Method and apparatus for the guided ablative therapy of fast ventricular arrhythmia

Method and apparatus for guiding ablative therapy of abnormal biological electrical excitation. The excitation from the previous excitatory wave is significant at the beginning of the next excitation. In particular, it is designed for treatment of fast cardiac arrhythmias. Electrical signals are acquired from recording electrodes, and an inverse dipole method is used to identify the site of origin of an arrhythmia. The location of the tip of an ablation catheter is similarly localized from signals acquired from the recording electrodes while electrical pacing energy is delivered to the tip of the catheter close to or in contact with the cardiac tissue. The catheter tip is then guided to the site of origin of the arrhythmia, and ablative radio frequency energy is delivered to its tip to ablate the site

Boundary element method in spatial characterization of the electrocardiogram

The electrochemical activity of the heart gives rise to an electric field. In electrocardiography, cardiac electrical activity is assessed by analyzing the potential distribution of this field on the body surface. The potential distribution, or the set of measured surface-voltage signals, is called the electrocardiogram (ECG). Spatial properties of the ECG can be captured with body surface potential mapping (BSPM), in which the electrocardiogram is measured using dozens of electrodes. In this Thesis, methods for solving the forward and inverse problems of electrocardiography are developed and applied to characterization of acute myocardial ischemia. The methodology is based on numerical computation of quasi-static electric fields in a volume conductor model. An open-source Matlab toolbox for solving volume conductor problems with the boundary element method (BEM) is presented. The Galerkin BEM and analytical operator-integrals are, for the first time, applied to the epicardial potential problem; the formulation for a piece-wise homogeneous volume conductor is presented in detail, enabling straightforward inclusion of the lungs or other inhomogeneities in the thorax model. The results show that errors due to discretization and forward-computation are smaller with the linear Galerkin (LG) method than with the conventional methods. These benefits do, however, not reflect to the Tikhonov-regularized inverse solution. If the lungs are omitted, as commonly is done, the choice of the computational method is not significant. In a set of 22 patients measured with BSPM during coronary angioplasty (PTCA), the application of a BEM thorax model with dipolar equivalent sources enabled accurate discrimination between occluded coronary arteries: the correct classification was obtained in 21 patients using the BSPM and in 20 patients using a 5-electrode set suggested elsewhere. The ischemic regions could also be localized anatomically correctly with simplified epicardial potential imaging, even though patient-specific thorax models were not used. In another set, comprising 79 acute ischemic patients and 84 controls, dipole-markers performed well in detection and quantification of acute ischemia. These results show that the modeling-approach can provide valuable information also without patient-specific models and complicated protocols

Method and apparatus for guiding ablative therapy of abnormal biological electrical excitation

This invention involves method and apparatus for guiding ablative therapy of abnormal biological electrical excitation. In particular, it is designed for treatment of cardiac arrhythmias. In the method of this invention electrical signals are acquired from passive electrodes, and an inverse dipole method is used to identify the site of origin of an arrhytmia. The location of the tip of the ablation catheter is similarly localized from signals acquired from the passive electrodes while electrical energy is delivered to the tip of the catheter. The catheter tip is then guided to the site of origin of the arrhythmia, and ablative radio frequency energy is delivered to its tip to ablate the site

Reconstructing Electrocardiogram Leads From a Reduced Lead Set Through the Use of Patient-Specific Transforms and Independent Component Analysis

In this exploration into electrocardiogram (ECG) lead reconstruction, two algorithms were developed and tested on a public database and in real-time on patients. These algorithms were based on independent component analysis (ICA). ICA was a promising method due to its implications for spatial independence of lead placement and its adaptive nature to changing orientation of the heart in relation to the electrodes. The first algorithm was used to reconstruct missing precordial leads, which has two key applications. The first is correcting precordial lead measurements in a standard 12-lead configuration. If an irregular signal or high level of noise is detected on a precordial lead, the obfuscated signal can be calculated from other nearby leads. The second is the reduction in the number of precordial leads required for accurate measurement, which opens up the surface of the chest above the heart for diagnostic procedures. Using only two precordial leads, the other four were reconstructed with a high degree of accuracy. This research was presented at the 33rd International Conference of the IEEE Engineering in Medicine and Biology Society in 2011.1 The second algorithm was developed to construct a full 12-lead clinical ECG from either three differential measurements or three standard leads. By utilizing differential measurements, the ECG could be reconstructed using wireless systems, which lack the common ground necessary for the standard measurement method. Using three leads distributed across the expanse of the space of the heart, all twelve leads were successfully reconstructed and compared against state of the art algorithms. This work has been accepted for publication in the IEEE Journal of Biomedical and Health Informatics.2 These algorithms show a proof of concept, one which can be further honed to deal with the issues of sorting independent components and improving the training sequences. This research also revealed the possibility of extracting and monitoring additional physiological information, such as a patient\u27s breathing rate from currently utilized ECG systems

