NOTION and UK TAVI Report Good Long-term Function of Transcatheter Aortic Valves

Although quality data on the long-term durability of TAVR valves are sparse, follow-up from the NOTION trial of low-risk patients and the UK TAVI Registry are suggesting that valve deterioration and failure rates beyond 5 years are low.

The findings, from a variety of devices, should help assuage fears that arose in 2016 when investigators suggested that up to half of all TAVR patients who survive for 5 years will experience valve degeneration by 10 years after implantation. The two new studies, published online February 4, 2019, ahead of print in the Journal of the American College of Cardiology, provide a glimpse of valve degeneration rates through 6 years in the randomized NOTION trial and to a median of 5.8 years (range, 5-10 years) in the UK TAVI Registry.

Josep Rodés-Cabau, MD (Quebec Heart and Lung Institute, Canada), who commented on the findings for TCTMD, characterized the results as reassuring in the context of the available data, including the strong 5-year data from PARTNER I.

“There is no signal that these valves deteriorate more frequently or more erratically than surgical valves overall,” he said. “You don’t see any differences in device hemodynamics between surgical and transcatheter valves.”

NOTION and UK TAVI Details

In the NOTION low-risk trial of patients randomized to TAVR (n = 139) with the self-expandable CoreValve (Medtronic) or SAVR (n = 135), 6-year follow up showed similar all-cause mortality in the transcatheter and surgical groups (42.5% vs 37.7%; P = 0.58), Lars Søndergaard, MD, DMSC (Rigshospital, Copenhagen, Denmark), and colleagues report.

However, moderate/severe structural valve degeneration (SVD) occurred in 24% of SAVR patients compared with only 4.8% of TAVR patients (P < 0.001). Valve failure, defined as valve-related death, aortic valve reintervention, or severe hemodynamic SVD, occurred at similar rates in the TAVR and SAVR groups (6.7% vs 7.5%; P = 0.89), as did definite endocarditis (5.9% vs 5.8%; P = 0.95) and nonstructural valve degeneration (57.8% vs 54.0%; P = 0.52). No cases of clinical thrombosis were seen in either group.

Pressure gradients ≥ 20 mm Hg through 6 months postprocedure were observed in 2.9% of TAVR patients versus 22.2% of SAVR patients, with nine in the surgery group having mean gradients that remained ≥ 20 mm Hg at 3 months compared with just one of the TAVR patients.

NOTION has a number of limitations, including the use of echocardiography instead of CT imaging to size the aortic annulus and the lack of annular enlargement techniques or an algorithm to avoid patient-prosthesis mismatch. Additionally, adjudication of the echocardiographic readings was not performed by a core laboratory.

In their new paper, the NOTION investigators conclude that SVD was “significantly greater for SAVR compared with TAVR mainly due to higher mean valve gradients present shortly after the procedure,” but Rodés-Cabau urged caution in making such a conclusion. "We know that surgical valves have higher gradients than transcatheter valves, but this does not mean that they deteriorate more rapidly or more frequently," he said.

For the UK TAVI analysis, Daniel J. Blackman, MD (Leeds Teaching Hospitals NHS Trust, United Kingdom), and colleagues looked at durability in 149 patients treated with CoreValve, 80 treated with the balloon-expandable Sapien/Sapien XT valve (Edwards Lifesciences), four treated with a Portico valve (Abbott Vascular), and eight in whom the valve type was not recorded.

Overall incidence of moderate SVD was 8.7%; more than half of those cases were due to new aortic regurgitation and 43% to restenosis. Approximately 60% of patients with moderate SVD had received a self-expandable valve, while 38% had received a balloon-expandable valve. The mean time to degeneration was 6.1 years (range, 4.9 to 8.6 years).

There were no cases of nonstructural valve deterioration in the UK TAVI cohort. Severe SVD was rare, occurring in just one patient at 5.3 years after implantation with a self-expandable valve. Importantly, among 15 patients who underwent TAVR for degeneration of a previous surgical aortic valve bioprosthesis, there were no cases of moderate or severe SVD at long-term follow-up.

Concern About Durability in Low-Risk Patients

In an editorial accompanying both studies, Patrizio Lancellotti, MD, PhD (University of Liège Hospital, Belgium), and colleagues add that the European definition of SVD—which both NOTION and UK TAVI used—overestimates the true incidence, especially among those with a higher prevalence of patient-prosthesis mismatch (PPM), who would be categorized as having SVD despite no evidence of hemodynamic deterioration.

They say the European definition thus may bias the comparison of valve degeneration incidence in favor of TAVR, adding that “the true incidence of SVD in the NOTION trial as well as in UK TAVI was likely much (~twofold) lower than reported.”

However, Lancellotti and colleagues note that even with more restrictive criteria based on hemodynamic deterioration, the rates of moderate and severe structural valve deterioration “remained significantly higher in SAVR versus TAVR, which is an interesting and encouraging testimony to TAVR durability.”

The editorialists conclude that while data from NOTION and the UK TAVI registry are very reassuring, “further long-term studies are warranted, particularly with respect to the desire to extend the indications of TAVR to young, low-risk patients.”

To TCTMD, Rodés-Cabau agreed that the next few years will be important turning points for the TAVR field as longer follow-up time is achieved, although this process will be hampered somewhat by the loss of patients, many of whom will not survive to 10 years or longer due to comorbidities and other non-valve-related issues. Newer device iterations also will make comparisons uneven.

"These [NOTION and UK TAVI] data allow us in part to move forward with the treatment of younger and lower-risk patients. But, we have to continue to follow [them],” he observed. Beyond 10 years after treatment, he added, “it will be another game,” since experience from the surgical field shows that valve deterioration increases significantly beyond this time point.

Ultimately, though, proving durability will remain a challenge, said Rodés-Cabau, since the long-term data from these studies do not include newer devices.