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 the interatrial septum, the tip of the catheter including the optical fiber tip as well as the flow direction of contrast echoes during the laser firing. Blood clotting with thrombus formation was present following the cw mode of irradiation. The defects created in the interatrial septa of < or = 0.3 mm in diameter had irregular black borders and, histopathologically, were surrounded by a zone of coagulation necrosis of < or = 0.2 mm and vacuolization (vacuoles of < 0.1 mm in diameter). After 30 s of lasering a huge defect was conspicuous in the interatrial septum which extended up to the right and left atrial roof. The chopped mode of irradiation induced less blood clotting and narrow channels of < or = 0.08 mm through the interatrial septa with a small zone of coagulation necrosis of < or = 0.05 mm and without carbonization and vacuolization. This study demonstrates that laser atrial septostomy is technically feasible. However, prior to the extension of the method to humans, further investigation especially considering other laser power sources, possibly more suitable for this application such as Neodymium-YAG or Excimer lasers is warranted.