Indian Pacing Electrophysiol. J. 2003;3(3):143
Congenital Junctional Ectopic Tachycardia:
Presentation And Outcome
Berardo Sarubbi, MD, PhD,
Pasquale Vergara, MD, Michele D’Alto, MD, PhD, Raffaele Calabrò,
MD.
Second University of Naples,
Chair of Cardiology, Division of Paediatric Cardiology, Monaldi
Hospital.
Address for correspondence: Dr. Berardo Sarubbi, Via Egiziaca a
Pizzofalcone 11, 80132 Napoli, Italy. E-mail: berardo.sarubbi@virgilio.it
Introduction
Junctional ectopic tachycardia (JET) is a rare type of supraventricular
arrhythmia. Even if its management has improved in recent years, it
remains a great challenge for the cardiologist. Two are the possible
clinical presentations of this arrhythmia: as a primary idiopathic
disorder during infancy, configuring the so called “congenital” JET, or
more often as a transient phenomenon immediately after surgery for
congenital heart disease, giving rise to
the “post-operative” variety.
The
congenital form, firstly described as a distinct entity by Coumel et
al. in 19761, usually occurs in the first
six
months of life presenting as a persistent sustained form, lasting up to
90% of the time. Its clinical presentation may be dramatic, being
associated
in up to 60% of cases with cardiomegaly and/or heart failure.
Congenital JET is hampered by high mortality. Secondary dilated
cardiomyopathy, ventricular fibrillation and sudden cardiac death have
also been reported 2,3.
Clinical Presentation
Clinical presentation of congenital JET usually ranges from birth to 4
weeks
of age. Sporadic cases of history of intrauterine tachycardia, with
sometimes hydrops fetalis, have been reported in patients who at birth
showed overt
JET 2,4,5.
Usually, high percentage of patients present, at the time of referring,
echocardiographyc evidences of impaired left ventricle function and
clinical signs of congestive heart failure. However, it has been noted
that age of tachycardia presentation is not related to the occurrence
of congestive heart failure or impaired left ventricular function. On
the contrary, clinical status seems related to the ventricular rate at
presentation6.
The
incidence of congenital heart disease in presence of congenital
junctional ectopic tachycardia has been reported sporadic6.
Diagnostic Assessment
The
diagnosis of junctional ectopic tachycardia usually is based on
electrocardiographic evidence of a narrow complex tachycardia (heart
rate ranging from 160
bpm to 300 bpm) and atrio-ventricular dissociation. (Figure 1)
Sometimes, it is possible to observe slight variation of heart rate
during
the 24 hours and irregularity in the RR due to sinus capture beats.
Distinct
P waves can be seen only in the tracing of the patients with slower
heart
rate following drug treatment.
Prenatal diagnosis of JET has been also reported, with the superior
vena cava/ascending aorta Doppler echocardiography approach 4. Doppler wave showed AV dissociation with aortic
ejection occurring at smaller interval than venous retrograde flow due
to atrial contractions and “a” waves occurring at a very short interval
after aortic ejection, during periods of 1:1 AV relationship
tachycardia.
Figure 1: Junctional
ectopic tachycardia : a narrow complex tachycardia with
atrio-ventricular dissociation
Click here to see
enlarged view (203 kb)
Electrophysiological Mechanism
Electrophysiological mechanism of JET is thought to be abnormal
automaticity within the His bundle 7. JET
typically presents a “warming-up” phase at its onset and a
“cooling-down” phase at its termination. It is usually unresponsive to
overdrive pacing or DC shock. When there is
retrograde conduction, adenosine infusion can rule out the diagnosis of
AV reciprocating tachycardia, because of tachycardia cycle lengthening
without
termination of the arrhythmia 8.
Tachycardia is not inducible by programmed stimulation in baseline
status, but can be elicited after sympathetic stimulation with
isoproterenol. Programmed atrial and ventricular stimulation usually
are not able to terminate tachycardia, that can be only transiently
suppressed by atrial and/or ventricular pacing, exhibiting a resetting
curve-response to extrastimuli
during tachycardia.
JET
can coexist with the occurrence of other types of arrhythmias.
Scheinman et al.9 reported the development
of JET after catheter ablation of persistent junctional reciprocating
tachycardia in one patient, but a differentiation between a masking
effect of the latter tachycardia on JET and a procedure related genesis
of JET itself could not be argued.
Familiar occurrence
Even
more interest is attributed to this arrhythmia by the fact that it is a
familiar condition. In a multicenter study, Villain reports a familiar
history of JET positive in 50% of the children2.
In our experience up to three members of the same family (2 sisters, 1
cousin) were affected by JET with a family history of JET recognised in
up to
55.6% of the patients6. These
characteristics suggest a possible Mendelian inheritance but, at the
moment, a specific gene has not been identified.
Outcome
Congenital JET is hampered by high mortality, with up to 34% mortality
rate.
The exact mechanism related to death in congenital JET is still
unclear. Most are sudden death, that has been found also in children
with “well compensated” tachycardia2.
Sporadic case of sudden death has been attributed to a dramatic
evolution to paroxysmal complete AV block (2; 10). Probably, the
dramatic clinical course of these patients is the extreme expression of
the pathological process occurring in the His bundle region, causing
JET in a first time and finally the complete loss of AV conduction.
Necropsy reports underlined the importance of His-bundle fibbers severe
disruption11,12 or focal
degeneration
and split2. In other cases the arrhythmia
has
been attributed to extensive abnormalities involving the whole
atrio-ventricular junction13 or to an
intra-His bundle tumour originating from Purkinje cells14.
Henneveld reported a case of an 8 months old girl affected by a rapid
ventricular rate JET, who developed two years later a complete heart
block with rapidly increasing left ventricular end diastolic diameter10. The patient was not assuming therapy at the
time of the onset of complete heart block.
