Copyright © 1980 by the European Society of Cardiology.
© 1980 The European Society of Cardiology
Atrioventricular nodal tachycardia with and without discontinuous anterograde atrioventricular nodal conduction curves: a reappraisal of the dual pathway concept
Department of cardiology, University of Limburg. Annadal Hospital Maastricht, The Netherlands
Received 23 June 1980; .
Requests for reprints to: Hein J. J. Wellens, Department of Cardiology, University of Limburg, Annadal Hospital, Maastricht, The Netherlands.
To illustrate the complexity of the electrophysiological behaviour of the human alrioventricular (AV) node, two patients suffering from AV nodal tachycardia are described. During tachycardia an AV nodal slow pathway was used for anterograde conduction, and an AV nodal fast pathway for retrograde conduction. Patient 1 showed smooth AV nodal conduction curves in both the anterograde and the retrograde direction. Tachycardia could only be initiated by ventricular premature beats. No critical delay in ventriculo-atrial conduction time was required for initiation of tachycardia. Patient 2 showed smooth AV nodal conduction curves at the lowest rate of pacing during atrial and ventricular stimulation. The curves became discontinuous in both directions when the basic drivencycle length was decreased. Tachycardia could only be initiated by atrial premature beats. Ventricular premature beats induced non-sustained AV nodal reentry that used an AV nodal fast pathway for anterograde conduction, and an AV nodal slow pathway for retrograde conduction. Accepting dual pathways in the anterograde and retrograde directions in the AV node, means that depending upon their electrophysiological properties a large number of combinations of anterograde and retrograde conduction are possible. When more than two AV nodal pathways are present, the number of possible combinations will increase markedly. These considerations are of help in understanding electrophysiological findings in patients with AV nodal tachycardia. They are also useful to explain the importance of autonomic tone and the results of drug administration in these patients.
Key Words: AV nodal tachycardia dual pathway