Left Atrial Relaxation Index is an Independent Predictor of the Presence of a Left Atrial Low Voltage Zone in Patients with Atrial Fibrillation

In atrial fibrillation (AF), low voltage zones (LVZs) on cardiac electro-anatomic mapping reflect atrial fibrosis and are associated with difficulty in maintaining sinus rhythm after catheter ablation (CA). Although left atrial (LA) remodeling is associated with an increment in left atrial pressure (LAP), the importance of assessing LAP and relaxation index as a marker of early left atrial reservoir function in patients who undergo CA for AF is not known. We retrospectively evaluated 102 patients (68 males, age: 67.6 ± 11.4 years) who underwent CA between January and December 2019. We measured LAP during sinus rhythm and the total area of LVZs on the electro-anatomical map during pacing from the coronary sinus, and calculated the relaxation index. We defined LVZs as being significant when they occupied an area of more than 10 % of the entire LA. Seventeen patients (16.7 %) who had significant LVZs were compared with patients without significant LVZs. Age, sex, LA volume index and relaxation index differed significantly between the two groups. In multiple regression analysis, relaxation index was significantly lower in the group with compared to without LVZs (OR 0.22, p = 0.015). In conclusion, relaxation index might be a marker of not only early LA reservoir function, but also LVZs, reflecting LA fibrosis.