Editorial

Transcatheter aortic valve replacement for bicuspid aortic valve stenosis

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Bicuspid aortic valve is the most common congenital cardiac abnormality in humans and is a significant risk factor for premature aortic valve dysfunction due to accelerated leaflet deterioration and calcification from altered hemodynamics. From 20% to 50% of patients with bicuspid aortic valve need aortic valve replacement during their lifetime, mostly for aortic stenosis.1,2

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While 0.5% to 2% of the general population are born with a bicuspid aortic valve, more than 40% of patients (mainly younger patients) who undergo surgical or transcatheter intervention for aortic valve disease in some cohorts have this abnormality, suggesting that its true prevalence may be underreported.3

In the past decade, transcatheter aortic valve replacement (TAVR) has cemented its place as an option for patients with severe tricuspid aortic stenosis who cannot undergo surgery because their surgical risk is intermediate or high.4 However, most of the studies of balloon-expandable and self-expanding TAVR devices have excluded patients with bicuspid aortic valve.

BICUSPID AORTIC VALVE POSES CHALLENGES FOR TAVR

As TAVR is explored in younger and lower-risk populations, in which the prevalence of bicuspid aortic valve is presumably higher, the discussion of feasibility, safety, and efficacy of TAVR in patients with bicuspid aortic valve is both important and timely.

Bicuspid aortic valve is commonly categorized according to the Sievers classification,5 which describes 3 main morphologic types (designated types 0, 1, and 2) according to the number of raphes connecting the leaflets. Unique anatomic features of bicuspid aortic valve render the TAVR procedure challenging in these patients and merit consideration. These include, but are not limited to:

  • Asymmetric calcification of the valve leaflets and calcified raphes. This results in asymmetric and incomplete expansion of the prosthesis, leading to incomplete sealing and paravalvular leak.
  • A larger and more elliptically shaped aortic annulus, leading to challenges with proper sizing and apposition of the prosthesis
  • Concomitant aortopathy, posing a higher risk of aortic rupture, dissection, paravalvular leak, and other complications during implantation.

Thus, compared with patients with tricuspid degenerative aortic stenosis, patients undergoing TAVR who have bicuspid aortic valve have a higher short-term risk of death and a higher risk of residual aortic regurgitation, and are more likely to need implantation of a second valve.

PARAVALVULAR LEAK

Paravalvular leak, arguably an independent marker of higher morbidity and mortality risk after TAVR, is more common in patients with bicuspid aortic valve undergoing TAVR than in those with tricuspid aortic valve. Earlier studies reported rates of moderate or severe paravalvular leak between 16% and 32%.6,7

The newer-generation balloon-expandable Sapien 3 valve (Edwards Lifesciences, Irvine, CA) is associated with a lower incidence of moderate or severe paravalvular leak than earlier devices, mainly attributable to its outer skirt, which allows more complete sealing.8 There are also reports of successful treatment of bicuspid aortic valve stenosis using the Lotus device (Boston Scientific, Marlborough, MA).9 This device features adaptive sealing along with retrievability and repositioning ability, which may facilitate optimal positioning and prevent paravalvular leak.

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