Nigerian Journal of Cardiology

: 2019  |  Volume : 16  |  Issue : 2  |  Page : 116--119

Regular broad complex tachycardia in a patient with Ebstein's anomaly

Bello Abdullahi Ibrahim1, Mohammed Abdullahi Talle2, Faruk Buba2, Sa'ad Yauba1,  
1 Department of Paediatrics, University of Maiduguri Teaching Hospital, Maiduguri, Nigeria
2 Department of Medicine, Cardiology Unit, University of Maiduguri Teaching Hospital, Maiduguri, Nigeria

Correspondence Address:
Dr. Mohammed Abdullahi Talle
Department of Medicine, Cardiology Unit, University of Maiduguri Teaching Hospital, Maiduguri


Ebstein's anomaly (EA) is an uncommon congenital heart disease characterized by apical displacement of the tricuspid valve and atrialization of the right ventricle (RV). EA is associated with accessory pathways, especially right-sided, often multiple, providing a substrate for supraventricular tachycardia (SVT). Stretching and fibrosis of the right atrium and dysplastic RV provides additional substrates for other atrial and ventricular tachyarrhythmias. Differentiating preexcited antidromic tachycardia from ventricular tachycardia can be quite challenging, especially where there are no cardiac electrophysiology services. We present a case of regular broad complex tachycardia in a 1-year-old child admitted with heart failure.

How to cite this article:
Ibrahim BA, Talle MA, Buba F, Yauba S. Regular broad complex tachycardia in a patient with Ebstein's anomaly.Nig J Cardiol 2019;16:116-119

How to cite this URL:
Ibrahim BA, Talle MA, Buba F, Yauba S. Regular broad complex tachycardia in a patient with Ebstein's anomaly. Nig J Cardiol [serial online] 2019 [cited 2023 Mar 31 ];16:116-119
Available from:

Full Text


Ebstein's anomaly (EA) is an uncommon congenital heart disease characterized by apical displacement of the tricuspid valve (TV) resulting in portion of the right ventricle (RV) becoming atrialized. Accessory pathways are common in EA, occurring in 15%–30% of patients and are often multiple and right-sided, providing a substrate for atrioventricular reciprocating tachycardia.[1] Morphological alteration of the right atrium (RA) from stretching and fibrosis provides additional substrate for atrial fibrillation, atrial flutter, and ectopic atrial tachycardia. The atrialized RV contains right ventricular myocytes (morphologically and electrically), and mechanical stimulation could trigger a ventricular arrhythmia.[2]

EA is associated with Mahaim accessory pathway, a term used to describe pathways characterized by the following: (1) normal baseline QRS or different degrees of preexcitation with left bundle branch block (LBBB) morphology, (2) programmed atrial pacing leading to obvious manifest preexcitation following an increase A-V interval along with shortening of H-V interval at shorter pacing cycle length, and (3) right bundle electrogram preceding His-bundle activation during antegrade preexcitation and supraventricular tachycardia (SVT).[3] The electrocardiography (ECG) in Mahaim accessory pathway is unremarkable during sinus rhythm with only subtle abnormalities such as the absence of septal Q-waves in lead I and V6, rS pattern in lead III, and terminal QRS slurring or notching.[4]

Orthodromic atrioventricular reentrant tachycardia typically presents with regular narrow QRS complex tachycardia. The less common antidromic atrioventricular reentrant tachycardia can result in QRS complex tachycardia. Mahaim accessory pathways could result in intermittent LBBB or SVT with LBBB morphology and superior axis. Atrial flutter, ectopic atrial tachycardia, and atrial fibrillation with aberrant conduction or bundle branch block and ventricular tachycardia (VT) are other causes of broad complex tachycardia. We present a case of regular broad complex tachycardia in a child with EA and heart failure. This case illustrates the challenges in differentiating VT from antidromic atrioventricular reentrant tachycardia and SVT with aberrant conduction, especially in EA where the substrate for either (or both) exists.

 Case Report

A 1-year-old girl was brought to the emergency pediatric ward with fever, vomiting, and shortness of breathing. She had no premorbid history of cardiorespiratory dysfunction. Physical examination revealed a distraught child with marked respiratory distress and SpO2 of 90%. The pulse was thready with a blood pressure of 60/40 mmHg. Precordium was hyperactive with apex in the fifth left intercostal space and a summation gallop. There was a holosystolic murmur of 4/6, loudest at the left mid sternal edge. The liver was soft, tender, and 2 cm below the right costal margin. There was a bronchovesicular breath sounds with bilateral basal crepitations.

12-lead ECG revealed regular tachycardia with LBBB morphology and superior axis (−75°). The QRS complexes showed negative concordance across the precordial leads [Figure 1].{Figure 1}

Direct current (DC) cardioversion was promptly carried out using single dose of 50J which resulted in restoration of sinus rhythm [Figure 2] and improvement in clinical and other hemodynamic parameters. The postcardioversion ECG showed sinus tachycardia with QSR axis of +150° (right-axis deviation), Himalayan P-waves consistent with marked RA enlargement, deep Q-waves in leads II, III, and aVF, and loss of septal Q-waves in leads I and V6(features consistent with Mahaim accessory pathway). The P-R interval was 120 ms (normal), and there was no delta wave or obvious fragmentation of the QRS complex.{Figure 2}

Transthoracic echocardiography revealed markedly dilated RA with apical displacement of the septal leaflet of the TV and reduction in the size of the functional RV due to atrialization [Figure 3]. There was torrential tricuspid regurgitation, but no other congenital anomaly was observed. Chest X-ray revealed marked cardiomegaly. Serum electrolytes and blood urea nitrogen were within normal limits. Thyroid function test was not done.{Figure 3}

A diagnosis of EA and Mahaim tachycardia was made and the child was placed on conventional treatment for heart failure under the care of the pediatrician.


