Cannon, Bryan C.

Cundiff, Nicholas M.

Robinson, Jeffrey A.

Snyder, Christopher S.

English

University of Nebraska Medical Center Research: DigitalCommons@UNMC

University of Nebraska Medical Center DigitalCommons@UNMC Journal Articles: Pediatrics Pediatrics 2018 Atrioventricular Junctional Tachycardia with Exit Block in an Adolescent Nicholas M. Cundiff Heritage College of Osteopathic Medicine Jeffrey A. Robinson University of Nebraska Medical Center, jeffrey.robinson@unmc.edu Bryan C. Cannon Mayo Clinic Christopher S. Snyder Case Western Reserve University School of Medicine Tell us how you used this information in this short survey. Follow this and additional works at: https://digitalcommons.unmc.edu/com_peds_articles  Part of the Pediatrics Commons Recommended Citation Cundiff, Nicholas M.; Robinson, Jeffrey A.; Cannon, Bryan C.; and Snyder, Christopher S., "Atrioventricular Junctional Tachycardia with Exit Block in an Adolescent" (2018). Journal Articles: Pediatrics. 33. https://digitalcommons.unmc.edu/com_peds_articles/33 This Article is brought to you for free and open access by the Pediatrics at DigitalCommons@UNMC. It has been accepted for inclusion in Journal Articles: Pediatrics by an authorized administrator of DigitalCommons@UNMC. For more information, please contact digitalcommons@unmc.edu. Atrioventricular junctional tachycardia with exit blockin an adolescentNicholas M. Cundiff, DO,* Jeffrey A. Robinson, MD,† Bryan C. Cannon, MD, FHRS,‡Christopher S. Snyder, MD, FAAP, FACC†From the *Centers for Osteopathic Research and Education, Heritage College of Osteopathic Medicine,Athens, Ohio, †The Congenital Heart Collaborative, Rainbow Babies and Children’s Hospital, CaseWestern Reserve University School of Medicine, Cleveland, Ohio, and ‡Division of PediatricCardiology, Mayo Clinic, Rochester, Minnesota.IntroductionAtrioventricular (AV) junctional tachycardia is an abnormalrhythm that arises from a focus of enhanced automaticitywithin or adjacent to the His bundle or AV junction.1,2This dysrhythmia is often described as arisingidiopathically or postoperatively.3 Exit block is defined asthe failed electrical propagation of an impulse, generatedby any cardiac pacemaker, into the surrounding myocar-dium.4Here we report the case of an otherwise healthy adolescentfemale who presented with a history of vasovagal syncope.Independent of symptoms, the patient had what seemed tobe intermittent episodes of advanced, second-degree AVblock. Medical evaluation identified a final diagnosis of idio-pathic AV junctional tachycardia with exit block that wassuccessfully managed with flecainide and eventually curedwith cryoablation. This arrhythmia has not previously beendescribed in a pediatric patient.Case reportA 17-year-old, healthy Caucasian girl presented with a 2-yearhistory of post–exercise-related palpitations, shortness ofbreath, and chest tightness. Episodes lasted up to 45 minutesand resolved with rest. An ambulatory heart rhythm monitor(ZIO XT Patch, iRhythm Technologies, Inc, San Francisco,CA) showed sinus rhythm during symptoms. Independently,episodes of second-degree (Mobitz type I) AV block as wellas advanced, second-degree AV block with asymptomaticpauses in AV conduction lasting up to 4.8 seconds occurred(Figure 1).The patient was admitted to the hospital telemetry unit forevaluation and management of AV block. Workup revealed anormal physical examination, vital signs, and 15-lead elec-trocardiogram (ECG). Results of a laboratory panel revealednormal serum electrolytes, complete blood count, erythrocytesedimentation rate, antinuclear antibody panel, Lyme anti-body panel, and streptolysin O antibodies. Transthoracicechocardiography and cardiac magnetic resonance imagingshowed normal cardiac structure and function with no evi-dence of myocarditis. The patient continued to have episodesof advanced, second-degree AV block, particularly duringperiods of startle (awakening by alarm clock). A treadmillstress test revealed sinus rhythm throughout exercise and re-covery, with a peak heart