Antegrade and retrograde conduction characteristics in three patterns of paroxysmal atrioventricular junctional reentrant tachycardia

In 20 patients with PSVT without ventricular pre-excitation, the site of reentry and functional characteristics of Ant. and Ret. pathways were studied. Three distinct patterns of PSVT were observed. In 13 patients (group I) in whom A-V node was the site of reentry, the interval between the Ant. H bundle deflection and the following atrial echo response (H-Ae) measured 30 to 85 msec. and the Ae was partially or completely obscured by ventricular electrogram. The ratio between the H-Ae and the subsequent Ae-H interval ranged 1:3.1-17.3. In a majority of Group I patients (eight out of 13) the Ret. conduction was better than Ant. conduction, as the VACS sustained a 1:1 response at faster paced rates than AVCS. The FRP of the AVCS in Group I was determined by the A-V node in all patients and significantly exceeded the FRP of the VACS; the latter was determined by the HPS in 12 out of 13 patients. In four patients (Group II) a V-A AP silent antegradely was operative during PSVT. The H-Ae in Group II valued 145 to 200 msec. and the Ae clearly followed the ventricular electrogram, the H-Ae: Ae-H being 1:0.5-1.7. The V-A conduction in all Group II patients was better than the A-V conduction. A-V node determined the FRP of the AVCS, whereas AP determined the FRP of the VACS in Group II patients, and the former significantly exceeded the latter. Good correlation existed between PSVT, Ant. and Ret. conduction patterns in Group I and Group II patients. In three patients (Group III) the H-Ae measured 270 to 470 msec. with an H-Ae:Ae-H of 1:0.2-0.4, a relationship quite the opposite of Group I patients. No definite relationship existed between PSVT, Ant. and Ret. conduction patterns in Group III patients. The data in Group III patients were compatible with (1) A-V nodal reentry with reversal of conduction balance compared to Group I, (2) intra-atrial reentry, and (3) enhanced atrail automaticity. It is concluded (1) the site of reentry in patients with PSVT is variable, (2) a fair estimation of reentry site can be made from H-Ae and Ae-H relationship, (3) all patients with PSVT have intact V-A conduction and in most the V-A conduction is better than A-V conduction, and (4) in the majority of patients with PSVT refractoriness of the AVCS exceeds that of the VACS.