This case illustrates the occurrence of a hemodynamically compromising cardiac arrhythmia in a patient with EA and the difficulties associated with differentiating VT from SVT as a cause of regular broad complex tachycardia. Accessory pathways are common in patients with EA, particularly right-sided pathways of the Mahaim type, but also WPW pattern, providing a substrate for SVT. In addition, patients with EA are prone to other atrial tachyarrhythmias as well as VT from atrialized portion of the RV composed of morphologically and electrically right ventricular myocytes. We considered three potential differential diagnoses for the regular broad complex tachycardia in this patient, namely: antidromic SVT resulting in Mahaim tachycardia, VT, and atrial flutter with conduction over Mahaim accessory pathway.

Antidromic atrioventricular reentrant tachycardia over a Mahaim accessory pathway presents with broad complex regular tachycardia with LBBB morphology and a superior axis, similar to the presentation in this case [Figure 1]. Tachycardia with LBBB morphology and at the rate of 134–270 beats/min, QRS 0 to −75°, QRS duration of 0.15 s or less, R-wave in I, rS in V1, and transition zone in V4 is predictive of nodoventricular accessory pathway.[5] Our patient had four of the six criteria. Lending credence to the presence of Mahaim accessory pathways is the normal P-R interval with no features of preexcitation and absent septal Q-waves in lead I and V6 in the sinus ECG.

The morphological RV usurped by RA has the electrical properties of RV myocytes and can generate a VT. The patient's ECG during tachycardia showed negatively concordant QRS complexes in the chest leads with a leftward swing in the electrical axis by 195° from baseline [Figure 1] and [Figure 2]. Other features that may indicate VT with LBBB morphology include notching of the S-wave in V1, slurring of the QRS (beginning of QRS to nadir of the S-wave lasting >70 ms) in V1, and QS or qR complexes in V6. Atrioventricular dissociation, fusion beats, and capture beats are very difficult to demonstrate at high rates and were not convincingly observed.

Atrial flutter is an extremely rare occurrence in patients with Mahaim accessory pathway. There was no report of this occurrence prior to the two cases reported by Bohora[6] The ECG in our patient demonstrated undulating baseline (sawtooth pattern) in lead II consistent with atrial flutter [Figure 1]. Although the rate is commonly 250–350 per min in atrial flutter, it could be higher in children. Atrial flutter can conduct over a Mahaim accessory pathway in antidromic fashion to result in broad complex regular tachycardia. This to the best of our knowledge has not been reported in clinical practice.

In line with the principles of management of hemodynamically compromising cardiac arrhythmias, the patient was successfully restored to sinus rhythm with DC cardioversion using a single shock of 50J. The response to DC cardioversion will not be helpful in determining the actual arrhythmia since all the ones considered will respond to DC cardioversion. However, the sinus ECG showed features suggestive of Mahaim accessory pathway, lending credence to our first consideration of Mahaim Tachycardia. She remained stable in sinus rhythm under the care of the pediatrician.

Discerning the exact diagnosis will require electrophysiology mapping, which will also allow for targeted treatment by ablation. This is currently unavailable in Nigeria, and decisions involving care of patients with cardiac arrhythmias are made purely on clinical grounds reducing many of the diagnoses to probable ones. This limitation characterizes the care of patients with cardiac arrhythmias in Nigeria and most countries of Sub-Saharan Africa.[7]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


1Wei W, Zhan X, Xue Y, Fang X, Liao H, Deng H, et al. Features of accessory pathways in adult Ebstein's anomaly. Europace 2014;16:1619-25.
2Ho SY, Goltz D, McCarthy K, Cook AC, Connell MG, Smith A, et al. The atrioventricular junctions in Ebstein malformation. Heart 2000;83:444-9.
3Katritsis DG, Wellens HJ, Josephson ME. Mahaim accessory pathways. Arrhythm Electrophysiol Rev 2017;6:29-32.
4Sternick EB, Timmermans C, Sosa E, Cruz FE, Rodriguez LM, Fagundes MA, et al. The electrocardiogram during sinus rhythm and tachycardia in patients with mahaim fibers: The importance of an “rS” pattern in lead III. J Am Coll Cardiol 2004;44:1626-35.
5Bardy GH, Fedor JM, German LD, Packer DL, Gallagher JJ. Surface electrocardiographic clues suggesting presence of a nodofascicular mahaim fiber. J Am Coll Cardiol 1984;3:1161-8.
6Bohora S, Dora SK, Namboodiri N, Valaparambil A, Tharakan J. Electrophysiology study and radiofrequency catheter ablation of atriofascicular tracts with decremental properties (Mahaim fibre) at the tricuspid annulus. Europace 2008;10:1428-33.
7Talle MA, Bonny A, Scholtz W, Chin A, Nel G, Karaye KM, et al. Status of cardiac arrhythmia services in Africa in 2018: A PASCAR sudden cardiac death task force report. Cardiovasc J Afr 2018;29:115-21.