This master thesis deals with QRS complex detection and ECG delineation. The theoretical part of this work describes wavelet transform, some of QRS detection approaches and some of ECG delineation approaches. For algorithm realization in Matlab is used redundant dyadic discrete wavelet transform. Algorithm is designed for experimental electrocardiograms of isolated rabbit hearts and it is evaluated through manually determined references.

This dissertation deals with QRS complex detection and ECG delineation. The theoretical part of the work describes basics of electrocardiography, QRS detection approaches, ECG delineation approaches, the standard CSE database and the wavelet transform theory. The practical part of the work describes designed methods of QRS complex detection and ECG delineation. The designed methods are based on a continuous wavelet transform, appropriate scales, appropriate mother wavelet, cluster analysis and leads transformation. The introduced algorithms were evaluated on the standard CSE database. The obtained results are better, than directly comparable results of other methods and accomplished given database criteria. The robustness of designed algorithms was successfully tested on CSE database signals modified by compression and filtering. The proposed ECG delineation algorithm was successfully used as a tool for evaluation of diagnostic distortion of ECG signals modified by compression.

This thesis focuses on the issue of atrial fibrillation and the success of their detection in the ECG signal. It provides a description of electrical activity of the heart with the theoretical analysis of atrial fibrillation and methods for their detection. Additionally the work describes procedures for the implementation of three selected methods for the detection of atrial fibrillation in the MATLAB environment, presents the results of their tests on two atrial fibrillation signal databases and assesses the accuracy of each method.

Apple WatchTM huserar funktionaliteter inom medicinteknik. Detta är ett examensarbete inom medicinteknik som ställer frågan om hur pass bra mätningar den utför i förhållande till motsvarande medicinteknisk produkt. Smartklockan kan identifiera R-toppar i EKG mycketväl, och därigenom också förmaksflimmer. I förhållande till pulsoximeter presenteras syremättnad några procentenheter för högt och följsamheten är något stel. Apple WatchTM mäter puls bra vid högre hjärtslagsfrekvenser, men har kraftigt begränsad träffsäkerhet och sämre följsamhet vid mätningar i vila. Det kan inte styrkas att Apple WatchTM kan användas som verktyg för att ställa någon medicinsk diagnos, utifrån testerna i detta arbetet, där datamängd och urvalsgrupp samtidigt varit för liten för att kunna ge riktig statistisk signifikans. / The Apple WatchTM has functionalities related to the field of medical technology. This is a degree project in medical engineering that raises the question how adequate measurements it can acquire, in relation to a corresponding medical device. The Apple WatchTM can identify R waves in ECG very well and thereby also atrial fibrillation. In relation to pulse oximeters, oxygen saturation is given a few percentage points too high and the compliance is somewhat rigid. Apple WatchTM measures heart rate well at higher heart rates, but has severely limited accuracy and has poorer compliance when measuring at rest. The tests of this work shows that the Apple WatchTM should not be used as a tool for making any medical diagnosis, but the amount of data and test subjects were not sufficient enough to make it statistically significant.