rate of 206 bpm but nodysrhythmia.Because of her conduction system’s response to startle,the patient underwent a 30-minute head-up tilt table test toassess for increased vagal tone. Ten minutes into the tilt,the patient developed symptoms consistent with her chiefcomplaints of palpitations, shortness of breath, chest tight-ness, dizziness along with pallor, and syncope. At thattime, sinus bradycardia (40 bpm) and a decrease in bloodpressure were documented; however, no significant ectopyor arrhythmia was noted on continuous ECG. The patientmaintained normal sinus rhythm with 1:1 AV conductionthroughout the tilt and during recovery.The patient continued to demonstrate frequent episodes ofprolonged advanced, second-degree AV block every day ontelemetry. A dose of atropine 1 mg was administered intrave-nously to inhibit potential elevated vagal tone with no effect.Based on the intermittent character of the advanced,second-degree AV block and the patient’s symptoms duringtilt table test elicited during sinus rhythm, the diagnoses ofAV junctional tachycardia with exit block and concurrentvasovagal syncope were considered. To prove this, the deci-sion was made to initiate flecainide 130 mg/m2/day by mouthdivided twice daily, which was prescribed based on standardadult dosing. By the third dose of flecainide, the patient’stelemetry and ECG monitoring showed normal sinus rhythmwithout episodes of advanced, second-degree AV block. Thepatient was observed for 3 additional days without any symp-toms and was discharged home. Outpatient HolterKEYWORDS Atrioventricular block; Cryoablation; Flecainide; Junctionaltachycardia; Vasovagal syncope(Heart Rhythm Case Reports 2018;4:594–597)Address reprint requests and correspondence: Dr Christopher S. Snyder,Division of Pediatric Cardiology, Rainbow Babies and Children’s Hospital,MS RBC 6011, 11100 Euclid Ave, Cleveland, OH 44106. E-mail address:Christopher.Snyder@UHhospitals.org.2214-0271/©2018PublishedbyElsevier Inc.onbehalf ofHeartRhythmSociety. This is anopenaccessarticle under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).https://doi.org/10.1016/j.hrcr.2018.07.019monitoring identified no episodes of AV junctional tachy-cardia over a period of 1 year. However, she was later foundto be noncompliant with the medication, and the dysrhythmiareturned on subsequent Holter monitoring.The patient was then referred for electrophysiological(EP) study. EP study showed normal intervals at baseline(AH interval 66ms, HV interval 41ms) and decremental con-duction over the AV node (AVWenckebach with rapid atrialpacing at 410 ms, AV nodal effective refractory period 600/310 ms), with no evidence of dual AV nodal physiology. Theabnormal rhythm was not inducible during EP study.A junctional modification was performed, and the ectopicfocus was empirically identified based on previous clinicalexperience. It was localized anatomically by mapping theHis bundle and moving the catheter inferiorly where nofurther His bundle was recognized. Three-dimensional map-ping placed the lesion,5 mm from the His position. A broadcryothermal lesion set was placed in the right inferior input ofthe AV node using a Medtronic Freezor AX 8-mm tip, 9Fcryoablation catheter (Medtronic CryoCath LP, Pointe-Claire, Quebec, Canada). AV nodal conduction propertieswere unchanged after the lesion set as determined by incre-mental atrial pacing and a single atrial extrastimulus. Nocomplications or signs of transient heart block occurred dur-ing the procedure. Flecainide was discontinued, and thepatient was discharged to home the next day. Follow-upover the next year showed no recurrence of AV junctionaltachycardia without flecainide on multiple ambulatory heartrhythm monitors.DiscussionAV junctional tachycardia is an abnormal rhythm that arisesfrom a focus of enhanced automaticity within or adjacent tothe His bundle or AV junction.1,2 This results in a narrowcomplex tachycardia, heart rates that vary from 120–220bpm, and classic signs of AV dissociation.5 This arrhythmiaoften presents with normal sinus