Abstract 11088: Electrophysiologic and Anatomical Substrates of Atypical Atrial Flutter: Importance of Electrically Abnormal, Low-Amplitude Lesion in the Circuit
Atrial flutter (AFL) is due to reentry around the tricuspid annulus (typical AFL) or other anatomical obstacle and/or electrically abnormal lesion (atypical AFL). Atypical AFL is considered to have a smaller circuit than typical AFL, but its electrophysiologic characteristics are not fully understood. In 26 patients with typical (n=10) and atypical right atrial AFL with (incisional reentry, n=12) or without surgical scar (non-incisional reentry, n=4), CARTO map during AFL was created by electroanatomical data from 224±88 right atrial sites. Low amplitude electrogram (LAE) was defined as the electrogram <0.5 mV and scar as the electrogram <0.1 mV. In all patients, the reentry circuit confined to the right atrium was identified by CARTO map and by entrainment mapping. AFL cycle lengths (CL) of typical AFL and atypical non-incisional and incisional AFL were 219±25, 282±75, and 290±61 msec, respectively (p<0.05 among 3 groups by Kruskal-Wallis), lengths of reentry path 163±18, 162±42, and 124±46 mm, respectively (P=NS among 3 groups), and mean conduction velocities (mCV) along the whole reentry circuit 0.74±0.09, 0.58±0.16, and 0.46±0.24 m/sec, respectively (p<0.05 among 3 groups). Conduction time through the LAE lesion occupied 16.4±17.9% of AFL CL in typical AFL, 63.7±42.3% in atypical non-incisional AFL, and 78.0±27.0% in atypical incisional AFL (p<0.001 among 3 groups). Similarly, conduction time through the scar lesion occupied 13.6±17.1% of AFL CL in typical AFL, 51.7±37.3% in non-incisional AFL, and 58.9±30.2% in incisional AFL (p<0.005 among 3 groups). Among these parameters, atypical incisional AFL had longer AFL CL, slower mCV along the circuit, and greater areas of the LAE and scar lesions than typical AFL (all p<0.05 by Scheffe's test). There were no differences in these parameters between non-incisional and incisional AFL. In conclusion, the electrophysiologic and anatomical substrates of atypical AFL, especially those of incisional AFL markedly differ from those of typical AFL. The reentry circuit of atypical AFL is largely composed by the LAE and scar lesions which are closely related to the slow mCV along the circuit. The notion of such substrates is important in precisely delineating CARTO map of atypical AFL.
- © 2010 by American Heart Association, Inc.