Is proximal coronary sinus involved in the circuit in some cases of ECG "typical" atrial flutter?

Aim: It is commonly conceived that coronary sinus (CS) participates in atrial flutter (AFL) circuit but limited to the fibers surrounding its ostium. We evaluated the involvement of proximal CS in typical AFL.

Methods: Twenty AFL patients underwent entrainment mapping using postpacing interval minus AFL cycle length (PPI-AFL CL) including CS where a decapolar catheter was positioned with proximal bipole 1 cm from the ostium.