P-wave conduction that issubsequently blocked by the ectopic junctional beat. Insome patients, conduction from the junctional focus to theatrium may be seen. P waves, if present, may arise before,during, or after the QRS complex and classically are invertedin the inferior leads (II, III, and aVF) and upright in aVR.3,6AV junctional tachycardia can be described based onetiology (idiopathic and postoperative) or timing(paroxysmal and nonparoxysmal). In the pediatricpopulation, junctional tachycardia presents in 3 forms:congenital, postoperative, or an “adult” form.3Exit block is the failed electrical propagation of animpulse, generated by any cardiac pacemaker, into the sur-rounding myocardium.4 Exit block is described as type I,or Wenckebach, with a progressive delay in conductionthat is apparent by grouped beating or a decreasing P-P(atrial) or R-R (junctional or ventricular) interval before theblocked beat; or type II, which is characterized by a blockedbeat that occurs in the absence of preliminary signs with alength that is a multiple of the basic interval. ECG diagnosisof an exit block is based on intermittent P-P interval prolon-gation in multiples (doubling, tripling, etc) of the normal P-Pinterval.7Nonpostoperative AV junctional tachycardia with exitblock in the pediatric population has not been previouslydescribed. Historically, this arrhythmia has been documentedin the elderly population, most commonly associated withdigoxin toxicity or myocardial infarction.4,8–11 One casestudy described this arrhythmia, which occurrednonpostoperatively in the context of normal digoxin levelsand exercise and was successfully managed withpropranolol.12Few cases have strong parallels to our particular case pre-sentation. One report described at 72-year-old previouslyhealthy man with complete AV block and AV junctionaltachycardia with exit block.7 Another report described a52-year-old previously healthy man with a negative workupwho in the absence of digoxin demonstrated on His-bundleelectrogram a junctional ectopic rhythm with exit blockthat blocked the sinus P wave. The patient was successfullymanaged with flecainide 50 mg/day by mouth.13The case presented here exhibited both AV junctionaltachycardia with exit block and vasovagal syncope. Evalua-tion for the arrhythmia included a differential diagnosis ofhigh vagal tone, Lyme carditis, rheumatic fever, myocarditis,lupus, and fibrosis/sclerosis of the conduction system, yet therespective studies were negative. Because of the vague corre-lation of symptoms, the patient underwent a 30-minute head-up tilt test, which reproduced her presenting symptoms butwith maintenance of sinus rhythm and fully conducting allP waves, consistent with vasovagal syncope. We workedthrough the preliminary diagnosis of advanced, second-degree AV block that was suspected; however, the intermit-tent occurrence of the arrhythmia suggested AV junctionaltachycardia with exit block. This diagnosis is consistentwith the recordings shown in Figure 1, which show consis-tent P-wave intervals with intermittent failure to conduct aQRS secondary to junctional extrasystoles with exit block.KEY TEACHING POINTS! Atrioventricular (AV) junctional tachycardia withexit block should be considered in the differentialdiagnosis of an adolescent with intermittentadvanced, second-degree AV block.! Flecainide is useful for the diagnosis and treatmentof AV junctional tachycardia with exit block.! The diagnosis of arrhythmia does not excludeconcurrent vasovagal syncope.Cundiff et al AV Junctional Tachycardia With Exit Block in an Adolescent 595Flecainide, which is contraindicated in patients with AVblock, was found to effectively treat the AV junctional tachy-cardia with exit block. After a year of successful treatmentwith flecainide, the patient started to experience recurrentepisodes of dysrhythmia secondary to noncompliance.Because cryoablation has been shown to effectively treatnonpostoperative junctional tachycardia in the pediatric pop-ulation, an elective cryoablation of the AV junction was