Atypical atrial flutter originating in the right atrial free wall

Background-Data from experimental models of atrial nutter indicate that macro-reentrant circuits may be confined by anatomic and functional barriers remote from the tricuspid annulus-eustachian ridge atrial isthmus. Data characterizing the various forms of atypical atrial nutter in humans are limited. Methods and Results-In 6 of 160 consecutive patients referred for ablation of counterclockwise and/or clockwise typical atrial nutter, an additional atypical atrial nutter was mapped to the right atrial free wall. Five patients had no prior cardiac surgery. Incisional atrial tachycardia was excluded in the: remaining patient, High-density electroanatomic maps of the reentrant circuit were obtained in 3 patients. Radiofrequency energy application from a discrete midlateral right atrial central line of conduction block to the inferior vena cava terminated and prevented the reinduction of atypical atrial nutter in each patient. Atrial nutter has not recurred in My patient (follow-up, 18+/-17 months; range, 3 to 40 months). Conclusions-Atrial nutter can arise in the right atrial free wall. This form of atypical atrial flutter could account for spontaneous or inducible atrial flutter observed in patients referred for ablation and is eliminated with linear ablation directed at the inferolateral right atrium.