The Influence of Using a Static Diastolic Geometry in ECG Imaging

Job Stoks, Matthijs Cluitmans, Ralf Peeters, Paul Volders
Maastricht University


Electrocardiographic imaging (ECGI) is a modality that noninvasively imag-es electrical activation and recovery directly on the heart surface. One of the common assumptions when performing ECGI is that the cardiac geometry is in a static, diastolic state. To test the influence of this assumption, we com-pared ECGI reconstructions during systolic and diastolic geometries in four patients. Zero-th order Tikhonov regularization was used to reconstruct ven-tricular epicardial potentials. A spatiotemporal estimation method was then used to determine the activation and recovery times from the reconstructed epicardial electrograms. Geometries were segmented in a fully automated manner, to minimize the user influence. Activation times (AT), recovery times (RT) and electrogram correlation coefficients (CC) were compared for both geometries. Furthermore, CC and differences in AT/RT were correlated against the linear movement and a substitute for rotational movement (namely, distance to the apex). Overall, agreement between the inverse solu-tion of both geometries was high (rAT=0.86, rRT=0.80, CC=0.98 on average) when assessed quantitatively, but regional differences may occur for qualita-tive interpretation. Poor correlation was found between linear or rotational movement and inverse solution differences (average r<0.09) between both geometries, suggesting that movement of the heart does not affect recon-struction accuracy. Still, while overall quantitative differences of epicardial potential maps and isochrones were low, using a constant diastolic geometry might influence clinical interpretation of ECGI, especially for areas of large repolarization heterogeneities. This first systematic investigation of the as-sumption of a static geometry may further help in interpreting ECGI.