EFECTOS DE LOS PERIODOS DE WENCKEBACH INTRAAURICULAR SOBRE EL BLOQUEO A-V 2:1 Y 4:1 NODAL E INFRANODAL. [SU IMPORTANCIA EN LA ELECTROGENESIS DE LOS ILAMADOS PERIODOS DE WENCKEBACH ALTERNANTES.]

Intra-atrial Wenckebach patterns coexisting with distal, A-V nodal, and His-Purkinje blocks occurred in eight patients during high right atrial stimulation at rapid rates. In two patients with 2:1 St-H block and in two with 4:1 St-V block, an increase in the degree of block occurred when the proximal intraatrial Wenckebach cycle was completed with the stimulus which otherwise would have been propagated to the distal levels. However, the degree of block did not increase when the intraatrial Wenckebach terminated in distally blocked stimuli. In one patient progression of 4:1 into 5:1 St-V block was due to the association of intraatrial Wenckebach with alternating 2:1 block at the A-V nodal, and His-Purkinje levels. Contrasting with most reports dealing with the mechanisms of alternating Wenckebach in a single structure, this study permitted the determination of the boundaries between proximal and more distal levels. The electrophysiology of documented two or three level block in different structures has validated previously made assumptions regarding multilevel block in a single structure.