ECG Pointers: Pediatric Junctional Ectopic Tachycardia (JET)

Author: Rachel Bridwell, MD (@rebridwell, EM Resident Physician, Brooke Army Medical Center) and Lloyd Tannenbaum, MD (Attending Emergency Physician, Brooke Army Medical Center) // Reviewed by: Jamie Santistevan, MD (@jamie_rae_EMdoc, EM Physician, Presbyterian Hospital, Albuquerque, NM); Manpreet Singh, MD (@MPrizzleER, Assistant Professor of Emergency Medicine / Department of Emergency Medicine – Harbor-UCLA Medical Center); and Brit Long, MD (@long_brit , EM Attending Physician, San Antonio, TX)

Welcome to this edition of ECG Pointers, an emDOCs series designed to give you high yield tips about ECGs to keep your interpretation skills sharp. For a deeper dive on ECGs, we will include links to other great ECG FOAMed!

The Case:

You’re rotating through the pediatric ICU covering the night shift.  The nurse comes to you, worried that her patient may be in Ventricular Tachycardia (VTach).  The patient she is concerned about is a 7-day-old male with a past medical history of transposition of the great vessels with an arterial switch operation 12 hours prior. You pull up the telemetry strip and see the following:

Do you think this is VTach?  Could this be something else?

Newborns with heart surgery are at risk for many different rhythm complications.  The most common of which is Junctional Ectopic Tachycardia (JET), occurring in 3.6-10.8% of cases [1].  JET is a common postoperative arrhythmia in children who undergo repairs of congenital heart abnormalities, especially arterial switch operation for transposition of the great vessels. These neonates will be tachycardic, hypotensive, and potentially fussy though after often intubated postoperatively without chest closure and thus vital sign changes will be key. The underlying physiology is thought to be secondary to an insult near the AV node or less commonly the bundle of His where an ectopic focus fires at a rate of 170-300, conducting through the atria and ventricles simultaneously which can cause retrograde conduction or ventriculoatrial dissociation; while this is most commonly seen after arterial switch operations JET can also be seen after Fontan procedures and cardiac transplant [2,3]. JET can be diagnosed on EKG with [1,4]:

• NARROW QRS complexes (can be wide in cases of Right Bundle Branch Blocks)
• Heart rate usually ranges from 170-300 beats per minute
• P waves are INVERTED
• A slower atrial than ventricular rate
• Retrograde ventriculoatrial conduction

This is an example of the narrow complex irregular tachycardia JET from the British Medical Journal, with red arrows pointing out retrograde p waves:

The exact cause of JET is unknown, but it is believed to be trauma to the AV node and bundle of His during surgery.  Risk factors for JET include [1,5,6]:

• Surgeries that involve the Right Ventricular Outflow Tract (especially with Tetralogy of Fallot repairs)
• Young age at repair
• Longer duration on cardiopulmonary bypass
• Longer duration on aortic cross clamp time
• Use of inotropes
• Low serum magnesium

Abdelaziz and Deraz suggest the following stepwise protocol for treating JET [1]:

Step 1: Avoid hyperthermia, optimize electrolytes and bolus magnesium sulfate at 30mg/kg

Step 2: Controlled hypothermia (goal core temp is 35-36 degrees Celsius)

Step 3: Minimize vasopressors if possible

Step 4:  Amiodarone is usually the first line antiarrhythmic drug used for patient with JET who are hemodynamically unstable.  A bolus of 5 mg/kg over 2 hours and then an infusion of 10-20mg/kg/24 hours are the dosing guidelines they suggest.

If the patient is still hemodynamically unstable after these interventions, overdrive pacing, ECMO, radiofrequency, or cryoablation are options for treatment resistant JET [4]. Often, atrial pacing wirings are implanted intraoperatively, which can be helpful for diagnosis and therapeutic treatment of JET [7]. This algorithm is key; in a study of 194 patients undergoing cardiac surgery, 27% experienced JET and 43% of those patients required amiodarone [1].

