Junctional Ectopic Tachycardia 

Updated: Sep 13, 2016
Author: M Silvana Horenstein, MD; Chief Editor: Stuart Berger, MD 

Overview

Background

Junctional ectopic tachycardia (JET) is characterized by rapid heart rate for a person's age that is driven by a focus with abnormal automaticity within or immediately adjacent to the atrioventricular (AV) junction of the cardiac conduction system (ie, AV node–His bundle complex). It does not have the electrophysiologic features associated with reentrant tachycardia (eg, AV node reentry) because this form of tachycardia does not respond to a single extrastimulus, does not convert with programmed stimulation or cardioversion, and may or may not have ventriculoatrial (VA) dissociation; also, administration of adenosine results in VA dissociation without termination. The QRS is usually normal, and retrograde P waves may be seen in the terminal portion of the QRS.

JET primarily occurs in 2 forms: idiopathic chronic junctional ectopic tachycardia, which is observed in the setting of a structurally normal heart, and transient postoperative junctional ectopic tachycardia occurs following repair of congenital heart disease.

In addition, nonparoxysmal junctional tachycardia is a related but rare pattern of arrhythmia that can be observed in the setting of digoxin toxicity.

For patient education resources, see Heart Health Center, as well as Supraventricular Tachycardia.

Pathophysiology

The pathophysiology of JET is unclear. Postoperative JET is associated with manipulation within the crux of the heart. It is believed to be secondary to trauma, infiltrative hemorrhage, or inflammation of the conduction tissue.[1] The incidence of JET after cardiac surgery is approximately 14%. Specifically, tetralogy of Fallot repair and longer aortic cross clamp times increase the risk of developing postoperative JET.[2] Congenital JET is rare and difficult to control. It is most often incessant, and many patients require multiple antiarrhythmic medications, ablation, and even pacemaker insertion due to resultant complete AV node block.

As implied by the synonym junctional automatic tachycardia, the mechanism may be automaticity. Others have suggested that triggered activity is responsible for this disorder.[3]

The location of the responsible tissue is probably truly ectopic to the primary conduction pathway of the AV junction because JET has been successfully treated by the application of radiofrequency catheter lesions without the production of AV block. Intracardiac mapping shows a normal heart volume interval and VA dissociation, or VA association if VA conduction is present.

Junctional acceleration, albeit at a lesser rate than typical JET, is a recognized phenomenon during and following radiofrequency energy delivery for modification of slow pathway conduction in the therapy of AV node reentry.

Histamine, eosinophil cation protein, or other products of mast cell, eosinophil, or basophil degranulation that are liberated in response to cardiopulmonary bypass have been implicated in the genesis of transient postoperative JET. The relative levels of various cytokines may also play a role. Low magnesium levels have been noted in children who develop JET following cardiopulmonary bypass surgery.

Prognosis

Spontaneous resolution of congenital junctional ectopic tachycardia (JET) has been observed in as many as one third of patients who reach age 1 year. Patients who continue to experience JET may do so at slower rates.

Curative attempts with radiofrequency catheter ablation therapy are probably warranted in patients with uncontrolled JET or if their size and age is sufficient to minimize procedural risks. Nevertheless, permanent AV block is a significant potential risk in the ablation of congenital JET.

Postoperative JET usually subsides after 36 hours without recurrence.

Morbidity/mortality

Although not a frequent type of arrhythmia, JET is one of the most serious and difficult-to-treat supraventricular tachycardias. Rare case reports have suggested that JET may be associated with progression to complete AV block. This does not appear to be the case in postoperative JET and has not been the author's experience in the rare cases of idiopathic JET.

Postoperative JET is usually transient and begins upon rewarming the patient. Its morbidity and mortality relates to the fact that it occurs at an extremely vulnerable period following cardiac surgery, when nodal inflammation and ischemia may be present and ventricular function is often diminished. The additional insults of poor ventricular filling because of tachycardia and the loss of AV sequential contraction are considered to significantly contribute to morbidity and mortality. However, if the JET rate is not too fast or is somewhat faster than the sinus node rate, it can be well tolerated until JET spontaneously subsides.

In a large series of patients with postoperative JET, dopamine use and an age less than 6 months were associated with the development of this tachycardia.[4] However, only 39% of patients required intervention.

Congenital JET occurs in neonates and infants as an incessant tachycardia that usually results in tachycardia-induced cardiomyopathy. Mortality in these patients has been reported to be as high as 34% and may occur secondary to congestive heart failure, sudden onset of ventricular fibrillation, and sudden evolution to paroxysmal complete AV block and as result of proarrhythmic effect of drug therapy and medical interventions.

