A histological survey of pre-excitation syndrome and related arrhythmias.

The scanty available data in histology of accessory AV pathways, namely James', Mahaim's and Kent's fibres, together with Paladino's bundle, defects in the fibrous annuli and "Ring tissue", were considered for their bearing on old and new pathophysiological questions about ventricular pre-excitation and complicating tachy-arrhythmias. The histological findings in nine hearts allowed for a realistic and synthetic schematization of all the main types of anomalous AV bypasses, which have been emphasized in discussing the subject. The inadequacy of basic knowledge concerning the anatomoclinical significance of James and Mahaim fibres and "Ring tissue" in ventricular pre-excitation is pointed out, and the importance of Kent bundles in pathogenesis of WPW is confirmed. In a case of supraventricular paroxysmal tachycardia, without pre-excitation, a Kent bundle was demonstrated, which suggests the possible existence of latent forma of WPW with antegrade-blocked AV bypass, underlying reciprocating tachycardias of this kind. New trends in morphological investigation on the AV junction and anatomophysiological bypasses in the area are outlined.