Contribution of altered working myocardium to intraventricular conduction disturbances.

• The terms "fascicular and/ or bundle branch blocks" imply conduction alteration in the His-Purkinje system. • These QRS patterns are in majority cases associated with altered structure of ventricular working myocardium. • The altered structure of working myocardium can cause alterations in electrical impulse propagation itself. [ABSTRACT FROM AUTHOR]