TAVR in Bicuspid Aortic Valves: Insights From BIVOLUT-X

LONDON, England—Treatment with the self-expanding Evolut PRO/R transcatheter heart valve (Medtronic) for severe symptomatic aortic stenosis significantly improves hemodynamics and effectively enlarges the valve area in patients with bicuspid aortic valves (BAV), according to preliminary data from the BIVOLUT-X registry.

But while the echocardiographic outcomes looked good in the study, investigators did observe an increased risk of stroke. In an interim look at the first 75 BAV patients treated with an Evolut device, there were four disabling strokes at 30 days, amounting to a rate of 5.3%.

Chiara De Biase, MD (Clinique Pasteur, Toulouse, France), who presented the results at PCR London Valves 2019, noted that the majority of patients underwent pre- and postdilatation, which may have contributed to the heightened stroke risk. Use of cerebral embolic protection was infrequent, ranging from 10% to 15%, and De Biase suggested that more systematic use of dual filter protection with Sentinel (Boston Scientific) could potentially mitigate the risk.

Cameron Dowling, MBBS (Cardiology Clinical Academic Group/St George’s, University of London, England), who was not involved in the study, said the core laboratory-adjudicated echocardiographic data are extremely encouraging in that excellent valve hemodynamics and no moderate paravalvular regurgitation were observed among the TAVR-treated patients.

“However, there are some concerning safety signals among the data set,” he told TCTMD, referring to the rate of disabling stroke BIVOLUT-X’s low-to-intermediate risk patient population (mean STS score 2.9%). The stroke rate in the registry to date is consistent with data from bicuspid patients in the STS/ACC TVT Registry presented in March 2019 by Raj Makkar, MD (Cedars-Sinai Medical Center, Los Angeles, CA), he noted. In that analysis, the 30-day stroke rate was 2.4% for patients with bicuspid valves versus 1.6% for those with tricuspid aortic stenosis (P = 0.02).  

“It certainly stresses the importance of considering systematic cerebral embolic protection in patients with bicuspid valves,” agreed Dowling. “In bicuspid patients we need to improve neurological outcomes.”

Bicuspid valves tend to be heavily calcified, often requiring pre- and postdilatation, said Dowling. “Furthermore, in this study there was frequent repositioning of the transcatheter heart valve,” he said. “All of these factors could potentially provide a mechanism for stroke.”

BIVOLUT-X and Bicuspid Valves

BIVOLUT-X is a prospective, multicenter registry with a planned enrollment of 150 patients with severe symptomatic BAV receiving Evolut PRO (23, 26, or 29 mm) or Evolut R XL (34 mm) at 22 centers from Europe, Canada, Israel, and Japan. At PCR London Valves, De Biase presented data on the first 75 patients treated with TAVR, including echocardiographic and clinical outcomes at 30 days.

Most patients (85%) had a type 1 raphe positioned between the left and right coronary sinuses (type 1 L/R) or type 0 (no raphes). Depending on the valve configuration, operators used two different sizing strategies: based on the aortic annulus or by using a combined approach that measured the intercommissural distance (ICD) and aortic annulus. Overall, 96% of patients were treated with just one valve, which De Biase attributed to the repositionability of the Evolut PRO/R device.

At 30 days, the effective orifice area was 2.1 cm² (up from 0.7 cm² at baseline) and the mean aortic gradient was 9.1 mm Hg (down from 51.9 mm Hg). There was no moderate/severe paravalvular leak, while 9.7% had leaks considered mild-to-moderate. There was no significant difference in the echocardiographic and clinical outcomes based on the valve sizing strategy. The rate of permanent pacemaker implantation was 25.3%, again with no difference between the two sizing approaches.

Dowling said there are a number of different sizing strategies proposed for BAVs, including annulus-based sizing which is used for trileaflet aortic valves. The second approach consists of supra-annular measurements, which typically involve measuring the ICD at a height of 4 mm above the annulus.

“It’s been felt that for the majority of bicuspid patients, annular-based sizing is feasible, but in patients who have a tapered supra-annular structure, selective downsizing could be considered,” he said. “The main concern is oversizing for the bicuspid, with potential complications of embolization and valve underexpansion. At the same time, undersizing the valve could lead to significant paravalvular regurgitation. In bicuspid valves, it’s a matter of balancing these two considerations.”

At their center, Dowling said they size the prothesis based on patient-specific computer simulation (HEARTguide, FEops). Dowling, along with senior investigator Stephen Brecker, MD (Cardiology Clinical Academic Group/St George’s, University of London), presented data at TCT 2019 showing that the technology, which uses preoperative CT images to model the aortic root and simulate device performance upon implantation, could identify those with BAV who would be good candidates for TAVR.

Right now, Dowling said they only consider BAV patients for TAVR if they are at high or extreme risk for surgical valve replacement and have favorable anatomic characteristics.

Janarthanan Sathananthan, MBChB (St. Paul’s Hospital, Vancouver, Canada), who was not involved in the study, said that patients with congenital BAV will often have concomitant aortopathy and a large proportion of those cases are destined for surgery. For a BAV, the annulus tends to more elliptical and calcification is often different than what is seen with a trileaflet aortic valve. “There is concern in terms of how the transcatheter heart valve would expand,” he told TCTMD. Certainly, among the highest-risk bicuspid patients, TAVR “seems to be favorable, but we don’t know all the answers yet.”