs, and 23 had inducible VA. The diagnoses for those with studies positive for VA included tetralogy of Fallot (n = 12), d-transposition of the great arteries (n = 6), pulmonary stenosis (n = 2), double outlet right ventricle (n = 1), double inlet left ventricle (n = 1), and Ebsteins anomaly (n = 1). Men were significantly more likely to have a S-EPS positive for VA (p = 0.015). Increasing QRS duration, decreasing peak oxygen uptake (percentage of predicted), and ventricular fibrosis with cardiovascular magnetic resonance imaging were significantly associated with studies positive for VA (p <0.05). Combined fibrosis and a peak oxygen uptake <80% of predicted had 100% sensitivity for positive VA findings. In conclusion, almost 30% of those with adult congenital heart disease undergoing S-EPSs had inducible VA. A prolonged QRS duration, diminished exercise capacity, and the presence of ventricular fibrosis were significantly associated with findings positive for VA and might improve patient selection for screening evaluations.

Managed Ventricular Pacing in Pediatric Patients and Patients With Congenital Heart Disease

Ventricular dyssynchrony induced by ventricular pacing (VP) may predispose patients to congestive heart failure. The detrimental effects of VP are directly related to the cumulative percentage of VP (Cum%VP). Managed VP (MVP) is a novel pacing algorithm developed to minimize unnecessary VP by uncoupling atrial pacing from VP. This retrospective analysis assessed the feasibility of using MVP in pediatric patients and patients with congenital heart disease (CHD). A multicenter review evaluated all pediatric patients <22 years old and older patients with CHD that had an implanted device using a MVP algorithm. Primary outcome variables were Cum%VP and adverse events. A subgroup analysis evaluated patients that had a DDD(R) pacemaker before a MVP device and compared Cum%VP before and after initiation of MVP. From 6 centers 62 patients (mean age 21.5 +/- 9.6 years) were included; 64% had CHD. With a MVP device, mean Cum%VP was 4.3 +/- 14.6% (range 0 to 83.7): Eleven patients were eligible for subgroup analysis. Compared with DDD(R), Cum%VP significantly decreased with MVP (67.1 +/- 29.4% vs 9.2 +/- 24.8%, p = 0.002). One MVP-related adverse event occurred; a patient with intermittent atrioventricular block had symptoms with frequent nonconducted atrial depolarizations and was reprogrammed to DDD. In conclusion, MVP can be used safely and can significantly reduce unnecessary VP in pediatric patients and patients with CHD.

Effects of β-Adrenergic Antagonists on the QT Measurements from Exercise Stress Tests in Pediatric Patients with Long QT Syndrome

It has been proposed that β-adrenergic antagonist protection against cardiac events in patients with long QT syndrome (LQTS) may be related to a decrease in baseline QTc dispersion. To determine the effects of β-blocker therapy on QT measurements, we evaluated the exercise tests of 25 pediatric patients with LQTS. Measurements were made of the maximum QTc interval and QTc dispersion during the various segments of the exercise test. There was no statistically significant difference between the pre-β-blocker and post-β-blocker maximum QTc interval during the supine (0.473 ± 0.039 vs 0.470 ± 0.038 sec), exercise (0.488 ± 0.044 vs 0.500 ± 0.026 sec), or recovery (0.490 ± 0.031 vs 0.493 ± 0.029 sec) phases of the exercise stress test. There was also no statistically significant difference between the pre-β-blocker and post-β-blocker QTc dispersion during the supine (0.047 ± 0.021 vs 0.058 ± 0.033 sec), exercise (0.063 ± 0.036 vs 0.063 ± 0.028 sec), or recovery (0.045 ± 0.023 vs 0.052 ± 0.026 sec) phases of the exercise stress test. Therefore, the protection that β-blockers offer appears not to be related to a reduction of the baseline QTc interval or a decrease of QTc dispersion.

