The Role The Ligament Of Marshall In The Development Of Atrial Fibrillation In Canines And Its Electrical Isolation Method

Aim: To investigate the role of the ligament of Marshall (LOM) in the development of atrial fibrillation (AF) in canines and to find an efficient electrical isolation method.Methods: In 20 normal healthy canines, intervention in LOM was carried out under general anesthesia. Before and after the procedures, epicardial mapping of LOM with a comb-like catheter and S1S2, S1S1 stimulations were applied to left atrial appendage (LAA), right atrial appendage (RAA), and all pulmonary veins (PVs) to induce AF. AF that could be repeated with same stimulation sequence more than 3 times, meanwhile with duration of more than 10 seconds was established as inducible one, otherwise, it's non-inducible AF. The 20 animals were divided into 2 groups according to the method of intervention: Group A, 7 dogs was intervened by cutting its proximal segment near coronary sinus; Group B, 11 dogs whose LOM potentials could be registered before intervention in LOM were ablated with ethanol at the entrance of LOM to coronary sinus and/or left atrial. The first dose is 0.2ml, plus 0.1ml each time if the potential couldn't be eliminated until it is totally disappearing. The inducing rate of AF was compared and statistically analyzed in each group and between two groups pro and post isolation of LOM respectively; P<0.05 was considered a significant difference.Results: LOM potentials could be registered in 18 canines, the registering rate was 90.0 %( 18/20). 7 dogs in group A still have LOM potentials at proximal segment afterintervened by cutting its proximal segment near coronary sinus; but they have no LOM potentials in the distal segment. AF could be induced in 6 dogs before intervention, and the inducing rate was 85. 7% (6/7) . After the procedures, AF could still be induced in 5 of them with a inducing rate of 71.4%(5/7), the inducing rate pro and post intervention in LOM presented no significant difference in this group at /M).05.In Group B, enough ablation was applied to 11 dogs whose LOM potentials could be registered before intervention at the entrance of LOM to coronary sinus and/or left atrial, until all the potentials disappear. AF was induced in 11 canines before intervention with an inducing rate of 81.8 %( 9/11), while post intervention in LOM, AF could only be induced in 1 of them, the inducing rate was 9.1 %( 1/11), the difference of inducing rate pro and post intervention in LOM was statistically significant at p<0.01. The inducing rate of AF from both groups was compared and statistically analyzed pro and post intervention, and the difference presented no significant at P>0.05 before intervention, the difference was significant at P<0.05 after intervention, the inducing rate from Group A(71.4%) is much higher than that in Group B (9.1%).Conclusions: LOM plays an essential role in the development of atrial fibrillation in canines. The influence of intervention on the inducing rate of AF relates to its influence on LOM potential; the critical ablation site may be the entrance of the LOM to the coronary sinus and/or left atrial; the end of the ablation is totally disappearing of LOM potentials.