Adenosine sensitivity of retrograde fast pathway conduction in patients with slow-fast atrioventricular nodal reentrant tachycardia: a prospective study

BACKGROUND: It is suggested that the adenosine resistance of retrograde fast pathway in slow-fast atrioventricular nodal reentrant tachycardia (AVNRT) confirms the participation of a concealed retrograde atrio-Hisian pathway rather than the conventional fast pathway in the arrhythmia circuit of slow-fast AVNRT.

OBJECTIVE: To prospectively assess the retrograde fast pathway response to the intravenous administration of adenosine in patients with typical AVNRT and the control group.

METHODS: Electrophysiological parameters and adenosine sensitivity of retrograde fast pathway were studied in 21 consecutive patients (18 women; mean age 57 ± 10 years) with slow-fast AVNRT and 24 patients (11 women; mean age 46 ± 16 years) as the control group.

RESULTS: Fifteen (71%) patients with AVNRT and 18 (75%) patients in the control group developed transient ventriculoatrial (VA) block after the intravenous administration of adenosine (P = .79). In patients with slow-fast AVNRT, female sex (P = .003), longer VA interval during right ventricular pacing (P < .001), and longer tachycardia cycle length (P < .001) predicted transient VA block after the intravenous administration of adenosine. In patients in the control group, a shorter VA interval during fixed rate right ventricular apical pacing (P = .009) and the presence of dual atrioventricular nodal physiology (P = .002) were associated with the adenosine resistance of the retrograde fast pathway.

CONCLUSIONS: The prevalence of the adenosine resistance of retrograde fast pathway's conduction is comparable between patients with and those without slow-fast AVNRT. This finding can be explained better by the existence of an insulated intranodal tract with Purkinje-like properties or a superior atrionodal connection to the nodo-Hisian region of the atrioventricular node rather than the presence of an atrio-Hisian pathway.