title: Magnetocardiographic QT interval dispersion in postmyocardial infarction patients with sustained ventricular tachycardia: validation of automated QT measurements.
abstract: QT dispersion is a measure of heterogeneity in ventricular repolarization. Increased ECG QT dispersion is associated with life-threatening ventricular arrhythmias. We studied if magnetocardiographic (MCG) measures of QT dispersion can separate postmyocardial infarction patients with and without susceptibility to sustained VT. Manual dispersion measurements were compared to a newly adapted automatic QT interval analysis method. Ten patients with a history of sustained VT (VT group) and eight patients without ventricular arrhythmias (Controls) were studied after a remote myocardial infarction. Single-channel MCGs were recorded from 42 locations over the frontal chest area and the signals were averaged. QT dispersion was defined as maximum-minimum or standard deviation of measured QT intervals. VT group showed significantly more QT and JT dispersion than Controls. QTapex dispersions were 127 +/- 26 versus 83 +/- 21 ms (P = 0.004) and QTend dispersions 130 +/- 37 versus 82 +/- 37 ms (P = 0.013), respectively. Automatic method gave comparable values. Their relative differences were 9% for QTapex and 27% for QTend dispersion on average. In conclusion, increased MCG QT interval dispersion seems to be associated with a susceptibility to VT in postmyocardial infarction patients. MCG mapping with automated QT interval analysis may provide a user independent method to detect nonhomogeneity in ventricular repolarization.
authors.affiliation: Department of Medicine, Helsinki University Central Hospital, Finland.
authors.forename: L
authors.initials: L
authors.lastname: Oikarinen
authors.forename: M
authors.initials: M
authors.lastname: Paavola
authors.forename: J
authors.initials: J
authors.lastname: Montonen
authors.forename: M
authors.initials: M
authors.lastname: Viitasalo
authors.forename: M
authors.initials: M
authors.lastname: Mäkijärvi
authors.forename: L
authors.initials: L
authors.lastname: Toivonen
authors.forename: T
authors.initials: T
authors.lastname: Katila
mesh_terms: D000465:Algorithms; D016022:Case-Control Studies; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications*; D010865:Pilot Projects; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000209:etiology