Defining the enigmatic annulus of the aortic valve

In the current issue of the Journal, Contino et al. [1] present a detailed investigation of the geometry of the components of the aortic root. Their discussion reminds me of an article we published more than 30 years ago, in which we commented on the debate regarding the definition of double outlet right ventricle, arguing that some investigators offered a ‘two steps forward and one step back’ approach [2]. Such is the case with their recent analysis of the structure of the aortic root. The details they provide of the inter-relations between the aortic valvar sinuses and the fibrous interleaflet triangles are exquisite, and will be difficult to improve upon. Their discussion of the potential need to reduce the width of the interleaflet triangles during reparative surgery on the root is equally impressive. In this regard, it is encouraging to note that cardiac surgeons are now placing increasing prominence on the role of the fibrous triangles in underscoring the dynamic changes occurring within the root during the cardiac cycle. It is not that long ago that we had argued that the interleaflet triangles had been almost forgotten [3]. Their backward step, however, relates to their discussion, and definition, of the ‘annulus’ of the aortic valve. In another investigation published over 20 years ago, we had pointed to the ‘mythical’ nature of the alleged annulus [4]. Little has changed over the subsequent years. In a recent commentary in the journal [5], nonetheless, I suggested that the proposals of Sievers et al. [6], when discussing the ‘Tower of Babel’ relating to the aortic root, represented the best way forward. In their current account, Contino et al. [1] choose to muddy the waters. Accepting that Sievers et al. [6] had presented a ‘very interesting review’, they argued that they preferred to ‘follow the one proposed by Anderson, more correct and complete from an anatomical and physiological point of view’. In my previous commentary, however, I had stated ‘The Working Group make a strong case for following the lead of echocardiographers, and defining as the annulus the virtual ring created by joining together the nadirs of the valvar attachments. This is to be preferred in the sense that this plane represents the diameter of a true ring’. I also commented that ‘A strong case can surely be made, therefore, for simply describing the plane as the diameter of the entrance to the aortic root’. This reflects my ongoing dislike of the use of ‘annulus’ in this context, for all of the reasons engendered by the current discussions. I continued, nonetheless, that ‘it is highly unlikely that “annulus” will disappear from the surgical lexicon’. This proves to be the case, but it is disappointing to find my comments are now taken out of context, since it is clear that I support the recommendation made by Sievers et al. [6]. Contino et al. [1] are also selective in their choice of references. This, of course, is their prerogative. The perspective they cite, offered by de Kerchove and El Khoury [7], has much to commend. Of particular importance in this analysis, and a point seemingly missed by the Italian investigators, de Kerchove and El Khoury show how myocardial crescents are incorporated at the bases of the two coronary aortic valvar sinuses. They then discuss the relevance of this finding in the context of the ‘sinking sinus’. Adjacent to this perspective, however, is an equally incisive perspective offered by Charitos and Sievers [8]. When discussing the attachments of the leaflets, the latter authors comment that ‘As the leaflet attachments insert in the wall of the aortic root they form a crown shaped, thick fibrous structure, often termed the “annulus”. This description is unfortunate as the word annulus implies a circular structure in contrast to the “crown” shape of the leaflet attachment’. I could not have better described the anatomic arrangement myself, nor its implications. They continue by discussing the virtual basal ring, arguing that ‘In order to avoid any misunderstanding due to the numerous definitions and terms employed, we have recently proposed the use of the term “annulus” to describe the virtual, circular ring defined by the nadirs of the semi-lunar leaflet attachments’. So as to ‘avoid any misunderstanding’ regarding my own recommendations, I take this opportunity further to endorse the excellence of their approach, and to add my voice to the recognition of the virtual basal plane as the aortic ‘annulus’.