NEW ELECTROCARDIOGRAPHIC CRITERIA FOR THE DIFFERENTIATION BETWEEN COUNTERCLOCKWISE AND CLOCKWISE ATRIAL-FLUTTER - CORRELATION WITH ELECTROPHYSIOLOGICAL STUDY AND RADIOFREQUENCY CATHETER ABLATION

Objective-To develop new electrocardiographic (ECG) criteria for the d ifferentiation between counterclockwise and clockwise atrial flutters. Background-Traditionally, the ECG differentiation between countercloc kwise and clockwise atrial flutters is based on the nutter wave polari ty in the inferior leads. However, determination of nutter wave polari ty is subjective and sometimes difficult, especially in nutter waves o f undulating pattern. Patients-The study comprised 37 consecutive pati ents with drug resistant atrial nutter; 30 had counterclockwise and 17 had clockwise atrial nutter (10 had both forms of atrial nutter). The isthmus dependence was confirmed by entrainment study and catheter ab lation. The ECG patterns of both types of atrial nutter were compared and the nutter wave polarity in the inferior leads was determined by f our independent cardiologists. Results-The nutter wave polarity in the inferior leads appeared negative in 24, positive in one, and equivoca l in five of the counterclockwise atrial flutters; polarity appeared n egative in one, positive in 10, and equivocal in six of the clockwise atrial flutters. However, the aVF/lead I nutter wave amplitude ratio w as > 2.5 in all counterclockwise but < 2.5 in all clockwise atrial flu tters. The nutter wave nadirs in the inferior leads corresponded to th e upstrokes in V1 in all counterclockwise atrial flutters, but corresp onded to the downstrokes in V1 in all clockwise atrial flutters. Concl usions-The nutter wave polarity in the inferior leads does not correla te well with the nutter wave rotating direction. However, counterclock wise and clockwise atrial flutters can be differentiated by new ECG cr iteria with high accuracy.