Exploring the borders of TAVI

Lars Søndergaard

The NOTION 2 trial, which recently enrolled a 64-year-old female with Society of Thoracic Surgeon (STS) score 1.2% as its first patient (using a Symetis Acurate Neo bioprosthesis), is comparing the use of transcatheter aortic valve implantation (TAVI) with the use of surgical aortic valve replacement in patients aged ≤75 years at low surgical risk (score STS score <4%). Co-principal investigator Lars Søndergaard (The Heart Centre, Rigshospitalet, Copenhagen, Denmark) talks to Cardiovascular News about the trial. 

What data are available for the use of TAVI in low-risk patients?

The NOTION-1 trial, which we conducted, showed that TAVI was associated with a similar rate of outcomes—all-cause mortality, stroke and myocardial infarction—to surgery in patients with a mean STS score of 3±1.7% at both one and two years.

NOTION 2 is enrolling younger patients (≤75 years) than those seen in previous TAVI studies. Why is this important?

So far, six randomised controlled trials on TAVI (two against best medical therapy in inoperable patients and four against surgery in operable patients) have been conducted. Although the surgical risk score in these studies ranged from “very high” (STS score >11%) to low (STS score 3%), the average age of the patients was around 80 years in all studies. This means that despite TAVI now being considered for use low-risk patients, it has not been evaluated in younger patients (age 60-75 years). Also, most sites today will already today treat all 80-year-old aortic stenosis patients with TAVI even if they have a low STS score; therefore, new low-risk trials may not change clinical practice unless they include younger patients.

Are you concerned about the durability data presented at EuroPCR, which indicated that valve degeneration occurs in 50% of TAVI patients by eight years?

The data for the very first TAVI patients treated were interesting and raise awareness of potential degeneration of bioprosthetic aortic valves. However, in the study, only few patients were alive after six years and the definition of degeneration was based on echocardiographic findings rather than the need for re-intervention (as used as the definition of degeneration for surgical bioprostheses).

Furthermore, the only studies with intermediate follow-up on both transcatheter and surgical bioprostheses (PARTNER 1A—five years’ data; CoreValve High Risk—three years’ data) showed no difference between the two techniques regarding durability. However, since these trials included older patients (mean age >80 years), they are unlikely to provide long-term data for durability. Therefore, trials on younger patients are again important.

NOTION 2 allows the use of any commercially available device. Why is this important?

A number of TAVI devices are available today. Most devices can be used in approximately 80% of the patients with excellent outcomes. However, for the remaining 20% of patients, a specific device may optimise the procedural outcome. So a trial that is not restricted to one specific device may be a better reflection of real-life practice. Similarly, all completed and ongoing trials on TAVI vs. surgery allow the surgeon to use any surgical bioprostheses.

The study is also exploring the use of TAVI in patients with bicuspid aortic valves. What do we already know about TAVI in this patient population?

Bicuspid aortic valves are more common finding in younger patients than in elderly patients. Attempts to extend TAVI into younger patients should, therefore, include patients with bicuspid valves.

In the early TAVI experience, bicuspid valves were associated with a lower procedural success rate. However, with newer generations of TAVI prostheses, as well as better understanding of procedural planning and implantation techniques, these patients can be treated with excellent outcomes.