QT analysis of intrauterine growth retarded and normal children at 10 years old

The main objective of the work described in this paper is to develop an algorithm to detect QT, other ECG intervals and to find any correlation between QT, ST, QRS, Heart rate (HR) of normal and IUGR children at 10 yrs. The cohort under study is described in chapter 2 as 41 IUGR and 34 as normal. The ECGs of 24 hour for each child were used to find any differences between the two groups. Normal children have QRS intervals during awake (73.96 ±13.65 ms) and asleep (78.75±14.76 ms), and IUGR has (73.94 ±12.85 ms day, 75.98±14.80 ms night), and IUGR children have a slightly higher corrected QTc (418.25±28.92ms Day, 437.22±20.17 ms night), compared to normal (411.37 ±36.13 ms day, 431.79±20.12 ms night). At 10 years of age the measured ECG intervals of all normal and IUGR children was unable to show any deviation from the normal paediatric limits. IUGR children are relatively more prone to longer QTc intervals

Analysis of spatial variability for the development of reduced lead body surface maps

The spatial frequency of measurement points from standard ECG systems lacks accuracy to diagnose local variability in cardiac activity on the torso. Body Surface Mapping (BSM) improves this accuracy, but lacks the simplicity to be implemented in clinic on a regular basis. Reduced-lead BSM system improves applicability, but currently no standardization of lead reduction has been agreed upon. This research investigates the reduction of BSMs based on Lomb-Scargle Spectral Analysis to determine an appropriate electrode positioning through spatial frequency assessment. Based on the measurement of 13 healthy volunteers, a 128 electrode system could be reduced to a 36 electrode system and an 84 electrode system for ventricular and atrial activity measurements, respectively, with up to 10% loss of the full information provided by the original body surface potential map. Further research will investigate the appropriate positions of these electrodes and the effect of lead reduction for various cardiac abnormalities

Patient-specific three-dimensional torso models for analysing cardiac activity

Standard electrocardiogram (ECG) is routinely used for recording cardiac electrical activity but lacks 3D details. Body surface potential mapping techniques have been developed more recently. A major challenge related to this technique is the projection of body signals back to their original sources in the heart. For an accurate projection, one needs to take into account patient-specific electrophysiological data of tissues surrounding the heart. Much information regarding physiological variations, as well as the exact position of organs in the torso, can be obtained from magnetic resonance (MR) images. Here, a patient-specific methodology for building 3D torso models from transverse MR images is proposed. Torso contour detection is based on edge detection using a canny filter and indicating contour points with a polar coordinate system. Organ detection is performed using an interpolation technique with Active Contour modelling. Results show that accurate torso models can be constructed with short processing time

Visualizing intracardiac atrial fibrillation electrograms using spectral analysis

Atrial fibrillation is the most common cardiac arrhythmia, and it is associated with increased risk of stroke, heart failure, and mortality. This work describes spectral analysis techniques that are being used in conjunction with visualization algorithms to help guide catheter ablation procedures that aim at treating patients with arrhythmia

A platform to guide catheter ablation of persistent atrial fibrillation using dominant frequency mapping

Dominant frequency (DF) mapping has been widely used to study the pathophysiology of atrial fibrillation (AF). In this study, a DF mapping system was developed to guide catheter ablation on electro-physiology (EP) procedures of persistent AF patients. The proposed platform has an automated graphical user interface (GUI) that processes non-contact unipolar electrograms (EGMs) recorded simultaneously by St. Jude Ensite Velocity System and provides 3D representation of the left atrium with DF behaviours and phase analysis

Are atrial fibrillation highest dominant frequency (HDF) areas the source of dominant excitation patterns? A left atrial panoramic view

Atrial fibrillation (AF) catheter ablation success depends on the possibility to accurately determine areas on the atrial endocardium at which AF activation originates. One way to determine if major AF activation pathways originate at identified source is through causality analysis. This work assessed to what extent left atrial highest dominant frequency (HDF) areas can be identified as sources of activation pathways in 10 male subjects suffering from persistent AF. Virtual electrograms were collected from 64 endocardial locations for at least 5 minutes. Frequency and causality were analyzed on 4 s signal segments Causality was assessed using the directed transfer function (DTF) algorithm, and AF activation sources were identified as endocardial locations of which the VEGM signal had high influence on other VEGM signals. Co-localization of high influence and HDF areas was evaluated for different area overlap and spectral organisation (OI) thresholds. Results show that, on average, good overlap only existed in 64.6% (± 8.8%) over all subject using the lowest threshold settings. Good overlap rates reduced with more conservative thresholds. This indicates that HDF areas might not always identify origins of main AF activation pathways

Propagation of meandering rotors surrounded by areas of high dominant frequency in persistent atrial fibrillation