Artefakter försvårar analys av långtids-elektrokardiografi-registrering (LTER) och resulterar i en försämrad diagnostisk säkerhet. Minimering av mängden artefakter spelar således en väsentlig roll för ställandet av rätt diagnos. Syftet med denna studie var att jämföra om mängden artefakter, som uppkom vid 24-timmars LTER på patienter, skiljde sig åt med och utan fixering av elektroderna. Populationen bestod av trettio patienter som var inbokade för 24-timmars LTER vid Länssjukhuset Ryhov i Jönköping. Patienterna delades in i två grupper med femton patienter i varje grupp. På grund av fyra externa bortfall bestod det slutgiltiga urvalet av tretton studiedeltagare i vardera gruppen. I grupp A användes ett tubnät för att hålla kablarna på plats och i grupp B fixerades varje elektrod och kabel med Mefix. Grupperna jämfördes sedan avseende mängden artefakter som uppkom under registreringsperioden.  För att analysera om det förelåg någon signifikant skillnad i artefaktuppkomst mellan grupperna användes Wilcoxons rangsummetest. Rangsummorna för respektive grupp beräknades och jämfördes med ett kritiskt intervallvärde. Rangsummorna låg inom intervallet för det kritiska värdet, varpå nollhypotesen ej kan förkastas. Följaktligen förelåg ingen signifikant skillnad i mängden uppkomna artefakter mellan grupperna. På grund av ett litet urval samt brister i undersökningsförfarandet kunde dock inga grundade statistiska slutsatser konkluderas. / Artefacts complicate the analysis of long-term electrocardiography-registration (LTER) and result in a worsened diagnostic accuracy. Thus, minimization of the amount of artefacts plays a vital role in the making of a correct diagnosis. The aim of this study was to compare if the amount of artefacts that occurred during 24-hour LTER on patients, differed with and without electrode fixation.  Thirty patients who underwent a 24-hour LTER, at Länssjukhuset Ryhov in Jönköping, were included in the study and divided into two groups. In group A; a tubular net bandage was used to keep the electrocardiography (ECG) cables in place. In group B, the electrodes and ECG cables were fixated with Mefix. A comparison was made, between the groups, regarding the amount of artefacts that occurred during the registration period.  To analyze if there was a significant difference between the groups, Wilcoxon rank sum test was applied. The result proved to be within the range limits of the critical value, which implies that the null hypothesis cannot be rejected. Hence, there was no significant difference regarding the amount of artefacts that occurred. However, because of a small sample volume and shortfalls in the study procedure, no founded statistical conclusions could be drawn.

Darbe tyrėme veloergometrinių mėginių metu užregistruotus elektrokardiogramos parametrus JT ir RR, kurie gali atspindėti organizmo būklę: reguliacinę, aprūpininančiąją ir vykdančiąją sistemas. Nors šie parametrai ir pakankamai informatyvūs, tačiau dažnai esant nedideliems širdies ir kraujagyslių sutrikimams jokių pokyčių neparodo. Todėl reikalingi nauji analizės metodai, kurie padėtų atskleisti kokybiškai naują informaciją glūdinčią EKG parametruose ir jų kaitoje. Sukūrėme taikomoją programą, kuri parašyta „Matlab“ aplinkoje. Ši programa grupuoja duomenis, atlieka reikiamus skaičiavimus ir rezultatus, įvairius grafikus, pateikia vartotojui ekrane. Tyrimo eigoje sukūrėme tris metodus: EKG parametrų kitimo greičio skaičiavimo ir vaizdavimo fazinėje plokštumoje; EKG parametro glodumo koeficiento skaičiavimo ir vaizdavimo; EKG parametro duomenų grupavimo metodą, Pirmajame metode pastebėjome EKG JT parametro fazinių plokštumų kitimo greičių skirtumus tarp ligonių ir sveikų asmenų grupių, antrajame EKG JT parametro glodumo koeficiento a, o trečiajame EKG JT parametro sudarytų porų diskriminantų vidurkių skirtumus. Norėdami įsitikinti gautų hipotezių teisingumu pritaikėme šių metodų rezultatams neparametrinį Manio-Vitnio-Vilkoksono testą (ZM) su reikšmingumo lygmeniu . Gavome, kad gautos hipotezės yra teisingos. Tai yra pastebėti skirtumai yra reikšmingi tarp sveikų asmenų ir asmenų su tam tikrais kardiologiniais nusiskundimais grupių. Atliktas darbas – tai tik dar vienas žingsnis... [toliau žr. visą tekstą] / For correct specification human’s physiological state, it is very important to evaluate the changes of main human organism systems. In this paper, the parameters that characterize the function of periphery, regulation and supplying systems, JT and RR interval have been studied. Interpolation of discrete data from the physical load obtained by provocative incremental bicycle ergometry stress test was made by cubic spline. The differences for various groups of person (sportsmen and patients with ischemic heart disease) were investigated. EKG parameters were applied in three methods: EKG parameters changes in speed computing and imaging in phase plane, EKG parameters smoothness level calculation, EKG parameters data grouping method. The study revealed that the JT interval’s changes in speed reliably differences between healthy and ill people. Also JT parameter’s smoothness level and JT parameter’s discriminants difference between the groups.

