On the detection of myocardial scar based on ECG/VCG analysis

In this paper, we address the problem of detecting the presence of myocardial scar from standard ECG/VCG recordings, giving effort to develop a screening system for the early detection of scar in the point-of-care. Based on the pathophysiological implications of scarred myocardium, which results in disordered electrical conduction, we have implemented four distinct ECG signal processing methodologies in order to obtain a set of features that can capture the presence of myocardial scar. Two of these methodologies: a.) the use of a template ECG heartbeat, from records with scar absence coupled with Wavelet coherence analysis and b.) the utilization of the VCG are novel approaches for detecting scar presence. Following, the pool of extracted features is utilized to formulate an SVM classification model through supervised learning. Feature selection is also employed to remove redundant features and maximize the classifier's performance. Classification experiments using 260 records from three different databases reveal that the proposed system achieves 89.22% accuracy when applying 10- fold cross validation, and 82.07% success rate when testing it on databases with different inherent characteristics with similar levels of sensitivity (76%) and specificity (87.5%)

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

Background: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. Methods: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). Findings: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29–146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0– 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25–1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39–1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65–1·60]; p=0·92). Interpretation: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

Background: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. Methods: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). Findings: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29–146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0– 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25–1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39–1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65–1·60]; p=0·92). Interpretation: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

BACKGROUND: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. METHODS: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). FINDINGS: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29-146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0- 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25-1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39-1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65-1·60]; p=0·92). INTERPRETATION: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention. FUNDING: British Heart Foundation

Detection of myocardial scar from the VCG using a supervised learning approach

This paper addresses the possibility of detecting presence of scar tissue in the myocardium through the in- vestigation of vectorcardiogram (VCG) characteristics. Scarred myocardium is the result of myocardial infarction (MI) due to ischemia and creates a substrate for the manifestation of fatal arrhythmias. Our efforts are focused on the development of a classification scheme for the early screening of patients for the presence of scar. More specifically, a supervised learning model based on the extracted VCG features is proposed and validated through comprehensive testing analysis. The achieved accuracy of 82.36% (sensitivity 84.31%, specificity 77.36%) indicates the potential of the proposed screening mechanism for detecting the presence/absence of scar tissue

Wireless sensor and actor networks: event detection algorithms based on fuzzy logic with regards to real time response prediction

