Diagnosis of Concealed Accessory Pathway Due to Administration of Adenosine in Sinus Rhythm

pp 589-596

Abstract

Background

The role of adenosine in patients with concealed accessory pathways has not been previously defined. During sinus rhythm it occurs a permanent conduction from ventricles to atria through the accessory pathway, which is not overt because of the refractoriness of the latter. The administration of adenosine in sinus rhythm induces a delay into the AV node allowing the retrograde conduction by the accessory pathway. This impulse called "echo" can be seen both in the surface and intracavitary electrograms.

Methods

Twelve patients with paroxysmal supraventricular tachycardia mediated by concealed accessory pathway underwent radiofrequency ablation. At the end of electrophysiologic study, 12 mg of adenosine were administered as an intravenous bolus. Immediatly after, continuous registries of surface and intracavitary electrograms were performed for two minutes

Results

Accessory pathways were localized in the left ventricular free wall in ten patients and the septum intwo additional subjects. Eighty percent (10/12) of the study population showed atrial echoes. There were 20 echoes(1-4 per patient) detected in a mean interval of 9.4 sec. We observed prolongation of AH interval from 73±13 msec to 114 ±33 msec (p < 0.001). Seven out of nine surface electrograms showed retrograde P wave. In two patients self-limited orthodromic supraventricular tachycardia was induced after the echo. One patient had asymptomatic complete AV block lasting four seconds.

Conclusions

Up to 80% of patients with concealed accessory pathways have retrograde conduction after the administration of adenosine in sinus rhythm. This atrial activation called "echos" is seen in the surface and intracavitary electrograms. This simple non-invasive test allows the identification of the mechanisms underlying some supraventricular tachycardias.