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Vol. 73. Issue 8.
Pages 664 (August 2020)
ECG Contest
DOI: 10.1016/j.rec.2019.12.017
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Response to ECG, July 2020
Respuesta al ECG de julio de 2020
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Francisco Ribes
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fribestur@gmail.com

Corresponding author:
, Ángel Martínez-Brótons, Ricardo Ruiz-Granell
Unidad de Arritmias, Servicio de Cardiología, Hospital Clínico Universitario de Valencia, Valencia, Spain
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Rev Esp Cardiol. 2020;73:58010.1016/j.rec.2019.12.016
Francisco Ribes, Ángel Martínez-Brótons, Ricardo Ruiz-Granell
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The electrocardiograms show a constant 1:1 A/V ratio. His activation always precedes local ventricular activation and QRS onset, so a ventricular origin can be ruled out1 (response 1, incorrect). Transient narrowing of QRS leads to shortening of the time from activation of the His-Purkinje-ventricular system to the earliest atrial activation (HA interval), showing that the atrial cycle depends on preceding ventricular activation; this rules out atrial tachycardia and intranodal re-entry (responses 2 and 4, incorrect). In view of the above, along with the observation that the time from His-Purkinje-ventricular activation to the first atrial activation (HA) is longer during left bundle branch morphology than with narrow QRS, a hidden left accessory pathway is confirmed to be present.2 Thus, during left bundle branch block, the ventricular circuit is extended and the activation front has to travel through more tissue to reach the atrium (response 3, correct).

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References
[1]
R. García Civera, R. Sanjuan, J.A. Ferrero, et al.
Valor del hisiograma en el diagnóstico diferencial de las taquicardias ventriculares.
Rev Esp Cardiol., 28 (1975), pp. 191-204
[2]
M.E. Josephson.
Preexcitation syndromes.
Clinical Cardiac Electrophysiology., 4th ed., pp. 322-424
Copyright © 2019. Sociedad Española de Cardiología
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