per-formed, which successfully treated the dysrhythmia.14,15After the EP study, the patient has shown normal cardiacconduction without episodes of AV junctional tachycardiawith exit block based on multiple ambulatory heart rhythmmonitors recorded over the following year.ConclusionIdiopathic AV junctional tachycardia with exit block is a rarearrhythmia in pediatric patients. In this case, AV junctionaltachycardia exit block was initially resolved by flecainideand definitively treated by junctional modification withcryoablation. Symptoms of vasovagal syncope persistedand were conservatively managed with increased intake offluids and salt.AcknowledgmentsThe authors would like to thank Albert L. Waldo, MD, PhD,for his critical appraisal of this manuscript. The authorswould like to thank Jennifer M. Staley, MLIS, for assistingwith the literature review for this manuscript.References1. Cannon B, Snyder C. Disorders of cardiac rhythm and conduction. In: Allen HD,Driscoll DJ, Shaddy RE, Feltes TF, eds. Moss and Adams’ Heart Disease inInfants, Children, and Adolescents, Including the Fetus and Young Adult, 8thed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013:441–482.2. Page R, Joglar J, Caldwell M. 2015 ACC/AHA/HRS guideline for the manage-ment of adult patients with supraventricular tachycardia: executive summary. JAm Coll Cardiol 2016;67:1575–1623.3. Van Hare G. Supraventricular tachycardia. In: Gillette PC, Garson A, eds. Clin-ical Pediatric Arrhythmias, 2nd ed. Philadelphia, PA: WB Saunders; 1999:113.4. Watanabe Y. Terminology and electrophysiologic concepts in cardiac arrhyth-mias. III. Exit block, entrance block, and protection block. Pacing Clin Electro-physiol 1978;1:498–509.5. Ruder M, Davis J, Edler M, Abbott J, Seger J, Scheinman M. Clinical andelectrophysiologic characterization of automatic junctional tachycardia in adults.Circulation 1986;73:930–937.6. Rosen K. Junctional tachycardia—mechanisms, diagnosis, differential diagnosis,and management. Circulation 1973;47:654–664.7. Mirowski M, Antonopoulos A, Mower M. Exit block around a junctional pace-maker. Chest 1974;65:687–688.Figure 1 Ambulatory electrocardiographic recordings showing (A) the rhythm suspected to be advanced, second-degree atrioventricular (AV) block with postblock AV conduction variability; (B) an episode of second-degree, Mobitz type I AV block; and (C) a rhythm showing the regularity of the P-wave intervals.596 Heart Rhythm Case Reports, Vol 4, No 12, December 20188. Fisch C. Junctional tachycardia with a 2:1 exit block. Cardiol Rev 1999;7:172.9. Barold S, Hayes D. Non-paroxysmal junctional tachycardia with type I exit block.Heart 2002;88:208.10. Kastor J. Digitalis intoxication in patients with atrial fibrillation. Circulation 1973;47:888–896.11. Spodick D. 4:3 Atrioventricular Wenckebach exit block with (probable) Ashmanphenomenon during junctional tachycardia. Am J Geriatr Cardiol 2004;13:285.12. Luca C. Nonparoxysmal AV junctional tachycardia with 2/1 exit block duringatrial fibrillation in the absence of digitalis toxicity. The effect of exercise. MedInterne 1981;19:247–249.13. Shin W, Kim S, Oh Y, Jang S, Kim J, Choi M, Lee M, Seung K, Rho T. Pseudoa-trioventricular block manifesting as a 2:1 atrioventricular block and advancedatrioventricular block because of concealed junctional ectopic impulses. J AmColl Cardiol 2010;56:e17.14. Collins K, Van Hare G, Kertesz N, et al. Pediatric nonpost-operative junctionalectopic tachycardia medical management and interventional therapies. J AmColl Cardiol 2009;53:690–697.15. Pierick A, Muldonado J, Von Bergen N. Junctional ectopic tachycardia localiza-tion and procedural approach using cryoablation. Pacing Clin Electrophysiol2017;40:655–660.Cundiff et al AV Junctional Tachycardia With Exit Block in an Adolescent 597

Atrioventricular Junctional Tachycardia with Exit Block in an Adolescent

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Atrioventricular Junctional Tachycardia with Exit Block in an Adolescent

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