BackgroundAtrial tachycardia (AT) from the right superior pulmonary vein (RSPV) may mimic right atrial (RA)-AT due to its proximity to the superior vena cava (SVC) and the preferential connections between the left atrium and right atrium. ObjectiveRA electroanatomical mapping was performed and analyzed during RSPV-AT to differentiate it from RA-AT. MethodsElectroanatomical mapping of the RA was performed in 16 consecutive patients with RSPV-AT and eight consecutive patients with SVC-AT served as control group. ResultsRA mapping revealed single breakthrough in six patients and double breakthroughs in 10 patients in the RSPV-AT group. The initial 10-ms atrial depolarization area averaged 4.3 1.5 cm(2). None of the SVC-ATs exhibited double breakthrough sites with an initial 10-ms atrial depolarization area of 2.0 +/- 0.6 cm(2) (P = 0.001). A cutoff value of activation area of initial 10 ms > 3.15 cm(2) was able to predict RSPV-AT with a sensitivity of 87.5% and a specificity of 100%. Preceding far-field RSPV potentials could be documented in the RA in six patients during RSPV-AT. ConclusionsDuring RSPV-AT, diffused initial depolarization and one or two separated breakthrough sites consistent with the preferential connections as revealed by RA mapping could help rule out RA-AT and avoid unnecessary ablation at the RA.