Reentrant pathway during ventricular echoes is confined to the atrioventricular node - High-resolution mapping and dissection of the triangle of Kochin isolated, perfused canine hearts

Background-During ventricular echoes, reentrant excitation is supposed to i nvolve 2 functionally distinct pathways in the atrioventricular (AV) nodal area. The exact pathway of reentrant excitation is unknown. The objectives of this study were to analyze electrical activity in the AV nodal area afte r ventricular stimulation and during ventricular echoes and to assess the r ole of perinodal atrial tissue in AV nodal reentry. Methods and Results-In 16 isolated, blood-perfused canine hearts, multiterm inal electrodes were used to map electrical activity in Koch's triangle aft er ventricular stimulation and during ventricular echoes, The subendocardia l cell layers were chemically destroyed in 3 hearts. Incisions in the poste rior approach to the compact node were made in 6 hearts. The apex of the tr iangle of Koch was surgically dissociated from the perinodal atrial tissue in 5 hearts. Retrograde atrial activation occurred via 2 distinct endocardi al exit sites. Ventricular echoes could be induced in all hearts irrespecti ve of the atrial activation pattern. Simultaneous retrograde activation of both exit sites often preceded reciprocation. Ventricular echoes were demon strable after chemical destruction of the endocardium and after surgical di ssociation of the perinodal atrial tissue from the AV node. Conclusions-Our data show that the reentrant pathway during ventricular ech oes is confined to the AV node. The tissue that connects the node to the en docardial exit sites has to be excluded from the reentrant circuit responsi ble for single echoes.