The Use of Electroanatomical Mapping to Facilitate Redo Ablation of an Accessory Pathway
Dr Stuart Tan, Mr Jonathan Sibley & Dr Stuart Harris
Dept of Electrophysiology, Essex Cardiothoracic Centre, Basildon and Thurrock NHS Trust.
Radiofrequency ablation is established as an effective and safe treatment of narrow complex tachycardia. Evidence shows that acute success is in the region of 90-95% and if so it has a 90-95% cure rate. In the minority of case where recurrence does occur redo procedures are very often successful. The de-facto method is to utilise conventional mapping and fluoroscopy to find earliest activation points and perform ablation. We present the case of a redo SVT ablation where we chose to employ electroanatomical mapping systems to facilitate mapping and ablation.
Mr SR is a 49 year of man who presented with evidence on 12L ECG of regular narrow complex tachycardia. He has a history of palpitations stretching back for 15 years with episodes of sudden onset lasting up to 30 minutes. Baseline ECG showed no evidence of pre-excitation and he continued to have symptoms despite therapy with Sotalol. He was taken forward for EPS +/- ablation.
At EPS a standard four wire study was performed with a decapolar catheter in the coronary sinus (CS) and three quadripolar catheters placed at the high right atrium (HRA), His position and the right ventricular apex (RVA). During formal electrophysiological testing retrograde conduction was clearly non-decremental with CS 9-10 leading. Anterograde testing was decremental with no evidence of pre-excitation. Tachycardia was initiated after programmed stimulation in the atrium with proximal CS leading. Pacing manoeuvres were performed; atrial reset was observed with His-synchronous VPBs. The tachycardia spontaneously changed between left and right bundle branch block with a change in tachycardia cycle length. This was all consistent with pathway mediated orthodromic AVRT.
The accessory pathway was mapped during tachycardia both on the right side in the region of the proximal CS and also in the left atrium via trans-septal puncture. The earliest signals were seen in the proximal CS and ablation here terminated tachycardia and resulted in decremental retrograde conduction on testing. Thus ablation of a Right sided Postero-Septal Accessory Pathway was acutely successful.
Mr SR suffered recurrent symptoms 10 days after ablation and after consultation in clinic came forward for a redo procedure. Again orthodromic AVRT was demonstrated on EPS and following conventional mapping energy was once again delivered in the region of the proximal CS.
Mr SR remained well for 18 months but began to suffer palpitations once more. He was brought back to the EP lab for a third procedure and this time we elected to use electroanatomical mapping with CARTO3 to allow us to create an accurate activation map and locate his current pathway. He was in sinus rhythm at the start of the case and programmed stimulation from the ventricle showed non-decremental conduction with His A leading (figure 1). During further retrograde testing tachycardia was induced again with His A leading (figure 2). Hissynchronous ventricular beats caused clear atrial reset consistent with a pathway (figure 3). Using CARTO 3 we mapped around the right atrium creating a local activation map (figure 4). The earliest signal was seen in the postero-septal region distant from but not very far from the His bundle which we had previously marked on our map. Radiofrequency energy was delivered in sinus rhythm and retrograde block of the pathway was demonstrated (figure 5)
As this was a second redo case we felt if we used CARTO it would improve our chances of achieving long term success. The use of CARTO in this case allowed us to very accurately map the atrial insertion of the AP during tachycardia. We created a dense activation map with over 60 points in a small area of the right atrium. We were conscious that on fluoroscopy our catheter marking His looked very close to the ablation catheter both in LAO and RAO projections but the electroanatomical map gave us confidence that as well as not seeing His electrograms we were definitely away from the AV node. The activation map would also theoretically allow an operator to deliver RF to the area shown to have earliest activation were the pathway to become physically “bumped” whereas during conventional mapping this would not be possible.
- Blomstrom-Lundqvist, C., et al., ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias--executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for the Management of Patients With Supraventricular Arrhythmias). Circulation, 2003. 108(15): p. 1871-909.
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