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Biomedical subjects

M E Nygårds

Publications and source records attributed to M E Nygårds.

13 recordsLinked to original sources
PubMed1988

Computer simulation of cardiac pacing.

A mathematical model of the cardiac conduction system, including external pacemakers, has been developed. The heart is modeled as a network in which the impulse propagation is described by differential equations; several arrhythmia-generating mechanisms, such as modulated parasystole, reflection, macro and micro re-entry and block, can be simulated. Different kinds of pacemaker modes have been incorporated in the model, thus making it possible to simulate the interaction between the heart and the pacemaker. The model can be tuned by the user according to electrophysiological data so that pacemaker programs can be tested under different underlying conditions. During a simulation, the program generates ECG signals and pacemaker diagnostic diagrams. This model can be used for training and testing, and also as a support system when searching for the optimal pacing therapy for a particular patient.

Computer Simulation↗
PubMed1987

Computer simulation of cardiac arrhythmias.

A mathematical model of the cardiac conduction system has been developed. The mechanisms of cardiac arrhythmias are described mathematically, and the heart is modeled as a network, where each element is defined by a unique set of time parameters from the action potential. The mathematical description is separated from the network structure, thus making it possible to run the model with different network sizes. Simulated ECG curves are produced in each case. This model is especially suited for rhythm studies, and a variety of different cardiac arrhythmia mechanisms has been simulated such as reentry, reflection, modulated parasystole, and different kinds of block.

Action Potentials↗
PubMed1976

On-line computer processing of pressure data from cardiac catheterizations.

A flexible program system for on-line analysis of pressure data from cardiac catheterizations is described. The programs are implemented on an IBM 1800 computer, equipped with remote oscilloscope/keyboard terminals. The current computer system can handle any combination of up to 4 pressure signals. During catheterization, measurement specifications (i.e. calibration levels or sites of pressure recordings) are entered via the keyboard immediately before each recording. As an option the whole expected measurement sequence may be stored on disk before the catheterization starts. This method will minimize the necessary interaction with the computer when the same catheterization procedure is used on several occasions. Changes from the predetermined scheme may, however, be undertaken before each recording to meet with unexpected events that may arise during the catheterization. After computer detection of calibration levels, the recorded signals are digitized during 20 seconds and analysed beat-by-beat. Calculated values are averaged and presented on the terminal oscilloscope in tabular and/or graphic form. The waveform analysis performed by the program system is validated in a statistical comparison between manually and automatically computed values.

Cardiac Catheterization↗
PubMed1976

Evaluation of a computer-based system for detecting ventricular arrhythmias.

A digital system for real-time arrhythmia monitoring in the coronary care unit has been designed. The system is based on an algorithm for discrimination between normal complexes and ventricular ectopic beats (VBs). A beat is classified as normal if the absolute difference from a running average of the patient's normal QRS is below an adaptive threshold. To prevent artifacts and beats of non-ventricular origin from being falsely interpreted as VBs, each abnormal beat is correlated with a typical VB waveform, incorporated into the program. A VB is recognized only when the correlation coefficient exceeds 0.8. In a performance study, ECGs from 15 patients were recorded on magnetic tape and replayed to the computer. Independent evaluation by two physicians showed a total of 1 306 VBs, 94% correctly classified by the computer. In the group labelled "suspected VBs" the detection rate was lower (average 69%). Out of the whole number of complexes (53 260), 0.45% were falsely interpreted as VBs by the computer. Artifacts giving rise to false VBs are included in this figure. The causes of false positive and false negative VBs were thoroughly investigated and on the basis of these results, possible improvements in the system are discussed.

Arrhythmias, Cardiac↗