A new electrocardiographic algorithm to differentiate upper loop re-entry from reverse typical atrial flutter.

Objectives: This study was performed to differentiate upper loop re-entry (ULR) from reverse typical atrial flutter (AFL).
Background: Right atrial ULR and reverse typical AFL have different mechanisms and ablation strategies, but similar electrocardiographic characteristics.
Methods: This study included 26 patients with reverse typical AFL and 20 patients with ULR. The noncontact mapping system (EnSite-3000, Endocardial Solutions, St. Paul, Minnesota) was used to confirm diagnosis and guide successful radiofrequency ablation. Flutter wave polarity and amplitude in the 12-lead surface electrocardiogram were determined by two independent electrophysiologists.
Results: The flutter wave polarity in leads I and aVL was significantly different between the reverse typical AFL and ULR groups (p < or = 0.001). Voltage measurement revealed significant differences between reverse typical AFL and ULR in leads I, II, aVR, aVF, V1, and V2 (p < 0.001). A new diagnostic algorithm based on negative or isoelectric/flat flutter wave polarity and amplitude < or =0.07 mV in lead I was useful for diagnosis of ULR, with an accuracy of 90% to 97%, a sensitivity of 82% to 100%, and a specificity of 95%.
Conclusions: Polarity and voltage measurement of flutter wave in lead I can differentiate reverse typical AFL from ULR.