Investigation of Inaccuracies in the Assessment of Ventricular Late Potentials Using 12-lead ECG Recordings

Introduction. Ventricular late potentials (VLP) are predictors of cardiac disorders such as sudden death syndrome, myocardial infarction and ventricular tachyarrhythmias. Therefore, VLP assessment allows the severity and possible dangerous consequences of such disorders to be predicted.Aim. To determine errors associated with VLP assessment by high-resolution 12-lead ECG recordings.Materials and methods. VLPs were determined by the modulus of the cardiac electrical vector using signals from orthogonal leads. The conversion error was assessed using synchronous ECG recordings of 12-channel and orthogonal leads, the method of digital filtering (to reduce noise and interference) and the method of identifying characteristic points of the QRS complex and VLPs.Results. The conversion of 12-lead ECG signals into orthogonal signals results in errors associated with the assessment of both the modulus of the cardiac electrical vector and all VLP indicators. The Kors transformation was shown to provide the minimum errors when assessing the cardiac electrical vector modulus in the QRS area, with the errors related to the VRMS assessment not exceeding 0.084 %. The estimation of the QRSd and LAS errors should consider the nature of VLP variations and the zone of uncertainty in their assessment. The ambiguity of the results of assessing the boundaries of violations and the absence of pathologies in cardiac ventricular depolarization indicates the influence of a large number of factors on research accuracy. Errors in the assessment of these factors may result in under- and overestimation of dangerous heart rhythm disturbances and incorrect prediction of the patient' state.Conclusion. The obtained results can be used for reducing errors associated with the assessment of VLP indicators, improving the diagnostic accuracy of dangerous heart rhythm disturbances and predicting disease exacerbation due to structural and morphological disorders of the myocardium.

Impact of channels identification and ablation in ventricular tachycardia patients through high-density mapping: preliminary experience from an Italian registry

Funding Acknowledgements Type of funding sources: None. Background Ventricular tachycardia (VT) ablation techniques in ischemic cardiomyopathy have evolved during the recent years. However, the long-term success rate remains disappointing. A technique based on channel identification and ablation through a novel automated algorithm may limit the extent of ablation needed and possibly lead to higher successful rate. Purpose To report preliminary data on feasibility and safety of a channel identification approach and to characterize late potentials (LPs) features using an ultra-high density mapping system with a novel analysis tool in ischemic VT procedures. Methods Consecutive patients (pts) indicated for ischemic VT ablation were enrolled in the CHARISMA study. A complete map of the left ventricle was performed prior and after ablation through the Rhythmia mapping system. For our purpose channels were defined as any signal activity bounded by anatomic and functional barriers and characterized through a novel map analysis tool (Lumipoint-LM-) that automatically identifies fragmented late potentials (LPs) and continuous activation was used on the whole ventricular substrate. Procedural endpoint was the elimination of all identified conducting channels (CCs) by ablation at the CC entrance and exit followed by abolition of any residual LPs inside the CC. The ablation endpoint was noninducibility. Results A total of 18 channels were identified through LM from 14 pts: 71.4% of the pts had 1 CC, 28.6% had 2 CCs. In the majority of the cases LPs where identified only inside CCs (57.1%), whereas in 6 cases (42.9%) LPs were present both inside and outside. The mean conduction time inside CCs was 50.3 ± 30ms, the mean CC length was 32.6 ± 17mm and the conduction velocity was 0.8 ± 0.5 mm/ms. LPs covered a mean area of 7.0 ± 5mm2 (ratio between LPs area and CCs’ area = 52.4 ± 33.7%). At voltage map analysis 1 CC was present in 78.6% of the cases (2 CCs in 21.4%). LPs were identified only inside CCs in 42.9% of the cases, both inside and outside in 50% and only outside in 7.1%. Healthy tissue (voltage level≥0.5mV) was prevalent (61.2 ± 13.8%), followed by intermediate voltage areas (0.5-0.05mV; 37.5 ± 13.7%) and very low voltage areas (<0.05mV; 1.2 ± 2%). LPs were found mostly at intermediate voltage areas (54.1 ± 31.7% of the covered area; 39.1 ± 28.4% at healthy tissue and 6.8 ± 17.8% at very low voltage areas). Agreement in CCs identification between advanced analysis through LM and voltage map was fair (9/14 with complete agreement). In 3 cases voltage map overestimated LPs areas, in 2 cases failed to fully identify LPs. All CCs’ entrance and exit were successfully ablated and abolition of any residual LPs inside the CC was achieved in all pts. No complication occurred. Noninducibility was achieved in all the cases. Conclusions In our preliminary experience, a new channel identification approach through the advanced Lumipoint algorithm seems to be safe, feasible and effective at least in the acute setting of ischemic VT ablation.

QRS dispersion using 252-leads Body Surface Mapping (BSM) – an explorative study of a novel diagnostic tool for Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)

Background The diagnosis of ARVC is complex and challenging requiring multiple investigational tools, most of which include the demonstration of depolarization/conduction abnormalities, described in recent HRS consensus documents 2019. A simple and user friendly diagnostic tool is warranted. Purpose The purpose of our study was therefore to explore whether the analysis of QRS dispersion obtained from 252-leads recorded by a Body Surface Mapping (BSM) system can be used to identify ARVC patients as compared to the traditional ECG criteria including QRS dispersion measured by conventional 12 lead surface ECG. Methods 12 definite ARVC patients (10/12 with known pathogenic mutation) (Group 1) and 8 healthy family members tested negative for the family mutation served as controls (Group 0), were included. All patients underwent 12-lead ECG (50mm/sec), Signal-averaged ECG for late potentials and 252 lead BSM recordings. The QRS duration was measured in each of the 12 ECG leads manually with digital caliper. The QRS duration from the BSM leads were manually analyzed in Matlab by two observers unaware of the diagnosis. For each lead, the mean value of three randomly chosen beats was calculated. The QRS dispersion was calculated as the difference between the minimum and maximum value for both the 12 lead ECG and the BSM recordings. Results The mean age was 49,6 and 38,8 years in ARVC patients and controls, respectively. The number of males in the two groups were 8/12 and 5/8, respectively. Epsilon waves and Terminal Activation Duration (TAD) >55msec were detected in 6/12 and 8/12 ARVC patients, respectively, but in no controls. Late potentials were detected in 11/12 ARVC patients and in 2 controls. The QRS duration and QTc duration was not statistically different in the two Groups. The ECG-QRS dispersion was significantly more pronounced in Group 1 (42 ms ± 15, range 20–70 ms) than in Group 0 (26 ms ± 8, range 16–36 ms) (p=0.013). The BSM-QRS dispersion was significantly longer in Group 1 (68 ms ± 17, range 29–90ms) than in Group 0 (30 ms ± 7, range 22–41ms) (p=0.001). Only one ARVC patient had a BSM-QRS dispersion <50 msec, whereas none of the controls had a QRS dispersion over 50 msec (Fig. 1). Conclusion BSM-QRS dispersion, specifically using the cut off <50 ms, can potentially be a more sensitive and specific method than other ECG related techniques for diagnosing ARVC patients versus non-ARVC patients. Larger patient cohorts and further studies are required to confirm our findings. Figure 1. ECG and BSM-QRS dispersion Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Selanders Stiftelse