Although cryoenergy safety profile is appropriate for the ablation of arrhythmogenic foci near the conduction system, mapping using the cryoablation catheter is of limited precision. Combining the safety of cryoenergy and the high precision of a 3D mapping system therefore appears the most appropriate set-up for ablation in the vicinity of the His bundle.
A 29-year-old woman with a 3-year history of increasing shortness of breath and palpitations refractory to medical treatment was sent to the electrophysiology (EP) laboratory for catheter ablation. Surface electrocardiogram showed sinus rhythm and frequent ectopic beats with narrow QRS complexes similar to those of the sinus beats. The left ventricular ejection fraction was impaired (38%) with no other aetiology found, apart from frequent ectopies. Detailed intracardiac mapping, using a 3D electroanatomical system, revealed that the ectopy originated from the distal His bundle, which was indicated by both antegrade and reversed His bundle activation sequence during ectopy compared to that during sinus rhythm. Due to the proximity of the conduction system, cryoenergy rather than radiofrequency was chosen to target this Hisian ectopy. A special set-up was made in order to allow the cryoablation catheter to be visualized into the 3D mapping system. Cryoenergy delivered to the site of earliest Hisian ectopy activation completely abolished it.
Such a combined approach may help to improve the therapeutic strategy for ablation procedures with a high risk of injury to the conduction system. It could notably be extended to the ablation of para-Hisian ectopy or accessory pathways.

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