Bioelectromagnetic localization of a pacing catheter in the heart

The accuracy of localizing source currents within the human heart by non-in vasive magneto- and electrocardiographic methods was investigated in 10 pat ients. A non-magnetic stimulation catheter inside the heart served as a ref erence current source. Biplane fluoroscopic imaging with lead bail markers was used to record the catheter position. Simultaneous multichannel magneto cardiographic (MCG) and body surface potential mapping (BSPM) recordings we re performed during catheter pacing. Equivalent current dipole localization s were computed from MCG and BSPM data, employing standard and patient-spec ific boundary element torso models. Using individual models with the lungs included, the average MCG localization error was 7 +/- 3 mm, whereas the av erage BSPM localization error was 25 +/- 4 mm. In the simplified case of a single homogeneous standard torso model, an average error of 9 +/- 3 mm was obtained from MCG recordings. The MCG localization accuracies obtained in this study imply that the capability of multichannel MCG to locate dipolar sources is sufficient for clinical purposes, even without constructing indi vidual torso models from x-ray or from magnetic resonance images.