Angiographic anatomy of the inferior right atrial isthmus in patients withand without history of common atrial flutter

Background-Although most ablative procedures undertaken for common atrial f lutter target the inferior right atrial isthmus, comparative studies of the morphology of this area are lacking. Our study examines its angiographic a natomy, making correlations with postmortem specimens, to provide a better understanding of the anatomic substrate of this arrhythmia. Methods and Results-The gross morphological features and dimensions of the area between the orifice of the inferior caval vein and the attachment of t he septal leaflet of the tricuspid valve were determined from angiograms ma de in 23 patients with documented atrial flutter and 30 control subjects. F or comparison, we studied 20 normal heart specimens. When viewed in right a nterior oblique projection, 2 morphologically distinct areas were identifie d. In the specimens, the inferior isthmus measured a mean length of 30+/-4 mm, not significantly different from the dimensions obtained from angiogram s of control subjects. The mean length of the isthmus, however, was greater in patients with common atrial flutter than those without (37+/-8 Versus 2 8+/-6 mm). Patients with atrial flutter and structural heart disease had an even longer isthmus than those with flutter alone (39.6+/-8 versus 33+/-7 mm). Compared with those without flutter, the atrial diameter was also larg er in patients with flutter (57.6+/-9 versus 48.5+/-6 mm). Reevaluation car ried out at follow-up 10+/-2 months after ablation did not show any reducti on in atrial size, although contractility improved. Conclusions-The inferior isthmus and right atrium in patients with common a trial flutter were significantly larger than those in a control population.