TRANSCATHETER LASER ATRIAL SEPTOSTOMY IN RABBITS

The feasibility of percutaneous transluminal catheter-directed laser ( Argon multiline 488\514 nm) atrial septostomy under echocardiographic guidance was studied in eight rabbits. In five animals the interatrial septum was exposed to laser energy for 30 s (n = 1) or for 10 s (n = 4) by using the continuous wave (cw) mode of irradiation. In the other three animals chopped mode of irradiation was applied for 10 s at 7 W . Echocardiography allowed visualization of both atrial cavities and t he interatrial septum, the tip of the catheter including the optical f iber tip as well as the flow direction of contrast echoes during the l aser firing. Blood clotting with thrombus formation was present follow ing the cw mode of irradiation. The defects created in the interatrial septa of less than or equal to 0.3 mm in diameter had irregular black borders and, histopathologically, were surrounded by a zone of coagul ation necrosis of less than or equal to 0.2 mm and vacuolization (vacu oles of < 0.1 mm in diameter). After 30 s of lasering a huge defect wa s conspicuous in the interatrial septum which extended up to the right and left atrial roof. The chopped mode of irradiation induced less bl ood clotting and narrow channels of less than or equal to 0.08 mm thro ugh the interatrial septa with a small zone of coagulation necrosis of less than or equal to 0.05 mm and without carbonization and vacuoliza tion. This study demonstrates that laser atrial septostomy is technica lly feasible. However, prior to the extension of the method to humans, further investigation especially considering other laser power source s, possibly more suitable for this application such as Neodymium-YAG o r Excimer lasers is warranted.