A comprehensive framework for evaluation of high pacing frequency and arrhythmic optical mapping signals

Introduction: High pacing frequency or irregular activity due to arrhythmia produces complex optical mapping signals and challenges for processing. The objective is to establish an automated activation time-based analytical framework applicable to optical mapping images of complex electrical behavior.Methods: Optical mapping signals with varying complexity from sheep (N = 7) ventricular preparations were examined. Windows of activation centered on each action potential upstroke were derived using Hilbert transform phase. Upstroke morphology was evaluated for potential multiple activation components and peaks of upstroke signal derivatives defined activation time. Spatially and temporally clustered activation time points were grouped in to wave fronts for individual processing. Each activation time point was evaluated for corresponding repolarization times. Each wave front was subsequently classified based on repetitive or non-repetitive events. Wave fronts were evaluated for activation time minima defining sites of wave front origin. A visualization tool was further developed to probe dynamically the ensemble activation sequence.Results: Our framework facilitated activation time mapping during complex dynamic events including transitions to rotor-like reentry and ventricular fibrillation. We showed that using fixed AT windows to extract AT maps can impair interpretation of the activation sequence. However, the phase windowing of action potential upstrokes enabled accurate recapitulation of repetitive behavior, providing spatially coherent activation patterns. We further demonstrate that grouping the spatio-temporal distribution of AT points in to coherent wave fronts, facilitated interpretation of isolated conduction events, such as conduction slowing, and to derive dynamic changes in repolarization properties. Focal origins precisely detected sites of stimulation origin and breakthrough for individual wave fronts. Furthermore, a visualization tool to dynamically probe activation time windows during reentry revealed a critical single static line of conduction slowing associated with the rotation core.Conclusion: This comprehensive analytical framework enables detailed quantitative assessment and visualization of complex electrical behavior

Dynamics of cardiac re-entry in micro-CT and serial histological sections based models of mammalian hearts

Cardiac re-entry regime of self-organised abnormal synchronisation underlie dangerous arrhythmias and fatal fibrillation. Recent advances in the theory of dissipative vortices, experimental studies, and anatomically realistic computer simulations, elucidated the role of cardiac re-entry interaction with fine anatomical features in the heart, and anatomy induced drift. The fact that anatomy and structural anisotropy of the heart is consistent within a species suggested its possible functional effect on spontaneous drift of cardiac re-entry. A comparative study of the anatomy induced drift could be used in order to predict evolution of atrial arrhythmia, and improve low-voltage defibrillation protocols and ablation strategies. Here, in micro-CT based model of rat pulmonary vein wall, and in sheep atria models based on high resolution serial histological sections, we demonstrate effects of heart geometry and anisotropy on cardiac re-entry anatomy induced drift, its pinning to fluctuations of thickness in the layer. The data sets of sheep atria and rat pulmonary vein wall are incorporated into the BeatBox High Performance Computing simulation environment. Re-entry is initiated at prescribed locations in the spatially homogeneous mono-domain models of cardiac tissue. Excitation is described by FitzHugh-Nagumo kinetics. In the in-silico models, isotropic and anisotropic conduction show specific anatomy effects and the interplay between anatomy and anisotropy of the heart. The main objectives are to demonstrate the functional role of the species hearts geometry and anisotropy on cardiac re-entry anatomy induced drift. In case of the rat pulmonary vein wall with ~90 degree transmural fibre rotation, it is shown that the joint effect of the PV wall geometry and anisotropy turns a plane excitation wave into a re-entry pinned to a small fluctuation of thickness in the wall

Genetic algorithm based feature selection combined with dual classification for the automated detection of proliferative diabetic retinopathy

Proliferative diabetic retinopathy (PDR) is a condition that carries a high risk of severe visual impairment. The hallmark of PDR is the growth of abnormal new vessels. In this paper, an automated method for the detection of new vessels from retinal images is presented. This method is based on a dual classification approach. Two vessel segmentation approaches are applied to create two separate binary vessel map which each hold vital information. Local morphology features are measured from each binary vessel map to produce two separate 4-D feature vectors. Independent classification is performed for each feature vector using a support vector machine (SVM) classifier. The system then combines these individual outcomes to produce a final decision. This is followed by the creation of additional features to generate 21-D feature vectors, which feed into a genetic algorithm based feature selection approach with the objective of finding feature subsets that improve the performance of the classification. Sensitivity and specificity results using a dataset of 60 images are 0.9138 and 0.9600, respectively, on a per patch basis and 1.000 and 0.975, respectively, on a per image basis

Hypoxémie dans les dissections aortiques aiguës de type A

Médecine. Chirurgie généraleObjectifs : Déterminer les facteurs de risque d’hypoxémie postopératoire et la morbi-mortalité associée au cours des dissections aortiques aigues de type A (DAA). Patients et méthodes : Etude rétrospective sur la survenue d’hypoxémie chez 186 patients ayant bénéficié d’une chirurgie pour DAA. Résultats : L’hypoxémie est survenue chez 30,6% des patients. Le taux de mortalité hospitalier n’était pas significativement différent entre les groupes hypoxémie vs non hypoxémie. L’hypoxémie postopératoire était associée à un taux plus important de patients nécessitant une ventilation mécanique supérieure à 24 heures et une augmentation de la durée de séjour en réanimation. Un IMC élevé, l’utilisation des inotropes, un taux d’ASAT élevé et l’extension de la dissection aux artères rénales étaient des facteurs prédictifs indépendants. Conclu-sion : L’hypoxémie en postopératoire de DAA est fréquente et son degré d’extension semble en être un facteur prédictif important.Objectives : To determine risk factors and morbi-mortali-ty following surgical repair for type A acute aortic dissection (ATAAD). Methods : This was a retrospective study analyzing hypoxemia in 186 patients who underwent surgery for ATAAD. Results : Hypoxemia occurred in 30,6% of patients. Operative mortality was not statistically different between hypoxemia and non-hypoxe-mia groups. The proportion of patients requiring mechanical ventilation for more than 24hrs and the lengths of intensive care unit and hospital stays were significantly longer in patients with hypoxemia. Independent risk factors of postoperative hypoxemia were increased BMI, use of inotropic agents, elevated AST and extension of the dissection to renal arteries. Conclu-sions : Hypoxemia after surgery for ATAAD is common and the degree of extension of the dissection was found to be a major determining factor

SHR24ReEntry.avi

Re-entry activation in an 18 month old SHR atri

Poster_Valencia.pdf

Poster presented at atrial signals 2017, Valenci

Atrial flutter in a 12 month old SHR

This animation shows flutter in an isolated 12 month old SHR atrium with 6:1 RA->LA conduction block