Event detection in real environments is a research area that has attracted a lot ofinterest. The discipline of artificial intelligence seems to have gained significant ground.The main objective of these areas is the creation of appropriate algorithms and buildingmodels on real data sets, so that the evaluation metrics are able to confirm their abilityto detect whether or not the existence of real events. Assuming a reliable system(evaluated by the relevant metrics (Accuracy, Sensitivity, Specificity)) the basic researchproblem is to investigate the performance of the above system when the application ishosted in a WSN topology, and more particularly when the system is executed in realWSN hardware platforms which are characterized by limited-resources and under theerror-prone nature of wireless communications. Hence, the problem is examined fromtwo perspectives: i.) What are the limitations during the development and theimplementation of such systems in WSN infrastructures and ii.) how the performance ofsuch systems is affected while the Network QoS varies within the network topology.For these reasons we designed and developed two fuzzy logic systems, whichevaluated in the Matlab environment. Then the above systems implemented in C andexecuted by the embedded WSN platforms TelosB hardware platforms. Theexperimental evaluation confirmed our initial beliefs about the impact of networkconditions on the performance of the algorithm and the monolithic approach of localprocessing demonstrated to affect vital to the application itself.Driven by these observations, we propose novel techniques in order to implement fuzzylogic systems in WSN infrastructures targeting optimal resource allocation within anetwork topology. Towards this objective, the technique denoted as Directed AcyclicGraph to Network Graph (DAG2NG) is presented leading to the distributed implementation of the Fuzzy Logic. Moreover, the event triggered execution of theFuzzy Inference Systems is implemented in order to achieve optimal CPU utilization.The task scheduling problem, is extended beyond the framework of the fuzzy logic. Sowe design, study and evaluate a series of scheduling models that allow the distributionof tasks within the wireless nodes. The application of these models in the field of WSNsallows the study of the energy efficiency, response time and justice between nodes in aseries of algorithmic problems (parallel, nonparallel, hybrid), which can exist in variousWSN applications.The semantic relationship between the wireless nodes, is another object of this thesis.Both the event triggered implementation of fuzzy logic systems and the management ofthe nodes participating in a task assignment model, involve the discovery of semanticneighbors. So we propose two new semantic discovery algorithms neighbors, whom weevaluate.The thesis concludes with the proposal of a new algorithm that seeks to give a newdimension and answer to the problem of node-to-actor coordination.The assignment of the sensors at specific actors, taking into account the actors’capabilities as well as the heterogeneity of the network, lead to the proposal of a newsensor-to-actor coordination algorithm based on the Voronoi tesselation.H αναγνώριση γεγονότων κατά την παρακολούθηση ενός περιβάλλοντος αποτελεί έναιδιαίτερα ευρύ ερευνητικό αντικείμενο που έχει αποσπάσει το αντίστοιχο ερευνητικόενδιαφέρον. Ο επιστημονικός κλάδος της τεχνητής νοημοσύνης φαίνεται να έχει κερδίσεισημαντικό έδαφος. Ο βασικός στόχος των συγκεκριμένων περιοχών, είναι η δημιουργίακατάλληλων αλγορίθμων αλλά και η οικοδόμηση μοντέλων πάνω σε σετ πραγματικώνδεδομένων, ούτως ώστε οι μετρικές αξιολόγησης τους να επιβεβαιώνουν την ικανότητα τουςνα ανιχνεύουν πραγματικά γεγονότα αλλά και να ανιχνεύουν την μη ύπαρξη πραγματικώνγεγονότων. Δεδομένου λοιπόν ενός τέτοιου συστήματος που η απόδοση του έχει κριθεί από τιςαντίστοιχες μετρικές (Accuracy, Sensitivity, Specificity) θέτουμε στο προσκήνιο το ερευνητικόπρόβλημα της απόδοσης ενός τέτοιου συστήματος όταν η εφαρμογή του γίνεται εντός μιαςWSN τοπολογίας, και πιο συγκεκριμένα όταν η εκτέλεση του γίνεται από τις περιορισμένες σεπόρους WSN hardware πλατφόρμες, και κάτω από την επιρρεπή σε λάθη φύση τωνασυρμάτων επικοινωνιών.