Pranav Bhagirath

200 Chapter 10 DISCUSSION To our knowledge, this is the first study investigating whole-heart IPM using a 62 lead anterior BSP recording and an MRI derived inhomogeneous VCM. The evaluation of this model was performed in healthy volunteers and patients with idiopathic arrhythmias. Using this MRI based non-invasive method it was possible to estimate the PVC focus location with clinically sufficient accuracy using BSP’s of a single ectopic beat. In addition, a comparison between two independent observers demonstrated a high reproducibility of the results. Evaluation in healthy volunteers IPM localized the origin of atrial activity near the transition of the superior vena cave (crista terminalis) into the right atrium. This location has been described in the literature as the anatomical location of the sinus node (11) . These results suggest that atrial activity may be non-invasively assessed using this combined MRI IPM method. The first ventricular epicardial breakthrough was located at the RV free wall and corresponded with descriptions in the literature (1, 12) . Furthermore, it was also possible to visualize abnormal ventricular activation patterns such as a RBBB (Movie 1). These findings illustrate the potential sensitivity of IPM to detect minute changes in cardiac activation and demonstrate the ease of combining IPM with MRI acquisitions. This offers the prospect to use this method for screening purposes. Clinical impact in idiopathic PVC ablation IPM successfully approximated the ablation site in 8 of 8 patients, a surrogate for the clinical PVC focus. This finding suggests that routine application of this non-invasive technique as part of the clinical workup could have multiple benefits such as improved ablation planning due to accurate pre-procedural identification of the PVC focus (target ablation site), and reduction in procedural duration (and accompanying radiation exposure) due to reduced invasive mapping time. This may especially be valid for patients with a low PVC burden and/or multifocal PVC’s. Volume conductor models The current, most frequently utilized BSPM technique (ECVUE™) uses a homogeneous torso conductor model. The clinical utility of this method has been demonstrated after extensive investigation (13, 14) . However, recent research advocates the integration of the various organs with their own specific impedance (8, 15) . This may especially be the case