Features of ST segment and T-wave in exercise-induced myocardial ischemia evaluated with multichannel magnetocardiography.
OBJECTIVE
Magnetocardiography (MCG) is a novel, non-contact mapping technique to record cardiac magnetic field. We evaluated MCG criteria for myocardial ischemia in stress testing.


METHODS
Multichannel MCG over frontal chest was performed in 44 patients with coronary artery disease (CAD) and 26 healthy controls during supine bicycle exercise test. Of the 44 patients 16 had anterior, 15 posterior, and 13 inferior ischemia documented by coronary angiography and exercise thallium scintigraphy. ST amplitude, ST slope, T-wave amplitude, and ST-T integral were measured. The optimal sites for detecting the ischemia-induced changes on MCG were sought. The orientation of the magnetic field was also determined.


RESULTS
The optimal sites for the decrease of ST slope, ST amplitude, T-wave amplitude, and ST-T integral were over the abdomen. The reciprocal increase of these parameters was found over the left parasternal area. The optimal sites were approximately the same for all patient groups. In single-vessel disease patients without previous myocardial infarction (MI), ST slope increase and ST elevation performed the best (area under the receiver operating characteristic curve 92% and 90%, respectively). In post-MI patients with triple-vessel disease the decrease of T-wave amplitude and ST slope performed the best (area under curve 91%, for both). The magnetic field orientation at ST segment performed equally well as the other ST parameters. In stepwise logistic regression analysis, by use of the presence of CAD as the dependent parameter, ST slope increase and ST peak gradient orientation entered the model.


CONCLUSIONS
Various ST segment and T-wave parameters detect ischemia in MCG. ST amplitude performs especially well in non-MI patients with less severe CAD. In advanced CAD late development of T-wave amplitude might be more sensitive to ischemia than ST amplitude.
Hänninen
Helena
H
Division of Cardiology, Helsinki University Central Hospital, Finland. hahannin@sci.fi
Takala
Panu
P
Korhonen
Petri
P
Oikarinen
Lasse
L
Mäkijärvi
Markku
M
Nenonen
Jukka
J
Katila
Toivo
T
Toivonen
Lauri
L
D000368:Aged; D018780:Body Surface Potential Mapping / Q000295:instrumentation / Q000379:methods*; D016022:Case-Control Studies; D003324:Coronary Artery Disease / Q000175:diagnosis / Q000503:physiopathology*; D025401:Echocardiography, Stress / Q000379:methods; D005080:Exercise Test; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000503:physiopathology*; D012107:Research Design; D012680:Sensitivity and Specificity