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Unusual induction of slow-fast atrioventricular nodal reentrant tachycardia. Report of two cases.
G Ital Cardiol. 1999 Nov; 29(11):1318-22.GI

Abstract

INTRODUCTION

Generally, the induction of typical atrioventricular nodal reentrant tachycardia (AVNRT) occurs with a premature atrial stimulus that blocks in the fast pathway and proceeds down the slow pathway slowly enough to allow the refractory fast pathway time to recover. We describe two cases in which a typical AVNRT was induced in an unusual fashion.

RESULTS

The first case is a 41-year-old man with paroxysmal supraventricular tachycardia. During the electrophysiology study, the atrial extrastimulus inducing the typical AVNRT was conducted simultaneously over the fast (AH) and the slow pathway (AH'). A successful ablation of the slow pathway was performed. During the follow-up no recurrence was noted. The second case is a 52-year-old woman with a Wolff-Parkinson-White syndrome due to a left posterior accessory pathway. After 5 minutes of atrioventricular reentrant tachycardia (AVRT) induced by a ventricular extrastimulus, a variability of the antegrade conduction was noted in presence of the same VA conduction. In fact, a short AH interval (fast pathway) alternated with a more prolonged AH intervals (slow pathway) that progressively lengthened until a typical AVNRT was induced. The ablation of the accessory pathway eliminated both tachycardias.

DISCUSSION

A rare manifestation of dual atrioventricular nodal pathways is a double ventricular response to an atrial impulse that may cause a tachycardia with an atrioventricular conduction of 1:2. In our first case, an atrial extrastimulus was simultaneously conducted over the fast and the slow pathway inducing an AVNRT. This nodal reentry implies two different mechanisms: 1) a retrograde block on the slow pathway impeding the activation of the slow pathway from the impulse coming down the fast pathway, and 2) a critical slowing of conduction in the slow pathway to allow the recovery of excitability of the fast pathway. Interestingly, in the second case, during an AVRT the atrial impulse suddenly proceeded alternately over the fast and the slow pathway. The progressive slowing of conduction over the slow pathway until a certain point which allows the recovery of excitability of the fast pathway determines the AVNRT. This is a case of "tachycardia-induced tachycardia" as confirmed by the fact that the ablation of the accessory pathway eliminated both tachycardias.

Authors+Show Affiliations

Division of Cardiology, Hospital of Asti.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Case Reports
Journal Article
Review

Language

eng

PubMed ID

10609133

Citation

Calò, L, et al. "Unusual Induction of Slow-fast Atrioventricular Nodal Reentrant Tachycardia. Report of Two Cases." Giornale Italiano Di Cardiologia, vol. 29, no. 11, 1999, pp. 1318-22.
Calò L, Riccardi R, Scaglione M, et al. Unusual induction of slow-fast atrioventricular nodal reentrant tachycardia. Report of two cases. G Ital Cardiol. 1999;29(11):1318-22.
Calò, L., Riccardi, R., Scaglione, M., Caponi, D., Golia, P., & Gaita, F. (1999). Unusual induction of slow-fast atrioventricular nodal reentrant tachycardia. Report of two cases. Giornale Italiano Di Cardiologia, 29(11), 1318-22.
Calò L, et al. Unusual Induction of Slow-fast Atrioventricular Nodal Reentrant Tachycardia. Report of Two Cases. G Ital Cardiol. 1999;29(11):1318-22. PubMed PMID: 10609133.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Unusual induction of slow-fast atrioventricular nodal reentrant tachycardia. Report of two cases. AU - Calò,L, AU - Riccardi,R, AU - Scaglione,M, AU - Caponi,D, AU - Golia,P, AU - Gaita,F, PY - 1999/12/28/pubmed PY - 1999/12/28/medline PY - 1999/12/28/entrez SP - 1318 EP - 22 JF - Giornale italiano di cardiologia JO - G Ital Cardiol VL - 29 IS - 11 N2 - INTRODUCTION: Generally, the induction of typical atrioventricular nodal reentrant tachycardia (AVNRT) occurs with a premature atrial stimulus that blocks in the fast pathway and proceeds down the slow pathway slowly enough to allow the refractory fast pathway time to recover. We describe two cases in which a typical AVNRT was induced in an unusual fashion. RESULTS: The first case is a 41-year-old man with paroxysmal supraventricular tachycardia. During the electrophysiology study, the atrial extrastimulus inducing the typical AVNRT was conducted simultaneously over the fast (AH) and the slow pathway (AH'). A successful ablation of the slow pathway was performed. During the follow-up no recurrence was noted. The second case is a 52-year-old woman with a Wolff-Parkinson-White syndrome due to a left posterior accessory pathway. After 5 minutes of atrioventricular reentrant tachycardia (AVRT) induced by a ventricular extrastimulus, a variability of the antegrade conduction was noted in presence of the same VA conduction. In fact, a short AH interval (fast pathway) alternated with a more prolonged AH intervals (slow pathway) that progressively lengthened until a typical AVNRT was induced. The ablation of the accessory pathway eliminated both tachycardias. DISCUSSION: A rare manifestation of dual atrioventricular nodal pathways is a double ventricular response to an atrial impulse that may cause a tachycardia with an atrioventricular conduction of 1:2. In our first case, an atrial extrastimulus was simultaneously conducted over the fast and the slow pathway inducing an AVNRT. This nodal reentry implies two different mechanisms: 1) a retrograde block on the slow pathway impeding the activation of the slow pathway from the impulse coming down the fast pathway, and 2) a critical slowing of conduction in the slow pathway to allow the recovery of excitability of the fast pathway. Interestingly, in the second case, during an AVRT the atrial impulse suddenly proceeded alternately over the fast and the slow pathway. The progressive slowing of conduction over the slow pathway until a certain point which allows the recovery of excitability of the fast pathway determines the AVNRT. This is a case of "tachycardia-induced tachycardia" as confirmed by the fact that the ablation of the accessory pathway eliminated both tachycardias. SN - 0046-5968 UR - https://www.unboundmedicine.com/medline/citation/10609133/Unusual_induction_of_slow_fast_atrioventricular_nodal_reentrant_tachycardia__Report_of_two_cases_ DB - PRIME DP - Unbound Medicine ER -