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Aim: Reentry circuits of a rare typical atrial flutter (AFL) involving the cavo-tricuspid isthmus (CTI) and proximal coronary sinus (CS) are described based on electrophysiological data and effects of radiofrequency (RF)., Methods and Results: Twelve patients with ECG-typical AFL in whom entrainment demonstrated that CTI and proximal CS were both part of the circuit were included. Initial RF target was CTI in 8 patients and proximal CS in 4. Success was defined as AFL termination/noninducibility. After CTI ablation, AFL cycle length (CL) increased in all: AFL persisted in 3, while in the other 5 AFL was interrupted but subsequently induced with the same morphology; before induction CTI bi-directional block was validated; success was obtained at the CS, targeting fragmented atrial potentials (APs). In those with first ablation at CS, AFL was interrupted in 3 with no AFL inducibility; in 1 AFL persisted with CL prolongation and was terminated at CTI. Two reentry patterns were identified: in 5 patients the inter-atrial septum as well as the mid-distal CS were outside of the circuit, while the CTI, proximal CS and Bachmann's bundle zone were inside, suggesting a left atrial component; in 1 patient electrophysiological mapping suggested an intra-CS circuit component. RF was successful in all without recurrence., Conclusion: Electrophysiological mapping and RF effects suggest a continuum between the CTI and proximal CS in rare cases with ECG-typical AFL. RF inside the proximal CS, targeting fragmented APs, should be considered in any patient in whom CTI ablation failed to interrupt a typical AFL., (© 2013.)

Background: The efficacy of radiofrequency (RF) ablation of an uncommon coronary sinus (CS)-dependent atrial flutter (AFL) was evaluated using conventional electrophysiological criteria in a highly selected subset of patients with typical and atypical AFL., Methods: Fourteen patients with atrial flutter (11 males, mean age 69 ± 9 years) without previous right or left atrial RF ablation were included. Heart disease was present in eight patients. Baseline ECG suggested typical AFL in 12 patients and atypical AFL in two. Mean AFL cycle length was 324 ± 64 ms at the time of RF ablation in the CS. Lateral right atrium activation was counterclockwise (CCW) in 13 patients and clockwise in one. CS activation was CCW in all. Criteria for CS ablation included the presence of CS mid-diastolic fractionated atrial potentials (APs) associated with concealed entrainment with a postpacing interval within 20 ms. Success was defined as termination of AFL and subsequent noninducibility., Results: The initial target for ablation was the cavotricuspid isthmus (CTI) in 11 patients and the CS with further CTI ablation in three. AP duration at the CS target site was 122 ± 33 ms, spanning 40 ± 12% of the AFL cycle length. CS ablation site was located 1-4 cm from the CS ostium. Ablation was successful in all patients. Mean time to AFL termination during CS ablation was 39 ± 52 s (<20 s in eight patients). No recurrence of ablated arrhythmia occurred during a follow-up of 18 ± 8 months., Conclusions: The CS musculature is a critical part of some AFL circuits in patients with typical and atypical AFL. AFL can be terminated in patients with CS or CTI/CS AFL reentrant circuits by targeting CS mid-diastolic fragmented APs.

Limited information is available on the efficacy of cryoablation in the coronary venous system in humans. A patient with a lateral accessory pathway was referred to our center after several unsuccessful endocardial and epicardial (within the coronary sinus) attempts using standard radiofrequency energy. Ablation was subsequently performed successfully by applying cryoenergy distally into the coronary sinus, using a temperature of -50 degrees C and a freezing application time of 45 s. There were no complications. Angiography of the left coronary circumflex artery and coronary venous system was performed at 12 months follow-up using cardiac multislice computed tomography, and no coronary stenosis or anatomic anomaly was found. Neither pre-excitation or any arrhythmia recurred during follow-up. This experience suggests that ablating in the distal coronary sinus can be safely performed using cryoenergy.