Impact Of Intervention In Left Atrial Isthmus On The Inducing Rate Of Atrial Fibrillation In Canines And Its Underlying Mechanism

Aim: To investigate the effect of intervention in left atrial isthmus (LAI) on potentials registered from Ligment of Marshall(LOM) and the inducing rate of atrial fibrillation(AF) in canines, together with the relationship between electrical isolation of LOM and the inducing rate of AF.Methods: In 19 mongrel dogs , intervention in LAI was carried out under general anesthesia with a linear transmural lesion from left inferior pulmonary vein(LIPV) to coronary sinus(CS) , the incision was closed immediately after excision. Before the procedures, epicardial mapping of LOM with a comb-like catheter and measuring conduction time of LAI were made, then S1S2, S1S1 stimulations were applied to left atrial appendage (LAA), right atrial appe ndage(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 noninducible AF. After intervention in LAI, above-mentioned strategies were redone . The animals were divided into 2 groups according to the changes of LOM potentials post intervention in LAI: Group A included the animals whose LOM potentials were abolished, while Group B included these whose LOM potentials remained unchanged after intervention in LAI. The inducing rate of AF was compared and statistically analyzed in each group and between 2 groups pro and post intervention in LAI respectively; and the conduction time of LAI in each group was also compared and statistically analyzed before and after procedures. P<0.05 wasconsidered a significant differenceResults: LOM potentials could be registered in all 19 canines, and the registering rate was 100%(19/19). LOM potentials were abolished in 12 of them after intervention in LAI, and they are pertain to Group A; in the rest 7 canines, LOM potentials could still be recorded, and they belong to Group B. In Group A, AF could be induced in 10 of the 12 canines before intervention in LAI with a inducing rate of 83.3%(10/12), while post intervention in LAI, AF could only be induced in 2 of them, and the inducing rate was 16.7%(2/12), the difference of inducing rate pro and post intervention in LAI in this group was statistically significant at P<0.05. In Group B, AF could be induced in 6 of them before intervention in LAI, 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 77.4%(5/7), the inducing rate pro and post intervention in LAI in Group B presented no significant difference at P>0.05. The inducing rate of AF from both groups was compared and statistically analyzed after intervention in LAI, and the difference was significant at P <0.05 , the inducing rate from Group A(16.7%) is much lower than that in Group B (77.4%). When the conduction time of LAI in each group was compared pro and post intervention in LAI, no significant difference was seen with P>0.05 Conclusions: Intervention in LAI could reduce the inducing rate of AF in canines, and it is resulted from the concomitantly electrical isolation of LOM-accompanied isolation of LOM after intervention in LAI can significantly reduce the inducing rate of AF, and the inducing rate of AF from canines whose LOM staying intact remained unchanged after intervention in LAI...