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.