Opinion | Epicardial Ablation of Previously Failed R/L Accessory Pathway 

Background

Catheter ablation is a potentially curative treatment for accessory pathways. However, ablation of right lateral accessory pathways is challenging and has a lower procedural success rate and high recurrence rate due to catheter instability and difficulty in catheter manipulation, inadequate tissue contact and structural heart disease like Ebstein’s anomaly. We describe a challenging case of WPW syndrome with the right lateral accessory pathway, where the pathway was located epicardially.

Results

A 23-year-old female with history of recurrent palpitations was evaluated and diagnosed as a case of WPW syndrome with right free wall pathway with structurally normal heart and normal biventricular function and failed ablation twice in 2018 and 2020. In view of recurrent symptoms, the patient was started on antiarrhythmic therapy. As the patient was refractory to flecainide, sotalol and amiodarone , she was referred to our center for a repeat ablation.

Baseline ECG showed manifest pre-excitation.

A standard electrophysiology study was performed under general anaesthesia with sequential endocardial and epicardial mapping approach.

Retrograde ERP (effective refractory period) of the pathway was 240 ms whereas antegrade ERP was 340 ms (on amiodarone and general anaesthesia). Orthodromic atrio-ventricular reciprocating tachycardia was easily induced by programmed stimulation with a tachycardia cycle length of 470 ms with the earliest atrial electrogram noted in the lateral right atrium.

However, despite extensive mapping of the tricuspid annulus, ablation at the earliest endocardial site failed to terminate the tachycardia. Hence, epicardial access was obtained using Sosa’s technique and mapping along the tricuspid annulus was performed. At lateral tricuspid annulus epicardially, fused atrial and ventricular signals were obtained with local ventricular signals preceding the surface delta wave by 35 ms. Right coronary angiography revealed a safe distance between the right coronary artery and the site of ablation. Epicardial ablation at this site led to loss of accessory pathway conduction within 5 seconds. Post ablation, no tachycardia was inducible despite aggressive pacing protocols and bidirectional AV block was demonstrated using intravenous adenosine. At 1-year follow-up, the patient is asymptomatic with no evidence of accessory pathway conduction.

Conclusion

Epicardial mapping and ablation should be considered in previously failed cases of endocardial ablation of right lateral accessory pathways.

– The author is MBBS, MD, DNB CARDIOLOGY & PDF CARDIAC ELECTROPHYSIOLOGY, currently serving as Consultant at Shree Balaji Hospital