Sequential Electro-Anatomical Mapping Methodology and Preliminary Results for Reentry Vulnerability Index Estimation

Michele Orini1, Ben Hanson2, Peter Taggart2, Fernando Campos3, Aldo Rinaldi3, Jaswinder Gill4, Martin Bishop3, Pier Lambiase2
1University College London, Department of Mechanical Engineering, 2University College London, 3King's College London, 4St Thomas' Hospital


Introduction: Ventricular tachycardia (VT) recurrence after catheter ablation remains frequent and improved ablation strategies are needed. The re-entry vulnerability index (RVI) is an activation-repolarization marker to localize critical sites for VT initiation. Its use is limited since current electro-anatomical mapping systems (EAMS) cannot provide global measurement of activation and repolarization times within one beat. Here we aim to (1) Assess a simple methodology to map RVI using sequential EAMS and (2) Provide preliminary results about the algorithm’s ability to localize re-entry initiation sites.

Methods: This mapping method assumes that beats showing similar surface ECGs are representative of the same underlying activation-repolarization dynamics and can be used to estimate RVI. The mean correlation coefficient between single ECG beats and a representative template is used as inclusion/exclusion criterion. In simulation, local action potentials were generated using analytical functions at 257 nodes covering both ventricles. The corresponding unipolar electrograms were measured using a simple model recently validated in-vivo while surface ECGs were computed using ECG-Sim. Data from two catheter ablations were recorded using CARTO3 and analyzed off-line.

Results: Localization of the vulnerable region associated with 5% bottom RVI was accurate (sensitivity>80±8%, specificity>99±1%) for moderate to large repolarization variability (5≤σRT≤20 ms) and moderate level of noise (SNR≥10 dB) but it deteriorated for larger repolarization fluctuations (σRT≥25 ms) and SNR≤5 dB. Sensitivity remained high even when RVI estimates were only moderately accurate (CC>0.67±0.05, MAE<25±1 ms). The number of ectopic beats did not affect the results and the best ECG correlation coefficient was CC=0.95. In the two in-vivo cases analyzed the sites of low RVI and VT exit were close (distance: 6.5 and 5.1 mm).

Conclusion: A simple analytical simulation suggests that RVI can be estimated from sequential EAMS and first results during in-vivo VT ablations are encouraging.