Electrocardiographic Patterns and Results of Radiofrequency Catheter Ablation of Clockwise Type I Atrial Flutter

INTRODUCTION: Counterclockwise right atrial propagation is usually observed in common atrial flutter, but little is known regarding flutter with clockwise right atrial rotation. The aim of this study is to describe the ECG characteristics and results of catheter ablation of atrial flutter with clockwise right atrial rotation. METHODS AND RESULTS: Among the 38 patients with type I atrial flutter in this study population, right atrial impulse propagation was counterclockwise in 20 and clockwise in 8. In the remaining 10 patients, both clockwise and counterclockwise patterns were seen. Clinical and ECG parameters associated with clockwise flutter were compared to those of 28 cases of counterclockwise atrial flutter. Ablation was performed in 11 of 18 cases using a technique identical to that used for counterclockwise flutter. A classical "sawtooth" pattern of the flutter wave was observed in 28 of 28 counterclockwise and 14 of 18 clockwise flutter. A shorter plateau phase, a widening of the negative component of the F wave in the inferior leads, and a negative F wave in V1 were the most consistent findings in clockwise flutter. Coronary sinus recording always showed septal to lateral left atrial impulse propagation. Ablation was successful in 11 of 11 cases of clockwise flutter in whom this procedure was performed, with 9.5 +/- 11.6 radiofrequency pulses delivered between the tricuspid valve and the coronary sinus ostium (n = 5) or the inferior vena cava (n = 5), and in the proximal coronary sinus (n = 1). After a follow-up of 46.6 weeks, two recurrences of clockwise flutter were encountered, which were successfully treated with a second session. CONCLUSION: Contrary to commonly accepted concepts, clockwise rotation of atrial flutter is not an infrequent phenomenon and can mimic counterclockwise rotation. It can also be successfully ablated by radiofrequency pulses.