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?
Highlights
We hypothesize that a temporary shortening of the effective refractory period (ERP) of the left bundle branch block (LBBB) could lead to a conduction over both branches, with a narrow complex
Two tetrapolar diagnostic catheters were placed in the right ventricule apex and in the His bundle region
The progressive narrowing of the QRS with subsequent shortening in the tachycardia cycle length which predicts changings in the A-A interval,[1] proves the dependence of the His-Purkinje system or ventricular myocardium in the tachycardia circuit. To these findings, the differential to this tachycardia would be a ventricular tachycardia with ventriculoatrial (VA) conduction or an atrioventricular reentrant tachycardia (AVRT), and the diagnostic clue would be the His Bundle (HB) activation pattern
Summary
Correspondence Francisco Ribes, Arrhythmia Unit, Department of Cardiology, Hospital Clínico Universitario Valencia, Av. Blasco Ibañez, 17, Valencia, Spain. KEYWORDS : accessory pathway, concealed conduction, orthodromic atrioventricular reentrant tachycardia, wide QRS tachycardia The electrocardiogram (ECG) showed a regular wide QRS tachycardia with left bundle branch block (LBBB) like in morphology at 200 beats per minute (bpm).
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