Atrio-ventricular Block Produced by Ligation of Septal Arteries in the Dog

Complete A-V block was observed in 18.4 per cent of 38 dogs with the anterior septal artery ligation and in 56.5 per cent of 23 dogs in which both anterior and posterior septal arteries were ligated. No complete A-V block appeared when only the posterior septal artery was ligated.In dogs which survived one day or more, A-V conduction disturbances were mostly transient even when both anterior and posterior septal arteries were ligated.Marked histological changes of the A-V conduction tissue were observed in dogs which had suffered from complete A-V block even after normal sinus rhythm was restored.The results of this study indicate that a rather small part of the crosssectional area of the A-V conduction tissue can carry impulses from the atrium to the ventricle in normal way.