Background: Identification of arrhythmogenic regions remains a challenge in persistent atrial fibrillation (persAF). Frequency and phase analysis allows identification of potential ablation targets. Objective: This study aimed to investigate the spatiotemporal association between dominant frequency (DF) and reentrant phase activation areas. Methods: A total of 8 persAF patients undergoing first-time catheter ablation procedure were enrolled. A noncontact array catheter was deployed into the left atrium (LA) and 2048 atrial fibrillation electrograms (AEGs) were acquired for 15 seconds following ventricular far-field cancellation. DF and phase singularity (PS) points were identified from the AEGs and tracked over consecutive frames. The spatiotemporal correlation of high DF areas and PS points was investigated, and the organization index at the core of high-DF areas was compared with that of their periphery. Results: The phase maps presented multiple simultaneous PS points that drift over the LA, with preferential locations. Regions displaying higher PS concentration showed a degree of colocalization with DF sites, with PS and DF regions being neighbors in 61.8% and with PS and DF regions overlapping in 36.8% of the time windows. Sites with highest DF showed a greater degree of organization at their core compared with their periphery. After ablation, the PS incidence reduced over the entire LA (36.2% ± 23.2%, P < .05), but especially at the pulmonary veins (78.6% ± 22.2%, P < .05). Conclusion: Multiple PS points drifting over the LA were identified with their clusters correlating spatially with the DF regions. After pulmonary vein isolation, the PS’s complexity was reduced, which supports the notion that PS sites represent areas of relevance to the atrial substrate

Spatiotemporal behaviour of high dominant frequency during persistent atrial fibrillation

Atrial electrograms (EGMs) with high dominant frequency (DF) are believed to represent atrial substrates with periodic activation responsible for the maintenance of persistent atrial fibrillation (persAF). This study aimed to assess the DF spatiotemporal behavior using high density noncontact mapping in persAF. For 8 patients undergoing left atrial (LA) persAF ablation, 2048 noncontact virtual unipolar EGMs were simultaneously collected and after the removal of ventricular far-field activity, Fourier based spectral analysis was used to identify DF on each EGM. Atrial areas with the highest DF (HDF, DF ± 0.25 Hz) were delimited in each frame for all EGMs, creating HDF `clouds'. Cumulative HDF clouds found at each frame were counted in the 3-D LA representation. To further assess the temporal stability of the cloud, the number of EGMs not hosting any HDF was determined for each window over time. The results show the number of occurrences of HDF clouds in the LA. The temporal behavior was analyzed by counting the number of positions on the 3-D representation of the LA not visited by HDF along time. Our results show HDF in persAF is not temporally stable and spatial distribution throughout the atria suggests the existence of driver regions with very rapid and regular activity maintaining AF. Therefore mapping the cumulative HDF might be an interesting strategy for ablation

Dynamic behavior of rotors during human persistent atrial fibrillation as observed using non-contact mapping

Rotors have been related to atrial fibrillation (AF) maintenance. We analyzed the behavior of rotors in persistent AF (persAF) utilizing a novel non-contact methodology and compared this to real time dominant frequency (DF) analysis. 2048 noncontact virtual unipolar atrial electrograms (VEGMs) were collected simultaneously (EnSite Array, St. Jude Medical) from 10 persAF patients (duration: 34 ± 25 months) undergoing left atrial (LA) ablation. After QRST-removal, FFT was used to identify the global DF of the LA (range 4-10 Hz; 1 s time-window; 50 % overlap; highest DF (HDF) (DF -0.25 Hz); up to 20 s/patient). The organization index (OI) was measured and phase was found via Hilbert-transform. Phase singularities (PSs) were tracked and were categorized according to their lifespan into short (lifespan 100 ms). A total of 4578 PSs were tracked. 5.05 % (IQR: 2.75 ~ 30.25 %) of the tracked PSs were long-lived and were observed in 11 % (IQR: 2.75 ~ 17.5 %) of the windows. The windows with rotors showed significantly higher HDF (mean ± SD, 8.0 ± 0.43 Hz vs 7.71 ± 0.50 Hz, p<; 0.0001) and lower OI (0.76 ± 0.04 vs 0.79 ± 0.03, p<; 0.0001) when compared with the short-lived PSs windows. During persAF, the LA showed distinct behaviors as characterized by rotors. Often, no rotors were observed during sustained AF and, when present, the rotors continually switched between organized and disorganized behaviors. Long-lived rotors correlated with higher atrial rates. Our results suggest that rotors are not the sole perpetuating mechanism in persAF

Unifying automated fractionated atrial electrogram classification using electroanatomical mapping systems in persistent atrial fibrillation studies

Ablation targeting complex fractionated atrial electrograms (CFAE) for treating persistent atrial fibrillation (persAF) has shown conflicting results. Differences in automated algorithms embedded in NavX (St Jude Medical) and CARTO (Biosense Webster) could influence CF AE target identification for ablation, potentially affecting ablation outcomes. To evaluate this effect, automated CFAE classification performed by NavX and CARTO on the same bipolar electrograms from 18 persAF patients undergoing ablation was compared. Using the default thresholds, NavX classified 69±5% of the electrograms as CFAEs, while CARTO detected 35±5%% (Cohen's kappa κ≈0.3, P<0.0001). Both primary and complementary metrics for each system were optimized to balance CF AE detection for both systems. Using revised thresholds found from receiver operating characteristic curves, NavX classified 45±4%, while CARTO detected 42±5% (κ≈0.5, P<0.0001). Our work takes a first step towards the optimization of CFAE detection between NavX and CARTO by providing revised thresholds to reduce differences in CF AE classification. This would facilitate direct comparisons of persAF CFAE-guided ablation outcome guided by NavX or CARTO