Electrophysiological mechanisms of arrhythmias after thoracoscopic Maze procedure

Object of the study: combination of thoracoscopic epicardial ablation with subsequent catheter procedures is a modern and effective approach for the treatment of long-standing atrial fibrillation (LSAF). Given the standard method of epicardial ablation, the design of which depends mainly on the tools and technologies used, subsequent catheter ablation should eliminate all typical weaknesses of the epicardial stage.

The aim of this study was to establish the main causes of recurrence of atrial arrhythmias in patients with LSAF after primary epicardial ablation using the Dallas lesion set technique.

Methods: thoracoscopic ablation was performed for 330 patients, standard bipolar pulmonary vein (PV) isolation and monopolar linear lesions were performed to isolate the posterior wall of the left atrium (LA) (AtriCure Inc.). 47 of them, because of the recurrence of various atrial arrhythmias, the second endocardial stage of electrophysiological examination and radiofrequency catheter ablation (RFCA) was performed, with the vast majority of repeat procedures in a period of 3-6 months. The protocol for endocardial RFCA, in addition to mapping and eliminating the main cause of recurrence (atrial tachycardia, atrial flutter, or AF), included PV and posterior wall isolation control.

Results: the study showed that after Dallas lesion set thoracoscopic ablation in patients with recurrence of atrial arrhythmias: 1) it is often necessary to re-isolate LA posterior wall (a typical area for restoration of the conduction is the roof, however, rare variants of conducting through the posterior connection of the right PV are also possible); 2) after epicardial ablation of the LA roof with a monopolar electrode, a wide non-homogeneous scar forms with numerous zones of slow conduction, low-amplitude, fragmented signals, not reaching the mitral valve, this scar is the main cause of incisional flutter; 3) as a cause of arrhythmia recurrence, additional AF drivers are also possible, that are not covered by the design of epicardial ablation - ectopic/micro-reentrant tachycardias, various arrhythmias from the right atrium.

Conclusions: catheter ablation after thoracoscopic MAZE procedure allows to eliminate the existing limitations of the epicardial lines and supplementing them with the effect on the mechanisms of maintaining AF that are unique to a particular patient.

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