A low-cost circuit board design is presented, which in one embodiment is smaller than a credit card, for biopotential (EMG, ECG, or EEG) data acquisition, with a focus on EEG for brain-computer interface applications. The device combines signal conditioning, low-noise and high-resolution analog-to-digital conversion of biopotentials, user motion detection via accelerometer and gyroscope, user-programmable digital pre-processing, and data transmission via Bluetooth communications. The full development of the device to date is presented, spanning three embodiments. The device is presented both as a functional data acquisition system and as a template for further development based on its publicly-available schematics and computer-aided design (CAD) files. The design will be made available at the GitHub repository https://github.com/kellygs/eeg.

Rapporter 'j'ai vu le stimulus' est la marque de la vision consciente et implique deux caractéristiques fondamentales de l'expérience consciente, à savoir son aspect qualitatif et la subjectivité. L'aspect qualitatif correspond à la perception vive du stimulus, alors que la subjectivité correspond à la conscience implicite que j'ai fait l'expérience du stimulus. Afin de déterminer les bases neurales de la subjectivité, nous introduisons le concept de cadre neural subjectif ('neural subjective frame') qui correspond aux mécanismes biologiques définissant le sujet en tant qu'une entité biologique, un point d'ancrage à partir duquel des expressions relatives à l'expérience consciente à la première personne peuvent être formulées. De plus, je propose que la représentation neurale de l'information viscérale pourrait constituer ce cadre neural subjectif. Afin de tester expérimentalement cette hypothèse, à l'aide de la magnétoencéphalographie, nous avons enregistré les réponses neuronales aux battements cardiaques, pendant que les participants réalisaient une tâche de détection visuelle. Nous avons trouvé que les réponses neuronales aux battements cardiaques avant la présentation du stimulus, dans le cortex cingulaire ventral antérieur et le lobule postérieur intrapariétal droit, pouvaient prédire la détection d'un stimulus visuel de faible contraste. Les réponses neuronales aux battements cardiaques de plus forte amplitude s'accompagnaient d'un taux de détection et d'une sensibilité plus importants, sans changement du critère de décision. Ni les fluctuations des paramètres corporels ni l'excitabilité corticale générale ne semblent contribuer à ces résultats. Par ailleurs, le fait de voir consciemment le stimulus a ralenti le battement cardiaque après la réponse des participants et cet effet de décélération cardiaque pouvait être prédit par la réponse neuronale aux battements cardiaques du cortex cingulaire antérieur ventral, avant la présentation du stimulus. Ainsi, nos résultats sont en faveur de l’hypothèse selon laquelle la cartographie des afférents viscéraux façonne notre expérience subjective perceptive. Au-delà de la vision consciente, ces résultats suggèrent que les signaux internes du corps et leurs représentations neuronales peuvent être la source de fluctuations dans des aires corticales multi-fonctionnelles. / Reporting “I saw the stimulus” is the hallmark of conscious vision and implies two fundamental characteristics of conscious experience, namely qualitativeness and subjectivity. Qualitativeness refers to the vivid feeling of the stimulus, whereas subjectivity refers to the implicit awareness that the experience occurred for me. To account for the neural basis of subjectivity, we introduce a concept termed the neural subjective frame which corresponds to the basic biological mechanisms defining the subject as a biological entity, as an anchoring point from which the first-person statements of conscious experience can be expressed. I further propose that neural representation of visceral information could constitute the neural subjective frame. To experimentally test this proposal, using magnetoencephalography, we recorded neural events locked to heartbeats while participants conducted visual detection task. We found that neural responses to heartbeats before stimulus onset in ventral anterior cingulate and right posterior intraparietal lobule could predict the detection of faint visual stimulus. Larger amplitude of neural responses to heartbeats were accompanied by enhanced hit-rate and sensitivity, but without changes in decision criterion. Neither fluctuations in measured bodily parameters nor in overall cortical excitability could account for this finding. In addition, consciously seeing the stimulus decelerated heartbeat after participants responded and the heartbeat slowing effect could be predicted from the prestimulus neural responses to heartbeats in ventral anterior cingulate cortex. Our findings therefore support the hypothesis that neural mapping of visceral afferents shape perceptual subjective experience. Beyond conscious vision, our findings suggest that signals from internal body and their neural representations could be sources of fluctuations in multi-functional cortical areas.

