Different patterns of interatrial conduction in clockwise and counterclockwise atrial flutter.

Area of Science:

• Electrophysiology
• Cardiology
• Cardiac Electrophysiology

Background:

• Atrial flutter (Afl) is classified as counterclockwise (CC) or clockwise (C) based on right atrial activation.
• Left atrial activation patterns during Afl have not been systematically studied using coronary sinus (CS) recordings.

Purpose of the Study:

• To systematically evaluate and compare left atrial activation patterns during CC and C atrial flutter using CS recordings.

Main Methods:

• Electrophysiological study in nine patients with both CC and C Afl.
• Coronary sinus (CS) recordings using a decapolar catheter during both flutter types and sinus rhythm.
• Categorization of CS activation patterns into sequential proximal-to-distal, sequential distal-to-proximal, and fused.

Main Results:

• Distinct CS activation patterns were observed in 7 out of 9 patients between CC Afl (proximal-to-distal) and C Afl (fused).
• Pacing near Bachmann's bundle during sinus rhythm in two patients replicated the fused CS activation pattern seen in C Afl.

Conclusions:

• Different CS activation patterns in CC and C Afl suggest distinct left atrial activation pathways.
• C Afl activation likely involves Bachmann's bundle, while CC Afl activation may occur via the CS os.
• Findings may impact understanding of Afl maintenance, ECG interpretation, and atrial function.