Characteristics and coexistence of two forms of ventricular echo phenomena.

During the scanning of paced basic ventricular cycle lengths (V1V1) with extrastimulus method (V2) two forms of ventricular echo phenomena (Ve) were recognized. The Ve resulting from A-V nodal re-entry (VeAVN) occurred in 12 of 45 patients, from re-entry in the His-Purkinje system (Ve-HPS) in 20 of 45 patients, and simultaneous dual re-entry (Ve-AVN and Ve-HPS) occurred in five of 45 patients. The Ve-AVN (1) appeared at longer V1V2 intervals, (2) was dependent on retrograde A-V nodal conduction delay, (3) had normal QRS complexes and H-V intervals, and (4) did not occur when V2 blocked in the A-V node. (5) Ve-AVN had aberrant QRS complexes when preceded by Ve-HPS. The Ve-HPS (1) appeared at shorter V1V2 intervals, (2) was dependent upon retrograde conduction delay in the HPS, (3) its QRS morphology and axis orientation resembled V2, i.e., left bundle branch block pattern, when right ventricular apex was the site of stimulation, (4) persisted when V2 blocked in the A-V node and was abolished when V2 blocked below the bundle of His, and (5) rarely occurred in patients with pre-existing right bundle branch block. It is concluded that (1) at least two forms of Ve can result from induced premature ventricular beats, (2) Ve-HPS is more common than Ve-AVN in the presence of normal QRS complexes, and (3) coexistence of Ve-AVN and Ve-HPS can give rise to complex ECG pattern mimicking multiple multifocal premature ventricular beats.