[Atrio-ventricular block in rheumatoid polyarthritis. Histological study of the His-Tawara system. Apropos of 2 cases].

A histological study of the conduction pathways was performed by serial sections in two patients who died with atrio-ventricular block in the course of rhumatoid arthritis. In the first case, the conduction disturbance was preceded by attacks of supra-ventricular paroxysmal tachycardia. The His-Tawara system was wholly infiltrated by a cast of lympho-plamocytes starting from rhumatoid nodules located at the base of both mitral and tricuspid valves and at the root of the aorta. The sinus node was the seat of a common fibrosis. In the second case, the atrio-ventricular block was secondary to amylosis which predominated in the central fibrous node and in the adjacent small coronary vessels. The His-Tawara system was completely destroyed down to its bifurcation. The sinus node was normal.