Diagnostic accuracy of a novel functional extra-stimulus mapping metric: Ventricular Electrogram Duration Mapping of Extra-stimulus (VEDUM-X) in defining the ventricular tachycardia substrate
J Mayer, X U E Z H E Wang, J A F F A R Al-Sheikhli, I A N Patchett, R A F A E L Siang, F A Y Y A Z Minhas, C H R I S O'shea, T A R V DhanjalAbstract
Background
Ventricular tachycardia (VT) ablation performed with functional extra-stimulus (ES) mapping, such as Decremental Evoked Potential (DeEP) mapping, reduces VT recurrence compared to Isochronal Late Activation Mapping and Ventricular Electrogram Duration Mapping (VEDUM)¹. Functional ES mapping identifies delayed and decremental electrogram (EGM) components crucial for VT initiation and maintenance. In contrast, conventional VEDUM measures EGM duration during intrinsic rhythm². The VEDUM study showed that many VT isthmuses lie within regions of prolonged EGM duration during sinus rhythm (SR). We hypothesize that the diagnostic accuracy of VEDUM may be improved if the principles are applied to extra-stimuli to further unmask functional substrate.
Aim
The aim of this study is to determine the diagnostic accuracy of the VEDUM approach when applied to extra-stimuli (VEDUM-X) and compare to the conventional VEDUM approach in identifying critical components of the VT circuit.
Methods
Patients undergoing VT ablation were investigated. Following a 600ms S1 drive train, an S2 ES was delivered at the clinical VT cycle length to identify decremental EGM components. Electroanatomic maps were retrospectively processed using the First Deflection (FD) and Last Deflection (LD) detection algorithms and exported for offline analysis. Conventional VEDUM maps, VEDUM of S1 (VEDUM-X1) and VEDUM of S2 (VEDUM-X2) were constructed from the FD and LD maps of the SR, S1 and S2 maps, respectively. Detailed analysis of the spatial co-localisation of VEDUM, VEDUM-X1 and VEDUM-X2 maps to the region of interest (ROI) was performed. The ROI was identified by the presence of mid-diastolic activity during VT local activation time (LAT) mapping, or, in the absence of a complete mid-diastolic VT LAT map, a >95% 12-lead QRS morphology match to the clinical VT within a deceleration zone. Diagnostic accuracy testing was performed by comparing the ROI to the 3 VEDUM maps, to identify true positive (TP), true negative (TN), false positive (FP), and false negative (FN) regions. Receiver Operating Characteristic (ROC) curve and Area Under Curve (AUC) analyses of sensitivity and specificity were performed.
Results
A total of 21 patients were included. Baseline and procedural characteristics are listed in Table 1. The diagnostic performance of VEDUM, VEDUM-X1 and VEDUM-X2 maps is shown in Figure 1. Patient-wise averaged ROC curves within scar regions demonstrated the best AUC with VEDUM-X2 (AUC: 0.801±0.13), followed by VEDUM-X1 (AUC: 0.65±0.21) and conventional VEDUM (AUC: 0.57±0.20).
Conclusion
Functional VEDUM with an S2 ES (VEDUM-X2) demonstrates superior diagnostic accuracy in identifying critical components of the VT circuit compared to the conventional SR VEDUM approach. These findings support the prospective evaluation of VEDUM-X2 mapping to determine long-term VT recurrence rates.