Functional role of the epicardium in postinfarction ventricular tachycardia. Observations derived from computerized epicardial activation mapping, entrainment, and epicardial laser photoablation.

This study suggests that 1) chronic postinfarction ventricular tachycardia may result from subepicardial macroreentry, 2) slow conduction within the reentry circuit can be localized by computerized mapping and epicardial entrainment, and 3) ventricular tachycardia interruption by laser photocoagulation results from conduction delay and block within critical elements of the reentrant pathway. Viable subepicardial muscle fibers may constitute the underlying pathology.