Variable electrocardiographic characteristics of isthmus-dependent atrial flutter.

Objectives: The purpose of this study was to characterize variations in flutter-wave (F-wave) morphology among patients with clockwise isthmus-dependent (CWID) and counterclockwise isthmus-dependent (CCWID) right atrial flutter (AFL) and to attempt to correlate F-wave morphology with echocardiographic data and clinical patient characteristics.

Background: Variations in F-wave morphology on surface electrocardiogram (ECG) during CCWID and CWID flutter have been reported but never systematically characterized.

Methods: Over a four-year period, 139 patients with AFL on ECG underwent electrophysiologic study and echocardiography at our institution. Electrocardiographic data, intracardiac recordings, echocardiographic data, and patient characteristics were reviewed retrospectively.

Results: Of 156 AFLs evaluated, 130 were CCWID, 26 were CWID. Three types of CCWID flutter were observed: type 1 had purely negative F-waves inferiorly, types 2 and 3 had F-waves inferiorly with small (type 2) or broad (type 3) positive terminal deflections; CCWID flutter types 2 and 3 were associated with higher incidence of left atrial (LA) enlargement, heart disease, and atrial fibrillation (Afib) than type 1. Two types of CWID flutter were observed: type 1 had notched positive F-waves with a distinct isoelectric segment inferiorly. Type 2 had broader F-waves inferiorly with positive and negative components and a short isoelectric segment.

Conclusions: Variable ECG patterns for CCWID and CWID AFL exist. A positive component of the F-wave in the inferior leads during CCWID flutter is associated with an increased likelihood of heart disease, Afib, and LA enlargement.