ACTIVATION AND ENTRAINMENT MAPPING DEFINES THE TRICUSPID ANNULUS AS THE ANTERIOR BARRIER IN TYPICAL ATRIAL-FLUTTER

Background The importance of anatomic barriers in the atrial flutter r eentry circuit has been well demonstrated in canine models. It has bee n shown previously that the crista terminalis and its continuation as the eustachian ridge form a posterior barrier. In this study we tested the hypothesis that the tricuspid annulus forms the continuous anteri or barrier to the flutter circuit. Methods and Results Thirteen patien ts with typical atrial flutter were studied. A 20-pole halo catheter w as situated around the tricuspid annulus. A mapping catheter was used for activation and entrainment mapping from seven sequential sites aro und the tricuspid annulus and from three additional sites including th e tip of the right atrial appendage, at the fossa ovalis, and in the d istal coronary sius. Sites were considered to be within the circuit wh en the postpacing interval minus the flutter cycle length and the stim ulus time minus the activation time were less-than-or-equal-to ms: sit es were considered to be outside the circuit when these intervals were greater-than 10 ms. All seven annular sites were within the circuit; activation occurred sequentially around the annulus and accounted for 100% of the flutter cycle length. The fossa ovalis, the distal coronar y sinus, and the right atrial appendage were outside the circuit. Conc lusions Closely spaced sites around the tricuspid annulus are activate d sequentially, and are all within the flutter circuit according the e ntrainment criteria. The demonstrates that the tricuspid annulus const itutes a continuous anterior barrier constraining the reentrant wave f ront of human counterclockwise atrial flutter