TAVI has become a well-established therapy for severe aortic stenosis (AS), demonstrating favorable outcomes compared with surgical aortic valve replacement (SAVR). BAV stenosis accounts for a significant proportion of patients undergoing SAVR, and its prevalence decreases with age. As TAVI expands to younger and lower-risk populations, the number of BAV patients referred for transcatheter treatment continues to increase. However, outcomes in BAV remain inferior to those achieved in tricuspid anatomy.

This difference has been linked to several anatomic and procedural factors:

– Anatomic heterogeneity. BAV presents a wide spectrum of morphologies based on raphe patterns. The term raphe refers to the fused ridge or seam connecting two cusps that acts as an abnormal commissure. A recently proposed classification includes:

1. Raphe type:two fused cusps with a raphe and three sinuses of Valsalva.
2. No-raphe type (frustrated form):two cusps without a raphe and three sinuses of Valsalva.
3. Two-sinus type:two cusps and two sinuses without a raphe, resembling Sievers type 0.

– Annular dimensions and shape. The aortic annulus in BAV is typically larger and may fall outside the range of currently available transcatheter valve sizes. In tricuspid valves, the root is tubular with similar annular, LVOT, and supravalvular diameters, whereas BAV often shows elliptical annuli and conical configurations with smaller supra-annular diameters.

– Associated aortopathy, including aneurysm, horizontal root, and coarctation.

– Severe asymmetric calcification, which can result in suboptimal valve expansion, eccentric deployment, and paravalvular leakage (PVL).

– Coronary asymmetry and commissural alignment. In more than 50% of BAVs, marked commissural asymmetry and cusp dominance are present. Coronary ostia tend to arise higher, and coronary anomalies are more common. Optimal commissural and coronary alignment is challenging due to cusp asymmetry and coronary eccentricity.

Preprocedural cardiac imaging is critical for patient selection and sizing. Cardiac computed tomography (CT) is the gold standard for differentiating bicuspid from tricuspid valves, assessing the LVOT, aortic root, coronary height, and concomitant aortopathy. Traditionally, sizing is based on the annular plane defined by cusp hinge points. However, in BAV, the intercommissural diameter (ICD) above the annulus provides key information for morphological classification:
– Flared (ICD greater than annular diameter derived from perimeter)
– Tubular (ICD similar to annular diameter)
– Tapered (ICD smaller than annular diameter)

ICD is typically measured 4 mm above the annular plane or at the maximal raphe height. A particularly challenging subgroup includes patients with raphe-type (Sievers type 1) BAV combined with a tapered configuration.

Sizing methods for BAV TAVI include:
– BAVARD (Bicuspid Aortic Valve Anatomy and Relationship with Devices): ICD measured 4 mm above the annulus.
– LIRA (Level of Implantation at the Raphe): anchoring plane defined at maximal raphe protrusion.
– CASPER (Calcium Algorithm Sizing for bicuspid Evaluation with Raphe): accounts for calcium distribution, raphe length, and annular diameter.
– CIRCLE: used for balloon-expandable valves (BEV), while the others apply also to self-expanding valves (SEV). The projected device circle is increased by 3-mm increments from the annular plane; if it extends beyond the commissures, particularly in the presence of a calcified raphe or cusp, the risk of commissural rupture increases and downsizing is advised.

The largest BAV TAVI registry recently evaluated the accuracy and clinical impact of supra-annular sizing—where the raphe and resistance are most pronounced—compared with standard annular-based sizing. Supra-annular sizing led to smaller device selection. Although rates of residual PVL, pacemaker implantation, and second valve requirement were similar, higher gradients and a greater incidence of prosthesis–patient mismatch were observed.

COMMENTARY:

Studies comparing TAVI outcomes between BAV and tricuspid anatomy have shown lower procedural success in BAV due to increased rates of residual PVL, annular rupture, and stroke. When TAVI and SAVR are compared in BAV, mortality, stroke, and PVL outcomes are generally similar. Surgery carries a higher bleeding risk, whereas TAVI is associated with more conduction disturbances.

The NOTION-2 trial, which compared TAVI and SAVR in patients younger than 75 years, revealed worse outcomes with TAVI due to higher rates of stroke, pacemaker implantation, and moderate-to-severe PVL. These findings call for caution before expanding TAVI indications to younger BAV patients.

Existing BAV TAVI studies are often single-arm and have excluded patients with unfavorable anatomy (e.g., severe LVOT or raphe calcification, large ascending aorta), introducing selection bias. Nevertheless, new-generation devices are expected to improve procedural and clinical outcomes.

The most widely used systems are the Edwards SAPIEN® (BEV) and Medtronic Evolut® (SEV) prostheses. In BAV patients, both demonstrated similar mortality and periprocedural complication rates. However, moderate-to-severe PVL occurred more frequently with Evolut®, though it achieved larger effective orifice areas and lower residual gradients, particularly in small-to-medium annuli. In large annuli, Evolut® was associated with a higher incidence of PVL.

Valve selection should be individualized, considering both general and BAV-specific factors: coronary disease, pacemaker risk, operator experience, annular and LVOT calcification (balancing rupture vs PVL risk), aortic root angulation (favoring BEV in horizontal roots), annular size (SEV may perform better in small annuli), and raphe morphology (height, calcification, fibrosis), along with coronary eccentricity.

Four major unresolved issues affect clinical decision-making in BAV TAVI:

1. Aortopathy and ascending aorta dilation.Particularly relevant in younger patients, since the need for future aortic surgery after TAVI could represent a failure in Heart Team planning.
2. Infective endocarditis risk.Altered flow dynamics and tissue abnormalities increase susceptibility. As TAVI compresses native cusps against the aortic wall, it may theoretically elevate infection risk. Additionally, large neosinuses may promote thrombotic phenomena already observed in tricuspid anatomies.
3. Durability concerns.Anatomic differences raise uncertainty about extrapolating long-term valve durability data from tricuspid to bicuspid populations.
4. Morphological classification.The presence or absence of a raphe and flared vs tapered configuration are crucial parameters that must be considered in any TAVI vs SAVR comparison.

Long-term follow-up of BAV TAVI patients is essential to evaluate prosthesis durability and late complications. Randomized trials comparing TAVI and SAVR in BAV, with comprehensive clinical and echocardiographic follow-up, are strongly needed.

The number of BAV patients referred for TAVI will continue to increase. BAV anatomy presents unique challenges that influence procedural outcomes. Various sizing methods may improve device selection. While data comparing TAVI in BAV vs tricuspid anatomy, and TAVI vs SAVR in BAV, remain inconsistent, the risk of PVL and stroke appears higher with TAVI. Further randomized trials are necessary before expanding transcatheter approaches to younger, low-risk patients with bicuspid anatomy.

REFERENCE:
Alberto Alperi, Raquel del Valle, Isaac Pascual, Paula Antuna, Marcel Almendárez, Rut Álvarez et al. Transcatheter aortic valve implantation in bicuspid aortic valves: present and future. Rev Esp Cardiol. 2025;78(8):724–735