The Electrophysiological Cardiac Ventricular Substrate in Patients After Myocardial Infarction

Objectives To noninvasively image the electophysiologic substrate of human ventricles after myocardial infarction and define its characteristics. Background Ventricular infarct border zone is characterized by abnormal cellular electrophsyiology and altered structural architecture and is a key contributor to arrhythmogenesis. The ability to noninvasively image its electrical characteristics could contribute to understanding of mechanisms and to risk-stratification for ventricular arrhythmia. Methods Electrocardiographic Imaging (ECGI), a noninvasive functional electrophysiologic imaging modality, was performed during sinus rhythm in 24 subjects with infarct-related myocardial scar. The abnormal electrophysiologic substrate on the epicardial aspect of the scar was identified and its location, size, and morphology were compared to the anatomic scar imaged by other noninvasive modalities. Results ECGI constructs epicardial electrograms which have characteristics of reduced amplitude (low voltage) and fractionation. ECGI co-localizes the epicardial electrical scar to the anatomic scar with a high degree of accuracy (sensitivity 89%, specificity 85%). In nearly all subjects, sinus rhythm activation patterns were affected by the presence of myocardial scar. Late potentials could be identified and were almost always within ventricular scar. Conclusions ECGI accurately identifies areas of anatomic scar and complements standard anatomic imaging by providing scar - related electrophysiologic characteristics of low voltages, altered sinus rhythm activation, electrogram fragmentation and presence of late potentials.