Show Summary Details
Page of

Mapping the accessory pathway 

Mapping the accessory pathway
Chapter:
Mapping the accessory pathway
Author(s):

Hein Heidbuchel

, Mattias Duytschaever

, and Haran Burri

DOI:
10.1093/med/9780198766377.003.0039
Page of

PRINTED FROM OXFORD MEDICINE ONLINE (www.oxfordmedicine.com). © Oxford University Press, 2021. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy and Legal Notice).

Subscriber: null; date: 08 December 2021

Introduction to the case

The patient, a woman aged 59, was admitted for ablation of circus movement tachycardia over a left anterolateral accessory pathway. A mapping and ablation catheter (Figure 39.1) is introduced into the left atrium via a trans-septal sheath and positioned at two positions, 2mm apart, alongside the mitral annulus during ventricular pacing (Figure 39.2) from a para-Hisian position.

Figure 39.1 A mapping and ablation catheter is introduced into the left atrium via a trans-septal sheath and positioned at two positions, 2 mm apart, alongside the mitral annulus during ventricular pacing

Figure 39.1
A mapping and ablation catheter is introduced into the left atrium via a trans-septal sheath and positioned at two positions, 2 mm apart, alongside the mitral annulus during ventricular pacing

Figure 39.2 Electrograms on the mapping catheter at the two positions alongside the mitral annulus during ventricular pacing. RAA: right atrial appendage; HBp till HBd: His bundle recordings from proximal to distal; Map: mapping catheter (bipolar electrogram); CS: coronary sinus; H: His bundle deflection; S: stimulus

Figure 39.2
Electrograms on the mapping catheter at the two positions alongside the mitral annulus during ventricular pacing. RAA: right atrial appendage; HBp till HBd: His bundle recordings from proximal to distal; Map: mapping catheter (bipolar electrogram); CS: coronary sinus; H: His bundle deflection; S: stimulus

Question

A mapping and ablation catheter is introduced into the left atrium via a trans-septal sheath and positioned alongside the mitral annulus during ventricular pacing from a para-Hisian position. At which position would you ablate?

  1. A Based on the electrogram in Figure 39.3a

  2. B Based on the electrogram in Figure 39.3b

Answer

B Based on the electrogram in Figure 39.3b

Explanation

Electrograms during accessory pathway ablation

The timing of the earliest atrial activation on the ablation bipole (Map d) is similar in both panels. The atrial electrograms are smaller than the ventricular electrograms, as is desired for ablation. In the left panel, there is a clear polarity reversal of the atrial electrograms, being initially positive in the proximal mapping bipole and negative in the distal bipole. This indicates that the insertion of the accessory pathway is located in the middle between both bipoles. Delivering energy from the 4mm ablation tip would be too inferior in relation to the insertion and hence would fail to ablate the accessory pathway. At the right side, the catheter tip has been withdrawn a few millimetres more towards the anterior mitral annulus. The timing of the earliest atrial activation is the same, but there is now a small initial positive deflection on the distal ablation bipole. Therefore, the ablation tip now resides over the atrial insertion of the accessory pathway itself. Such finely titrated ablation position will usually lead to a block of the accessory pathway conduction within a few seconds after initiation of energy delivery.

Figure 39.4 helps to explain further.

Figure 39.4 Same figures as Figures 39.1 and 39.2, but with extra annotations. RAA: right atrial appendage; HBp till HBd: His bundle recordings from proximal to distal; CS: coronary sinus; Map: mapping catheter; A: atrial electrogram; H: His bundle deflection; S: stimulus

Figure 39.4
Same figures as Figures 39.1 and 39.2, but with extra annotations. RAA: right atrial appendage; HBp till HBd: His bundle recordings from proximal to distal; CS: coronary sinus; Map: mapping catheter; A: atrial electrogram; H: His bundle deflection; S: stimulus