[Atrioventricular blocks of bacterial endocarditis. 8 cases comprising histological study of the conduction system]

The authors report 8 cases of complete atrio-ventricular block (AVB) which came on during bacterial endocarditis. The aortic valve was more frequently affected (6/8). The conduction disorder is necessarily unstable. The prognostic significance of AVB is always very grave--all the patients have died. The valve lesions are often severe. A histological study of the conducting pathways has been carried out. The classically described aneurysm of the membranous septum was not responsable for any cases of AVB in this series. The most frequent cause of the AVB (5/8) was an infiltration of the prenodal area and the A-V nod itself, starting from the posterior aortic cusp and, in one case, from the tricuspid valve. The bundle of His is affected either by extension of the A-V node lesion or by the focus on the right cusp. Strings of inflammatory cells may follow the sheath of the bundle branches. Haematogenous micro-abscesses are sometimes found in the conducting tissues.