Bertrand A. Ross

Inadvertent Atrioventricular Block During Radiofrequency Catheter Ablation Results of the Pediatric Radiofrequency Ablation Registry

BACKGROUND Inadvertent atrioventricular block is a complication of radiofrequency ablation. The present study is an analysis of the incidence, significance, and factors associated with inadvertent atrioventricular block during radiofrequency catheter ablation in childhood and adolescence. METHODS AND RESULTS The records of the Pediatric Radiofrequency Ablation Registry were reviewed. Between January 1, 1991, and April 1, 1994, atrioventricular block occurred in 23 of 1964 radiofrequency ablations (1.2%): 14 as third-degree block (3 transient) and 9 as second-degree block (5 transient). Atrioventricular block occurred from 5 seconds to 2 months (mean, 4.1 days; median, 15 seconds) after the onset of the energy application. Eight transient cases lasted 1 hour to 1 month (mean, 9.4 days; median, 7 days). Inadvertent atrioventricular block was related to the ablation anatomic site: 3 of 111 (2.7%) anteroseptal, 11 of 106 (10.4%) midseptal, and 2 of 197 (1.0%) right posteroseptal sites (P = .0007) for anteroseptal, P = .0001 for midseptal, and P = .17 for right posteroseptal versus nonright septal sites). Five of 314 (1.6%) ablations for atrioventricular nodal reentrant tachycardia resulted in atrioventricular block (P = .004 versus nonright septal sites). Compared with a matched subgroup, radiofrequency ablation experience was the only significant risk factor (32.7 versus 106.6, P = .002) for the occurrence of atrioventricular block. CONCLUSIONS Inadvertent atrioventricular block may occur during or late after radiofrequency catheter ablation. It is associated with ablations for (1) anterior and midseptal accessory pathways and atrioventricular nodal reentry and (2) relative institutional inexperience.

Mapping and radiofrequency ablation of intraatrial reentrant tachycardia after the senning or mustard procedure for transposition of the great arteries

The Senning and Mustard procedures are often associated with the development of atrial tachyarrhythmias, which may be a cause of sudden death. We hypothesized that atrial surgery creates barriers to impulse propagation, establishing potential routes for atrial reentry, and that mapping combined with knowledge of the surgical anatomy could identify zones that are critical to the tachycardia to be targeted for radiofrequency catheter ablation. Patients underwent mapping to identify early sites of atrial activation that were related to anatomic or surgically created obstacles, with confirmation by pacing to demonstrate concealed entrainment. Radiofrequency lesions were placed to connect these obstacles, while observing for tachycardia termination. Thirteen tachycardias were attempted in 10 patients, 10 successfully. Three patients had 2 distinct tachycardias. Successful sites were in right atrial tissue, although in many, a retrograde approach to the pulmonary venous atrium was necessary. Ablation of the clinically documented tachycardia was successful in 9 of 10 patients. The most common successful site was the region of the coronary sinus mouth, approached antegrade or retrograde. Ablation of intraatrial reentrant tachycardias after the Senning or Mustard procedure is feasible using concealed entrainment mapping techniques, but requires a detailed knowledge of the individual surgical anatomy and the ability to approach the pulmonary venous atrium. Radiofrequency ablation offers significant advantages over other management modalities in this patient group.

The Effect of Exercise on the Atrial Electrogram Voltage in Young Patients

Atrial electrogram sensing is an important function in active individuals with permanently implanted bipolar dual chamber pacing systems. We undertook to determine the effect of vigorous exercise on the atrial electrogram size in 11 children and young adults (average age 12 years). Using a telemetry signal through a handheld programming wand, nine tracings were completely and clearly recorded for analysis. Six patients had tined/passive fixation atrial leads and three patients had screw‐in/active fixation lead systems. All leads were bipolar. The atrial electrogram size for each patient was measured at rest and at each minute of exercise. The atrial electrogram size decreased with exercise from a mean of 5.08 mV to 3.44 mV (range 0.9–4.25 mV) (P = 0.002). The 1.64 mV mean decrease represented a 33.8% reduction (range 19%–56%) (P < 0.001). There was no difference in the change in atrial electrogram size between the two lead types. Treadmill exercise testing with telemetric data of atrial electrograms showed a decrease in atrial electrogram size produced by exercise and may be helpful in determining appropriate atrial sensitivity settings in selected individuals. Because of the documented decrease in atrial electrogram size produced by exercise, we recommend obtaining maximal atrial electrograms at the time of implant and use of pacing systems that allow maximal flexibility in atrial sensing especially in athletically active individuals.

