Analysis of current source of the heart using isomagnetic and vector arrow maps

Vector arrow maps and isomagnetic maps were constructed with a second derivative SQUID (superconducting quantum interference device) gradiometer in normal subjects and in various pathological conditions to study the inverse problem of electromotive forces and to determine whether the magnetocardiogram (MCG) provides different information from the electrocardiogram (ECG). The current sources deduced from these maps corresponded well with the activation sequences in normal and pathologic conditions reported previously. As second derivative gradiometer measures of the spatial differentiation of the magnetic field, these maps reflected well the current sources close to the anterior chest, namely the right ventricle and right atrium. In addition, it was possible to better localize the sources with this detector than with the ECG or first order gradiometer, suggesting that the isomagnetic and vector arrow maps obtained with the second derivative gradiometer were useful for solving the inverse problem. The MCG also provided different information from the ECG, so use of the MCG in addition to the ECG might be helpful in determining current sources more accurately.