Ventricular preexcitation. A proposed nomenclature for its substrates.

The working party on ventricular preexcitation of the European Society of Cardiology has debated nomenclature of the syndrome at several meetings. This communication presents the terminology proposed by the morphologists within the study group on behalf of the other members. It is suggested that the problem should be approached on the basis of possibilities of avoiding the delay-producing area of the atrioventricular junctional region or short-circuiting the specialized ventricular conduction pathways. Thus we propose that the following pathways or contingencies are relevant to preexcitation: (1) accessory atrioventricular muscle bundles; (2) accessory nodoventricular muscle bundles, (3) atriofasicular bypass fibers, (4) fasciculoventricular accessory connections, (5) intranodal bypass fibers, and (6) nodal malformations. Each of these possibilities is defined, or, where only hypothetical, is discussed. In the case of the first two definitions, anatomical variations are indicated which satisfy the basic definition. Thus accessory atrioventricular bundles can be either septal or parietal, and can be composed of either specialized or nonspecialized myocardium. Nodoventricular bundles can connect either the transitional cell zone or the compact nodal region of the junctional area to the ventricular septum. Comparison is made of the new nomenclature with terms in present usage.