The Impact of Electrogram Type and Conduction Velocity Estimation Techniques on Assessments of Conduction Velocity During Ventricular Substrate Mapping

Mahmoud Ehnesh1, Johanna Tonko2, Alexander Zolotarev3, Edward Vigmond4, Pier Lambiase2, Caroline Roney5
1Queen Mary University of London, School of Engineering and Materials Science, 2University College London, Institute for Cardiovascular Sciences, Centre for Translational Electrophysiology, 3Queen Mary University of London, 4LIRYC - University of Bordeaux, 5King's College London

Abstract

Background: Identifying targets during substrate ablation of ventricular arrhythmias remains challenging. Conduction velocity (CV) mapping has the potential to identify critical regions of ventricular substrate ablation. However, it is unknown how electrogram choice and methodology affects CV estimation. We aimed to test these effects in a control population for patients with structural normal hearts and idiopathic ventricular ectopy.

Methods: Omnipolar mapping (Abbott Medical) was performed using the HD-grid for patients with structurally normal hearts undergoing ventricular ectopy ablation. Omnipolar, bipolar and unipolar EGMs were exported, together with wavefront speed, and LAT. LAT were interpolated to a 2mm resolution mesh using inverse distance weighting interpolation. CV was assessed using four methods: 1. Omnipolar wavespeed; 2. local gradient estimation from the interpolated LAT; 3. Fitting a planar wavefront to LAT measurements; 4. Fitting a circular wavefront and estimating CV. CV estimates were compared between methods, and between type of EGMs.

Results: We analysed a total of 25 maps for 5 cases. The overall mean CV did not depend on EGM or technique (t-test showed no significant differences). Gradient, Mean ±SD (m/s); Omnipolar 0.62± 0.04, bipolar 0.62±0.045 unipolar 0.66±0.3. Fitting a planar; Omnipolar 0.92± 0.09, bipolar 0.93±0.1, unipolar 0.99±0.1. Fitting a circular; Omnipolar 0.92± 0.09, bipolar 93.02±0.08, unipolar 1.02±0.1. However, the median pointwise difference between EGMs and across techniques is large. Omnipolar (m/s); wavespeed vs gradient: 0.51, wavespeed vs fitting planar: 0.37, gradient vs fitting planar: 0.43. Bipolar; wavespeed vs gradient: 0.51, wavespeed vs fitting planar; 0.39 gradient vs fitting planar: 0.44. Unipolar; wavespeed vs gradient: 0.46, wavespeed vs fitting planar; 0.39 gradient vs fitting planar: 0.46.

Conclusion: In structurally normal hearts undergoing ablation, the type of EGM recording does not affect the estimation of sinus rhythm CV. CV estimation technique has a large effect on CV maps calculated during ventricular substrate mapping.