[Relevance of magnetocardiography in coronary artery disease and myocardial infarction].

Multichannel magnetocardiography (MCG) noninvasively registers the magnetic activity of the heart at different points above the thorax. This information can be used to determine the magnetic field produced by cardiac activity as well to reconstruct the current density distribution in the myocardium, which can then be examined during cardiac de- and repolarisation. First studies have shown that the detection of disease specific changes of the magnetic field and current density permit the diagnosis and localization of myocardial infaction (MI) and myocardial ischemia within the context of coronary artery disease (CAD). In these studies various approaches were used to quantify and condense the temporal and spatial changes in the magnetic signals. The integration of defined time intervals of cardiac de- and repolarisation in form of iso-integral magnetic field maps allowed a discrimination between myocardial infarct groups. Furthermore residual maps, calculated by subtracting the MCG map components of MI patients from those of normal subjects, were used to describe the infarcted region. On the basis of trajectory plots which represent the course of magnetic map extrema, patients with ventricular tachycardia after MI could be identified. Current density reconstruction during ST-segment permitted the visualization of biological injury currents during induced ischemia and infarction. Beyond the consideration of the overall magnetic activity, the signal in single channels may be examined and interpreted as is done in the body surface electrocardiogram. Morphological criteria such as the course of the ST-segment as well as the spatial distribution of cardiac time intervals may be considered. Risk stratification of patients after MI with regard to an increased risk of malignant arrhythmia is possible by making use of the spatial distribution of QT dispersion. The promising preliminary results suggest that the current methods must be developed and investigated further in studies with the appropriate number and kind of subjects in order to assess the clinical value of the MCG in patients with CAD and MI.