The electrocardiogram (ECG) is a graphical representation of the electrical activity of the heart. The 12-lead ECG shows this activity in 12 "views" called "leads", relative to the location of sensors attached to the body surface. The ECG is a routinely applied cost effective diagnostic medical test, utilised in healthcare settings around the world. Although more than three hundred million ECGs are recorded each year, correctly interpreting them is considered a complex task. Failure to make correct interpretations can lead to injury or death and costs vast sums in litigation payments. Many automated attempts at interpreting ECGs have been implemented and continue to be developed and improved. Despite this, automated methods are still considered to be less reliable than expert human interpretation. As ECG interpretation is both a cognitive and visual task, eye-tracking holds great potential as an investigative methodology. This thesis aims to identify any cues in visual behaviour that may indicate differences in subsequent ECG interpretation accuracy. This is the first work that uses eye-tracking to analyse how practitioners interpret ECGs as a function of accuracy. In order to investigate these phenomenon, several experiments were carried out using eye-movements captured from clinical practitioners that interpret ECGs as part of their usual clinical role. The findings presented in this thesis have advanced research in the understanding of ECG interpretation. Specifically: Clinical history makes a difference to how people look at ECGs; different gaze patterns are often found in accurate and inaccurate interpretation groups. Grouping data to account for within ECG lead behaviour (eye-movement patterns within a lead) is more revealing than analysis at the level of the lead (eye-movements between leads). Findings suggest analysing visual behaviour at this level is crucial in order to detect behaviour in ECG interpretation. Further to this the thesis presents eye-tracking techniques that can be applied to wider areas of task performance. These methods work over complex stimuli, are able to deal post hoc with differently sized groups and generate appropriate areas of interest on a stimulus. These methods detect important differences in eye-movement behaviour between groups that are missed when applying standard inferential statistical techniques.

Didelė dalis širdies susirgimų diagnostinių kriterijų gaunama registruojant ir analizuojant kardiosignalus, kurie atspindi tiek elektrinės širdies veiklos sutrikimus (EKG), tiek ir hemodinaminės bei mechaninės veiklos pokyčius, t.y. impedanskardiograma (IKG) ir seismokardiograma (SKG). Dar daugiau, efektyvus širdies susirgimų diagnostikos problemų sprendimas yra naujų kardiosignalų analizės technologijų kūrimas. Jau kelis dešimtmečius Furjė transformacija taikoma EKG dažnumų analizei, tuo tarpu kai IKG ir SKG dažnio charakteristikų vertinimui šis metodas nebuvo naudojamas. Darbo tikslas buvo pritaikyti Furjė analizę įvertinant bei palyginant tris sinchroniškai užregistruotus kardiosignalus, nes jie atspindi elektrinės širdies, hemodinaminės bei mechaninės širdies veiklos pokyčius geriau nei vienas EKG signalas. Kitas darbo tikslas buvo pritaikyti Furjė analizę įvertinant bei palyginant trijų sinchroniškai užregistruotų signalų - EKG, IKG ir SKG dažnio charakteristikas ir koherenciją bei klasifikuoti dvi grupes - "sveikas" ir "ligonis". Rezultatai rodo, kad koherencijos vertinimas ir spektrinė analizė gali būti naudinga gali būti naudingas širdies kraujagyslių bei plaučių sistemų ligų diagnostikai. / A big part of heart disease diagnostics criteria is collected by registration and analysis of cardio signals that reflect the disturbances of the electric heart activity – electrocardiogram (EСG), changes of hemodynamic - impedance cardiograms (IСG) and mechanic activity - seismocardiogram (SСG). ECG analysis is generally applying in clinic practice, but usually in visual way only. Due to the development of the technologies, the bigger amount of data could be stored and more exact analysis of information could be carried out. Therefore, a solution of problem of effective diagnostics of heart diseases is the creation of new technologies for analysis of cardio signals. Previously Fourier series were applied to frequency analysis of ECG, but this method was not applied for estimation of ICG and SCG frequency characteristics. In this thesis the frequency analysis method was applied to three cardio signals, because they reflect the electrical and mechanical work of the human heart better as entirely ECG signal. The main aim of this work was to adapt Fourier transformation to assessing and comparing some characteristics of hereinbefore signals, such as coherence and classify two searching groups - “healthy” and “sick”. Results showed that rating of coherence and spectral analysis could be useful for rightly analyzing and classifying the searching groups.