Noninvasive electrocardiographic imaging (ECGI): Contributions to methodology, imaging repolarization and comparison to invasive mapping during surgery

Cardiac arrhythmias are a leading cause of death and disability, with more than 250,000 annual cases of sudden death in the US alone. However, a noninvasive imaging modality for cardiac electrophysiology and arrhythmias does not yet exist in clinical practice. Current noninvasive diagnosis of cardiac arrhythmias is based on electrocardiographic recordings made on the body surface. These recordings are a low resolution projection of cardiac activity. In contrast, direct measurements on the heart surface reflect underlying cardiac electrophysiology with high resolution. Electrocardiographic Imaging (ECGI) is used to noninvasively reconstruct potentials, electrograms and isochrones on the heart surface using body surface measurements and heart-torso geometry. The work presented here advances ECGI development by: (1) imaging dispersion of myocardial repolarization, (2) developing algorithms for determining heart-torso geometry, and (3) evaluating ECGI in open heart surgery patients.; Temperature induced dispersion of repolarization recorded from canine experiments was used in a torso model to generate body surface potentials which were perturbed with measurement and geometry errors. ECGI was then applied and accurately localized regions of dispersion of repolarization (regions with altered activation recovery intervals and QRST integrals).; As a prelude to clinical application of ECGI we developed methods for determining subject specific heart-torso geometry. An algorithm for heart surface reconstruction from multiplane fluoroscopy was developed based on computer vision theory and epipolar geometry and evaluated in phantom and normal volunteer studies. Test results showed that heart surface geometry could be reconstructed within 5mm (phantom) and 10mm (human) error resolution. Stereo photography was also used to localize body surface ECG electrodes within 2mm.; ECGI was evaluated during sinus rhythm and right ventricular (RV) endocardial and epicardial pacing through comparison to intraoperative mapping in open heart surgery patients. ECGI captured RV breakthrough sites, localized pacing sites to within ∼1cm, reflected the general patterns of activation and repolarization, and detected abnormal electrophysiological substrates.; This work constitutes a major milestone towards clinical application of ECGI procedure in the electrophysiology laboratory for patient risk stratification, monitoring and guidance of therapy and uncovering arrhythmia mechanisms.