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New Emirates Medical Journal

Volume 1, 2 Issues, 2020
ISSN: 0250-6882 (Online)
This journal supports open access

Open Access Article

A Case of 2:1 Atrio-Ventricular Block- Unraveled by Exercise Testing

Sharada S. Kalavakolanu1, *, Madan M. Balakrishnan1, Deepesh Venkataraman1
1 Department of Cardiology, MGM Healthcare, Aminjikarai, Chennai, Tamilnadu, India

Graphical Abstract:


We present a case of a 75-year-old lady with effort intolerance and baseline ECG showing 2:1 atrioventricular block, in whom it was unclear as to the requirement of permanent pacing, even after long term ECG monitoring. She underwent a treadmill test during which her QRS became wide and developed complete heart block within 2 minutes of the test. Thus, a simple exercise test confirmed the level of the block to be infra nodal without the need for the invasive study. In patients with exertional symptoms, even in elderly, and in those where ECG masquerades as a benign entity, exercise testing is useful to differentiate benign cases of atrioventricular block from the more serious cases that mandate pacemaker implantation.

Keywords: Atrioventricular block, Complete heart block, Exercise test, Intra-Hisian block, Infra nodal, Coronary angiogram.

Article Information

Identifiers and Pagination:

Year: 2020
Volume: 1
Issue: 2
First Page: 57
Last Page: 60
Publisher Id: nemj-1-57
DOI: 10.2174/0250688202002022001

Article History:

Received Date: 17/10/2019
Revision Received Date: 01/02/2020
Acceptance Date: 10/02/2020
Electronic publication date: 15/07/2020
Collection year: 2020

© 2020 Kalavakolanu et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: ( This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Cardiology MGM Healthcare, Nelson Manickam Road, Aminjikarai, Chennai, Tamilnadu, 600029, India; Tel: +91 44 45242444; E-mail:


Intra-Hisian atrio-ventricular (AV) block associated with 2:1 conduction is an uncommon phenomenon, but it is important for the development of complete AV block [1]. A 2:1 Atrio-Ventricular (AV) block with narrow QRS complexes, presents a diagnostic challenge as to the level of block, whether a benign entity of Mobitz Type I (Wenckebach) or more sinister form of Mobitz Type 2 block necessitating permanent pacing. This confirmation usually requires invasive workup of the cardiac conduction system by an electrophysiological study. We discuss a case of an elderly lady with exertional breathlessness presenting with 2:1 AV block having narrow QRS conducted beats, in whom a simple exercise test unraveled site of the block to be within the His bundle confirming the requirement for permanent pacing.

1.1. Patient Information

A 75-year old lady presented to the cardiology services of our hospital with complaints of exertional dyspnea and fatigue of 6 months duration, progressively limiting her activities but was comfortable at rest. She was a known hypertensive for the past 10 years on dihydropyridine calcium-channel blocker -amlodipine, 5mg once daily with fair control of her blood pressures.

1.2. Diagnostic Assessment

Her echocardiogram showed normal biventricular systolic function, moderate mitral regurgitation due to valve prolapse. Her blood tests, including electrolytes, lipid profile, cardiac biomarkers and thyroid function tests were within normal limits. As her baseline ECG showed dropped beats due to 2 to 1 atrioventricular conduction, she underwent 4-day Holter monitoring, which showed many asymptomatic episodes of second-degree AV block. This included episodes of Wenckebach block (Fig. 1A) as well as many episodes of 2:1 AV block (Fig. 1B) with narrow QRS, in which the level of conduction block was unclear. In view of her age and symptoms of effort intolerance, she underwent coronary angiogram which was normal. She then was subjected to a treadmill exercise test, during which within 2 minutes of modified Bruce protocol, there was chronotropic incompetence with progressive QRS widening of right and left bundle branch block pattern and then to complete heart block. (Fig. 2A and B).

1.3. Therapeutic Intervention

She was diagnosed as Intra Hisian AV block and underwent an uneventful dual-chamber pacemaker implantation.

1.4. Follow-up and Outcome

Over a short-term follow up of six months, she remains symptomatically improved with intermittent ventricular pacing dependence.