Of note, the treatment of JET is not standardized.  The above algorithm is just one of the many options available.  A recent study done in Germany, Austria, and Switzerland found that all 30 centers included in the study agreed that the patient needed to be cooled, needed antiarrhythmic drugs, and needed temporary pacing if those measures did not work.  All of the hospitals used amiodarone as their antiarrhythmic of choice.  However, there was significant variation in the timing and order of interventions and in dosing of amiodarone [8].  Aggressive management and termination of JET is crucial as arrhythmia after arterial switch operation and especially JET is associated with increased ICU length of stay and mortality [1,9-10].

Interestingly, neonates only need a QRS duration of 80msec to be considered “wide complex” and adolescents only need a QRS duration of 100 msec.  Initial interpretation of this EKG was JET vs VTach, and pediatric electrophysiology was consulted.  The QRS was determined to be wide which favored VTach, but there was AV dissociation and inverted p waves which favored JET, especially in the setting of his recent open-heart surgery. Further investigation found fusion beats and capture beats, and the diagnosis of VTach was made.

Take Home Points:

-JET is a narrow complex irregular tachycardia, with ventriculoatrial conduction.

-Atrial rates are slower than ventricular and P-waves are inverted in II and III.

-Cool the patients to 35-36C, correct electrolytes, minimize pressors, and then consider anti-arrhythmics.

-Post cardiac surgery neonates are at increased risk of JET and is associated with increased mortality.

-Wide complex tachycardia in neonates occurs at >80 msec.

References:

1. Abdelaziz O, Deraz S. Anticipation and Management of Junctional Ectopic Tachycardia in Postoperative Cardiac Surgery: Single Center Experience with High Incidence. Annals Of Pediatric Cardiology. 2014; 7(1): 19-24.
2. Kaulitz R, Ziemer G, Luhmer I, Kallfelz HC. Modified Fontan operation in functionally univentricular hearts: Preoperative risk factors and intermediate results. J Thorac Cardiovasc Surg. 1996;112:658–64.
3. Manning PB, Mayer JE, Jr, Wernovsky G, Fishberger SB, Walsh EP. Staged operation to Fontan increases the incidence of sinoatrial node dysfunction. J Thorac Cardiovasc Surg. 1996;111:833–9.
4. Cools E, and Missant C. Junctional Ectopic Tachycardia After Congenital Heart Surgery. Acta Anesthesiologica Belgica. 2014; 65(1): 1-8.
5. Andreasen, JB, Johnsen SP, and Ravn< HB. Junctional Ectopic Tachycardia after Surgery for Congenital Heart Disease in Children. Intensive Care Medicine. 2008. May; 35(5) 895-902.
6. Dodge-Khatami, A, Miller, O, Anderson, RH, Gil-Jaurena, JM, Goldman, PA, de Leval, MR. Impact of Junctional Ectopic Tachycardia on Postoperative Morbidity Following Repair of Congenital Heart Defects. European Journal of Cardiothoracic Surgery. 2002. Feb; 21(2): 255-9.
7. George E. Sarris, (Chairperson) (Greece), Christian Balmer, (Switzerland), Pipina Bonou, (Greece), et al. Clinical guidelines for the management of patients with transposition of the great arteries with intact ventricular septum, European Journal of Cardio-Thoracic Surgery. 2017;51(1):e1–e32
8. Michel, M, Herberg, U, Haas, N, Kumpf, M, and Gass, M. Management of Postoperative Junctional Ectopic Tachycardia in Pediatric Patient: A Survey of 30 Centers in Germany, Austria, and Switzerland. European Journal of Pediatrics. September 2017. 176(9). 1217-1226.
9. Decker JA , McCormackJ, CohenArrhythmia management in patients with a common arterial trunk and d-transposition of the great arteries. Cardiol Young. 2012;22:748–54.
10. Shamszad P, Moore RA, Ghanayem N, Cooper DS. Intensive care management of neonates with d-transposition of the great arteries and common arterial trunk. Cardiol Young. 2012;22(6):755-760.