In fetuses with JET (as well as those with ventricular tachycardia) third-degree AV block should be ruled out.[6]

Age

JET is one of the rarest forms of supraventricular tachycardia in infants. Congenital JET is presumed to be present from birth but may not be identified until months or years later.

Postoperative JET most commonly occurs in younger patients (it was found to occur more frequently in patients younger than 6 mo) but is also known to occur in teenagers and adults after cardiopulmonary bypass surgery.

Epidemiology

Frequency

United States

Postoperative JET occurred in 5.6% of 594 patients who underwent cardiac surgery.[4] JET was seen more frequently with postoperative use of dopamine and in younger patients.

International

In one series, postoperative JET was identified in 7.5% of young patients undergoing Fontan procedures. Another recent series described JET in 10.2% of 874 pediatric patients undergoing cardiopulmonary bypass.[5]

Postoperative JET that required intervention was identified in 1.5% of infants undergoing the arterial switch procedure. It was also seen in 21.9% of patients who had undergone cardiac surgery for tetralogy of Fallot.[1]

 

Presentation

History

In general, postoperative junctional ectopic tachycardia (JET) occurs in the hospital with rapid hemodynamic instability, whereas congenital JET may have a more insidious course before producing signs of congestive heart failure.

Postoperative JET usually begins 6-72 hours following cardiopulmonary bypass surgery for repair of congenital heart lesions. It is usually identified during monitoring in the ICU. A fall in blood pressure and cardiac output usually occurs concomitantly.

The onset of congenital JET is often insidious. The clinical presentation of congenital JET may occur from birth to age 4 weeks. However, sporadic cases of intrauterine tachycardia have been reported in infants who presented with JET at birth. Prolonged moderate tachycardia may not be recognized until myocardial dysfunction and signs of congestive heart failure ensue. Heart rate variability is decreased; the heart rate is very regular except for occasional sinus capture beats.

Physical

Patients with congenital JET present with moderate tachycardia and signs of congestive heart failure. If VA dissociation has occurred, which is usually the case, cannon waves may be present in the jugular venous pulse, and the intensity of the first heart sound varies.

Causes

The speculative causes of postoperative JET are discussed in Pathophysiology. The one fairly uniform finding is a preceding cardiopulmonary bypass surgery.

The cause of congenital JET is unknown. A family history of JET has been reported in 50-55% patients. It appears that patients with the angiotensin-converting enzyme insertion/deletion (ACE D/D) polymorphism have a greater than 2-fold increase in the incidence of postoperative JET. Therefore, it is hypothesized that the renin-angiotensin-aldosterone system plays an important role in the etiology of JET.[7]

Postoperative JET occurs more often after tetralogy of Fallot repair.[8] It has been associated with resection of muscle bundles, increased traction through the right atrium for relief of right ventricular outflow tract obstruction, and with higher bypass temperatures.

The nonparoxysmal form of junctional tachycardia, which may be a triggered arrhythmia, is observed following digoxin overdose.

 

DDx

Diagnostic Considerations

Important considerations

Identify junctional ectopic tachycardia (JET) in a neonate to avoid the potential for development of tachycardia-induced cardiomyopathy and sudden death.

Promptly identify postoperative JET to avoid the potential development of rapid hemodynamic compromise and death.

Special concerns

In patients undergoing surgery for tetralogy of Fallot, avoiding resection and excessive traction of the right ventricular outflow tract may decrease the chances of developing postoperative JET.

Differential Diagnoses

 

Workup

Laboratory Studies

In patients with postoperative junctional ectopic tachycardia (JET), assess serum magnesium levels, electrolyte levels, and lactate concentration.

In patients with other forms of JET, assess serum magnesium, electrolytes, and digoxin levels.

Electrocardiography

Electrocardiography is the single most important test in all forms of JET (see image below).

Lead II rhythm strip of a surface ECG from a patie Lead II rhythm strip of a surface ECG from a patient with postoperative JET. Atrial activity (P) is marked with blue lines and ventricular depolarization (QRS) is marked in red. Note the narrow QRS complexes due to their origin at the AV junction. Also note the dissociation between atrial and ventricular depolarizations where some of the QRS complexes seem to "follow" the P waves. However, this is not possible because the PR intervals are exceedingly short to allow conduction. In addition, some of the P waves fall after the QRS.

Diagnosis of JET is based on the following:

  • QRS morphology is similar to sinus or atrial-conducted beats.

  • JET usually starts gradually (ie, has a "warm-up" pattern).

