Introduction:

Electrical conduction between the right and left atria (RA, LA) occurs across muscular fibres like the Bachmann bundle, the posterosuperior bundle, the septopulmonary bundle and various muscular fibres along the foramen ovale. Mapping of these interatrial connections have been described before using conventional electroanatomical mapping systems during electrophysiological procedures or cardiac surgery. Catheter ablation for atrial arrhythmias alters atrial tissue via creation of specifical lesions inside the atria and may therefore alter interatrial electrical conduction with possible harming effects on electric and mechanical atrial function. The impact of atrial fibrillation (AF) ablation aiming at isolation of the pulmonary veins (PVI) on interatrial electrical conduction has not been investigated yet.

The current study sought to assess the interatrial electrical conduction in patients undergoing PVI for symptomatic AF and the effects of catheter ablation on LA electrical activation using a novel mapping algorithm facilitating high-density mapping of LA endocardial electrical activation and vector visualisation of electrical activation patterns.

Methods:

Patients who underwent first-time radiofrequency-based catheter ablation for symptomatic AF were analysed. Patients underwent AF ablation aiming at PVI. Electroanatomic mapping of the RA and LA was performed during sinus rhythm before and after PVI using a commercially available 3D mapping system. A novel mapping algorithm was used to visualise vectors of electrical activation patterns. Centrifugal patterns of electrical activation inside the LA based on local activation timing and the vector-based algorithm were identified. Electrical activation patterns of the LA before and after PVI were compared.

Results:

A total of 42 patients who underwent AF ablation were analysed. Earliest endocardial LA activation was observed at the anterior interatrial septum in 22 cases (52.4%), at the septal LA roof in 10 cases (23.8%), at the antero-inferior septum in 8 cases (19.0%) and at the inferior septum in 2 cases (4.8%). A centrifugal pattern of LA activation could be identified using the vector-based algorithm in all patients. Earliest endocardial LA activation was not affected by PVI in 34 patients (80.1%) and changed slightly in 8 patients (19.0%) with a change from superior activation to antero-septal activation in 6 cases (14.3%) and from an anterior to a superior activation in 2 patients (4.8%). P wave duration (124.7±22.8 ms vs. 126.4±24.6 ms, p=0.81) and intervals from P to earliest endocardial LA activation (56.0±23.6 ms vs. 62.4±33.6 ms, p=0.481) and P to endocardial LAA activation (116.2±23.2 ms vs. 119.1±26.5 ms, p=0.71) did not differ significantly before and after PVI.

Conclusion:

AF ablation did not lead to grossly altered interatrial electrical activation and endocardial LA activation in the majority of patients undergoing a first-time PVI. Our findings implicate that PVI does not induce harming effects with regards to interatrial conduction. The impact of more extensive ablation strategies on interatrial electrical conduction needs to be addressed in future studies.

Figure 1: Representative example of a patient with earliest endocardial activation of the left atrium during sinus rhythm at the antero-superior interatrial septum.

Pulmonary vein isolation did not affect results of the mapping of earliest LA activation in this individuum.