Catheterization Technique for Laser Photoahlation of Atrioventricular Conduction from the Aortic Root in Dogs

A simple catheterization technique for producing suppression or block of atrioventricular (AV) conduction in dogs by neodymium:YAG (Nd:YAG) laser photocoagulationfrom the aortic root is described. In 14 canines, electrode catheters were percutaneously advanced to the high right atrium, to the His bundle area at the tricuspid valve (right His (RHJ), and the noncoronary cusp of the aortic valve (left His [LH]). A 400μ optical fiber was fed into the lumen of the LH catheter. Continuous wave Nd:YAG lasing at λ= 1,064 nm at 15–20 watts was performed at the site of the largest recorded LH deflection, opposite ta the RH catheter, until complete AV block (CAVB, group I, eight dogs) or persistent A-H prolongation (AHPr, group 11, four dogs) occurred; in two animaJs, laser photoablation was unsuccessful. CAVB and AHPr were achieved in < 140 seconds of lasing. Mean lasing time was 51 ± 41 seconds, total energy delivered, 776 ± 601 J. There were no complications. Dogs were followed for up to 120 days. In group I, 6/6 dogs followed /or at least I week continued to have CAVB (three AV nodal, five infra-His). In group II, 1/4 dog progressed to infra-His CAVB^; 3/4 had depressed AV nodal function. AV block was not reversed by isoproterenol. Aortic root angiograms revealed intact valve function in all. Histology showed various degrees of damage and repair of AV functional tissue. There were no valvular perforations. Transcatheter Nd:YAG laser photocoagulation of the AV junction from the aortic root is a fast, simple, and safe method for creating AV conduction block in dogs.