Comparison of magnetocardiography and electrocardiography.
OBJECTIVE
Automated techniques were developed for the measurement of cardiac repolarisation using magnetocardiography.


METHODS
This was achieved by collaboration with the Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany and the Grönemeyer Institute of Microtherapy, Bochum, Germany, to obtain recordings of magnetocardiograms (MCGs) in cardiac patients and healthy subjects. Manual and automated ventricular repolarisation measurements from MCGs were evaluated to determine the clinical relevance of these measurements compared with electrocardiograms (ECGs).


RESULTS
Results showed that MCG and ECG T-wave shapes differed and that manual repolarisation measurement was significantly influenced by T-wave amplitude. Automatic measurements of repolarisation in both MCGs and ECGs differed between techniques. The effects of filtering on the waveforms showed that filtering in some MCG research systems could significantly influence the results, with 20 ms differences common. In addition, MCGs were better able to identify differences in the distribution of cardiac magnetic field strength during repolarisation and depolarisation between normal subjects and cardiac patients. Differences were also determined in ventricular repolarisation between MCGs and ECGs, which cannot be explained by channel/lead numbers or amplitude effects alone.


CONCLUSIONS
The techniques developed are essential, because of the many extra MCG channels to analyse, and will encourage the use of MCG facilities.
Smith
Fiona E
FE
Medical Physics Department, Freeman Hospital Unit, Newcastle upon Tyne, UK. f.e.smith@ncl.ac.uk
Langley
Philip
P
van Leeuwen
Peter
P
Hailer
Birgit
B
Trahms
Lutz
L
Steinhoff
Uwe
U
Bourke
John P
JP
Murray
Alan
A
D004562:Electrocardiography; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D053798:Magnetocardiography; D012815:Signal Processing, Computer-Assisted