dc.contributor.author Lamothe, M. J. Reina. en_US dc.date.accessioned 2014-10-21T12:36:22Z dc.date.available 2014-10-21T12:36:22Z dc.date.issued 1994 en_US dc.identifier.other AAINN93783 en_US dc.identifier.uri http://hdl.handle.net/10222/55416 dc.description 117-lead body surface potential maps (BSPM) and 56-point magnetic field maps (MFM) of human cardiac electrical activity were recorded and analysed to establish the feasibility of spatially separating concurrent electrophysiological events of the heart cycle. en_US dc.description The present study focusses on events in the PR interval and was broken up into 4 parts: development and evaluation of signal-extraction protocols; characterisation of atrial activation; detection and isolation of the His-Purkinje system (HPS) signal from atrial repolarisation during the late PR segment; and, finally, enhancement of the $\delta$-wave maps and localisation of accessory pathways associated with ventricular pre-excitation in patients suffering from Wolff-Parkinson-White (WPW) syndrome. The atrial activation and WPW studies included a comparative analysis of the BSPM and MFM patterns. en_US dc.description The signal-extraction protocols studied were orthogonal expansion techniques (SVD, KLT), a correlation technique, and a simple averaging method. We conclude that the orthogonal expansion and correlation techniques have inherent difficulties, primarily associated with their mathematical constructs. The signal averaging method, though it does present some limitations, can be used successfully in the WPW problem. en_US dc.description The dominant dipole direction associated with atrial activation is tangential to the atrial blood masses, resulting in a higher sensitivity of the magnetic field, than the potential measurements, to atrial electric events. Results show that atrial repolarisation starts immediately after P-wave offset and is not delayed until ventricular activation, as has been suggested by some authors. We determined that no HPS signal is present in the extracted maps of the PR segment. Further, the spatial patterns and ramps in the PR segment that were previously associated with the conduction system, actually reflect the continuous changes in the electric source due to atrial repolarisation as a function of time in both magnetic and electric signals. en_US dc.description On the other hand, the decreased sensitivity to atrial repolarisation in BSPM measurements the detection of the early $\delta$-wave signal in patients with left-sided accessory pathways (AP). We used pattern-matching techniques (12-lead ECG, BSPM distributions) and inverse-solution localisation of AP to confirm the successful extraction of the atrial repolarisation signal. With identified limits to the present accuracy of localisation procedures based on inverse solutions, we make suggestions for improved 12-lead and BSPM pattern-matching criteria and present a basis for the development of MCG criteria to locate the site of the AP. en_US dc.description Thesis (Ph.D.)--Dalhousie University (Canada), 1994. en_US dc.language eng en_US dc.publisher Dalhousie University en_US dc.publisher en_US dc.subject Biophysics, Medical. en_US dc.title The feasibility of separating concurrent sources in cardiac magnetic field and body surface potential maps. en_US dc.type text en_US dc.contributor.degree Ph.D. en_US
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