NON COMMON ATRIAL-FLUTTER AFTER SURGICAL ATRIOTOMY - RADIOFREQUENCY CATHETER ABLATION

A patient with a complex congenital abnormality required the implantat ion of an interatrial septum patch through a right lateral atriotomy. Nine years later he developed two different morphologies of an incessa nt uncommon atrial nutter refractory to antiarrhythmic drug treatment. The electrophysiological study localized a site on the right atrium l ateral mall where local activation time was 75 ms earlier than the ons et of the P wave, transient entrainment with concealed fusion was obta ined, the first postpacing interval after transient entrainment was 5 ms longer than tachycardia cycle length and the stimulus to P wave int erval was 50 ms. At this site, radiofrequency delivery terminated the atrial nutter in less than 1 second. No further induction or recurrenc es of any morphology of the atrial nutter mere observed after a four m onth follow up. These findings suggest the existence of a narrow condu ction isthmus amenable to interruption by focal delivery of radiofrequ ency. The isthmus was most probably located between the atriotomy and the crista terminalis, posterior to the former and anterior to the lat ter.