Determinants of left atrial impedance and its response to pulsed-field ablation with a variable-loop circular catheter
S Hamaura, M Kimura, M Hiyama, Y Toyama, Y Ishida, S Sasaki, H TomitaAbstract
Background
Left atrial (LA) impedance mapping is now feasible during pulmonary vein isolation (PVI) with a variable-loop circular pulsed-field ablation (PFA) catheter. However, the clinical and hematological determinants of LA impedance and the extent to which impedance changes reflect ablation effects remain unclear. A better understanding of these relationships is important for interpreting impedance maps in daily practice and for judging whether LA impedance can serve as a surrogate marker of lesion quality.
Purpose
To identify factors associated with baseline LA impedance and to characterize regional impedance changes following PFA-based PVI.
Methods
We retrospectively analyzed 15 patients undergoing initial catheter ablation for persistent and paroxysmal atrial fibrillation using a variable-loop circular PFA catheter capable of LA impedance mapping. Impedance maps of the LA were acquired immediately before and after completion of PVI. Impedance was sampled at predefined anatomical points: eight around each pulmonary vein (PV) antrum and 20 additional points at the carina, posterior LA wall, and central LA cavity. Clinical characteristics, echocardiographic indices, and pre- and post-procedural blood tests, including hematocrit, were collected. Correlations between baseline posterior-wall impedance and clinical or laboratory variables were assessed, and paired comparisons were used to evaluate pre–post changes at each anatomical region.
Results
Baseline posterior-wall impedance showed a positive correlation with body weight (r=0.61, P=0.015), left atrial diameter (r=0.53, P=0.038), and hematocrit (r=0.52, P=0.047), and a negative correlation with left ventricular ejection fraction (r=-0.56, P=0.031). However, no clear association was observed with age and sex. After PFA, impedance decreased significantly at the PV antra and carina. There was a tendency for impedance to decrease more readily in the anterior portion of the right PV. A significant decrease was also observed at non-energized regions, including the posterior LA wall and central LA cavity, indicating a global, rather than strictly focal, change in chamber impedance.
Conclusions
LA impedance measured with a circular PFA catheter appears to be influenced by patient-specific systemic factors such as body size and blood conductivity. Because both ablated and non-ablated regions show post-procedural decreases, absolute LA impedance values and simple pre–post changes may be insufficient as standalone markers of local lesion formation or ablation efficacy. These findings suggest that interpretation of LA impedance maps should take systemic factors into account and that additional work is needed to define normalization or region-specific indices if impedance is to be used to guide PFA in clinical practice.