Έτσι η διατριβή αυτή πιάνει το παραπάνω σύστημα από δύο σκοπιές: i.) ποιοι είναι οιπεριορισμoί που τίθενται σε έναν developer κατά την ανάπτυξη τέτοιων συστημάτων σε WSNinfrastrucures και ii.) πως επηρεάζεται η απόδοση τέτοιων συστημάτων όταν το Network QoSαλλάζει μέσα στο δίκτυο. Για το σκοπό αυτό σχεδιάστηκαν και αναπτύχθηκαν δύοσυστήματα ασαφούς λογικής που αφού αξιολογήθηκαν στο περιβάλλον του Matlab,υλοποιήθηκαν σε C και εκτελέστηκαν από τις ενσωματωμένες WSN πλατφόρμες υλικούTelosB. Η πειραματική αξιολόγηση, επιβεβαίωσε τις αρχικές μας πεποιθήσεις για την επίδρασητων δικτυακών συνθηκών στην απόδοση του αλγορίθμου ενώ η μονολιθική προσέγγιση τουlocal processing έδειξε να επηρρεάζει ζωτικά την ίδια την εφαρμογή.Ορμούμενοι από αυτά τα συμπεράσματα, η συγκεκριμένη διατριβή έρχεται να μελετήσει και ναπροτείνει νέες τεχνικές εκτέλεσης συστημάτων ασαφούς λογικής, επιδιώκωντας τη βέλτιστη κατανομή πόρων των κόμβων εντός μιας δικτυακής τοπολογίας. Στο πλαίσιο αυτόπροτείνεται η τεχνική Directed Acyclic Graph to Network Graph (DAG2NG) που επιδιώκει τηνκατανεμημένη υλοποίηση τέτοιων συστημάτων. Η event triggered στρατηγική εκτέλεσηςσυστημάτων ασαφούς λογικής σχεδιάζεται και υλοποιείται στη συγκεκριμένη διατριβήπροκειμένου να επιτύχει βέλτιστη χρήση του υπολογιστικού κόστους του αλγορίθμουασαφούς συμπερασμού.Η κατανομή των εργασιών μεταξύ των κόμβων μιας δικτυακής τοπολογίας, επεκτείνεται καιπέρα από το πλαίσιο της ασαφούς λογικής. Έτσι σχεδιάζουμε μελετούμε και αξιολογούμε μιασειρά μοντέλων επεξεργασίας που επιτρέπουν τη κατανομή εργασιών εντός των ασυρμάτωνκόμβων. Η εφαρμογή των μοντέλων αυτών στο χώρο των WSNs επιτρέπει τη μελέτη τηςενεργειακής απόδοσης, της χρονικής απόκρισης αλλά και της δικαιοσύνης μεταξύ των κόμβωνσε μια σειρά αλγοριθμικών προβλημάτων (parallel, nonparallel, hybrid), που μπορεί ναυπάρξουν σε διάφορες WSN εφαρμογές.Η σημασιολογική συγγένεια των ασυρμάτων κόμβων, έρχεται επίσης σαν αντικείμενο μελέτηςτης συγκεκριμένης διατριβής. Τόσο η event triggered υλοποίηση των συστημάτων ασαφούςλογικής όσο και η διαχείριση των κόμβων που συμμετέχουν σε ένα μοντέλο επεξεργασίας,προϋποθέτουν την ανακάλυψη των σημασιολογικών γειτόνων. Έτσι προτείνουμε δύο νέουςαλγορίθμους ανακάλυψης σημασιολογικών γειτόνων, τους οποίους και αξιολογούμε.Η παρούσα διατριβή καταλήγει με την πρόταση ενός νέου αλγορίθμου που επιδιώκει να δώσειμια νέα απάντηση στο πρόβλημα του node-to-actor coordination. Η κατανομή των sensors σεσυγκεκριμένους actors λαμβάνοντας υπόψιν, τις δυνατότητες των actors αλλά και τηνανομοιογένεια του δικτύου, οδηγεί στην πρόταση ενός νέου αλγορίθμου sensor-to-actorcoordination που κάνει χρήση του Voronoi tesselation

On Event/Time Triggered and Distributed Analysis of a WSN System for Event Detection, Using Fuzzy Logic

Event detection in realistic WSN environments is a critical research domain, while the environmental monitoring comprises one of its most pronounced applications. Although efforts related to the environmental applications have been presented in the current literature, there is a significant lack of investigation on the performance of such systems, when applied in wireless environments. Aiming at addressing this shortage, in this paper an advanced multimodal approach is followed based on fuzzy logic. The proposed fuzzy inference system (FIS) is implemented on TelosB motes and evaluates the probability of fire detection while aiming towards power conservation. Additionally to a straightforward centralized approach, a distributed implementation of the above FIS is also proposed, aiming towards network congestion reduction while optimally distributing the energy consumption among network nodes so as to maximize network lifetime. Moreover this work proposes an event based execution of the aforementioned FIS aiming to further reduce the computational as well as the communication cost, compared to a periodical time triggered FIS execution. As a final contribution, performance metrics acquired from all the proposed FIS implementation techniques are thoroughly compared and analyzed with respect to critical network conditions aiming to offer realistic evaluation and thus objective conclusions’ extraction