Magnetocardiography in unshielded location in coronary artery disease detection using computerized classification of current density vectors maps
The aim of this was to examine the capability of magnetocardiographic mapping at rest using a simple system, installed in unshielded location, to detect myocardial ischemia in a heterogeneous CAD population including subsets of patients with ischemia in any of the main coronary artery branches regions but without prior myocardial infarction and with normal 12-leads ECG at rest. A total of 110 patients with CAD and 98 healthy controls were included in the study. Another 15 volunteers with no history of any cardiovascular disease were used for run-torun and day-to-day reproducibility assessment. MCG recordings were taken with the help of four-channel SQUID-magnetometer system , installed in unshielded setting, at 36 pre-thoracic sites over the pericardial area. For further analysis the reconstruction of CDV maps within the ST-T interval was applied. Each CDV map was classified automatically by means of a classification system with a scale from 0 to 4 with increasing abnormality . The averaged class was calculated for each subject in order to discriminate between groups. The results showed that CDV maps of healthy volunteers have mainly dipolar structure with only one area of larger vectors directed left – downwards. In contrast the CDV maps of patients with CAD demonstrate mainly non-dipolar structure with additional areas of larger current vectors. With the threshold 1,75 of average map class sensitivity 74% , specificity 80%, PPV 81 %, NPV 73,5 % were achieved. The parameters tested had low disagreement between repeated measurements. Relatively simple 4-channals system, installed in unshielded location, was robust in operation, signal quality was good enough for the analysis. Results were discussed.