Electrocardiographic imaging of paced sequences and infarct substrate in canine hearts, and in patients undergoing cardiac resynchronization therapy

Coronary heart disease is the leading cause of mortality in the United States and worldwide, responsible for nearly 15 million deaths a year. It can lead to many problems including arrhythmias and heart failure. The work presented here aims at prompting the diagnosis, treatment, and understanding of these two conditions using a novel technology---electrocardiographic imaging (ECGI). ECGI is a modality that reconstructs cardiac electrical activity from measurements that are acquired at a certain distance away from the heart. When applied to the endocardial surface (noncontact endocardial ECGI), it reconstructs endocardial electrical activity from cavity potentials measured with a multielectrode catheter that is introduced into the heart chamber percutaneously. When applied to the epicardial surface (noninvasive epicardial ECGI), it reconstructs epicardial electrical activity from body surface potentials measured by a multielectrode vest.; The current approach of electrophysiologic (EP) study requires data collection from many heart beats and is incapable of mapping nonsustained or polymorphic arrhythmias. Simultaneous endocardial ECGI using a 9-French noncontact spiral-shaped catheter was evaluated during paced beats in an isolated canine LV. Endocardial potentials, electrograms, and isochrones were reconstructed with good accuracy. Pacing sites can be located to within 5mm of their actual position.; Abnormal EP substrates are highly arrhythmogenic. Detection of the location, extent and characteristics of such substrates is of great diagnostic value. Endocardial ECGI was applied to infarcted canine hearts and it faithfully reconstructed EP characteristics associated with the abnormal substrate, including low potentials, fractionated electrograms and slow discontinuous conductions.; Cardiac resynchronization therapy (CRT) was introduced recently to treat heart failure with delayed ventricular conduction; it generated encouraging clinical outcomes. However, the mechanism of its efficacy is not well understood, partially due to the difficulty of assessing cardiac electrical activity during CRT in humans. Noninvasive epicardial ECGI was conducted in conjunction with tissue Doppler imaging in patients who received CRT. Intriguing findings of fusion beats in all pacing modes and electromechanical dissociation provided important mechanistic insights. ECGI also demonstrated a potential capability in guiding optimal lead placement for CRT.