Transient narrowing of a wide QRS tachycardia. What is the mechanism?

Francisco Ribes; Ángel Martínez-Brótons; Ángel Ferrero-De-Loma-Osorio; Lourdes Bondanza; Cristina Albiach; Víctor Marcos-Garcés; Ricardo Ruiz-Granell

doi:10.1002/joa3.12334

Transient narrowing of a wide QRS tachycardia. What is the mechanism?

J Arrhythm. 2020 Mar 24;36(3):542-543. doi: 10.1002/joa3.12334. eCollection 2020 Jun.

Authors

Francisco Ribes^{1

2}, Ángel Martínez-Brótons¹, Ángel Ferrero-De-Loma-Osorio¹, Lourdes Bondanza¹, Cristina Albiach^{1

2}, Víctor Marcos-Garcés¹, Ricardo Ruiz-Granell¹

Affiliations

¹ Arrhythmia Unit Department of Cardiology Hospital Clínico Universitario Valencia Valencia Spain.
² Instituto de Investigación Sanitaria INCLIVA Valencia Spain.

Abstract

Electrocardiogram showing a regular wide QRS tachycardia with left branch block (LBBB) like in morphology at 200 beats per minute (bpm). During electrophysiology study, it suddenly gets narrow and faster. What is the mechanism of the switch from a broad complex to a narrow complex tachycardia?

Keywords: accessory pathway; concealed conduction; orthodromic atrioventricular reentrant tachycardia; wide QRS tachycardia.