Efficacy of Flecainide in the Treatment of Catecholaminergic Polymorphic Ventricular Tachycardia: A Randomized Clinical Trial

Importance Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a potentially lethal genetic arrhythmia syndrome characterized by polymorphic ventricular tachycardia with physical or emotional stress, for which current therapy with &bgr;-blockers is incompletely effective. Flecainide acetate directly suppresses sarcoplasmic reticulum calcium release—the cellular mechanism responsible for triggering ventricular arrhythmias in CPVT—but has never been assessed prospectively. Objective To determine whether flecainide dosed to therapeutic levels and added to &bgr;-blocker therapy is superior to &bgr;-blocker therapy alone for the prevention of exercise-induced arrhythmias in CPVT. Design, Setting, and Participants This investigator-initiated, multicenter, single-blind, placebo-controlled crossover clinical trial was conducted from December 19, 2011, through December 29, 2015, with a midtrial protocol change at 10 US sites. Patients with a clinical diagnosis of CPVT and an implantable cardioverter-defibrillator underwent a baseline exercise test while receiving maximally tolerated &bgr;-blocker therapy that was continued throughout the trial. Patients were then randomized to treatment A (flecainide or placebo) for 3 months, followed by exercise testing. After a 1-week washout period, patients crossed over to treatment B (placebo or flecainide) for 3 months, followed by exercise testing. Interventions Patients received oral flecainide or placebo twice daily, with the dosage guided by trough serum levels. Main Outcomes and Measures The primary end point of ventricular arrhythmias during exercise was compared between the flecainide and placebo arms. Exercise tests were scored on an ordinal scale of worst ventricular arrhythmia observed (0 indicates no ectopy; 1, isolated premature ventricular beats; 2, bigeminy; 3, couplets; and 4, nonsustained ventricular tachycardia). Results Of 14 patients (7 males and 7 females; median age, 16 years [interquartile range, 15.0-22.5 years]) randomized, 13 completed the study. The median baseline exercise test score was 3.0 (range, 0-4), with no difference noted between the baseline and placebo (median, 2.5; range, 0-4) exercise scores. The median ventricular arrhythmia score during exercise was significantly reduced by flecainide (0 [range, 0-2] vs 2.5 [range, 0-4] for placebo; P < .01), with complete suppression observed in 11 of 13 patients (85%). Overall and serious adverse events did not differ between the flecainide and placebo arms. Conclusions and Relevance In this randomized clinical trial of patients with CPVT, flecainide plus &bgr;-blocker significantly reduced ventricular ectopy during exercise compared with placebo plus &bgr;-blocker and &bgr;-blocker alone. Trial Registration clinicaltrials.gov Identifier: NCT01117454

Congenital superior vena cava obstruction causing anasarca and respiratory failure in a newborn: successful transcatheter therapy.

Superior vena cava (SVC) obstruction is a rare entity in the pediatric population. It usually presents in association with either previous cardiac surgery or external compression from a neoplasm. We present the case of an infant born with congenital SVC obstruction and significant bilateral chylothorax and anasarca necessitating mechanical ventilation. Successful placement of an intravascular stent led to resolution of the chylothoraces with rapid clinical improvement.

Changes in Near-Infrared Spectroscopy and the Bispectral Index During Tilt-Table Examination

The head-upright tilt-table test is an important tool for the diagnosis of vasodepressor or neurocardiogenic syncope. The use of noninvasive near-infrared spectroscopy (NIRS) monitoring and bispectral index (BIS) monitoring during these cases can add another tool to the real-time monitoring and aid in their diagnosis. The authors report their experience using NIRS and BIS monitoring during tilt-table testing to investigate syncope in a 14-year-old adolescent. In this case, changes in the NIRS occurred earlier than changes in either blood pressure or the development of clinical symptoms. The change in the NIRS and BIS values correlated with the patient’s level of consciousness. One major advantage of monitors such as the BIS, and more importantly, the NIRS is that they provide an instantaneous and continuous noninvasive measure of cerebral perfusion.

QRS duration changes in patients with hypoplastic left heart syndrome undergoing hybrid palliation: Prehybrid to post-fontan

QRS prolongation has been shown to be a predictor of mortality in patients with certain forms of congenital heart disease. QRS changes have not been well described in patients with single ventricle physiology, particularly in those undergoing the hybrid procedure.