What is in a name for bicuspid aortic valve aortopathy? Free

In one of the most comprehensive documents on bicuspid aortic valve (BAV) aortopathy written to date [1], it was proposed that although the Sievers’ classification is the commonest one used to describe the BAV morphology, a new and more comprehensive classification system that would take into consideration the BAV morphology and pathology, and the location and the extent of the associated BAV aortopathy, was required.

The current consensus statement by Michelena et al. [2] addresses this gap in a comprehensive and structured manner. Although some of the topics discussed in the document have been already reviewed elsewhere, the sections relating to the existing classifications, the definition of congenital BAV and aortic root complex and the consensus on BAV nomenclature and classification, represent an important effort that will impact clinical and research practice in the future.

The topographic anatomy of the thoracic aorta has been confusing at times. The authors provide here a simple and clear account of the elements of the aortic root and the aortic root complex, a structure defined by the sinotubular junction, the aortic sinuses and the aortic annulus. They also define the limits of what they name ‘tubular ascending aorta’ (‘ascending aorta’), these being the sinotubular junction proximally, and the take-off of the brachiocephalic artery distally.

The authors have identified and reviewed several different nomenclature systems previously proposed to define the morphology of BAV, and they have highlighted some of their shortcomings and deficiencies. In their document they offer a new and comprehensive classification that considers the morphological variables of the disease that impact the diagnosis, natural history and management, of patients with this condition.

Three different morphological types of BAV, the ‘fused’ type, the ‘2-sinus’ type and the ‘partial fusion’ type are proposed. In the ‘fused’ type, the most common of the three by far, the authors distinguish three specific BAV phenotypes (right-left cusp fusion, right-non cusp fusion and left-non cusp fusion), which are associated with different modes of valvular dysfunction (stenosis or regurgitation) and with different aortic phenotypes (for instance, the right-non cusp fusion type is associated with dilatation of the aortic arch). Interestingly, up to 30% of patients with the ‘fused’ type will have no raphe (defined here as the congenital fibrous ridge between the fused cusps). One of the important novelties in this document is the significance given to the evaluation of the BAV symmetry for the ‘fused’ type of BAV, which is defined by the angle between the commissures of the non-fused cusp. This is a fundamental factor in the planning and performance of BAV repair in pure aortic regurgitation. It has been suggested that symmetric BAV repair results in more physiological flow patterns and significantly reduces wall shear stress, as compared to asymmetric BAV repair [3]. Modification of the commissural orientation by plication of the fused sinuses in asymmetric valves appears to offer better short- and midterm stability in BAV repair [4].

The classification of the BAV aortopathy phenotype is simplified with respect to previous classifications, suggesting two main types: the ‘ascending’ and the ‘root’ phenotypes. The former is more commonly found in older patients with aortic stenosis and the later in younger patients with aortic regurgitation. Patients with a ‘root’ phenotype are more likely to suffer an acute aortic dissection if the aorta is not addressed during a primary aortic valve replacement or repair procedure. Regarding the aetiology of the aortic dilation, the authors propose that the aortic dilatation in the ‘root’ phenotype is likely to be driven by genetic factors, whereas in the ‘ascending’ phenotype it appears to be driven by the haemodynamics of abnormal blood flow patterns. The third and fourth phenotypes, defined according to the distal extension of the dilatation in the two main phenotypes, are termed ‘aortic phenotype extended’ and ‘root phenotype extended’, respectively.

The central part of the consensus document is Fig. 20. It summarizes the nomenclature proposed by the authors, and it is conceptually appropriate and intuitive. Nevertheless, it is probably too complex for daily use in reports and discussions. We propose to use a simplified version stating only the valve phenotype (V), the symmetry (S), and the aortic phenotype (A). For instance, a patient with a fused (R-L) BAV phenotype, with symmetric leaflets and a dilation of the aortic root, would be classified as V1 (R-L), S-1 (1 for symmetric, 2 for asymmetric and 3 for very asymmetric) and A-1 (0 for no aortic involvement, 1 for root, 2 for ascending and 3 for extended).

Although some of the elements affecting BAV repair are discussed in the document, from the surgical perspective we miss a more detailed review of others that are equally important. These are the annular diameter, the effective height (the distance between the central free margin and the annular plane in diastole, the geometric height (the distance from the nadir of the cusp to the central free margin), and the presence or absence of fenestrations. Attention to these parameters has contributed to the reproducibility of bicuspid aortic valve repair, improving results and acceptance as the procedure of choice in some cases [5]. A comprehensive analysis of these parameters should be part of the diagnostic workup for BAV repair. As discussed in the document, different cardiac imaging techniques are available to complete this analysis in a precise manner. Surgeons and cardiologists should be aware of the advantages and disadvantages of each of the techniques, as well as the specific information they offer. In this regard, the role of a multimodality imaging cardiologist who can evaluate and integrate the information provided by each of the techniques, should be emphasized. We would have welcomed a recommendation on an integrated multimodality imaging report for BAV aortopathy. This report should summarize information on the important anatomic and functional parameters obtained from the imaging technique that is most appropriate for each parameter.

For surgeons and cardiologist treating patients with BAV aortopathy, there can be a lot in a name. Nomenclature is important in this setting, not only for the day-to-day communication between health professionals, but also for the creation of registries and the design of trials and studies. We welcome and applaud the effort by these experts in the subject. The proposed nomenclature is highly likely to be used in daily practice across the world from now onwards.

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