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M Tysler

Publications and source records attributed to M Tysler.

9 recordsLinked to original sources
PubMed2002

Information on heart repolarization changes obtained from body surface ECG potentials.

Possibility to obtain information about local changes of heart repolarization from body surface potentials was studied on a model. Activation-recovery intervals (ARI) in surface ECG leads were tested as indicators of changed repolarization in the underlying myocardium. ECG signals corresponding to activation of myocardium with normal and changed action potential duration were simulated on the surface of a realistic inhomogeneous torso. ARI intervals were derived from all ECG signals and displayed as surface ARI maps. Results suggest that shortening and prolongation of action potentials in anterior myocardial regions can be visible in corresponding areas on surface ARI maps while only prolongation in postero-lateral regions can be observed. Reproducibility of ARI maps was checked on real measurements using 63 and 192 surface ECG leads. Obtained ARI maps exhibited acceptable reproducibility with correlation of 0.73 to 0.87. Based on the model and experimental results it is hoped that ARI maps can give some insight into the myocardium repolarization and help to recognize tissue with changed properties, primarily in heart regions underlying the anterior chest.

Body Surface Potential Mapping↗
PubMed2002

Cardio 7--portable system for high resolution ECG mapping.

One of the main difficulties in using body surface potential mapping (BSPM) techniques is the need of complicated multi-channel measuring system. In this paper practical portable ECG mapping system is introduced. The system consists of a notebook computer and a data acquisition system box connected to the computer by fast IEEE 1284 parallel interface working in ECP mode. Concept of the device enables to extend the basic 134-channel high-resolution multi-channel ECG amplifying unit up to 256 channels. Application software includes measurement and real time monitoring of ECG signals, computation and display of several types of body surface potential maps. System can be connected to hospital information networks and supply them with measured ECG data for advanced processing or central archiving.

Body Surface Potential Mapping↗
PubMed1996

The uniform double layer model and myocardial infarction: forward solution consideration.

The Uniform Double Layer (UDL) model of the cardiac generator is often used for forward simulation of body surface potentials (BSPs). The model also proved to be very useful for the inverse computation of heart activation. However, for the purposes of Myocardial Infarction (MI) modelling mostly the Multiple Dipole (MD) models are used. In our study, the ability of UDL model to represent the activation of the heart with an old MI was examined. The finite element model of the heart was used to simulate electrical activation of the heart with an old MI. Different locations of endocardial MI were used. For each of them three cases were considered according to the scale of the infarcted area: small and medium endocardial and large transmural. For the further computation of the electric field within the torso volume conductor two types of UDL representation of the cardiac generator were used. For the first UDL model, supposing the scared tissue to be unexcitable, an "infarcted" surface (different from the "healthy" surface) of activated myocardium was generated for each case of MI. Times when activation wavefront reached particular nodes on the surface served as an input for the forward computation of BSPs. To be able to understand the behaviour of the UDL, we also created the second UDL model, where the "infarcted activation sequence" was approximated on the original "healthy" heart surface. The BSPs were computed for each case of MI using both UDL cardiac generators. The boundary element method with the inhomogeneous volume conductor was used for computations. The BSPs generated by both models for the same case of MI were compared using the correlation coefficient. The results show, that it is possible to find an approximation of the "infarcted activation sequence" on the "healthy" heart generator surface in a way that BSPs generated by both models have a correlation coefficient higher than 0.96 for the entire period of depolarisation. Visualisation of the epicardial isochrones might help to understand the UDL model behaviour under the MI conditions. It would be useful for the correct interpretation of the results when using the UDL model for inverse solution. (Fig. 7, Ref. 5.)

Body Surface Potential Mapping↗
PubMed1996

Model study of influence of extracardial factors on the inverse localization of preexcitation sites.

