Marco J. W. Götte

Integration of whole-heart activation simulations and inverse potential mapping (IPM) could benefit the guidance and planning of electrophysiological procedures. Routine clinical application requires a fast and adaptable workflow. These requirements limit clinical translation of existing simulation models. This study proposes a comprehensive finite element model (FEM) based whole-heart computational workflow suitable for IPM and simulations. Three volunteers and eight patients with premature ventricular contractions underwent body surface potential (BSP) acquisition followed by a cardiac MRI (CMR) scan. The cardiac volumes were segmented from the CMR images using custom written software. The feasibility to integrate tissue-characteristics was assessed by generating meshes with virtual edema and scar. Isochronal activation maps were constructed by identifying the fastest route through the cardiac volume using the Möller–Trumbore and Floyd–Warshall algorithms. IPM’s were reconstructed from the BSP’s. Whole-heart computational meshes were generated within seconds. The first point of atrial activation on IPM was located near the crista terminalis of the superior vena cave into the right atrium. The IPM demonstrated the ventricular epicardial breakthrough at the attachment of the moderator band with the right ventricular free wall. Simulations of sinus rhythm were successfully performed. The conduction through the virtual edema and scar meshes demonstrated delayed activation or a complete conductional block respectively. The proposed FEM based whole-heart computational workflow offers an integrated platform for cardiac electrical assessment using simulations and IPM. This workflow can incorporate patient-specific electrical parameters, perform whole-heart cardiac activation simulations and accurately reconstruct cardiac activation sequences from BSP’s.

Background: Inverse potential mapping ( IPM ) noninvasively reconstructs cardiac surface potentials using body surface potentials. This requires a volume conductor model ( VCM ), usually constructed from computed tomography; however, computed tomography exposes the patient to harmful radiation and lacks information about tissue structure. Magnetic resonance imaging ( MRI ) is not associated with this limitation and might have advantages for mapping purposes. This feasibility study investigated a magnetic resonance imaging–based IPM approach. In addition, the impact of incorporating the lungs and their particular resistivity values was explored. Methods and Results: Three volunteers and 8 patients with premature ventricular contractions scheduled for ablation underwent 65‐electrode body surface potential mapping. A VCM was created using magnetic resonance imaging. Cardiac surface potentials were estimated from body surface potentials and used to determine the origin of electrical activation. The IPM ‐defined origin of sinus rhythm corresponded well with the anatomic position of the sinus node, as described in the literature. In patients, the IPM ‐derived premature ventricular contraction focus was 3‐dimensionally located within 8.3±2.7 mm of the invasively determined focus using electroanatomic mapping. The impact of lungs on the IPM was investigated using homogeneous and inhomogeneous VCM s. The inhomogeneous VCM , incorporating lung‐specific conductivity, provided more accurate results compared with the homogeneous VCM (8.3±2.7 and 10.3±3.1 mm, respectively; P =0.043). The interobserver agreement was high for homogeneous (intraclass correlation coefficient 0.862, P =0.003) and inhomogeneous (intraclass correlation coefficient 0.812, P =0.004) VCMs . Conclusion: Magnetic resonance imaging–based whole‐heart IPM enables accurate spatial localization of sinus rhythm and premature ventricular contractions comparable to electroanatomic mapping. An inhomogeneous VCM improved IPM accuracy.

Background With the advent of magnetic resonance imaging (MRI) conditional pacemaker systems, the possibility of performing MRI in pacemaker patients has been introduced. Besides for the detailed evaluation of atrial and ventricular volumes and function, MRI can be used in combination with body surface potential mapping (BSPM) in a non-invasive inverse potential mapping (IPM) strategy. In non-invasive IPM, epicardial potentials are reconstructed from recorded body surface potentials (BSP). In order to investigate whether an IPM method with a limited number of electrodes could be used for the purpose of non-invasive focus localization, it was applied in patients with implanted pacing devices. Ventricular paced beats were used to simulate ventricular ectopic foci. Methods Ten patients with an MRI-conditional pacemaker system and a structurally normal heart were studied. Patient-specific 3D thorax volume models were reconstructed from the MRI images. BSP were recorded during ventricular pacing. Epicardial potentials were inversely calculated from the BSP. The site of epicardial breakthrough was compared to the position of the ventricular lead tip on MRI and the distance between these points was determined. Results For all patients, the site of earliest epicardial depolarization could be identified. When the tip of the pacing lead was implanted in vicinity to the epicardium, i.e. right ventricular (RV) apex or RV outflow tract, the distance between lead tip position and epicardial breakthrough was 6.0 ± 1.9 mm. Conclusions In conclusion, the combined MRI and IPM method is clinically applicable and can identify sites of earliest depolarization with a clinically useful accuracy.

In inverse potential mapping, local epicardial potentials are computed from recorded body surface potentials (BSP). When BSP are recorded with only a limited number of electrodes, in general biophysical a priori models are applied to facilitate the inverse computation. This study investigated the possibility of deriving epicardial potential information using only 62 torso electrodes in the absence of an a priori model.