Detection of Myocardial Scars by Magnetic Field Imaging

This study identifies myocardial scars using three-dimensional magnetic field imaging. Vector magnetocardiograms (MCGs) were recorded for a healthy volunteer and ten patients (8 male, 65 ± 6 years old, 2 female, 70 ± 11 years old) ＞ 6 months after myocardial infarction. Based on thoracic magnetic resonance imaging (MRI) data, boundary element method models of the torso, lungs, and heart were segmented and served as the volume conductor. Minimum norm current density distributions were reconstructed from the MCG data on subject-specific heart models, resulting in a color-coded current amplitude map on each heart surface. The areas of myocardial scars were included from MRI late enhancement data. These maps were divided into 17 segments (”bull's eye plot” of the heart) and analyzed at the time point of the T wave maximum. Visual localization of myocardial scars by eye was performed with three patterns (circular/semi-circular edge phenomenon, lingual-shaped ridge, and low current density in the infarct area). For additional validation, all patients were classified by variance analysis comparing relative current density in the segments of scars and of viable myocardium at seven time points of the heart cycle. Myocardial scars were identified in all localizations with the visual patterns. Apical scars were the easiest to localize whereas lateral scars, perpendicular to the main measurement plane, were difficult to recognize. A combination of MCG and MRI result in a magnetic field image, offering the possibility of evaluating the functional biomagnetic effects of structural heart disease. Such functional imaging could be a useful diagnostic tool for non-invasive cardiac risk stratification or a guide before cardiac revascularization, which is only promising in viable myocardial segments.