In
other cases it can not be excluded that a pharmacological treatment can
be responsible of the depression of ventricular excitability, leading
to
a slow unsatisfactory ventricular escape rhythm in case of AV block and
sudden cardiac death. However, in some cases it can not be excluded the
potential proarrhythmic effect of the drugs used to control the
arrhythmia15. In our series, two patients
developed symptomatic non-sustained life-threatening ventricular
tachycardia as a spontaneous desincronization of junctional ectopic
tachycardia, due to a proarrhythmic effect of the combination of used
drugs (Amiodarone + Propafenone and
Amiodarone + Flecainide)6.
Pharmacological Treatment
Treatment is indicated in infants with symptoms, reduced ventricular
function or rapid rates 16,17.
The management of infants with slow JET (less than 150 beats/min)
without symptoms
appear to be debated. However, necessity to monitor accurately these
asymptomatic patients is undoubted. It has been reported a case in
which an asymptomatic patient at birth with junctional ectopic
tachycardia with a ventricular rate of 140 beats/min returned at 6
weeks of age in cardiovascular collapse due to a ventricular rate of
300 beats/min2.
The
pharmacological treatment of JET is hampered by a high rate of
failures. Several drugs have been tested, but a comprehensive analysis
of efficacy has not been performed yet.
The
largest study available is a multicenter study performed in nineties by
European and American teams who reviewed dates of 26 pts treated with
digoxin, propranolol and/or amiodarone 2.
The largest single centre experience of pharmacological treatment has
been recently
reported, with the use of Amiodarone, Flecainide or Propafenone alone
or
in combination6.
Digoxin did not affect ventricular rate in any patients and has been
demonstrated to be not completely safe in patients with congenital JET.
Sporadic cases have been reported in which patients affected by
congenital JET and severe cardiac failure developed ventricular
fibrillation or faster tachycardia (up to 400 beats/min) during
progressive digoxin loading 2.
Amiodarone seems to have the highest response rates: it has been shown
to
be effective alone in decreasing the ventricular rate to less than 150
beats/min in a percentage between 50-70% of the cases 2,6.
Sporadic reports of medical treatment efficacy exist also about
Propafenone (6; 18), Flecainide or Encainide6,19 and Sotalol20.
However, Propafenone has been shown to result particularly effective in
preventing or controlling
the tachycardia only in patients with lower heart rate6.
Other studies have also tested phenytoin, which was able to control
ventricular rate but caused ataxia, ajmaline, which intravenous
infusion was followed by ventricular tachycardia and verapamil which
caused cardiovascular
collapse2.
Personal experience has shown that in those cases not responding to a
single drug regimen, as association of antiarrhythmic agents with
different electrophysiological effects (Amiodarone + a Ic
antiarrhythmic drug) may control otherwise
untreatable congenital JET. Otherwise the association Propafenone or
Flecainide
plus Amiodarone could reduce the Amiodarone dose keeping an high
efficacy
of the pharmacological therapy6.
Recently Dorman et al. have described a protective effect of magnesium
supplementation on JET in paediatric patients undergoing surgery for
congenital heart defects21. This could be
due to the stabilization of the membrane potential and the reduction of
the automaticity, resulting in a low rate of development of the
arrhythmia. Further studies are needed to evaluate the potential role
of magnesium in the treatment of the congenital form of JET.
All
pharmacological therapies are burdened by a high risk of toxicity as
they have to be maintained at high dosage for long time in young
patients.
Congestive heart failure is a frequent complication of JET with high
ventricular rate and its management is even more difficult. In these
cases it has been underlined the negative inotropic effects of
antiarrhythmic drugs and
the limitations in the use of sympathomimetic agents. Isoproterenol,
dopamine, dobutamine and amrinone all increase the JET rate. Sodium
Nitroprusside has to be avoided too, since low blood pressure will
reflexly increase
adrenergic tone.
Non pharmacological treatment
A definitive treatment could be the removal of the arrhythmogenic area.
Surgical His ablation has been attempted in some critical patients,
with contrasting results2. In one case
cautery surgical ablation led to the development of ventricular
tachycardia. Radiofrequency catheter ablation of JET was reported for
the first time in the eighties22,23.
It required, in the first procedures, the elimination of AV conduction
tissue with the following pacemaker implantation. In nineties
radiofrequency catheter ablation technique was able to control the
tachycardia with the preservation of the normal AV conduction9. Lesions were carried out in
the region between the coronary sinus and the anterior septum, moving
progressively anteriorly to a site where a small His deflection was
recorded. In some cases His-bundle localization can be uncommon, in
view of the fact that a His-bundle has been found on the left sided of
the interventricular septum2. Recent
experiences have proven the feasibility of the selective modification
of the AV junction without the complete destruction of the conduction
system even in small children, less than one year old24.
Very
controversial is still the matter of prophylactic pacemaker implant to
prevent sudden death. In the multicenter study2
most part of patients did not undergo to pacemaker implantation, but
four patients with well compensated JET died suddenly and in one of
those a
slow ventricular rate was recorded during the terminal event.
Walsh suggested to evaluate AV conduction with transesophageal
electrophysiological test in all patients with congenital JET and
consider pacemaker insertion only if impaired conduction can be
demonstrated by atrial stimulation, or by the observation of
spontaneous AV block on ECG and Holter monitoring25.
Conclusions
Since JET therapy relay on different medical options, a staged
treatment protocol is advisable: a pharmacological approach should be
tested and carried on, also with a multi drug treatment, while catheter
ablation can
be a definitive option in critically ill patients, when drugs fail or
when tachycardia becomes chronic and the patient is dependent on a
potentially toxic therapy.
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