  • In junctional rhythm with 1:1 retrograde VA conduction, ventricular rate is equal to the atrial rate.

  • In junctional rhythm with retrograde VA dissociation, an irregular ventricular rate may be observed when appropriately timed atrial impulses conduct to the ventricles.

  • An exception to the last 2 patterns described above rarely occurs, when both JET and complete heart block are present.

The response to adenosine can also be used to identify whether the atrium or junction are driving the rhythm; however, this should be performed with care if the patient is severely ill. For example, in JET with 1:1 VA conduction, JET may be difficult to distinguish from other forms of supraventricular tachycardia with AV conduction. In this case, intravenous adenosine may be given to block VA conduction and, thus, help visualize atrial nonparticipation.

Imaging Studies

Chest radiography

Chest radiography is used to assess for ventricular dilatation and dysfunction (when signs of pulmonary edema are present) in all patients with JET.

Echocardiography

Transthoracic echocardiography is also used to assess for ventricular dilatation and dysfunction in all patients with JET.

Transthoracic echocardiography and transesophageal echocardiography may be used to assess for significant postoperative residual hemodynamic abnormalities in patients with postoperative JET.

Procedures

Rarely, cardiac catheterization is required in postoperative JET to assess for significant postoperative residual hemodynamic abnormalities.

Postoperatively, the use of atrial wire recordings to assess P-wave timing can facilitate determination of the diagnosis.

In some patients with 1:1 AV or VA association, whether the rhythm is being driven by the atrium or junction may be unclear. If this occurs, pacing the atrium faster than the intrinsic rhythm and then identifying the origin of the first escape beats following termination of pacing may be helpful.

In JET with 1:1 VA conduction, an atrial premature beat introduced immediately before the expected atrial depolarization does not conduct retrogradely because the origin of the intrinsic atrial depolarization is from retrograde conduction of the JET. However, if it were an atrial tachycardia with first-degree AV block (ie, with 1:1 AV association) a timed atrial premature beat would advance (ie, make it appear earlier in the electrogram) the next ventricular and atrial depolarizations. This would prove that ventricular depolarizations are being conducted from atrial depolarizations and not vice versa.

Histologic Findings

Histologic studies have shown His bundle degeneration, Purkinje cell tumors, and fibroelastosis.

 

Treatment

Medical Care

Congenital junctional ectopic tachycardia (JET) is usually initially treated with antiarrhythmic therapy, with the choice of medication guided by the degree of coexisting ventricular dysfunction. The most appropriate management of asymptomatic infants with "slow" JET (ie, 150 beats per minute [bpm]) is debatable. However, these asymptomatic patients should have close monitoring.

Numerous therapeutic options have been used for the treatment of postoperative JET, including the following:

  • Some propose that management of symptomatic infants with slow JET should consist of digoxin to control symptoms of cardiac failure and antiarrhythmic drugs to control the ventricular rate of the arrhythmia. However, caution should be used because development of ventricular fibrillation or faster tachycardia (≤400 bpm) during progressive digoxin loading has been described in patients with congenital JET and severe cardiac failure.

  • Propafenone has also been effective in preventing or controlling JET in some neonates, especially neonates with slower ventricular rates (approximately 170 bpm).

  • Amiodarone may successfully control ventricular rate. Furthermore, the combination of amiodarone and a class Ic antiarrhythmic drug can be used to reduce the dose of amiodarone. A multicenter study reported that success of intravenous amiodarone is dose-related.[9] However, so are its adverse effects. Therefore, the dose-related risks should be taken into account when treating children with incessant arrhythmias. It has been reported that prophylactic use of amiodarone being started in the operating room at the time of rewarming during cardiopulmonary bypass decreases the incidence of JET.[10]

  • True drug-refractory JET is very rare. Therefore, in patients who fail to respond to a single drug regimen, a second antiarrhythmic agent with different electrophysiological effects may be added.

  • Controlled hypothermia has been relatively effective in reducing JET rate in patients in the immediate postoperative period.[11, 12] These patients are often intubated and can be effectively paralyzed, sedated, and cooled. For refractory cases, adding procainamide has been effective.[13] Other traditional approaches include increase of ventricular preload and reduction of inotropic agents (which are also usually chronotropic) as much as possible.

  • The use of atrial or AV sequential pacing can help to restore AV sequence and cardiac output once the JET rate is reduced.

  • Multiple antiarrhythmic agents have been used and are considered somewhat effective in postoperative JET.

  • Occasionally, atrial high-rate pacing to the point of 2:1 AV block can provide a controlled ventricular response while continuing to suppress the JET focus. This finding suggests a relatively high insertion site of the JET focus into the AV conduction system.

