Narrow QRS tachycardia with 2:1 atrioventricular block during slow pathway modification: what is the mechanism?
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EP-Quiz Herzschr Elektrophys https://doi.org/10.1007/s00399-020-00702-x Received: 3 June 2020 Accepted: 25 June 2020 © Springer Medizin Verlag GmbH, ein Teil von Springer Nature 2020
Satoshi Higuchi1 · Harilaos Bogossian2 · Melvin M. Scheinman1 1 2
Division of Cardiology, Section of Cardiac Electrophysiology, University of California, San Francisco, USA Department of Cardiology and Rhythmology, Ev. Krankenhaus Hagen, Hagen, Germany
Narrow QRS tachycardia with 2:1 atrioventricular block during slow pathway modification: what is the mechanism?
Case presentation
Questions
A 22-year-old woman with a history of palpitations underwent catheter ablation for supraventricular tachycardia (SVT). At baseline, dual atrioventricular (AV) nodal physiology was observed, and the ventriculoatrial (VA) conduction was concentric and decremental. A regular narrow QRS tachycardia was induced by atrial extra-stimuli followed by a prolongation of the AH interval (. Fig. 1). The SVT showed an “A on V” sequence with concentric atrial activation identical to that during ventricular pacing. The tachycardia was diagnosed as typical slow-fast AV nodal reentrant tachycardia (AVNRT) and a radiofrequency (RF) application was delivered targeting the slow pathway (SP) guided by intracardiac electrograms and fluoroscopic landmarks (. Fig. 2). During RF energy delivery, a stable junctional rhythm could be obtained. However, in mid-application, there was an abrupt rhythm change from a junctional rhythm to another narrow QRS tachycardia with 2:1 AV block (. Fig. 3). The tachycardia induced during ablation had a concentric atrial activation pattern and the HH intervals were slightly irregular. The RF energy delivery was immediately interrupted and, after several beats, the tachycardia terminated.
1. What is the most likely mechanism of this spontaneous narrow QRS tachycardia during SP ablation and what are the possible mechanisms of the 2:1 AV block? 2. Is it safe to continue the RF application?
Ⅰ Ⅱ Ⅲ V1 V2 V3 V4 V5 V6 HRA
200ms
120ms
330ms
420ms
His 500ms
500ms
360ms
CS p
CS d RV
Fig. 1 8 Intracardiac tracings exhibiting the onset of the clinical supraventricular tachycardia. A narrow QRS regular tachycardia with a tachycardia cycle length of 420 ms was induced by atrial extra-stimuli followed by a prolongation of the AH interval of 330 ms.The paper speed was 25 mm/s. HRA high right atrium, CS p the proximal electrode pairs of the catheter in the coronary sinus, CS d the distal electrode pairs of the catheter in the coronary sinus, RV right ventricle Herzschrittmachertherapie + Elektrophysiologie
EP-Quiz HRA
RV His CS
ABL
LAO view
Fig. 2 9 Fluoroscopic image showing the position of the ablation catheter during slow pathway ablation in the left anterior oblique view. HRA high right atrium, CS coronary sinus, ABL ablation catheter, RV right ventricle, LAO left anterior oblique
Ⅰ Ⅱ Ⅲ V1 V2 V3 V4 V5 V6 HRA
200ms
630ms
630ms
648ms
His
CS p
CS d RV
Herzschrittmachertherapie + Elektrophysiologie
671ms
678ms
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