His bundle

Author: Doctor Elisabeth Villain1 Creation Date: January 2003

Scientific Editor: Doctor Damien Bonnet

1Service de cardiologie pédiatrique, Hôpital Necker - Enfants Malades, 149 Rue de Sèvres, 75743 Paris Cedex 15, France. [email protected]

Abstract Keywords Disease name and synonyms Excluded diseases Definition Differential diagnosis Clinical description Management Etiology Diagnostic methods Genetic counseling Antenatal diagnosis Unresolved questions References

Abstract Congenital His bundle tachycardia or junctional ectopic tachycardia (JET) is a rare observed in neonates and infants less than 6 months. Tachycardia is due to increased automaticity within the and the His bundle but its etiology remains unknown, although familial cases are frequent. The typical electrocardiogram of JET is characterized by a narrow QRS tachycardia with atrioventricular dissociation and occasional sinus capture beats. The ventricular rate usually ranges from 150 to 350 beats per minute (bpm). JET is a severe arrhythmia causing tachycardia-induced and death when it is undiagnosed or uncontrolled. It is resistant to conventional antiarrhythmic drugs and the most effective antiarrhythmic agent is oral which decreases the rate of JET, resulting in suppression of symptoms and normalization of echocardiography. The treatment has to be maintained until the sinus rhythm becomes faster than the ectopic rhythm, which may take years. Radiofrequency ablation of the His bundle has been proposed in patients who are refractory to antiarrhythmic drugs, but it carries a high risk of . Long-term prognosis of patients with JET is unknown but most patients of those who stopped medical treatment are doing well.

Keywords Supraventricular tachycardia, His bundle tachycardia, junctional ectopic tachycardia, amiodarone, neonatal arrhythmia.

Disease name and synonyms Definition Congenital His bundle tachycardia, congenital Congenital JET was first described as a distinct junctional ectopic tachycardia (JET) entity by Coumel and coworkers in 1875. JET is thought to be congenital since it was noted in Excluded diseases infants less than 6 months. The typical Post-operative junctional ectopic tachycardia electrocardiogram (ECG) of JET is characterized by narrow QRS tachycardia and atrioventricular (AV) dissociation, with sinus P wave wandering

Villain E; His bundle tachycardia. Orphanet encyclopedia, January 2003. http://www.orpha.net/data/patho/GB/uk-JET.pdf 1

through the QRS at a rate slower than the been conducted. Multifocal Purkinje cell tumors junctional rate; there may be occasional sinus have been found in the conduction system of a capture beats. JET with retrograde conduction 13-month-old boy with JET who died of cardiac has also been described. arrest. Histological studies have shown congenital abnormalities of the AV junction and Differential diagnosis left-sided AV bundle. JET with retrograde ventriculoatrial conduction may be difficult to differentiate from a supra- Diagnostic methods ventricular reciprocating tachycardia. In JET with Surface ECG is usually sufficient for diagnosis of retrograde conduction, intravenous adenosine or JET. Intracardiac recordings show that JET adenosine triphosphate will slow down originates in the atrioventricular junction, with a ventriculoatrial conduction, without changing the His bundle potential preceding each ventricular ventricular rate; in reciprocating tachycardia, depolarization with a normal HV interval. The these drugs have no effect on tachycardia or mechanism of JET is determined to be an convert it to sinus rhythm. automatic focus, as rapid atrial or ventricular pacing may temporally overdrive the Clinical description tachycardia, which resumes immediately after JET is a malignant arrhythmia causing cessation of pacing. Cardioversion does not stop tachycardia-induced cardiomyopathy and tachycardia. sudden death when it is undiagnosed or uncontrolled. Patients present with a varying Genetic counseling degree of congestive and a rapid JET was found to be familial in half of the 26 heart rate. In a multicenter study including 26 cases reported by Villain et al. No gene has infants with JET, the heart rate was reported to been identified yet. range from 150 to 350 beats per minute (bpm) with a mean of 230 bpm. Antenatal diagnosis The heart structure of these patients is normal, Cases of JET have been characterized and with a dilated left ventricle and reduced treated in utero in patients with antenatal shortening fraction at echocardiography. tachycardia and cardiac failure. When JET is diagnosed before birth, intrauterine management Management should aim at maintaining adequate cardiac After birth, ventilatory support and treatment of output to postpone the delivery until lung cardiac failure are often necessary. maturation is achieved. Treatment with sotalol JET is known for its resistance to conventional and amiodarone has been reported to slow down antiarrhythmic drugs and its potentially poor the ventricular rate of fetuses with JET. prognosis. Treatment is indicated in children with rapid heart rate symptoms and reduced cardiac Unresolved questions function. The most effective antiarrhythmic agent Etiology of JET remains unknown, as well as the is amiodarone, that should be given orally, with a late prognosis of patients who may have loading dose of 500 mg/m2 during eight days unrecognized His bundle lesions. followed by a maintenance dose of 250 mg/m2. Amiodarone results in slowing down tachycardia, References with a significant decrease of the ventricular rate Bharati S, Moskowitz WB, Scheinman M, et al. within the first days of treatment. The treatment Junctional : anatomic substrate and has to be maintained until the sinus rhythm its significance in ablative procedures. J Am Coll becomes faster than the ectopic rhythm, which Cardiol 1991;18:179-186. may take several years. Successful treatment of Coumel P, Fidelle JE, Attuel P, et al. JET with oral sotalol, propafenone and flecainide Tachycardies focales hisiennes congénitales. has also been reported. Etude coopérative de 7 cas. Arch Mal Cœur Radiofrequency ablation of the His bundle has 1976;69:899-903. been proposed in patients refractory to Coumel P, Fidelle JE, Attuel P, et al. antiarrhythmic drugs, including amiodarone. Risk Tachycardies focales hissiennes congénitales. of atrio-ventricular block is high. Etude coopérative de 7 cas. Arch Mal Coeur 1976;9:899-909. Etiology Garson A, Gillette PC. Junctional ectopic JET is due to increased automaticity within the tachycardia in children: electrocardiography, atrioventricular node and the His bundle but its electrophysiology and pharmacologic response. etiology remains unknown. JET evolving into Am J Cardiol 1979;44: 298-302. complete has been described. Very Janousek J, Paul T. Safety of oral propafenone little correlative pathoanatomical research has in the treatment of in infants and

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Villain E; His bundle tachycardia. Orphanet encyclopedia, January 2003. http://www.orpha.net/data/patho/GB/uk-JET.pdf 3