Problems in the nomenclature of the univentricular heart.

There are three main reasons why there are problems concerning the nomenclature of the univentricular heart. The first is that different authorities have used the same term to describe different varieties of the univentricular heart. The second is that many of the terms used in categorisation of these anomalies are derived from embryological concepts which are more or less speculative. The final reason, perhaps the major one, is that there is a lack of definition of a ventricle. Consequently there is no consensus as to precisely what constitutes a "univentricular" heart. Many of the heart described as "single" or "common" ventricle possess two chambers within their ventricular mass. For such hearts to be univentricular it is evident that one of these chambers cannot be a ventricle. Yet definitions have yet to be provided to distinguish ventricles from rudimentary chambers. The solutions to these problems can be produced firstly by using descriptive terms for categorisation of univentricular hearts which do not have multiple meanings. Secondly, the problems concerning usage of embryologic terms can be easily circumvented by eschewing all embryologic considerations in naming these malformations. The problem of definition of a ventricle is best solved by considering normal ventricles as possessing three portions -- an inlet portion, a trabecular portion and an outlet portion. It may then be proposed that the minimal requirements for a ventricle are that it possesses at least an inlet and a trabecular portion. Chambers without inlet portions are rudimentary chambers. Either ventricles or rudimentary chambers may possess a trabecular pattern of right or left ventricular type. Tue univentricular heart may then be categorised as composing all anomalies which have a sole chamber in their ventricular mass together with all anomalies which possess a rudimentary chamber.