Abstract 1840: Site Specific Transversal Conduction and Conduction Block at Posteromedial Right Atrium (Sinus Venosa Region) in Patients with Typical Atrial Flutter
Purpose: Posteromedial right atrium (PMRA) is thought to be a barrier forming a block during typical atrial flutter (AFL). But transversal conduction across PMRA is reported to be commonly observed during low rate pacing. Anatomical location of electrical barrier and site specific conduction across PRMA had not been evaluated by 3-D mapping.
Methods: We studied 24 patients (23 men, mean age 63 ± 9 years) with typical AFL documented by 12-leads ECG. Electro-anatomical mapping during typical AFL was performed in patients in whom AFL could be induced and sustained during session. After inferior vena cava-tricuspid annulus (IVC-TA) isthmus ablation, electro-anatomical mapping especially focusing on PRMA during postero-septum pacing of 100 ppm was performed. Transversal conduction capabilities of PMRA during typical AFL and low rate pacing were analyzed according to 3-D activation and propagation map.
Results: Mapping during typical AFL could be performed in 12 patients. A mean cycle length of AFL was 240 ± 40 msec. And in all 12 patients double potential, which indicated conduction block, was recorded all along PRMA and propagation gap across PRMA was not recoded during AFL. Bi-directional isthmus block could be achieved in all 24 patients. During posteroseptum pacing of 100 ppm, double potential was recorded all along PRMA without propagation gap in 9 patients (38%). Double potential was recorded in the lower one-third of PMRA in 5 patients (21%). Double potential was not observed along PMRA and conduction delay around PMRA was not detected in 5 patients (21%). Double potential was recorded along PMRA but propagation gap was observed in 5 patients (21%). Single gap was recognized in 3 patients (at middle of PMRA in 2 patients and at the lower one-third of PMRA in 1 patient). In 2 patients, there were 2 gaps at both middle and the lower one-third of PMRA.
Conclusions: PMRA forms a block line during typical AFL. PMRA provides a fixed block line in 38% of typical AFL patients. But transversal conduction across PMRA was commonly observed and conduction delay at PMRA was not detected in 21 % of AFL patients during low rate pacing. The lower one-third of PMRA shows a fixed transversal conduction block in two-third of AFL patients.