Reentrant circuit of adenosine-sensitive atrial tachycardia originating near the his bundle region revealed by entrainment pacing and catheter ablation of the 'entrance'.

The mechanism of adenosine-sensitive atrial tachycardia (AT) originating near the His bundle region has been reported to be due to reentry, as indicated by entrainment pacing at a site remote from the 'entrance' to the slow conduction zone of the postulated reentrant circuit. We report a case of AT, in which the change in response to the entrainment pacing following radiofrequency applications at the 'entrance' to the slow conduction zone not only suggested that the mechanism of the AT was reentry, but also the size of the reentrant circuit. <Learning objective: The mechanism of adenosine-sensitive atrial tachycardia (AT) with an earliest atrial activation site near the His bundle has been reported to be due to reentry, but the size of the postulated reentrant circuit remains uncertain. This case suggested not only the mechanism of the AT was reentry, but also the size of the reentrant circuit localized near the His bundle based on the response to entrainment pacing after the radiofrequency applications at the 'entrance' to the slow conduction zone of the reentrant circuit.>.