Transcatheter Aortic Valve Replacement in Bicuspid Aortic Valve Stenosis

Flavien Vincent, MD, PhD; Julien Ternacle, MD, PhD*; Tom Denimal, MD; Mylène Shen, MSc; Bjorn Redfors, MD, PhD; Cédric Delhaye, MD; Matheus Simonato, MD; Nicolas Debry, MD; Basile Verdier, MD; Bahira Shahim, MD, PhD; Thibault Pamart, MD; Hugues Spillemaeker, MD; Guillaume Schurtz, MD; François Pontana, MD, PhD; Vinod H. Thourani, MD; Philippe Pibarot, DVM, PhD; Eric Van Belle, MD, PhD


Circulation. 2021;143(10):1043-1061. 

In This Article

Diagnosis and Classification of BAV Anatomy in TAVR Patients

BAV has several morphological types and the identification of these phenotypes is challenging in degenerative and heavily calcified AS.[15] Diagnosis should be made using a CT scan, preferably with acquisition throughout the entire cardiac cycle.[16] Echocardiography (mainly transthoracic) has lower sensitivity and may miss up to 88.5% of BAV in elderly patients referred for TAVR.[14] There are various classifications of BAV but the classification proposed by Sievers is the most widespread. BAV phenotypes are categorized according to the number of raphe (0, 1, 2), and subcategorized according to the spatial position of the cusps or raphe and the functional status of the valve (Figure 1A).[17] Based on the Sievers classification, BAV type 1 is the most common phenotype (90%) and results in a fusion of the left and right coronary cusp in 70% of patients, the right coronary cusp with the noncoronary cusp in 10% to 20% of patients, and the left coronary cusp with the noncoronary cusp in 5% to 10% of patients.[17] Although widely used, this classification may not be the most appropriate for TAVR. A new classification designed for TAVR has been proposed based on the number of commissures and the presence of a raphe. This takes into account the interaction between the THV frame and the AV complex which may have important implications with regards to the THV expansion and orientation, as well as the postprocedural outcomes[18] (Figure 1B): bicommissural with raphe corresponding to a fusion of 2 cusps by a complete raphe; bicommissural with a fusion of 2 cusps but with neither raphe nor third commissure; and tricommissural corresponding to 3 cusps with an incomplete raphe or an acquired fusion of 2 cusps near the commissure (ie, type 1 Sievers with partial raphe; Figure 2). The latter subtype can be easily misclassified as TAV by echocardiography.

Figure 1.

Classification of bicuspid aortic valve anatomy.
Classification is made according to the Sievers17 (A) or Jilaihawi18 (B) classification systems. L indicates left coronary cusp; N, noncoronary cusp; and R, right coronary cusp.

Figure 2.

Computed tomography scan of bicuspid aortic valve anatomy and classified according to the Sievers17 or Jilaihawi18 classification systems.
Top, Volume-rendered computed tomography; Bottom, Two-dimensional computed tomography. Yellow arrow indicates raphe. Ant indicates anterior; LC, left coronary cusp; NC, noncoronary cusp; Post, posterior; and RC, right coronary cusp.

This classification included neither aortopathy, calcification burden, nor the type 2 Sievers classification because of its low prevalence in the TAVR series (Table 1). To date, there are no clear correlation of the BAV phenotypes with clinical outcomes after TAVR, regardless of the classification used. Lei et al did not observe differences in the outcomes of spatial position using Sievers classification[19] between type 0 BAV with lateral and anteroposterior cusps. Kim et al used the new classification in a cohort of 144 BAV patients referred for TAVR. The majority (54.1%) of patients had tricommissural valves, 41.6% had bicommissural BAV with raphe, and 4.1% had bicommissural BAV without raphe. No difference in clinical outcomes was observed between the different BAV types.[19] Conversely, Yoon et al were the first to identify the type 1 BAV with calcified raphe and excess leaflet calcification as associated with all-cause mortality and periprocedural complications.[20]

Overall, large-scale observational prospective studies with a core laboratory CT scan analysis are needed to delineate the value of existing classification systems and develop other dedicated risk stratifications tools that can predict procedural and long-term outcomes with TAVR. It should focus not only on the type of BAV, but also on the AV complex including the AV morphology, commissures and sinus numbers, presence or absence of raphe, degree and distribution of the calcifications of the raphe, leaflets, and left ventricle outflow track, and pattern and degree of aortopathy.

To address this, a roster of international experts is developing a consensus document aimed at establishing a uniform nomenclature and classification scheme for BAV and its associated aortopathy for universal use in surgery, interventional cardiology, and clinical research.[21]