Background: Voltage thresholds for ventricular scar definition are based on historic data collected using catheters with widely spaced bipoles in the absence of contact force. Modern multipolar mapping catheters employ smaller electrodes and interelectrode spacing that theoretically allows for mapping with increased resolution and reduced far-field electrogram (EGM) component. Despite the advancement in technology, historic cut-offs of <0.5 mV for dense scar and 0.5–1.5 mV for scar borderzone continue to be used in contemporary electrophysiology.
Purpose: We aimed to assess the optimal voltage cut-offs for ventricular scar substrate characterization using the HD Grid multipolar mapping catheter compared with standard linear collection. Voltage cut-offs were assessed against cardiac computed tomography (CT) and magnetic resonance imaging (MRI) derived scar. We compared optimal voltage cut-offs using conventional bipolar sampling, the Best Duplicate Algorithm and with the HD wave solution plus best duplicate algorithm.
Methods: A multicentre study of 30 patients undergoing VT ablation was conducted. Substrate mapping was performed using the high-density HD-grid multipolar mapping catheter. Bipolar voltage maps were co-registered with cardiac MRI (CMR) or CT obtained prior to the procedure to assess the voltage characteristics of scar defined by cardiac CT/CMR. Pre-procedure contrast-enhanced imaging data were analysed using ADAS software (Galgo medical). Data points were collected in regions of scar during: (1) HD wave mapping with best duplicate algorithm on (Waveon), (2) mapping with HD wave off and best duplicate on (Waveoff), and (3) with conventional bipolar mapping (Alloff).
Results: The median bipolar voltage for regions of dense CMR/CT scar using (Waveon) HD wave solution and best duplicate algorithm was 0.24 mV (IQR 0.12–0.43). The median voltage with (Waveoff) HD wave off was 0.29 mV (0.15–0.45). The median voltage with (Alloff) HD wave off and best duplicate off was 0.32 mV (0.19–0.5). ROC analysis using AUC suggested the optimal cut-off for endocardial dense scar using (Waveon) HD wave mapping and best duplicate algorithm was 0.31 mV (sensitivity 69.6%, specificity 60.74%) (Figure), (Waveoff) cut-off with the best duplicate and without the HD wave mapping was 0.34 mV (sensitivity 88.0%, specificity 42.96%), and (Alloff) without wave mapping or best duplication was 0.36 mV (sensitivity 84%, specificity 52%).
Conclusion: Ventricular substrate characterization with newer mapping technology using narrow electrode spacing and smaller electrode size suggests that traditional voltage cut-offs may need revision for delineation of scar characteristics. Additionally, the ability to repeat sample in a region to obtain the best signal (Best Duplicate), and the ability to obviate the effect of wavefront direction using the HD wave solution omnipolar technology, may further increase the fidelity of scar characterization. This has important implications for mapping VT and characterizing channels in order to identify VT circuits.