[Beat-to-beat AV nodal assessment] ECG-based beat-to-beat assessment of AV node conduction properties during AF

TL;DR

This study introduces a novel ECG-based method to assess AV node conduction properties on a beat-to-beat basis during atrial fibrillation, providing insights into autonomic nervous system effects and potential clinical applications.

Contribution

The paper presents a new methodology combining a network model, particle filter, and smoothing algorithm to estimate AV nodal conduction properties during AF from ECG data.

Findings

Accurately estimated refractory periods and conduction delays with mean absolute errors around 130-170 ms.

Detected expected changes in AV node properties during tilt test indicating sympathetic activation.

Method demonstrated feasibility with both simulated and real patient data.

Abstract

The refractory period and conduction delay of the atrioventricular (AV) node play a crucial role in regulating the heart rate during atrial fibrillation (AF). Beat-to-beat variations in these properties are known to be induced by the autonomic nervous system (ANS) but have previously not been assessable during AF. Assessing these could provide novel information for improved diagnosis, prognosis, and treatment on an individual basis. To estimate AV nodal conduction properties with beat-to-beat resolution, we propose a methodology comprising a network model of the AV node, a particle filter, and a smoothing algorithm. The methodology was evaluated using simulated data and using synchronized electrogram (EGM) and ECG recordings from five patients in the intracardiac atrial fibrillation database. The methodology's ability to quantify ANS-induced changes in AV node conduction properties was evaluated by analyzing ECG data from 21 patients in AF undergoing a tilt test protocol. The estimated refractory period and conduction delay matched the simulated ground truth based on ECG recordings with a mean absolute error ($\pm$ std) of 169$\pm$14 ms for the refractory period in the fast pathway; 131$\pm$13 ms for the conduction delay in the fast pathway; 67$\pm$10 ms for the refractory period in the slow pathway; and 178$\pm$28 ms for the conduction delay in the slow pathway. These errors decreased when using simulated ground truth based on EGM recordings. Moreover, a decrease in conduction delay and refractory period in response to head-up tilt was seen during the tilt test protocol, as expected under sympathetic activation. These results suggest that beat-to-beat estimation of AV nodal conduction properties during AF from ECG is feasible, with different levels of uncertainty, and that the estimated properties agree with expected AV nodal modulation.