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- ↵∗Address for correspondence:
Dr. Itsik Ben-Dor, Washington Hospital Center, 110 Irving Street, Northwest, Suite 4B-1, Washington, DC 20010.
Patients with aortic stenosis and bicuspid valve disease present an anatomic challenge to treatment with transcatheter aortic valve replacement (TAVR). In the true bicuspid patient, Sievers type 0, there is a 180/180° configuration of the valve and no raphe (1). Present in about 7% of bicuspid patients, the aortic annulus is more of an ellipse than a circle, which creates a sizing challenge and potentially increases the risk for paravalvular leakage. The more common configuration (88% of bicuspid patients) is Sievers type 1 with fusion of the left and right cusps (1). The main challenge for these patients is a calcified raphe that places differential stress on the expansion of a TAVR, increasing the risk of imprecise positioning.
In low-risk patients and in those with concomitant aortopathy (present in >25% of bicuspid patients) (2), surgical aortic valve replacement with or without root surgery remains the preferred option. Traditionally, bicuspid patients have been excluded from all clinical trials; however, data from bicuspid aortic valve registries of patients treated with TAVR are encouraging. Bicuspid aortic valve disease is present in 1% to 2% of the U.S. population, and nearly all affected persons require aortic valve replacement during their lifetimes. Because of this disparate incidence, there is a strong need to expand the use of TAVR to this population.
In this issue of the Journal, the paper by Yoon et al. (3) reports on the largest multicenter, collaborative registry of patients with bicuspid aortic valve treated with TAVR. This study was designed as a 1:1 propensity matched–pairs comparison of outcomes between patients with bicuspid and trileaflet aortic stenosis treated with TAVR. Tricuspid and bicuspid aortic stenosis had similar mortality after TAVR, but patients with bicuspid aortic stenosis had more procedural complications compared with those with tricuspid aortic valves when receiving the early-generation devices. The conversion to surgery was 2.5% versus 0.3%, the need for a second valve implantation 7.2% versus 2.2%, moderate-severe paravalvular leak 15.9% versus 10.3%, and aortic root injury 4.5% versus 0% in the bicuspid versus the tricuspid group, respectively. However, there were no significant difference in procedural complications between the bicuspid and tricuspid groups when receiving the new-generation devices (Sapien 3 [Edwards Lifesciences, Irvine, California], Evolut R [Medtronic, Minneapolis, Minnesota], Lotus [Boston Scientific, Marlborough, Massachusetts]).
There are many procedural challenges in treating bicuspid aortic valve with TAVR. The best method for sizing in bicuspid aortic valve stenosis is unclear; some advocate using the usual perimeter/area at the annulus level for sizing, but others report sizing at the commissural level, 4 to 8 mm above the annulus. A useful tool in sizing is balloon valvuloplasty. Aortic injection during balloon valvuloplasty may confirm a proper seal and aid in selection of an appropriately sized prosthesis. Given that larger valves may increase the incidence of annular rupture, selection of a smaller valve seems more prudent for bicuspid aortic valve patients. Because of the anatomic differences and annular positioning, sizing remains challenging and must be refined as data emerge from large, multicenter registries.
The study by Yoon et al. (3) provides new data with excellent outcomes when using second-generation TAVR devices for bicuspid aortic valves. However, there is still active debate with respect to the new-generation devices: which is better, balloon-expandable or self-expanding valves? Using first-generation devices with self-expanding valves is associated with less risk for annular rupture compared with balloon-expandable valves, but has a higher incidence or aortic regurgitation. As shown by Yoon et al. (3), aortic root injury occurred in 4.5% of bicuspid versus 0% of tricuspid aortic stenosis with TAVR using Sapien XT valves.
CoreValve had more frequent second valve implantation (11.6% vs. 2.9%) and moderate to severe paravalvular leak (19.4% vs. 10.5%) in bicuspid compared with tricuspid aortic stenosis. Mylotte et al. (4) report up to 28% moderate to severe paravalvular leak after TAVR using CoreValve for bicuspid aortic stenosis. Using the second-generation balloon-expandable Sapien S3 valve (5), there was 0% moderate to severe paravalvular aortic regurgitation and 0% annular rupture. In this series (3), annular rupture was low (0.6%), and moderate to severe paravalvular leak was low (1.9%) using Sapien 3. The lower incidence of paravalvular leak using Sapien 3 is due to the polyethylene terephthalate outer skirt designed to minimize paravalvular leaks. Evolut R was used in a very small number of patients (n = 23), with no data reported for device-specific complications. The newest iteration from Medtronic is the Evolut PRO, which has a porcine pericardial wrap on the lower 1.5 rows of inflow cells. This design promises to reduce paravalvular leaks, similar to Sapien 3, and will perhaps be the self-expanding valve of choice for patients with bicuspid aortic valve stenosis. Mechanical expanding valves (Lotus) equipped with an adaptive seal were used in a small number of patients in this study (N = 43), and as reported previously (N = 11) by Yoon et al. (6). In the Lotus bicuspid aortic stenosis study group, there was minimal risk of annular rupture and paravalvular leak.
The reported outcomes from this study do raise important concerns regarding the extension of TAVR to low-risk patients. Patients with bicuspid aortic stenosis seem to be more vulnerable to conduction system disturbances with TAVR than patients with trileaflet senile aortic stenosis. The rate of pacemaker implantation was high (15%) in both the bicuspid and tricuspid aortic stenosis groups in this study (3). These data are consistent with other reports, such as by Perlman et al. (5) with Sapien S3 (23%). This is much more frequent than previous reports of a 10.2% incidence with trileaflet valves using Sapien S3 (7), but comparable to the rate using the self-expanding Evolut R (16.4%) (8).
Although this study (3) did not reveal a difference in outcomes with Sievers types 0 and 1 aortic stenosis, the type 0 study group was quite small; therefore, it is hard to make a useful conclusion. As more data become available, it will likely be useful to consider the more frequent type (type I, left-right) as a separate entity. The type 0 population presents an anatomically abnormal elliptical annulus, more frequent valvular incompetence, and a more frequent association with aortopathy.
In the study by Yoon et al. (3) the follow-up was short (median: 460 days), but long-term data are important because a bicuspid valve is asymmetrically configured, and heavy calcification of the bicuspid aortic valve annulus may hinder valve positioning and expansion, which can subsequently impair the normal functioning and long-term durability of the prosthetic valve.
The study provided important preliminary data showing that the new-generation TAVR devices might be a reasonable treatment option to overcome the challenges of bicuspid anatomy. In low-risk patients and in those with any sign of aortopathy, surgery is still the gold standard. In light of the good outcome and low complication rate using second-generation devices, TAVR is a reasonable option for patients with high surgical risk.
↵∗ Editorials published in the Journal of the American College of Cardiology reflect the views of the authors and do not necessarily represent the views of JACC or the American College of Cardiology.
Both authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2017 American College of Cardiology Foundation
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