Three-dimensional recovery time dispersion map by 64-channel magnetocardiography may demonstrate the location of a myocardial injury and heterogeneity of repolarization.
BACKGROUND
QT dispersion reveals heterogeneities in the repolarization time in the three-dimensional (3D) structure of the ventricular myocardium. In this study, we report on a 3D function map of recovery time (RT) dispersions as measured by 64-channel magnetocardiography (MCG).


METHODS
MCG were simultaneously recorded in 29 controls and 21 patients with previous myocardial infarction (MI). The 3D current density was calculated from 64-channel MCG data in the Bz component using a space filter. The heart outline, reconstructed from the integrated the current density, revealed both the atrium and ventricle. The RT for the intervals between QRS onset and the time of the maximum dT/dt of T wave, and the peak to the end of the T wave (T(peak)-negative dT/dt) were automatically measured by means of a computer from 3D MCG data. The corrected RT (RTc) and corrected T(peak)-negative dT/dt were then calculated using Bazett's formula. The 3D RTc and the corrected T(peak)-negative dT/dt dispersion map were superimposed on the heart outline generated by MCG.


RESULTS
The RTc was significantly longer for the MI group than in the control group (67+/-25 ms1/2 vs. 16+/-6 ms1/2) (p<0.0001). The corrected T(peak)-negative dT/dt dispersions in each patient was also significantly longer for the MI group than in the control group (35+/-27 ms1/2 vs. 10+/-5 ms1/2) (p<0.0001). Furthermore, the 3D RTc and T(peak)-negative dT/dt dispersion maps corresponded with the space location of MI, as defined by Tc-99m tetrofosmin myocardial imaging


CONCLUSIONS
3D RTc and T(peak)-negative dT/dt dispersion maps in the ST segment, obtained by 64-channel MCG may be used demonstrate the location of a myocardial injury and heterogeneities of repolarization.
Nakai
Kenji
K
The Department of Laboratory Medicine, Iwate Medical University, 19-1 Uchimaru, Morioka, 020-8505, Japan.
Izumoto
Hiroshi
H
Kawazoe
Kohei
K
Tsuboi
Junichi
J
Fukuhiro
Yoshiaki
Y
Oka
Takanori
T
Yoshioka
Kunihiro
K
Shozushima
Masanori
M
Itoh
Manabu
M
Suwabe
Akira
A
Yoshizawa
Masahito
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D009206:Myocardium / Q000473:pathology*; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon
D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C078700:technetium tc-99m tetrofosmin