Fig. (1A)
Holter showing second degree, mobitz type 1 atrio-ventricular block.

Fig. (1B)
Holter showing 2:1 AV block.

Fig. (2A)
Exercise testing 2min: Widened QRS with right bundle block and left bundle block pattern.

Fig. (2B)
Exercise testing -recovery stage: Complete heart block with narrow QRS escape rhythm.


Intra-Hisian 2:1 AV block is a relatively rare entity. Our patient on Holter had many episodes of Wenckebach block as well as many episodes of 2:1 AV block, all with narrow QRS rhythm. AV block can occur at Supra-Hisian, Intra-Hisian and Infra-Hisian levels [3, 4]. Supra-Hisian block occurs due to AV nodal disease, usually presents with a narrow QRS escape rhythm of 40-60 Beats Per Minute (BPM), responsive to exercise and drugs, and is stable without abrupt deceleration in ventricular rates [3, 4]. Infra-Hisian AV block presents with unreliable wide QRS escape rhythm at <40 BPM, is unresponsive to exercise or drugs, and causes Stokes-Adams episodes necessitating emergency pacing [3, 4]. AV block due to disease within His bundle in early stages can present with QRS that is narrow in conducted beats but is unresponsive to drugs; when stressed with increasing atrial rates due to exercise or catecholamines or atropine, His bundle and branches conduct more slowly so that there is paradoxical slowing of heart rates with widening of QRS complexes [2-4]. One case report describes the occurrence of increasing right bundle branch block occurring in an elderly 78-year old male on exercise testing [5]. When the PR interval in conducted beats is >160ms, the level of block is likely to be supra-Hisian [3, 4], but as seen in our patient, the PR interval not only was more than 200ms but there was Wenckebach block despite having an infra-nodal disease. Intra-Hisian block can present rarely as Mobitz Type I with progressive PR prolongation [2], but more commonly presents as abrupt drop in QRS complexes. While Intra-Hisian AV block masquerades as supra-Hisian (AV nodal) block because the QRS is narrow, it behaves functionally like Infra-Hisian block which manifests as an unstable rhythm with wide QRS, unresponsive to drugs and exercise, leading to Stokes Adams episodes and even death, unless treated with ventricular pacing.


A 2:1 AV block with narrow QRS in conducted beat, offers a diagnostic challenge as to the level of block and need for a permanent pacemaker. Our patient had progressive QRS widening with subsequent complete heart block on low-level exercise testing, and hence we postulate that she was an unusual case of Intra-Hisian second degree 2:1 AV block presenting both as Mobitz Type 1 and Type 2 conduction abnormalities. In such a situation, when a patient’s symptoms are effort-related, a low dose exercise test performed even in an elderly population helps in reaching correct diagnosis without invasive electrophysiological testing.


Not applicable.


Not applicable.


Informed consent of the patient had been obtained for this case report.


CARE guidelines have been followed in this case report.




The authors declare no conflict of interest, financial or otherwise.


Declared none.


[1] Ishikawa T, Sumita S, Kikuchi M, Nakagawa T, Ogawa H, Hanada K, et al. Long-term follow-up in patients with intra-hisian atrioventricular block. J Artif Organs 2000; 3: 149-53.
[2] Lee YS, Kim SY, Kim KS, Kim YN. Intra-His bundle block in second-degree Mobitz I atrioventricular block with right bundle branch block. Europace 2009; 11(9): 1251-2.
[] [PMID: 19542538]
[3] Josephson ME. Clinical Cardiac Electrophysiology: Techniques and Interpretations 3rd ed. 2001.
[4] Issa ZF, Miller JM, Zipes DP. Clinical arrhythmology and electrophysiology: A companion to Braunwald’s heart disease 1st ed. 2009.
[5] Singh S. The mischievous bundle: A case of varying degrees of right bundle branch block on alternate beats during exercise stress testing. Ann Noninvasive Electrocardiol 2013; 18(3): 299-303.
[] [PMID: 23714091]


Abdullah Shehab
Emirates Cardiac Society
Emirates Medical Association

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