  • Ventricular paired pacing, with or without additional atrial pacing, has been used in rare cases when patients have not responded to other therapies. This technique is potentially dangerous and requires essentially constant monitoring and adjustment by personnel who are extremely familiar with electrophysiologic procedures. During ventricular paired pacing, electrolytes and antiarrhythmic medications should be administered by constant infusions only.

  • A small-case series advocates for radiofrequency catheter ablation for JET if antiarrhythmic drug therapy has failed.[14] Success was safely achieved by plotting the entire His-bundle using a modern navigation system that would permit marking the spot of earliest retrograde conduction during tachycardia, and, later, empirically ablating that spot during sinus rhythm.

  • A study suggested that supplementation with magnesium sulfate during cardiopulmonary bypass reduces the incidence of postoperative JET.[15]

Surgical Care

The primary functions of surgical care in postoperative JET are to correct major residual defects that may be contributing to morbidity, to ensure that atrial-based pacing can be achieved, and to provide extracorporeal life support (ie, extracorporeal membrane oxygenation [ECMO]) if required.

 

Guidelines

Guidelines Summary

In 2015 the American College of Cardiology, American Heart Association and the Heart Rhythm Society (ACC/AHA/HRS) released joint guidelines for the management of supraventricular tachycardia that includes recommendations for the management of junctional tachycardia.[17]  

Acute Junctional Tachycardia

Intravenous beta blockers, diltiazem, procainamide, or verapamil are all reasonable options. (Class IIa; Level of evidence: C-LD)

Treatment of nonparoxysmal junctional tachycardia due to digoxin toxicity or myocardial infarction is focused on addressing the underlying condition. In addition, there is some evidence that beta blockers, intravenous adenosine, or verapamil can terminate an accelerated junctional arrhythmia.

Ongoing Junctional Tachycardia

Treatment options include the following:

  • Oral beta blockers, diltiazem, or verapamil (Class IIa; Level of evidence: C-LD)
  • Flecainide or propafenone in patients without structural heart disease or ischemic heart disease (Class IIb; Level of evidence: C-LD)
  • Catheter ablation when medical therapy is not effective or contraindicated.  (Class IIb; Level of evidence: C-LD)
 

Medication

Medication Summary

The mechanism of junctional ectopic tachycardia (JET) is not well understood, and identifying a specific pharmacologic agent to target the disorder is difficult. Because some experimental forms of junctional tachycardia exhibit a triggered mechanism induced by digoxin toxicity, avoiding digoxin seems reasonable. Nevertheless, digoxin is frequently used in the treatment of JET without apparent adverse effect but with questionable efficacy. Ventricular dysfunction is often prominent in patients with postoperative and congenital JET; thus, calcium channel blockers are usually avoided because of their negative inotropic effects. One case report has documented use of calcium channel blockers with apparent effectiveness. Drugs effective against automatic tachycardias appear to be effective in the treatment of congenital and postoperative JET.

Congenital JET has been successfully controlled with amiodarone, propafenone, or cautious combinations of both medications. Postoperative JET has been successfully controlled with amiodarone, propafenone, procainamide, or moricizine (discontinued from the market in July 2007). Propranolol or sotalol have also been used in the therapy of these rhythm disorders.

Antiarrhythmic agents

Class Summary

These agents alter the electrophysiologic mechanisms responsible for arrhythmia.

Amiodarone (Cordarone)

May inhibit AV conduction and sinus node function. Prolongs action potential and refractory period in myocardium and inhibits adrenergic stimulation.

Before administration, control the ventricular rate and CHF (if present) with digoxin.

Propafenone (Rythmol)

Treats life-threatening arrhythmias. Possibly works by reducing spontaneous automaticity and prolonging refractory period.

Procainamide (Procan, Pronestyl)

Class IA antiarrhythmic used for PVCs, ventricular tachycardias, and supraventricular tachycardias. Increases refractory period of the atria and ventricles. Myocardiac excitability is reduced by an increase in threshold for excitation and inhibition of ectopic pacemaker activity.

Propranolol (Inderal)

Class II antiarrhythmic nonselective beta-adrenergic receptor blocker with membrane-stabilizing activity that decreases automaticity of contractions.

Sotalol (Betapace)

Class III antiarrhythmic agent, which blocks potassium channels, prolongs action potential duration (APD), and lengthens QT interval. Noncardiac selective beta-adrenergic blocker.

Atenolol (Tenormin)

Selectively blocks beta1-receptors with little or no effect on beta2 types.