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.

Pharmacokinetics and pharmacodynamics of sotalol in a pediatric population with supraventricular and ventricular tachyarrhythmia

This pharmacokinetic‐pharmacodynamic study was designed to define the steady‐state relationship between pharmacologic response and dose or concentration of sotalol in children with cardiac arrhythmias, with an emphasis on neonates and infants.

Congenital complete atrioventricular block.

The various etiologies, pathologic findings, clinical concerns, and features of congenital complete atrioventricular block are presented and discussed. In addition, prenatal and antenatal diagnostic techniques are explained and analyzed. Lastly, treatment and the issues involved in deciding proper treatment are discussed in such a way that the general pediatrician can help the family to understand and handle the problem.

Ventricular arrhythmias and sudden death in children.

In children, sudden death related to ventricular arrhythmias occurs virtually always in a patient with an abnormal heart. Therefore, children with ventricular tachycardia should be thoroughly investigated by anatomic cardiac catheterization and possibly electrophysiologic study. Sudden death may occur in a patient who had been relatively asymptomatic. This especially occurs in patients after repair of congenital heart disease. The patient may also never have had documented ventricular tachycardia, although most have had at least premature ventricular complexes on a Holter monitor recording. Finally, sudden death related to ventricular arrhythmias can often be prevented with vigorous medical and surgical therapy.

Orthostatic Versus Electrophysiologic Testing in Unexplained Syncope in Children and Adolescents

Orthostatic vs EP Testing in Pediatric Unexplained Syncope. Introduction: Unexplained syncope in the pediatric age group is a common problem that often requires cardiac evaluation. This work‐up is expensive and frequently unrevealing. Electrophysiologic and, more recently, tilt table or orthostatic testing have been used in the evaluation of unexplained syncope.

Acquired atrioventricular block

Abstract Acquired complete atrioventricular block in the pediatric patient is probably less common now than congenital complete atrioventricular block. However, it is not a rare finding. The causes vary from structural to inflammatory and infiltrative abnormalities. Corrected transposition of the great vessels has a 20% to 30% incidence of complete atrioventricular block. This block may develop after birth, and the timing of the development of the heart block varies from individual to individual. Histopathologic findings have detailed an anterior atrioventricular node with a long common bundle, which may be susceptible to ongoing trauma. Post-operative complete atrioventricular block, which at one time had an incidence of 5% to 16% in the early era of corrective surgery for congenital heart disease, now has an incidence of 1% to 4%, depending on the type of surgery. Structural damage from anterior and inferior myocardial infarctions have also been shown to produce heart block, although their occurrence in the childhood population is quite uncommon. Anterior myocardial infarctions appear more likely to produce a permanent complete atrioventricular block compared with an inferior myocardial infarction. Inflammatory or infectious diseases such as myocarditis and Lyme disease have also been associated with acquired heart block in the pediatric patient. This may be either transient or permanent. Rarely, bacterial endocarditis has been associated with complete atrioventricular block. This is generally associated with endocarditis involving the aortic valve. Finally, infiltrative as well as degenerative diseases and traumatic myocardial injury rarely have been found to cause acquired atrioventricular block in childhood.

Catheter Ablative Techniques for Treatment of Patients with Automatic Ectopic Atrial or Junctional Tachycardia

Automatic ectopic tachycardias represent 14% of pediatric supraventricular tachycardia and a somewhat smaller percentage of the adult population [1, 2, 3, 4]. These tachycardias have been shown to result from enhanced automaticity in the atrium or AV junction by catheter electrophysiologic studies.