Conversion of left ventricular endocardial positions from patient-independent co-ordinates into biplane fluoroscopic projections.

Electrocardiographic body surface mapping is used clinically to guide catheter ablation of cardiac arrhythmias by providing an estimate of the site of origin of an arrhythmia. The localisation methods used in our group produce results in left-ventricular cylinder co-ordinates (LVCCs), which are patient-independent but hard to interpret during catheterisation in the electrophysiology laboratory. It is preferable to provide these results as three-dimensional (3D) co-ordinates which can be presented as projections in the biplane fluoroscopic views that are used routinely to monitor the catheter position. Investigations were carried out into how well LVCCs can be converted into fluoroscopic projections with the limited anatomical data available in contemporary clinical practice. Endocardial surfaces from magnetic resonance imaging (MRI) scans of 24 healthy volunteers were used to create an appropriate model of the left-ventricular endocardial wall. Methods for estimation of model parameters from biplane fluoroscopic images were evaluated using simulated biplane data created from these surfaces. In addition, the conversion method was evaluated, using 107 catheter positions obtained from eight patients, by computing LVCCs from biplane fluoroscopic images and reconstructing the 3D positions using the model. The median 3D distance between reconstructed positions and measured positions was 4.3mm.