Methods for the computational localization of atrio-ventricular pre-excitation syndromes

Background: The site of atrioventricular pre-excitation can roughly be esti mated with the help of schemes basing on a few number of electrocardiogram (ECG) leads. Computer algorithms have been developed which utilize the body surface mapping of the pre-excitation signal for the localization purpose. We tested several new algorithms. Method: A patient suffering from Wolff-P arkinson-White syndrome was investigated prior the catheter ablation. The b ody surface mapping was performed with a 62-lead magnetocardiograph. The si te of pre-excitation was calculated by using different methods: the dipole method with fixed and moving dipoles, the dipole scan on the endocardium, a nd different current density methods (L1 norm method, L2 norm method, low r esolution electromagnetic tomography (LORETA) method, and maximum entropy m ethod). Three-dimensional (3D) magnetic resonance imagings (MRIs) of the he art were used to visualize the results. The source positions were compared to the site of catheter ablation. Results: The accessory pathway was succes sfully ablated left laterally. This site was correctly identified by the co nventional dipole method. By scanning the entire endocardial surface of the heart with the dipole method we found a circumscribed source area. This ar ea too, was located at the lateral segment of the atrio-ventricular grove. The current density methods performed differently. Whereas the L1 norm iden tified the site of pre-excitation, the L2 norm, the LORETA method and the m aximum entropy method resulted in extended source areas and therefore were not suited for the localization purpose. Conclusion: The dipole scan and th e L1 norm current density method seem to be useful additions in the computa tional localization of pre-excitation syndromes. In our single case study t hey confirmed the localization results obtained with the dipole method, and they estimated the size of the suspected source region.