Zusammenfassung
Die Mehrkanalmagnetokardiographie (MKG) registriert nichtinvasiv die magnetische Aktivität des Herzens an verschiedenen Positionen über dem Thorax. Diese Information kann genutzt werden zur Rekonstruktion der Stromdichteverteilung im Myokard wie auch zur Erstellung eines magnetischen Feldes, dessen Änderung im Verlauf der kardialen De- und Repolarisation zur verfolgen ist. In ersten Ansätzen belegen verschiedene Studien, daß eine Erkennung und Lokalisation von Myokardinfarkten (MI) und myokardialer Ischämie auf dem Boden einer koronaren Herzerkrankung (KHK) durch den Nachweis krankheitsspezifischer Abweichungen des magnetischen Feldes sowie der Stromdichteverteilung im Myokard möglich ist, wobei unterschiedliche Modelle zur Quantifizierung der magnetischen Information benutzt werden. Neben diesen globalen Beurteilungen der kardialen Aktivität kann auch das Einzelsignal analog zum Oberflächenelektrokardiogramm interpretiert werden. Hier bieten sich morphologische Kriterien wie die Analyse des ST-Streckenverlaufs an sowie die Berechnung entsprechender Zeitintervalle unter Nutzung des räumlichen Informationsgehalts. So ermöglicht die räumliche Darstellung der QT-Dispersion eine Risikostratifizierung von Patienten nach MI im Hinblick auf maligne Herzrhythmusstörungen. Aufgrund der vielversprechenden Ansätze sollten die derzeitigen Methoden weiterentwickelt und an entsprechenden Fallzahlen bestätigt werden, um den Stellenwert des MKG bei KHK und MI endgültig beurteilen zu können.
Summary
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.
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Hailer, B. Die Bedeutung der Magnetokardiographie bei koronarer Herzerkrankung und Myokardinfarkt. Herzschr Elektrophys 8, 167–177 (1997). https://doi.org/10.1007/BF03042399
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DOI: https://doi.org/10.1007/BF03042399
Schlüsselwörter
- Koronare Herzerkrankung
- Magnetokardiographie
- Ischämie
- Myokardinfarkt
- iso-integral map
- residual maps
- trajectory plot
- Stromdichterekonstruktion