Inverse solution techniques are expected to help in noninvasive localization of ventricular preexcitation sites. The influence of selected extracardial factors on the accuracy of the inverse localization of the initial activation sites was studied on a model. Each of 8 simulated activation sequences was initiated in a different single starting point at the atrioventricular ring. Corresponding ecg potentials on the surface of a realistic model of inhomogeneous torso were used for the inverse localization procedure. A multiple dipole (MD) model of the cardiac generator composed of 39 segmental dipoles was used in the inverse computations. As it was shown in a previous study, the method was able to localize the 8 starting points even if a simplified torso model and a limited number of leads was used. In this study, influence of another two factors was evaluated: inaccuracy of location of the MD generator and presence of noise in surface potentials. Several shifts and rotations of the heart generator relative to its exact position were modeled. When the mean deviation of starting points was about 1 cm the mean localization error varied from 0.5 cm up to 1.0 cm for complete model data--198 surface potentials and a torso model including lungs and ventricular cavities. When a noise with uniform and Gaussian distribution was added to the surface potentials, the use of averaged body surface potentials significantly improved accuracy and stability of the inverse solution. For root mean square value of noise sigma = 14 microV the mean error of localization was 0.9 cm. For higher noise (sigma = 30 microV) the results were substantially deteriorated. The influence of a noise was studied on complete model data. (Tab. 3, Fig. 5. Ref. 6.)

Body Surface Potential Mapping↗
PubMed1995

[Location of atrial and ventricular insertions of accessory atrioventricular pathways using surface ECG mapping and its importance in catheter ablation therapy].

BACKGROUND: The modern non-pharmacological therapy of the WPW syndrome by means of catheter ablation is based on the interruption of the accessory pathway(-s) by radiofrequency current energy. Destruction of the morphologic substrate of the arrhythmia alters the activation wave spread in the heart. OBJECTIVES: It was the aim of this report to demonstrate the diagnostic potential of BSM in localizing both overt and concealed accessory pathways. Presented study analyzes the alterations of the cardioelectric field by means of body surface ECG mapping in two female patients with accessory pathways before and after their successful curative treatment by radiofrequency catheter ablation. METHODS: Five patients were analyzed prior and after RF catheter ablation by BSM, two of them were selected for this presentation. One patient with WPW syndrome suffered from frequent supraventricular tachycardia due to in one female patient with an overt accessory pathway. The other patient was for several years incessantly in permanent junctional reentry tachycardia due to a concealed accessory pathway. The examination comprised 12-lead ECG, orthogonal vectorcardiogram according to Frank, BSM using a regular 80-electrode-array system and signal-averaged ECG. RESULTS: The RF ablation was successful in both patients and their arrhythmia was abolished. By means of a detailed analysis of the ventricular activation prior RF ablation in the patient with WPW syndrome the precise site of the ventricular insertion of the accessory pathway in the left lateral free wall was predicted. Furthermore, alterations of the terminal QRS complex were observed when comparing pre- versus post-ablation maps. In the second patient the atrial insertion of the accessory pathway with retrograde and decremental conduction was successfully localized to the right septal region by means of pre-ablation BSM. CONCLUSIONS: Both ventricular and atrial activation can be in detail analyzed by means of BSM. Such analysis offers more precise information on the spatial component of the activation wave spread. This case report gives further evidence that BSM is a useful method for precise localization of both ventricular and atrial insertion sites of accessory pathways in patients with paroxysmal tachycardias due to this electrophysiologic abnormality. This information gained recently clinical impact since it can be directly used for faster arrhythmogenic substrate targeting during ablation therapy. (Fig. 5, Ref. 17.)

Adolescent↗
PubMed1994

A model study of the sensitivity of body surface potential distribution to variations of electrode placement.

The effect of electrode displacement as one of the sources of reproducibility errors in body surface potential maps was studied using a realistic computer model of the cardiac electric field. A uniform dipole layer model of the cardiac generator and a realistic geometry of the torso, heart, and lungs was adopted for the simulation of surface potentials during ventricular activation. The effect of systematic electrode displacement in terms of longitudinal shifts and variations of longitudinal size (height) of the mapped area was studied. The map reconstruction error of three different limited lead systems and the variability of maps measured on all points of the mapping grid, as well as maps reconstructed from limited lead systems, were investigated and quantified. A mean relative error of map reconstruction of less than 3.5% was found for longitudinal shifts from -4.4 to +1.7 cm, and for longitudinal size changes from 65 to 108% of the initial area. For vertical displacements of electrodes between the limits of +/- 2.0 cm for full grid maps and +/- 1.4 cm if limited lead systems were used, the mean relative error of the maps remained under 5%.

Body Surface Potential Mapping↗