Electrocardiographic Consequences Of Electrical And Anatomical Remodeling In Diabetic And Obese Humans

Background. Diabetes and obesity are two major risk factors for cardiovascular disease. Both can cause changes due to cardiac sources in body-surface potentials: BSPs), that is, in electrocardiograms: ECGs). By identifying the major effects of diabetes and obesity on BSPs, we hope to reveal the electrical phenotype of diabetes in body-surface ECGs in the presence of obesity. Methods. A Bidomain Platform was constructed to link heart-surface transmembrane potentials: TMPs) and BSPs. The Forward-Problem Module of the platform calculates BSPs from a bidomain-model of myocyte TMPs and torso anatomy. The platform also contains a Cardio-myocyte TMP Estimation Module in which an innovative method, named regularized waveform identification: RWI), was developed. It is a new approach used to reconstruct the TMPs from BSPs, that is, solving the electrocardiographic inverse bidomain problem. Using normal TMPs, BSPs were simulated on obese torsos and compared to BSPs on a normal torso to determine ECG changes that might accompany certain obese habitus. BSPs on a normal torso were also simulated with both normal TMPs and TMPs whose duration was increased in a manner expected to occur in the diabetic. In addition, BSPs were measured, heart and torso models were found on two adult male subjects: one normal and one obese diabetic. BSPs and estimated TMPs in these subjects, found by using the RWI method, were compared to identify ECG changes that might be found in the obese diabetic in a clinical setting. Results. Forward-problem solutions found for obese heart-torso models with normal TMPs compared to normal had relative errors: RE) of 12, 30, and 68\% for 20\% left-ventricular hypertrophy, 16\% abdomen extension, and displaced heart, respectively. These results suggest that standard 12-lead ECG measurement could be significantly affected by the anatomical changes associated with obesity. Simulation results also showed diabetic electrical remodeling may have a strong impact on BSPs. An RE of 125\% was observed between normal and diabetic BSPs due to prolongation of recovery that might accompany diabetes. Energy reduction of BSPs was found in both simulated and measured BSPs with obesity. Although QT interval prolongation found in simulated BSPs was not seen in the ECGs recorded from the obese diabetic subject, QT dispersion(QTd) was found increased in diabetic in both simulated and measure ECGs. Obviously, no statistical conclusions can be reached with our limited data set, but the suggestive results call for further clinical observations. TMPs were estimated in realistic, normal heart-torso model simulations using the RWI method. REs of about 15\% were found for up to 10\% noise added to BSPs; and for errors in heart size of 10\% and heart location of $\pm 1$ cm, which were significant improvements over conventional regularization methods alone. Conclusions. In this study, we characterized electrical changes with diabetes and anatomical changes with obesity; then independently evaluated their influences on body surface potentials: BSPs). These results suggest that standard 12-lead ECG measurements could be strongly influenced by the anatomical changes associated with obesity. Body-surface maps and inverse solutions to the heart-surface that minimize volume-conductor effects are likely to be more useful in investigating the influence of diabetic electrical remodeling among obese diabetic patients. Simulation results showed that the RWI inverse solution performed much better than traditional regularization methods alone and is robust in the presence of noise and geometric error. By incorporating temporal information, in the form of the basic TMP wave shape, estimation accuracy was enhanced while maintaining computational simplicity

