[Intraventricular conduction block induced by ischemia]

The electrical consequences of experimental acute myocardial ischemia were studied in 50 dogs. The study was performed through unipolar epicardial leads and at different levels of the conducting system; bundle branch and Purkinje fibers. There is evidence that the block takes place at the Purkinje-muscle union or in the muscle-muscle conduction. In none of the experiments the block appeared in any of the components of the conducting system. Also, there is evidence that with severe ischemia muscle recordings disappeared while the Purkinje potentials remained unchanged, this suggests that conducting system cells are more resistant to hypoxia than the contractile cells. Ventricular arrhythmias usually appeared simultaneously with conduction blocks that favored reentries. Arrhythmias were more frequent when the blocks were more accentuated. Our data demonstrates that the conduction disorder precedes in some instances, the positive RS-T displacement and in others it hides the such displacement. It is concluded that the RS-T displacement, the distal conduction block and arrhythmias are manifestations, at different levels, of partial diastolic depolarization induced by acute myocardial ischemia.