Upper turnover portion of the reentry circuit for typical and reverse typical atrial flutter.

Background: The posteromedial right atrium (PMRA) forms a block line during typical atrial flutter (AFL). However, whether upper turnover portion exists at the anterior or posterior superior vena cava (SVC) has not been determined.

Methods: We performed right atrial mapping during AFL in 20 patients (typical AFL, n = 17; reverse typical AFL, n = 3) using an electroanatomical mapping system.

Results: Mean AFL cycle length was 224 +/- 20 ms and mean number of mapping points was 140 +/- 27. PMRA formed a block line during both typical and reverse AFL in all patients. However, in 16 of 17 patients mapped with typical AFL, PMRA did not extend superiorly to the orifice of the SVC and AFL wave propagated between the upper limit of the PMRA and the posterior SVC. In the remaining patient mapped with typical AFL, a double potential was recorded along the PMRA continuously between the orifices of the inferior vena cava (IVC) and SVC. In the three patients mapped with reverse typical AFL, a posterior barrier was detected from IVC to the upper limit of the PMRA and AFL wave propagated between the upper limit of the PMRA and the posterior SVC. Mean length from IVC to upper limit of the PMRA was 81 +/- 8% of the length from IVC to SVC.

Conclusions: PMRA forms a functional block line during both typical and reverse typical AFL. The upper turnover portion of reentry circuit for AFL was observed between the upper limit of the PMRA and the posterior SVC in the majority of isthmus-dependent AFL patients.