The L-Line: A novel approach to treat atrial tachycardia by catheter ablation in patients after orthotopic biatrial heart transplantation

M. Khalaph (Bad Oeynhausen)¹, C. Sohns (Bad Oeynhausen)¹, D. Guckel (Bad Oeynhausen)¹, G. Imnadze (Bad Oeynhausen)¹, P. Lucas (Bad Oeynhausen)¹, T. Fink (Bad Oeynhausen)¹, V. Nesapiragasan (Bad Oeynhausen)¹, V. Sciacca (Bad Oeynhausen)¹, M. Braun (Bad Oeynhausen)¹, J. Fleischhauer (Bad Oeynhausen)², R. Schramm (Bad Oeynhausen)², A. Costard-Jäckle (Bad Oeynhausen)², H. Fox (Bad Oeynhausen)³, J. Gummert (Bad Oeynhausen)², M. Mörsdorf (Bad Oeynhausen)¹, M. Didenko (Bad Oeynhausen)¹, P. Sommer (Bad Oeynhausen)¹, M. El Hamriti (Wetzikon)^4
1Herz- und Diabeteszentrum NRW Klinik für Elektrophysiologie/ Rhythmologie Bad Oeynhausen, Deutschland; ²Herz- und Diabeteszentrum NRW Klinik für Thorax- und Kardiovaskularchirurgie Bad Oeynhausen, Deutschland; ³Herz- und Diabeteszentrum NRW Zentrum für Herzinsuffizienz Bad Oeynhausen, Deutschland; ⁴GZO Spital Wetzikon Klinik für Kardiologie und Angiologie Wetzikon, Schweiz

Background:
Atrial tachycardia (AT) is commonly observed following orthotopic biatrial heart transplantation (O-BA-HTX). There remains some controversy regarding their clinical presentation, relationship with atrial anastomoses, and electrophysiologic characteristics. Novel radiofrequency-guided catheter ablation (RFCA) strategies combining electroanatomical activation mapping and myocardial substrate characterization have emerged. Data on the successful treatment of ATs in this specific patient cohort are limited. 

Objective:
The aim of this prospective study was to provide an easy electrophysiologic strategy for mapping and ablation of AT in patients post O-BA-HTX. It sought to assess the efficacy and safety of a novel, first-in-human approach for RFCA in this patient group. Additionally, the study aimed to evaluate long-term arrhythmia-free survival in these patients.

Methods:
A total of 35 consecutive O-BA-HTX patients who underwent RFCA for AT between 2017-2024 were included in this study. Data on procedural parameters, acute and long-term success und complications were analyzed. The primary endpoint was defined as recurrence of ATs longer than 30 seconds.

Results:
A total of 35 patients (mean age 57±16 years, 85% male) presented with therapy-refractory AT post O-BA-HTX. All patients underwent 3-demensional electroanatomic mapping and RFCA of their AT. Procedure time was 61.65±20.73 min; fluoroscopy time 2.74±1.66min; ablation time 9.35±2.78min. The electrophysiologic diagnoses were CTI-depended atrial flutter (AFL) in 62.9% (n = 22); RA-lateral line dependent AT (RA-LL) in 28.6% (n = 10); perimitral AFL in 5.7% (n = 2) and atrio-atrial (AA)-associated left atrial AT in 2.8% (n =1).  AA association was the responsible mechanism for AT in 31.43% (n=11, 10 in RA und 1 in LA), but the AA association was different in AA conduction (types of AA conduction: 1:1, 2:1 and variable AA conduction). A linear lesion incorporating CTI and a RA lateral line (L-Line, Figure 1) led to termination of atrial tachycardia in 91.5% (n = 32). All procedures were performed without any major complications. During a mean follow up of 18 months 1 patient developed AT-recurrence (n=1, 2.86%).No patient developed atrial fibrillation during follow-up.

Conclusion:
The novel L-Line approach offers a simple and effective ablation strategy that enhances long-term arrhythmia-free survival in patients following O-BA-HTX. This strategy offers promising results and could potentially standardize treatment protocols in this unique patient population. Further studies are needed to validate these initial observations.

Figure 1:
Flowchart for stepwise identification and ablation of AT post O-BA-HTX. Left, anatomical scheme. Right, Ablation lines depicted as a tree.