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

Abstract

It is commonly conceived that coronary sinus (CS) participates in the atrial flutter (AFL) circuit, but limited to fibers surrounding its Ostium. Some authors described proximal CS (pCS) involvement in rare cases of typical AFL or recurrent AFL after successful cavo-tricuspid isthmus (CTI) radiofrequency ablation. Evaluation of pCS involvement in the circuit of unselected pts with typical AFL. Twenty consecutive pts with typical AFL were included: mean age was 72 ± 12 years, 8 had heart disease, 8 associated atrial fibrillation, and 5 were on amiodarone; left atrial dimension was 21 ± 4 cm 2 , right atrial 20 ± 5 cm 2 , AFL cycle length (CL) 253 ± 34 ms. A decapolar catheter (5–5 mm) was positioned inside the CS with proximal bipole 1 cm far from Ostium, confirmed by retrograde CS angiography. Two groups were compared: pts with pCS within the circuit (GR1, PPI ≤ 20 ms + concealed entrainment) and those without (GR2, PPI > 20 ms). GR1 pts were older: 77,5 ± 4 yrs vs 72 ± 12 yrs; P < 0.05. There was no difference between the two GRs concerning other clinical variables, AFL CL, PII at CTI entry, CTI plateau, and septal CTI. GR1 pts had shorter PPI at pCS (9 ± 3 ms vs 40 ± 15 ms; P < 0.001), and fragmented mesodiastolic pCS APs (106 ± 27 ms vs 58,5 ± 22 ms; P < 0.001) with a lower amplitude (0,98 ± 7 ms vs 1,9 ± 1 ms; P = 0.07). A mid-septal unexcitable scar was found in 5/8 GR1 vs. 1/12 GR2 pts ( P < 0,05). All pts were successfully ablated at CTI. A GR1 pt had AFL recurrence and underwent a second attempt: PPI was 60 ms at CTI entry, and ≤ 20 ms at septal CTI and pCS. Septal-CTI RF ablation was ineffective, and AFL was terminated 1 cm inside CS, applying RF at a fragmented AP. pCS appears involved in a substantial subset of pts with typical AFL, in which advanced age, low voltage fragmented pCS APs, and presence of a mid-septal scar are prevalent. pCS might be considered as an un “innocent by-stander”, but able, in rare cases, to generate a second AFL circuit.