Junctional ectopic tachycardia evolving into complete heart block

Abstract

Transition from congenital junctional ectopic tachycardia to complete AV block was observed in an 8 month old girl, over a 36 hour period, during initial hospital admission. Two years later she had evidence of a rapidly increasing left ventricular end diastolic diameter, associated with lowest heart rates during sleep of < 30 beats/min. A transvenous permanent pacemaker was therefore implanted. This finding supports the idea that a pathological process in the area of the AV junction, initially presenting as junctional ectopic tachycardia may later extend to sudden complete atrioventricular block. (Heart 1998;80:627-628) Keywords: junctional ectopic tachycardia; heart block; congenital heart disease; paediatrics Junctional ectopic tachycardia (JET) is one of the rarest forms of supraventricular tachycardia in infancy. The mechanisms of termination of the congenital form of JET are unclear from most clinical series.1 2 Histological studies have shown His bundle degeneration and Purkinje cell tumours as well as fibroelastosis.3 Progression to complete atrioventricular block has been proposed, 3 but has not been described in the clinical setting. We present a girl who presented with JET at the age of 8 months who went into complete AV block during hospital admission 36 hours later. Case reportAn 8 month old girl presented to her local hospital after a period of crying, apnoea, and cyanosis at home. After stimulation she had recovered fully but at the hospital tachycardia was noted at a frequency of 230 beats/min. The ECG at admission showed a regular, narrow QRS complex tachycardia with AV dissociation consistent with the diagnosis JET (fig 1). Echocardiography showed an anatomically normal heart with decreased contractility (shortening fraction 15%) and left ventricular dilatation, suggesting longstanding tachycardia. Intravenous adenosine was ineVective, and digoxin was started (10 µg/kg at 8 hourly intervals). Thirty six hours later she exhibited complete AV dissociation with QRS rate of 100 beats/min (fig 2), and was discharged from hospital. At follow up ventricular function had normalised within three months (shortening fraction 38%). Two years later digoxin was discontinued. Routine Holter recordings at follow up showed no episodes of tachyarrhythmia and she was asymptomatic. At the age of 2 years and 8 months, she had evidence of a rapidly increasing left ventricular end diastolic diameter, associated with lowest heart rates during sleep of < 30 beats/min. A transvenous permanent pacemaker was therefore implanted.

Use of a Modified, Commercially Available Temporary Pacemaker for R Wave Synchronized Atrial Pacing in Postoperative Junctional Ectopic Tachycardia

“…Atrial pacing may restore AV synchrony in a subset of patients with JET at the price of a slightly higher heart rate. However, as observed in this and other reports, 6 impaired AV conduction is frequently revealed after institution of atrial pacing. An attempt on AV resynchronization by atrial pacing is then impossible and results in first‐ or higher degree AV block.…”

Intrahisian Conduction Disease and Junctional Ectopic Tachycardia

“…JET is considered a rare arrhythmia presenting at the ECG with narrow ventricular complexes, AV dissociation, and QRS morphology resembling that of sinus beats 1–18 . Invasive electrophysiology has demonstrated that each ventricular electrogram is preceded by a “leading” His bundle deflection with an HV interval that has to be compatible with ante grade conduction (> 35 ms) 1–3,14,15 …”

“…Some authors underlined the importance of His bundle fibers extensive disruption or focal degeneration and split, 3,19 while others described structural abnormalities of the whole AV junction 20 . A recent report of a congenital JET evolving into complete AV block supported the idea of a progressive disease involving the AV junction that had manifested in different ways 11 . Whatever the pathological background, JET may be more commonly encountered in pediatric patients, occurring as a postoperative complications of surgical interventions that involve interventricular septum manipulation or cause damage to the AV conduction system 6 .…”

“…Junctional ectopic tachycardia (JET) is an uncommon arrhythmia mostly observed in pediatric patients, presenting as a congenital or postoperative form 1–13 . Its incessant nature is responsible for a poor prognosis even when JET is occasionally observed in adulthood 14–16 …”

Whole exome sequencing identifies the TNNI3K gene as a cause of familial conduction system disease and congenital junctional ectopic tachycardia

“…The mother has subsequently developed symptomatic palpitations and shows electrocardiographic features consistent with typical atrioventricular nodal re-entrant tachycardia (AVNRT) on symptom-rhythm correlation observed on loop recorder. Thus, the conduction defects in this family were of varying severity and the relationship to congenital JET in the three children is important as it is well recognized that congenital JET may progress to heart block [1,2]. At this stage the conduction abnormalities are minor in the twins who presented with the JET and have not progressed.…”