Trans-catheter cryoablation of parahisian accessory pathways: a single centre experience
Authors: Perrotta L , Brogni F D , Ricciardi G , Checchi L , Porcedda G , De Simone L , Ciliberti D , Zaccaria C , Michelucci A , Pieragnoli P 
Published: May 2024

Abstract

Introduction
Transcatheter radiofrequency (RF) ablation of perinodal accessory pathways (parahisian/midseptal APs) is still challenging especially in young patients due to a high risk for inadvertent atrioventricular block (AVB) requiring permanent pacing.
Recently, cryo-ablation (CA) has evolved as an RF alternative, thanks to a safer profile and a better catheter stability.

Purpose
To evaluate the safety, efficacy and outcomes of CA in patients with parahisian/midseptal APs.

Methods
73 pts undergoing a first ablation of septal APs at our institution were retrospectively analyzed. Among these, we selected 20 patients with a diagnosis of para-hisian/midseptal AP confirmed by EP study (EPS) and 3D-electro-anatomic mapping (EAM), ablated using cryoenergy.
Before delivering CA, a cryomapping (CM) at the target AP site was performed at −30°C using a 6- mm-tip catheter. Successful CM was defined as: (1) loss of delta wave in case of manifest pre-excitation, (2) termination of a sustained AVRT, (3) retrograde conduction block through the AP during ventricular pacing in case of concealed AP. CA was initiated following successful CM, at a temperature of −75°C for 300 s with an additional "bonus" CA application (300s).
Acute procedural endpoint was permanent complete abolition of AP conduction; long-term clinical endpoint was defined as no recurrence of delta wave or AVRT on serial ECG monitoring at follow-up (1, 6, 12 months).
RESULTS Baseline characteristics are summarized in Fig. 1. Fifty-five % were pediatric patients, only 3/20 presented a structural HD. Up to 90% of the patients experienced a symptomatic AVRT, while delta-wave was present at baseline ECG in 19/20 patients.
EPS combined with 3D-EAM showed a para-hisian AP in 80% and a mid-septal AP in 20%. Mean distance between His bundle electrogram and AP site was 5.72 mm (4-6.8 mm, Fig. 2). Orthodromic AVRT was induced in all the 20 pts.
Maen procedural and fluoroscopy times were, respectively, 103.4 ± 26.4 and 3.15± 1.76 min .
Acute success was achieved in 20/20 patients (100%) with AP block of conduction obtained within few seconds (&lt;10s) after a mean CM number of 3.3 ± 1.2 (Fig. 2).
Two patients developed transient 2:1 AV block and 1 patient transient RBBB during CM, with immediate recovery within 20s from CM termination. No peri-procedural complications or permanent AV block were observed. One patient had an early AP re-conduction (6 hours later) and was successfully re-ablated the following day.
During a mean FU of 361 ± 34 days, only two patients (10%) experienced an AVRT recurrence and underwent a second successful CA.

Conclusions
Cryoablation of parahisian and midseptal APs is a safe and effective alternative to RF, resulting in a low risk of recurrence over 12-months-follow-up with no incidence of permanent AV block.
A near-zero fluoroscopy approach combining CA and 3D-EAM is feasible and should be considered especially in very young patients with parahisian APs.Fig. 1Fig. 2