Abstract
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. Patientspecific
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