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SHORT COMMUNICATION
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doi:10.1093/europace/eup450
Online publish-ahead-of-print 26 January 2010
Infra-Hisian block as cause of Wenckebach’s phenomenon in an
asymptomatic middle-aged man
Antonios P. Antoniadis, Nikolaos K. Fragakis*, George C. Maligkos, and George A. Katsaris
2nd Cardiology Department, General Hospital G. Papanikolaou, Exochi, Thessaloniki 57010, Greece
*Corresponding author. Tel: þ30 694 426 7643; fax: þ30 231 330 7676, Email: nfrag@vodafone.net.gr
Received 2 November 2009; accepted after revision 29 December 2009
Figure 1 Twenty-four hour Holter ECG recording. Episodes of Wenckebach-type block with 4:3 conduction ratio as well as
episodes of 2:1 block were revealed. Note the change in QRS morphology which appears clearly prolonged in the last conducted
beat of the Wenckebach sequence.
Published on behalf of the European Society of Cardiology. All rights reserved. &The Author 2010. For permissions please email: journals.permissions@oxfordjournals.org.
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We report the case of a 60-year-old man with asymptomatic sinus bradycardia and Holter recording showing episodes of Wencke-
bach block alternating with episodes of 2:1 block. Electrophysiological testing revealed Infra-Hisian block with progressive prolongation
of the H-V interval resulting in block after H potential. This produced typical Wenckebach-type block on surface electrocardiogram
resembling the clinical one. The patient was successfully treated with permanent dual-chamber pacemaker implantation.
Introduction
Type I second-degree atrioventricular (AV) block (Wenckebach block) is usually regarded as a disease of the cardiac conduction
system at the AV-node level. We describe the case of a middle-aged man with episodes of Wenckebach-type block on surface elec-
trocardiogram (ECG) which was demonstrated to be due to infra-Hisian conduction disturbance.
Case presentation
A previously healthy 60-year-old man was referred to our institution for further investigation of an accidentally discovered asympto-
matic bradycardia. Clinical examination was unremarkable without the evidence of cardiac failure. Initial surface ECG showed sinus
rhythm with bifascicular block (right bundle branch block and left anterior hemiblock) and PR interval within upper normal limits
(185 ms). Routine haematological and biochemical examinations, as well as echocardiographic examination, were normal. The
patient underwent 24-h Holter ECG recording which revealed the presence of Wenckebach-type block with 4:3 conduction ratio
alternating with episodes of 2:1 block (Figure 1). The patient remained asymptomatic throughout the recording. An electrophysiologi-
cal study (EPS) followed, while the patient was in sinus rhythm, in which basic intervals showed a prolonged H-V (103 ms) with normal
A-H interval (Figure 2). Several patterns of intraventricular conduction disturbance were subsequently induced by atrial pacing at rela-
tively slow rates. First, progressive prolongation of the H-V interval resulting in block after H potential was induced by pacing at a cycle
length of 750 ms (Figure 3A). This produced typical Wenckebach-type block on surface ECG with 3:2 conduction ratio resembling the
clinical one (Figure 3B). Slight increase of the pacing rate at a cycle length of 700 ms caused typical Mobitz Type II 2:1 block (Figure 4).
Administration of atropine caused high-degree AV block (Figure 5). The patient was offered permanent dual-chamber DDD-R pace-
maker implantation, without rate response function activated initially. At 6 months follow-up, the pacemaker was functioning as VDD
with a very good chronotropic response on physical activity and the patient remained free of symptoms.
Figure 2 Basic intervals at the beginning of the electrophysiological study. A-H interval was normal, whereas H-V prolonged
(103 ms). Basic cycle length (BCL) was 940 ms. From top to bottom: surface leads I, aVF, V
1
,V
6
, and endocardial recordings
from high right atrium (HRA), His bundle (HIS), and right ventricular apex (RVA).
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Figure 3 (A) Electrophysiological study with pacing at a cycle length of 750 ms. Progressive prolongation of the H-V
interval resulting in block after H potential was induced, producing typical Wenckebach block with 3:2 conduction ratio.
From top to bottom: surface leads I, aVF, V
1
,V
6
, and endocardial recordings from high right atrium (HRA), His bundle
(HIS), and right ventricular apex (RVA). (B) Twelve-lead ECG demonstrating Wenckebach block with 3:2 conduction
ratio induced by atrial pacing.
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Figure 4 Electrophysiological study with pacing at a cycle length of 700 ms causing typical Mobitz
Type II 2:1 block. From top to bottom: surface leads I, aVF, V
1
,V
6
, and endocardial recordings from
high right atrium (HRA), His bundle (HIS), and right ventricular apex (RVA).
Figure 5 High-degree atrioventricular block following administration of atropine. From top to bottom:
surface leads I, aVF, V
1
,V
6
, and endocardial recordings from high right atrium (HRA), His bundle (HIS),
and right ventricular apex (RVA).
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Discussion
As its first description over 100 years ago, Wenckebach block has been regarded as a disease of the cardiac conduction system at the
AV-node level. Infra-Hisian Wenckebach block is rare with only sparse literature reports.
1,2
The present case report adds to these,
suggesting that wide QRS with Wenckebach block on surface ECG may indicate infra-Hisian conduction abnormalities. The pro-
longation of the last conducted QRS of the Wenckebach sequence seen in Holter recording made this assumption even more
likely. An extended H-V interval is almost always associated with abnormal QRS complex as impairment of infra-Hisian conduction
makes the activation of the ventricle less homogeneous. This could explain the clear prolongation of the last conducted QRS of
4:3 Wenckebach sequence (Figure 1) compared with 3:2 sequence produced during atrial pacing (Figure 3B).
This is a group of patients that requires further investigation with EPS,
3
given that Wenckebach block due to infra-Hisian conduction
disturbance carries the same prognostic implications as Mobitz type II block demanding specific treatment.
4
Interestingly, our patient
demonstrated rate-dependent transition of infra-Hisian block from Type I to Type II during atrial pacing, which however was not
observed during the Holter recordings. Previous studies showing that atrial pacing-induced distal His block carries a high-positive pre-
dictive value for the development of complete AV block in patients with bifascicular block support further our decision to proceed to
pacemaker implantation.
5
Conflict of interest: none declared.
References
1. Marijon E, Combes N, Boveda S, Albenque JP. Wenckebach type block on surface ECG due to infra-Hisian location in a patient with repaired tetralogy of Fallot. Europace
2008;10:641–2.
2. Gray R, Kaushik VS, Mandel WJ. Wenckebach phenomenon occurring in the distal conducting system in a young adult. Br Heart J 1976;38:204 – 6.
3. Narula OS, Samet P. Wenckebach and Mobitz type II A-V block due to block within the His bundle and bundle branches. Circulation 1970;41:947 –65.
4. Vardas PE, Auricchio A, Blanc JJ, Daubert JC, Drexler H, Ector H et al. Guidelines for cardiac pacing and cardiac resynchronization therapy. The Task Force for Cardiac
Pacing and Cardiac Resynchronization Therapy of the European Society of Cardiology. Developed in collaboration with the European Heart Rhythm Association. Euro-
pace 2007;9:959– 98.
5. Dhingra RC, Wyndham C, Bauernfeind R, Swiryn S, Deedwania PC, Smith T et al. Significance of block distal to the His bundle induced by atrial pacing in patients with
chronic bifascicular block. Circulation 1979;60:1455 – 64.
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