Contributions to electrocardiographic science

This thesis reports original theoretical and experimental studies related to the measurement and interpretation of the electrical activity of the heart. The relevant literature and clinical practice are reviewed at length. Part I is a review of the science of electrocardiography. Included in the review are the electrophysiology of the heart, the potential theory which relates the electrocardiogram (E.C.G.) to its source, the various schemes used to measure and interpret the E.C.G. and the use of computer modelling to aid in E.C.G. interpretation. The effects of body shape and internal conductivity inhomogeneities on the E.C.G. are studied by means of a computer model. A simple form of the model has a piecewise homogeneous interior with spherical boundaries and a surface admittance is invoked to model changes in the surface shape. An extended form of the model allows the boundaries to be irregular and it is solved by means of an integral equation and the extended boundary condition. Representative numerical results are presented, illustrating the practical utility of the model. The sensitivity of the E.C.G. to certain types of inhomogeneity and surface shape changes is established. An experimental study, supported by a computer model based on the techniques outlined above, of the non-invasive detection of the signals from the ventricular specialised conduction system is reported. Thirty-five subjects were studied using a measurement system with a frequency response extending from 0.1 Hz to 500 Hz (-3 dB points) and using a pair of chest electrodes (similar to Lead CM1), Signal averaging was performed on groups of approximately 50 beats, using the onset of the QRS wave as a timing reference. The signals were detected with certainty in 85% of the subjects studied. The typical measured signal waveform is remarkably similar to that predicted by the aforementioned computer modelling technique. Two features are identified: an initial positive deflection (which probably represents the initial activation of the bundle branches) and a notch approximately 10 msec later (which may represent the passage of the activation into the bundle branches)

Extracting heart rate dependent electrocardiogram templates for a body emulator environment

Abstract. Medical device and analysis method developments often include tests on humans, which are expensive, time consuming, and sometimes even dangerous. In order to perform human tests, special safety conditions and ethical and legal requirements must be taken into account. Emulators that can emulate the physiological functions of the human body could solve these difficulties. In this study, the heart rate depended electrocardiogram templates for this kind of an emulator were extracted. The real-life electrocardiogram preprocessing included a high-pass filter and a Savitzky-Golay filter. A beat detection algorithm was developed to detect QRS complexes in the signals and classify beat artefacts based on the RR interval sequences and two adaptive thresholds. Heart rate levels were detected using the K-means clustering technique. Vectorcardiogram signals were converted from the electrocardiogram signals using the inverse Dower’s transformation matrix, and vectorcardiogram templates were extracted to the respective heart rate levels. Finally, a graphical user interface was created for the mentioned methods. The developed beat detection algorithm was tested with the MIT-BIH Arrhythmia Database and the comparison was made with the state-of-the-art algorithms. The beat detection algorithm resulted the sensitivity of 99.77 \%, precision of 99.65 \%, and detection error rate of 0.58 \%. Based on the results, the proposed methods and extracted vectorcardiogram templates were successful.Sykkeestä riippuvien elektrokardiogrammimallien poiminta kehoemulaattoriympäristöön. Tiivistelmä. Lääketieteellisten laitteiden ja analyysimenetelmien kehitystyö sisältää usein ihmisille suoritettavia testejä, jotka ovat kalliita, aikaa vieviä ja joskus jopa vaarallisia. Ihmiskokeiden toteuttamiseksi on otettava huomioon erityisiä turvallisuusehtoja, sekä eettisiä ja laillisia vaatimuksia. Emulaattorit, jotka pystyvät jäljittelemään ihmiskehon fysiologisia toimintoja, voivat olla ratkaisu näihin ongelmiin. Tässä tutkimuksessa sykkeestä riippuvia elektrokardiogrammimalleja poimittiin tämän tyyppiselle emulaattorille. Tosielämän elektrokardiogrammisignaalien esikäsittely sisälsi ylipäästösuodattimen ja Savitzky-Golay suodattimen. Sydämen lyöntien tunnistussalgoritmi kehitettiin tunnistamaan QRS-komplekseja signaaleista ja luokittelemaan lyöntiartefakteja RR-intervallisekvenssien ja kahden adaptiivisen kynnysarvon perusteella. Syketasot tunnistettiin käyttämällä K-means klusterointitekniikkaa. Vektorikardiogrammisignaalit muunnettiin elektrokardiogrammisignaaleista käyttämällä käänteistä Dowerin muunnosmatriisia ja vektorikardiogrammimallit poimittiin vastaaville syketasoille. Lopuksi luotiin graafnen käyttöliittymä mainituille menetelmille. Kehitetty lyöntien tunnistusalgoritmi testattiin MIT-BIH Arrhythmia Database-tietokannalla ja vertailu suoritettiin vastaavien algoritmien kanssa. Algoritmi suoriutui 99,77 % herkkyydellä, 99,65 % spesifsyydellä ja 0,58 % virheprosentilla. Tulosten perusteella ehdotetut menetelmät ja poimitut vektorikardiogrammimallit olivat onnistuneita

Development of electrocardiographic image processing software

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1993.Includes bibliographical references (leaves [40]-[41]).by Ken Justin.B.S

Estimation of epicardial electrical potentials from body surface measurements based on a digital simulation of the human theory

Imperial Users onl