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21-05-2019 | Rhythm Puzzle - Answer | Uitgave 7-8/2019 Open Access

Netherlands Heart Journal 7-8/2019

Between Scylla and Charybdis

Tijdschrift:
Netherlands Heart Journal > Uitgave 7-8/2019
Auteurs:
H. J. te Kolste, G. J. Kimman, T. Germans, S. A. J. Timmer

Answer

The electrocardiogram (Fig.  1) shows a sinus tachycardia with third-degree atrioventricular block. Two very broad QRS complexes with identical morphology occur with regular intervals (V1 and V2). These complexes are caused by antegrade conduction of consecutive sinus beats a1 and a2 entirely over the accessory pathway, resulting in a fully pre-excited QRS complex. The following sinus beats (a3 and a4) are not conducted due to refractoriness of the accessory pathway and either retrograde invasion of the left posterior fascicle (LPF) by the previous conducted sinus beats or consistent antegrade atrioventricular block. The possibility of an intermittent antidromic circus movement tachycardia seemed less likely, due to strictly regular p‑p intervals. Atrioventricular conduction was improved after administration of isoprenaline (Fig.  2), and resulted in 1:1 conduction of sinus beats alternating between the His-Purkinje system and accessory pathway, the latter QRS complex being slightly narrower than before as a result of fusion with native conduction. Obviously, flecainide was discontinued and the patient was planned for definitive pacemaker implantation prior to electrophysiology studies.
In patients with Wolff-Parkinson-White syndrome, flecainide mainly prolongs the refractoriness of the accessory pathway and is used to prevent atrial tachyarrhythmias (e.g. atrial fibrillation) from rapidly conducting in the presence of a ‘malignant’ pathway [ 1]. However, flecainide may lead to third-degree atrioventricular block, especially in patients with advanced conduction disease. Fortunately for this patient, asystole was presumably averted by preserved atrioventricular conduction over a ‘life-saving’ accessory pathway. We must emphasise that caution is advised prescribing flecainide to patients with pre-existent chronic bifascicular block.

Conflict of interest

H.J. te Kolste, G.J. Kimman, T. Germans and S.A.J. Timmer declare that they have no competing interests.
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://​creativecommons.​org/​licenses/​by/​4.​0/​), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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Netherlands Heart Journal

Het Netherlands Heart Journal wordt uitgegeven in samenwerking met de Nederlandse Vereniging voor Cardiologie en de Nederlandse Hartstichting. Het tijdschrift is Engelstalig en wordt gratis beschikbaa ...

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Rhythm Puzzle – Question

Between Scylla and Charybdis