Key result
Radiofrequency ablation successfully abolished atrial flutter in 67% of dogs with linear transverse applications and 70% with isthmus ablation, indicating the tricuspid annulus is not essential.
Why the study?
Does radiofrequency ablation at specific anatomical sites abolish atrial flutter in a canine model with an intercaval obstacle?
Does radiofrequency ablation at specific anatomical sites abolish atrial flutter in a canine model with an intercaval obstacle?
In a canine model of atrial flutter, the tricuspid annulus is not an essential part of the reentrant pathway, and transmural ablation of the entire atrial tissue between anatomical barriers is required for successful termination.
Answers are grounded in this paper and cite their sources.
Should not change clinical ablation practice; leaves open whether non-isthmus targets suffice in human atrial flutter circuits.
In humans, the isthmus in the low right atrium between the tricuspid annulus and the inferior vena cava or the coronary sinus ostium is a well-established target of catheter ablation of common atrial flutter. In the canine model of atrial flutter with a Y-shaped incision, the tricuspid annulus was thought to constitute the essential reentrant pathway. The present study was designed to determine whether the supravalvular tissue around the tricuspid annulus is essential to atrial flutter in the canine model with an intercaval obstacle on the basis of the results of radiofrequency ablation. Epicardial approach of radiofrequency ablation was tested in 4 groups of dogs. Group A (5 dogs): Single application of radiofrequency energy (20 W) for 5 sec to the mid right atrial free wall. Group B (9 dogs): One to two applications to the tricuspid annulus. A ligature was also placed encircling the tricuspid annulus from the supravalvular atrial tissue to the subvalvular ventricular tissue. Group C (9 dogs): Linear transverse applications to the mid right atrial free wall between the tricuspid annulus and the intercaval obstacle. Group D (10 dogs): The isthmus between the inferior vena cava and the tricuspid annulus was ablated. After the experiment, the heart was excised for anatomical and histological studies. Atrial flutter was never abolished in all dogs in Groups A and B. A ligature encircling the tricuspid annulus also failed to terminate atrial flutter in 2 dogs tested. In contrast, atrial flutter was successfully abolished in 6 dogs (67%) of Group C and in 7 dogs (70%) of Group D. Total energy delivered was significantly higher in Group C than in Group D (364 +/- 133 versus 139 +/- 65 joules, p < 0.003). The total energy required for successful ablation was related to the cross sectional area of the ablation site (r = 0.55, p < 0.05). These results indicate that the tricuspid annulus is not an essential part of the reentrant pathway in the canine model of atrial flutter with an intercaval obstacle. The entire atrial tissue between the anatomical barriers could be involved in the reentrant pathway, and should therefore be ablated transmurally for successful ablation.
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Tani et al. (1997) studied Atrial flutter (n=33). Radiofrequency ablation at various right atrial sites vs. Different ablation sites (Groups A, B, C, D) was evaluated on Abolition of atrial flutter. Radiofrequency ablation successfully abolished atrial flutter in 67% of dogs with linear transverse applications and 70% with isthmus ablation, indicating the tricuspid annulus is not essential.
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