A new screening method to diagnose coronary artery disease using multichannel magnetocardiogram and simple exercise.
BACKGROUND
Magnetocardiography (MCG) is a non-contact mapping technique to record cardiac action currents. The Master's two-step electrocardiogram (ECG) test is a simple exercise method for screening coronary artery disease (CAD), but it is inadequate concerning the sensitivity. Our aim was to develop a new screening method using multichannel MCG instead of ECG.


METHODS
Thirty subjects (aged 54 +/- 16 years, 27 males), 17 of whom had CAD confirmed by coronary angiography, underwent the Master's exercise ECG test. After the exercise, MCG signals were acquired every minute during recovery with a 64-channel MCG system (MC-6400, Hitachi Ltd). We integrated tangential components of the MCG signals within QRS (during 20, 40, 80, and 120 ms centering on R-wave peak) immediately after exercise (Iex) and 5 minutes after exercise (Irec). The exercise-induced change of currents [(Iex-Irec)/Irec] was determined and normalized for each channel, and the maximal change among 64 channels, maximal QRS integral change, was used as a diagnostic index for myocardial ischemia.


RESULTS
The maximal QRS integral change during 40 ms was significantly higher in the CAD group than in the control group (0.81 +/- 0.51 vs. 0.36 +/- 0.19, p < 0.01). A sensitivity and specificity for predicting CAD by the change > 0.44 were 82 % and 85 %, respectively, yielding a diagnostic accuracy of 83 %. The conventional Master's ECG test identified the CAD patients with a diagnostic accuracy of 63 % (sensitivity 47 %, specificity 85 %).


CONCLUSIONS
The Master's two-step exercise test with a 64-channel MCG system showed the high diagnostic accuracy, despite of non-contact recording and simple exercise. The magnetic field in the depolarization process has the potential to detect the subtle myocardial ischemia induced by exercise.
Kanzaki
Hideaki
H
National Cardiovascular Center, Department of Cardiology, 5-7-1, Fujishiro-dai, Suita, Osaka 565-8565, Japan. nakatas@hsp.ncvc.go.jp
Nakatani
Satoshi
S
Kandori
Akihiko
A
Tsukada
Keiji
K
Miyatake
Kunio
K
D000328:Adult; D018780:Body Surface Potential Mapping; D003324:Coronary Artery Disease / Q000175:diagnosis*; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006334:Heart Function Tests / Q000379:methods; D006801:Humans; D008280:Magnetics; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D012680:Sensitivity and Specificity