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Junctional Ectopic Tachycardia Workup

  • Author: M Silvana Horenstein, MD; Chief Editor: Stuart Berger, MD  more...
 
Updated: Feb 11, 2014
 

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.

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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.

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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.

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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.

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Histologic Findings

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

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Contributor Information and Disclosures
Author

M Silvana Horenstein, MD Assistant Professor, Department of Pediatrics, University of Texas Medical School at Houston; Medical Doctor Consultant, Legacy Department, Best Doctors, Inc

M Silvana Horenstein, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Medical Association

Disclosure: Nothing to disclose.

Coauthor(s)

Robert Murray Hamilton, MD, MSc, FRCPC Electrophysiologist, Senior Associate Scientist, Physiology and Experimental Medicine, Labatt Family Heart Centre; Professor, Department of Pediatrics, University of Toronto Faculty of Medicine

Robert Murray Hamilton, MD, MSc, FRCPC is a member of the following medical societies: American Heart Association, Canadian Medical Association, Ontario Medical Association, Royal College of Physicians and Surgeons of Canada, Canadian Medical Protective Association, Heart Rhythm Society, Canadian Cardiovascular Society, Cardiac Electrophysiology Society, Pediatric and Congenital Electrophysiology Society, Society for Pediatric Research

Disclosure: Nothing to disclose.

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Hugh D Allen, MD Professor, Department of Pediatrics, Division of Pediatric Cardiology and Department of Internal Medicine, Ohio State University College of Medicine

Hugh D Allen, MD is a member of the following medical societies: American Academy of Pediatrics, American Society of Echocardiography, Society for Pediatric Research, Society of Pediatric Echocardiography, Western Society for Pediatric Research, American College of Cardiology, American Heart Association, American Pediatric Society

Disclosure: Nothing to disclose.

Chief Editor

Stuart Berger, MD Medical Director of The Heart Center, Children's Hospital of Wisconsin; Associate Professor, Department of Pediatrics, Section of Pediatric Cardiology, Medical College of Wisconsin

Stuart Berger, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American College of Chest Physicians, American Heart Association, Society for Cardiovascular Angiography and Interventions

Disclosure: Nothing to disclose.

Additional Contributors

Charles I Berul, MD Professor of Pediatrics and Integrative Systems Biology, George Washington University School of Medicine; Chief, Division of Cardiology, Children's National Medical Center

Charles I Berul, MD is a member of the following medical societies: American Academy of Pediatrics, Heart Rhythm Society, Cardiac Electrophysiology Society, Pediatric and Congenital Electrophysiology Society, American College of Cardiology, American Heart Association, Society for Pediatric Research

Disclosure: Received grant/research funds from Medtronic for consulting.

References
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  15. Manrique AM, Arroyo M, Lin Y, El Khoudary SR, Colvin E, Lichtenstein S, et al. Magnesium supplementation during cardiopulmonary bypass to prevent junctional ectopic tachycardia after pediatric cardiac surgery: a randomized controlled study. J Thorac Cardiovasc Surg. 2010 Jan. 139(1):162-169.e2. [Medline].

  16. Emmel M, Sreeram N, Brockmeier K. Catheter ablation of junctional ectopic tachycardia in children, with preservation of atrioventricular conduction. Z Kardiol. 2005 Apr. 94(4):280-6. [Medline].

 
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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.
 
 
 
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