[Uncommon atrial flutter related to cicatrix from atriotomy surgery: radiofrequency catheter ablation]

A patient with a complex congenital abnormality required the implantation of an interatrial septum patch through a right lateral atriotomy. Nine years later he developed two different morphologies of an incessant uncommon atrial flutter refractory to antiarrhythmic drug treatment. The electrophysiological study localized a site on the right atrium lateral wall where local activation time was 75 ms earlier than the onset of the P wave, transient entrainment with concealed fusion was obtained, the first postpacing interval after transient entrainment was 5 ms longer than tachycardia cycle length and the stimulus to P wave interval was 50 ms. At this site, radiofrequency delivery terminated the atrial flutter in less than 1 second. No further induction or recurrences of any morphology of the atrial flutter were observed after a four month follow up. These findings suggest the existence of a narrow conduction isthmus amenable to interruption by focal delivery of radiofrequency. The isthmus was most probably located between the atriotomy and the crista terminalis, posterior to the former and anterior to the latter.