Production of chronic heart block in closed-chest dogs: an improved technique.

Chronic complete heart block was produced in 38 closed-chest anesthetized dogs with a special cannula introduced via a jugular vein. A Formalin mixture (0.2-1.0 ml, consisting of equal amounts of 40% Formalin and radiopaque material) was injected through this cannula into the His bundle, which was located with a His-bundle catheter. The entire procedure took approximately 30 min and was successful in 90% of the cases.