The Isolated and Cross-circulated AV Node Preparation of the Dog

Abstract

The isolated AV node preparation of the dog consists of the right atrium and ventricular septum, and thus includes the main conducting pathways from the sinoatrial node through peripheral Purkinje fibers. The preparation is cross-circulated with a donor dog through the cannulated right coronary, anterior septal (ASA), and posterior septal arteries (PSA). The preparation permits close-arterial injection of drugs into the AV nodal area selectively via either the PSA or the ASA. The preparation also permits direct visual placement of recording electrodes at desired sites along the main conducting system. The preparation runs for 12 hr or more. Relation of AV conduction to rates of atrial pacing observed in this preparation is essentially the same as that observed in the isolated hearts. Occlusion of the PSA causes impairment of AV conduction, while that of the ASA causes only diminution of ventricular potentials. Acetylcholine causes a negative dromotropic effect and l-norepinephrine a positive one via both the PSA and the ASA. However, the two substances are more effective via the PSA than via the ASA.