title: Discrimination between myocardial infarct and ventricular tachycardia patients using magnetocardiographic trajectory plots and iso-integral maps.
abstract: Magnetocardiograms were recorded from 30 normal (N) subjects, 15 myocardial infarct (MI) patients, and 15 ventricular tachycardia (VT) patients. Discrimination between the groups was affected by iso-integral magnetic field mapping (MFM) and trajectory plotting of MFM extrema. Iso-integral MFM for the QRST, QRS, and ST-T intervals was created for each test group member. A polarity score, based on the number of extrema features present, was assigned to each iso-integral MFM. Differences in group mean integral of QRST map polarity scores were significant (p less than 0.05) between MI and N, between VT and N (p less than 0.005), and between MI and VT (p less than 0.05) subjects. integral of ST-T map polarity scores were significantly (p less than 0.0001) different between VT and N and between MI and VT (p less than 0.001) subjects. Discrimination between MI and VT patients, based on polarity score difference, was 56% accurate using integral of QRS maps and 73% accurate using integral of ST-T maps. For each subject, time-normalized MFM was used to construct trajectory plots of the maxima and minima in the QRS and ST-T intervals. Discrimination between MI and VT patients was based upon intergroup differences in fragmented trajectory plots. When the number of discrete trajectories and/or the total number (F) of trajectory points at which discrete trajectories coexist were considered, QRSmin trajectory plots were significantly (p less than 0.05) different for VT and N, but not for MI and N subjects. The significant (p less than 0.05) difference between MI and VT trajectory plots enabled 76% accuracy for MI and VT identification. ST-Tmax trajectory plots show significantly (p less than 0.0001) higher F values for VT patients facilitating accurate (87%) discrimination between MI and VT patients. These results suggest that the abnormalities of repolarization processes, displayed by MFM as multipolar integral of ST-T maps and/or as fragmented trajectory plots of ST-T extrema, may be useful indicators of the arrhythmia substrate/processes that characterize VT and vulnerable MI patients.
authors.affiliation: Department of Physics, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Stroink
authors.forename: J
authors.initials: J
authors.lastname: Lant
authors.forename: P
authors.initials: P
authors.lastname: Elliott
authors.forename: P
authors.initials: P
authors.lastname: Charlebois
authors.forename: M J
authors.initials: MJ
authors.lastname: Gardner
mesh_terms: D003937:Diagnosis, Differential; D004562:Electrocardiography / Q000295:instrumentation / Q000379:methods*; D005069:Evaluation Studies as Topic; D006801:Humans; D008280:Magnetics; D009203:Myocardial Infarction / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D013610:Tachycardia / Q000175:diagnosis*