Noninvasive mapping of electrical dyssynchrony in heart failure and cardiac resynchronization therapy.

Causes for diverse effects of cardiac resynchronization therapy (CRT) are poorly understood. Because CRT is an electrical therapy, it may be best understood by detailed characterization of electrical substrate and its interaction with pacing. Electrocardiogram (ECG) features affect CRT outcomes. However, the surface ECG reports rudimentary electrical data. In contrast, noninvasive electrocardiographic imaging provides high-resolution single-beat ventricular mapping. Several complex characteristics of electrical substrate, not decipherable from the 12-lead ECG, are linked to CRT effect. CRT response may be improved by candidate selection and left ventricular lead placement directed by more precise electrical evaluation, on an individual patient basis.