Despite the advancement in technology, historic cut-offs of <0.5mV for dense scar and 0.5-1.5mV for scar borderzone continue to be used in contemporary electrophysiology. 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.

Dynamic substrate changes play a key role in facilitating conduction delay and re-entry in ventricular tachycardia (VT) circuits. Extrastimuli pacing can unmask functional channels demonstrated by dynamic delay, which may play a role in the VT circuit. We have previously developed sense protocol mapping, using short coupled single extrastimuli to delineate areas of maladaptive conduction delay, which play an essential part in VT development.

We have previously developed the sense protocol functional substrate mapping technique for VT ablation. This involves targeting areas of decremental signal delay during single extra pacing at short coupling interval. However, functional substrate characterization can involve protracted mapping time.

Abstract Funding Acknowledgements Type of funding sources: None. 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 <0.5mV for dense scar and 0.5-1.5mV 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. Voltage cut-offs were assessed against cardiac 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 on. Methods A multicentre study of twenty 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 obtained prior to the procedure to assess the voltage characteristics of scar defined by cardiac MRI (CMR) (Figure 1). Pre-procedure contrast enhanced CMR 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 scar using (Waveon) HD wave solution and best duplicate algorithm was 0.27mV (IQR 0.14 – 0.46). The median voltage with (Waveoff) HD wave off was 0.29mV (0.15 – 0.45). The median voltage with (Alloff) HD wave off and best duplicate off was 0.32mV (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 0.30mV (sensitivity: 69.6%, specificity: 60.74%), (Waveoff) cut-off with the best duplicate and without the HD wave mapping was 0.34mV (sensitivity: 69.78%, specificity: 64.46%) and (Alloff) without wave mapping or best duplication was 0.36mV (sensitivity: 84%, specificity: 52%) Figure 2. 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.

Abstract Funding Acknowledgements Type of funding sources: None. Background We have previously developed the sense protocol functional substrate mapping technique for VT ablation(1). However, functional substrate characterizaiton can involve protracted mapping time. Purpose We incorporated the integration of MRI data using ADAS-3D software into the mapping workflow, to integrate structural mapping information into the functional mapping substrate characterization, in order to improve procedural efficiency. Methods CMRs were performed in 20 patients with ischemic related VT and VT therapy in the previous 6 months. These were processed with the ADAS-3D software to characterize the extent of ventricular scars and also ADAS corridors which may correlate with VT channels. Focused substrate maps were then performed in patients, guided by the extent of ADAS scar and corridors, looking at the scar substrate in intrinsic rhythm and then functional channels using single extra pacing from the RV at 20ms above ERP (SENSE2 Protocol). Specifically healthy areas 2cm beyond the scar borderzone based on ADAS were not mapped, in order to reduce substrate mapping time and complete geometries were not created. Following delineation of functional channels pacemapping and entrainment mapping were used to confirm targets for ablation. The ADAS 3D MRI was integrated into the into the VT substrate map on Ensite-Precision with alignment to the aorta, RV and PA (Figure 1). We compared our data with previous functional mapping data without the integration of MRI. Results 20 patients (age 70 years; 19 male subjects) underwent ablation. Mean EF 28%. Median procedure time was 161 minutes compared with 246 minutes (in our previous study)(p=<0.001) Mean substrate mapping time was 32 mins vs 63 mins (p=<0.001). Mean ablation time was 22 mins vs 32 mins (p=0.11). 85% (17 of 20) patients were free from symptomatic VT/ anti-tachycardia pacing or implantable cardioverter defibrillator shocks at a median follow-up of 171 days. The mean VT burden was reduced from 22 events per patient in the 6 months’ pre-ablation to 1 event per patient in the median follow up period of 171 days post ablation (p=0.02). Mean shocks per-patient burden decreased from 3.5 to 0.08 in the same time period(p=0.03). Conclusion The SENSE2 protocol involves the integration of structural and functional data into the VT workflow for substrate characterization. It enables focused substrate maps to be performed without the need for complete geometry to be created in large ventricles. Outcomes compare favourably with our previous data but with significantly shorter procedure times. This streamlined workflow has the potential to improve care in VT ablation by shortening procedure times with similar outcomes which may reduce risks for the patient. Figure 1: Comparison of Voltage Map with MRI scar & corridors using ADAS

Implantable cardioverter-defibrillators (ICD) reduce the risk of sudden cardiac death in patients who are at risk and amongst among heart failure (HF) patients with a reduced left ventricular ejection fraction (LVEF). The aim of this study was to determine the differences in outcomes amongst patients in a contemporary ICD implant population based on primary or secondary indications and an ischaemic or non-ischaemic aetiology. The primary outcome was death or appropriate device therapy for a ventricular arrhythmia. The secondary outcome was inappropriate shock therapy. The study cohort included consecutive patients who had an ICD or CRT-D implanted at a high-volume regional referral centre in Essex between 2014 and 2015. The censor point for follow up was 31/12/2018. Cumulative incidences were analysed by the method of Kaplan–Meier and compared using the log-rank test. In addition, the relationship between several clinical variables were tested in a multivariate Cox model to predict long-term mortality and this is described with hazard ratios (HR) and 95% CI. 407 patients who received ICD treatment were followed up for a mean of 50±4 months. 63% had an Ischaemic cardiomyopathy and 60% had a primary prevention indication. Majority were men (81.5%), mean LVEF was (31±11) and mean age (71±11). The incidence of appropriate ICD therapy at 1-year post ICD insertion was 6.8% in all patients. This was significantly higher in patients with a secondary prevention indication compared to primary prevention (11.7% v 3.6% p=0.015) but similar in ischaemic compared to non-ischaemic patients (7.8% v 5.2% p=0.46). 1.9% patients had an inappropriate shock at 1 year and between group rate was similar. Overall 8.1% of patients did not survive beyond 1-year post implant with a mean time to death of 5.6±3.6 months. The cumulative incidence of the primary end-point at 1 year was similar in ischaemic and non-Ischaemic patients (7.8% v 8.6%; HR: 1.04, 95% CI 0.7–1.5, p=0.83) but was significantly higher at the end of study period in patients with an ischaemic aetiology (32.4% v 21%; HR: 1.59, 95% CI: 1.1–2.4, p=0.024) (Fig.1). In an adjusted Cox Hazard model, appropriate ICD therapy at 1 year (HR: 0.28, 95% CI: 0.17–0.47, p<0.001) and a secondary indication for ICD treatment (HR: 0.47, 95% CI: 0.31–0.73, p=0.001) were strongly associated with long-term mortality. Figure 1 Our study highlights outcomes in a long-term follow up of ICD patients and in light of the debate around the DANISH trial, we have shown that at 1 year, the benefit of ICD therapy is comparable in non-ischaemic compared to ischaemic cardiomyopathies. Moreover, patients who had an ICD implanted for secondary prevention had a 3-fold mortality benefit at 1 year and had a higher rate of death. Appropriate ICD therapy and a secondary prevention indication predicted long term mortality.