Cardiac arrhythmias are a major cause of death (7 million cases annually worldwide; 400,000 in the U.S. alone) and disability. Yet, a noninvasive imaging modality to identify patients at risk, provide accurate diagnosis and guide therapy is not yet available in clinical practice. In my conference presentation and proceedings article, I will describe examples of the application of Electrocardiographic Imaging (ECGI) in humans. ECGI is a new noninvasive imaging modality for cardiac arrhythmias developed in our laboratory. It combines recordings of 224 body-surface electrocardiograms and a thoracic CT scan to reconstruct potentials, electrograms and isochrones (activation sequences) on the heart surface. Examples include: (1) normal activation and repolarization; (2) activation during ventricular pacing; and (3) atrial flutter.
A fluoroscopy based method for determining heart surface geometry has been developed and validated in phantom and human studies. Biplane fluoroscopic projections were calibrated independently. The heart contour was segmented in each projection and corresponding contour points were matched using epipolar geometry. Points in 3D were reconstructed from the corresponding contour points using point reconstruction. B-splines were approximated from the reconstructed points and meshed to form the heart surface. The fluoroscopy-reconstructed heart was validated in a phantom and human study by comparison to CT imaging. Mean, minimum, maximum and standard deviation of the absolute distance errors were computed for the fluoroscopy-reconstructed heart relative to the CT heart. The mean absolute distance error for the phantom was 4mm. The mean absolute distance error for the human subject was 10 mm. In addition to validating the geometry, we also evaluated in the human subject the feasibility of noninvasive imaging of normal cardiac electrical activity on the fluoroscopy-reconstructed heart by comparing the results to those obtained on the CT heart. Noninvasive images on the fluoroscopy-reconstructed heart by showed close correlation with those obtained on the CT heart (CC=0.70).
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