This study presents an electrocardiogram (ECG) monitoring and processing system which can observe subjects in real time and display the resultant ECG signals on a computer for observation. The primary application is for the remote observation of cardiac patients. This paper aims to determine its reliability by analysing its portability and wireless connectivity. The system is comprised of three principal units, namely the data acquisition circuit, where cardiac electrical signals are detected using three surface electrodes placed at three different positions on the chest wall to follow the Einthoven Triangle. The signals measured are amplified and filtered by components in a circuit and are then carried to a data processing unit where a ATmega328P microcontroller with a ZigBee interface module are used to transfer the biosignal wirelessly to the Graphical User Interface (GUI) unit which has the capacity to observe ECG biosignals on a computer. The results demonstrated that the design successfully produced a distortion-free signal, namely the hardware and software elements operated and intercommunicated correctly. In both LabVIEW and MATLAB configurations, the GUI characteristics were examined and found to yield unproblematic, user-friendly displays in real-time. Thus, this research provides a novel ECG system design to effectively analyse cardiac patients, however, it would be useful to develop a tool that can differentiate the various forms of cardiac arrhythmia.

Funding Acknowledgements This work was supported by the NIHR Leicester Biomedical Research Centre. XL was funded by MRC(MR/S037306/1) and BHF (PG/18/33/33780) Background It remains controversial as to whether rotors detected using phase mapping during persistent atrial fibrillation (persAF) represent main drivers of the underlying mechanism as others found rotors to be located near line of conduction block. Regional electrogram desynchronization (RED) has been suggested as successful targets for persAF ablation, but automatic tools and quantitative measures are lacking. Purpose We aim to use mean phase coherence (MPC) to automatically identify RED regions during persAF. This method was compared with phase singularity density (PSD) maps. Methods Patients undergoing left atrial (LA) persAF ablation were enrolled (n = 10). 2048-channel virtual electrograms (VEGMs) were collected from each patient using non-contact mapping (St Jude Velocity System, Ensite Array) for 10 seconds.  To remove far field ventricular activities, QRS onset and T wave end locations were detected from ECG lead I (Figure 1A) and only the VEGM segments from T end to QRS onset were included in the analysis. VEGMs were reconstructed using sinusoidal wavelets fitting and the phase of VEGMs determined using Hilbert transform. Phase singularities (PS) were detected using the topological charge method and repetitive PSD maps were generated. RED was defined as the average of MPC of each node against direct neighbouring nodes on the 3D mesh (Figure 1A-B). Linear regression analysis was used to compare the average MPC vs. PSD and vs. the standard deviation of MPC (MPC_SD). Results A total of 221,184 VEGM segments were analysed with mean duration of 364.2 milliseconds.  MPC has shown the ability to quantify the level of synchronisation between VEGMs (Figure 1B). Inverse correlation was found between PSD and average MPC values for all 10 patients (p < 0.0001, Figure 1C). Average MPC and MPC_SD were found to be inversely correlated (p < 0.0001, Figure 1C). Spatially, similar graphic patterns can be found from LA MPC maps and PSD maps for all patients (Figure 1D). Conclusion We have proposed a method to quantify the level of synchronisation between VEGMs. Phase density mapping showed a considerable agreement with RED regions reflecting regional conducting delays, which supports the previous finding where rotors found at conduction block. Inverse correlation between local average MPC and MPC_SD suggests that conduction delays of the identified regions are not heterogenous, posing directional preferences. Rather than solely looking for rotational activities, this method could identify comprehensive RED regions, which may also explain the conflicting results from different studies targeting rotational activities, where incomplete subsets of RED regions could have been targeted. Atrial RED regions can easily be identified with simultaneously collected electrograms from multi-polar catheters and should be targeted in future persAF studies. Abstract Figure 1

Purpose: Several studies have emphasised the significance of high dominant frequency (HDF) and rotors in the perpetuation of AF. However, the co-localisation relationship between both attributes is not completely understood yet. In this study, we aim to evaluate the spatial distributions of HDF regions and rotor sites within the left atrium (LA) pre and post HDF-guided ablation in PersAF.Methods: This study involved 10 PersAF patients undergoing catheter ablation targeting HDF regions in the LA. 2048-channels of atrial electrograms (AEG) were collected pre- and post-ablation using a non-contact array (EnSite, Abbott). The dominant frequency (DF, 4–10 Hz) areas with DF within 0.25 Hz of the maximum out of the 2048 points were defined as “high” DF (HDF). Rotors were defined as PSs that last more than 100 ms and at a similar location through subsequent phase frames over time.Results: The results indicated an extremely poor spatial correlation between the HDF regions and sites of the rotors in pre-versus post-ablation cases for the non-terminated (pre: CORR; 0.05 ± 0.17. vs. post: CORR; −0.030 ± 0.19, and with terminated patients (pre: CORR; −0.016 ± 0.03. post: CORR; −0.022 ± 0.04). Rotors associated with AF terminations had a long-lasting life-span post-ablation (non-terminated vs. terminated 120.7 ± 6.5 ms vs. 139.9 ± 39.8 ms), high core velocity (1.35 ± 1.3 mm/ms vs. 1.32 ± 0.9 mm/ms), and were less meandering (3.4 ± 3.04 mm vs. 1.5 ± 1.2 mm). Although the results suggest a poor spatial overlapping between rotors’ sites and sites of AFCL changes in terminated and non-terminated patients, a higher correlation was determined in terminated patients (spatial overlapping percentage pre: 25 ± 4.2% vs. 17 ± 3.8% vs. post: 8 ± 4.2% vs. 3.7 ± 1.7% p < 0.05, respectively).Conclusion: Using non-contact AEG, it was noted that the correlation is poor between the spatial distribution of HDF regions and sites of rotors. Rotors were longer-lasting, faster and more stationary in patients with AF termination post-ablation. Rotors sites demonstrated poor spatial overlapping with sites of AFCL changes that lead to AF termination.

Understanding the spatiotemporal behaviour of 'rotors' in human atrial fibrillation (AF) is important for using them as targets for ablation. This study aims to track the spatiotemporal stability of rotors over 5 min time interval during persistent atrial fibrillation (PersAF). This study involved 10 PersAF patients, who underwent catheter ablation. 2048 non-contact virtual unipolar electrograms (VEGMs) were simultaneously collected and resampled at 512Hz, QRST interval removed and reconstructed using a sinusoidal wavelet fitting approach (Kuklik et al. Subsequent density maps of rotors were generated. The VEGM were divided into a total of 60 segments of different durations starting from 5s, 10s, 15s and so on. The segments were further divided into; group A ≤ 30 s, group B > 30, density maps of different time durations were compared with the full 300 s. Rotor density maps in segments recorded in group A differed significantly from group B, (CORR: group A 10 s = 0.47 ± 0.064 Vs. 30 s = 0.69 ± 0.067 Vs. group B 45 s = 0.76 ± 0.066 Vs. 60 s = 0.80 ± 0.063; P<0.0001). Rotor density maps for group B showed higher similarity and lower variation (0.88 ± 0.092) when compared to group A (0.53 ± 0.134). Our results suggest that time duration ≤ 30 s is not sufficient to detect/track spatiotemporal organization of rotors in PersAF patients.

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