Insights Into Atrioventricular Nodal Function From Patients Displaying Dual Conduction Properties

Abstract

Two patients with suspected and subsequently confirmed diagnosis of double firing were studied in the electrophysiology laboratory at University of Pittsburgh Medical Center Shadyside Hospital. All exhibited spontaneous episodic 1:2 tachycardia under baseline conditions, with minimal difference between all conducted QRS complexes on surface electrocardiogram recording.During electrophysiological study, standard quadripolar recording catheters were placed in the right ventricular apex, His bundle, and high right atrial positions. A decapolar catheter was placed into the coronary sinus. Spontaneous recording of A1A1 intervals and A1H1, A1H2 (for double firing), and A1H (single conduction) were © 2013 American Heart Association, Inc. Background-There is a significant variability observed in the conduction properties of the atrioventricular node. In a subset of hearts, impulse transmission tends to fall into two distinct conduction regions, termed the slow and fast pathway, and a further subset are capable of dual conduction of a single input stimulus, termed double firing. Methods and Results-In this article, we closely characterize two distinct responses in patients with double firing properties of the atrioventricular node, separating these into discrete types: those with slow and fast pathway interaction and interdependence (interactive), and those with independent pathway properties (orthogonal). We use novel mathematical techniques to evaluate the relative decrement and unique properties of conduction during the overlapping slow and fast pathway conduction zones. Conclusions-Our analysis demonstrates two distinct patterns of pathway conduction in double firing patients, termed interactive and orthogonal. We show parallel overlapping segments of slow and fast pathway decremental conduction curves in interactive pathways, with no such findings with orthogonal conduction. These findings suggest anatomic correlates of pathway conduction, with interactive pathways likely having a common distal segment and orthogonal pathways able to independently activate downstream structures. (Circ Arrhythm Electrophysiol. 2013;6:364-370.) Circ Arrhythm Electrophysiol

Interesting electrophysiological findings in a patient with coexistence of atrial tachycardia originating from coronary sinus and slow-fast atrioventricular nodal reentrant tachycardia

“…The most common cause of concomitant arrhythmia with slow-fast AVNRT was reported to be atrial fibrillation, followed by AT which accounted for 8% of all cases [5]. However, the exact mechanism of the coexistence of AVNRT with AT, especially the AT originating from Koch triangle, remains indeterminable although there is estimated to be an interaction between AV nodal tissue and perinodal tissue [6]. Focused on the SVT2 mechanism, especially regarding the high sensitivity to ATP or adenosine, there are some reports about a validation of the response to adenosine for AV nodal conduction.…”

Coexistence of Atrioventricular Nodal Reentrant Tachycardia with Other Forms of Arrhythmias

“…However, most arrhythmias have different mechanisms and the relationship appears to be more or less incidental. The exact mechanism of AVNRT remains elusive; however, some interactions or interdependence may exist between atrial myocardium and AV nodal or perinodal tissue [ 17 ].…”

Interesting changeover from short VA to long VA tachycardia with single atrial premature depolarisation: What is the mechanism?

“…P wave morphology and earliest EGM can localize the same [3]. The exact mechanism of the coexistence of AVNRT with AT especially originating from Koch triangle remains indeterminable, although an interaction between AV nodal tissue and perinodal tissue has been postulated [4]. There is only one similar report of AT and AVNRT ablated successfully with SP modification [5].…”