TAVR for Bicuspid Aortic Valve Stenosis Feasible, but Associated With Higher Rate of Permanent Pacemaker Implantation

In patients with bicuspid aortic valve stenosis, transcatheter aortic valve replacement results in “favorable” rates of 30-day mortality and cerebrovascular events regardless of bicuspid valve leaflet morphology, although one in four patients require a permanent pacemaker following the procedure, a new study has shown. 

The rate of permanent pacemaker implantation at 30 days was similar regardless of whether patients received the self-expanding CoreValve (Medtronic) or the balloon-expandable Sapien, Sapien XT, and Sapien 3 (Edwards Lifesciences) devices.

“TAVR for [bicuspid aortic valve] stenosis appeared not only feasible but achieved favorable rates of complications, with the exception of increased rates of predominantly mild paravalvular leak (particularly in the absence of baseline contrast CT scan) and permanent pacemaker regardless of device design and leaflet morphology,” Hasan Jilaihawi, MD (Cedars-Sinai Heart Institute, Los Angeles, CA), and colleagues write in their paper published online June 29, 2016, in the JACC: Cardiovascular Imaging.

Overall, 18.1% of patients developed moderate or severe paravalvular aortic regurgitation, although the rate was just 11.5% in patients who underwent preprocedural CT, say investigators. They add that CT-guided assessment should be an “integral part of procedural planning” and is particularly important given the heterogeneity of bicuspid aortic valve phenotypes.

For Azeem Latib, MD (San Raffaele Scientific Institute, Milan, Italy), one of the study authors, the imaging study and morphological classification criteria “will help our understanding of the device-anatomy interaction for bicuspid valves, particularly as TAVR moves to younger and lower risk patients where the incidence of bicuspid aortic stenosis will be more common.”

In an editorial, Jeffrey Popma, MD, and Ronnie Ramadan, MD (Beth Israel deaconess Medical Center, Boston, MA), write that bicuspid aortic valve disease is the most common congenital heart anomaly in the general population, with the progressive calcification and reduced movement of the leaflets contributing to the development of aortic stenosis in these patients. Surgery is the treatment of choice in bicuspid aortic valve stenosis, but for those poorly suited for surgical valve replacement, TAVR is an alternative, they add.

However, TAVR in patients with a biscuspid aortic valve is associated with higher rates of residual aortic regurgitation, higher early mortality, and higher rates of requiring a second valve when compared with patients with tricuspid degenerative aortic stenosis, explain Popma and Ramadan. 

To TCTMD, Latib said there are specific concerns regarding the use of TAVR for the treatment of bicuspid aortic valve stenosis. For example, the elliptically-shaped annulus might impair valve positioning and sealing while assymetrical and heavy calcification of the leaflets might impede valve expansion and hemodynamics. There are also questions regarding long-term durability, particularly if the valve is underexpanded or situated within an elliptical-shaped annulus. In addition, the presence of aortic disease increases the risk of dissection or rupture during valvuloplasty, postdilatation, or the implantation of balloon-expandable valves. The fused commissures—the site of the junction between adjacent leaflets—are also susceptible to disruption during valvuloplasty, and this can result in severe aortic regurgitation.

“Bicuspid aortic stenosis was an exclusion criterion for all the pivotal TAVR studies and even though many centers are routinely treating high- and extreme-risk bicuspid aortic stenosis with TAVR, it still remains an off-label indication,” Latib explained in an email. He added that physicians still don’t know the best way to percutaneously treat these patients. “Our sizing algorithm is different compared to tricuspid aortic valves, and we don’t know if a specific valve would be better in this type of anatomy.”  

Classifying Bicuspids

In the present study, the researchers evaluated the clinical outcomes of TAVR in 130 patients with biscuspid valve aortic stenosis treated at 14 clinical centers. Of these patients, 91 underwent contrast CT and had the anatomic morphology of their bicuspid aortic valve classified by the CT laboratory. For the remaining patients, anatomic morphology was classified with either transthoracic or transesophageal echocardiography.

For the novel classification system, the bicuspid valve was identified by the number of commissures (either two or three). Among those with two commissures, patients were further identified by the presence or absence of a raphe (the fusion of two adjacent cusps). The researchers explain that the three descriptive subtypes—tricommissural, bicommissural with raphe, and bicommissural without raphe—were created as a simplified representation of bicuspid aortic valve disease relevant to TAVR. A raphe, for example, can become calcified and influence device expansion and apposition at the annulus.

In the overall population, the 30-day mortality rate was 3.8%, with no significant differences between self-expanding and balloon-expandable TAVR devices. Similarly, the 30-day rate of cerebrovascular events was 3.2%, with no difference in event rates for CoreValve- and Sapien-treated patients. When the researchers stratified the bicuspid aortic valve patients by leaflet morphology, they did not observe any significant difference in procedural and 30-day outcomes in those with two versus three commissures, nor did they observe any difference in the 30-day event rates among bicommissural patients with versus without raphe (there were two procedural deaths in the bicommissural-without-raphe group and none in non-raphe subgroup; P = 0.047).

Latib told TCTMD the study had a limited sample size and the morphological distinctions did not seem to affect clinical outcomes with the balloon-expandable and self-expandable valves. Still, he would like to see this tested in a larger study. For him, the study does suggest that physicians are getting better at TAVR in bicuspid valves as evidenced by the lower rate of paravalvular leak in this series compared with previous reports. The study also highlights the importance of preprocedural CT planning for TAVR prosthesis selection and sizing.

He acknowledged the high rate of permanent pacemaker implantation observed in patients treated with CoreValve and the Sapien valves (26.9% vs 25.5%; P = 0.83). He said they would normally expect much lower pacemaker rates with the balloon-expandable valves compared with what was observed in this study. It is hoped that newer, second-generation valves currently available might be better suited to treating bicuspid aortic valves, said Latib.   

The editorialists add that the study is important, because it continues the conversation about the best way to classify patients with bicuspid aortic valve disease being considered for TAVR. “As the [transcatheter heart valve] technology continues to rapidly advance and potentially move to lower-risk patients, creating a morphologic classification system that can predict outcomes with TAVR and enhance case planning will become critical,” write Popma and Ramadan.  

Sources:

• Jilaihawi H, Chen M, Webb J, et al. A bicuspid aortic valve imaging classification for the TAVR era. J Am Coll Cardiol Img. 2016;Epub ahead print.
• Popma JJ, Ramadan R. CT imaging of bicuspid aortic valve disease for TAVR. J Am Coll Cardiol Img. 2016;Epub ahead print.

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