Accuracy of a non-invasive mapping system for the localisation of re-entrant VT site of origin and its relationship to myocardial scar on cross-sectional imaging
Authors: Al-Sheikhli J , Mahdy T , Siang R , Patchett I , Marshall L , Khan J , Dhanjal T 
Published: October 2024

Abstract

Introduction
View in ventricular onset (VIVO) is a non-invasive mapping system used for localising the site of earliest activation in ventricular arrhythmia, utilising a mathematical algorithm, patient specific cardiac model (constructed using cross-sectional imaging data), 3D images of the patient’s torso (for localising surface electrodes), and a 12-lead electrocardiogram (ECG).(1, 2) Several publications have examined its role in the localisation of premature ventricular contractions (PVCs), and a 5 patient case series assessed its role in scar related re-entrant VT.(1-4) However, its validity in a larger cohort and of the relationship to the relevant myocardial scar has not been investigated.

Objective
Assess the accuracy of the VIVO mapping system in localising the VT-SoO for patients with scar related re-entrant VT and its relationship to the relevant myocardial scar on cross-sectional imaging.

Methods
20 patients with structural heart disease (18 ischaemic cardiomyopathy (ICM), 1 dilated cardiomyopathy (DCM), 1 hypertrophic cardiomyopathy (HCM)) (Male n=18, 63±14 years) and recent cross-sectional cardiac imaging, were recruited over a 16-month period (table 1). All patients had a clinical indication for VT ablation and were on optimal medical therapy, 19 had an implantable cardiac defibrillator. Invasive electro-anatomical mapping (EAM) was performed with the Advisor HD Grid multipolar catheter and maps were generated using Omnipolar electrograms (EGMs). The VT-SoO was identified using an activation- or pace-map by an experienced operator and the location defined using the American heart association’s 17 segment model of the left ventricle during the procedure.(5) VIVO maps were reviewed by a second independent operator and a segment allocated, scar segments were obtained from cross-sectional imaging. A "complete match" was defined as exact segment concordance between allocated segments, "partial match" as adjacent segments, and "no match" if it does not satisfy either of those requirements.

Results
Mean left ventricular ejection fraction was 35.5 ± 10.6%. Mean procedure time was 242 ± 70 minutes, with a mean ablation time of 20 ± 11.1 minutes. A total of 32 re-entrant VTs were mapped. The VT exit site was identified in all cases (11 activation-map; 21 pace-map). A complete match between the EAM and VIVO map was seen in 75% of VTs and partial match in a further 15% (table 2). The VT-SoO was located withing the myocardial scar (or directly adjacent to is) in 83% of accurately mapped VTs. Procedural success (defined as freedom from device treated episodes) was seen in 90% of patients at mean follow up of 7.3 ± 4.7 months.

Conclusion
VIVO non-invasive mapping system was able to accurately map the VT-SoO in scar dependent VT, and identify the relevant myocardial scar as seen on cross sectional imaging. Further research assessing its ability to accurately identify relevant ablation targets is ongoing.