Pivotal trials of transcatheter aortic valve implantation (TAVI) in low-risk patients have, so far, demonstrated excellent clinical results, but should be extrapolated “with caution” to younger patients. These are the comments of Charan Yerasi, Toby Rogers, Ron Waksman (all from Medstar Washington Hospital Center, Washington, DC, USA) and colleagues, writing in a state-of-the-art review published in JACC: Cardiovascular Interventions this week considering the benefits TAVI or surgical aortic valve replacement (SAVR) in young, low-risk patients with severe aortic stenosis.
In the paper, Yerasi, Rogers, Waksman et al consider the current unanswered questions around TAVI in these patients, including the durability of transcatheter valves, safety and effectiveness of TAVI in patients with bicuspid aortic valves, and future coronary access. The authors predict that balancing these questions with patients’ “clear preference” for less invasive treatment will become more common.
TAVI has “revolutionised” the treatment of patients with severe aortic stenosis, Yerasi, Rogers, Waksman et al write, and while it was initially limited to inoperable or high-risk patients, indications have been expanded to intermediate and low-risk patients through a series of clinical trials comparing TAVI and SAVR. In young (<65 years), low-risk patients with severe aortic stenosis, current guidelines recommend shared decision-making, taking into account the values and preferences of patients, the authors add.
The authors note that although TAVI has shown good short-term, one-year, and two-year outcomes low-risk patients in their 70s, several unanswered questions remain when considering TAVI in young, low-risk patients.
Current evidence on TAVI in low-risk patients include data from randomised clinical trials including PARTNER 3, NOTION, and Evolut Low Risk. Yerasi, Rogers, Waksman et al note that the mean age of patients participating in these trials was above 65 years, and patients had an overall low prevalence of comorbidities. However, consolidating all of the evidence gathered through these trials, they write that the “overwhelming message” is that TAVI has acceptable clinical outcomes compared with SAVR and can be the preferred option in low-risk patients.
Among the “unanswered questions” considered in the paper are patients with bicuspid aortic valves. The authors note that these patients tend to present at a younger age, and many undergo surgery with mechanical valves. All of the randomised trials of TAVI in low-risk patients excluded these patients—however, in the real world, many patients with bicuspid valves with intermediate and high surgical risk have undergone TAVI.
Overall, they note, TAVI in patients with bicuspid aortic valve stenosis has shown satisfactory clinical outcomes—adding that significant paravalvular leak (PVL) is rarely seen with new-generation transcatheter valves, and haemodynamic status by echocardiography is excellent. However, they add, higher stroke rates remain a genuine concern, and studies are needed to determine if cerebral embolic protection devices could mitigate this risk.
Discussing coronary access after TAVI, the authors suggest that this could be difficult due to the obstruction of displaced leaflets of the native aortic valve, for example. A recent computed tomographic simulation has predicted that coronary access may be challenging in 9–13% of patients after TAVI, they note.
“Although the prevalence of significant coronary artery disease will probably be lower in young, low-risk patients with aortic stenosis, coronary access for future intervention remains a genuine concern,” Yerasi, Rogers et al write. They add that it is important to remember that coronary access after SAVR is typically easy because of anatomically correct commissural alignment, resection of the native leaflets, and low threshold for concomitant coronary artery bypass graft (CABG) surgery in patients with severe coronary artery disease. “Commissural alignment remains an important feature that can facilitate coronary access,” they comment.
On the durability of transcatheter valves, the paper’s authors add that most of the current data come from older, high-risk patient populations. However, they add that many young patients prefer tissue, rather than mechanical valves, as they have active lifestyles and do not want to take lifelong anticoagulation. Summarising the data currently available, the authors write that there does not appear to be any signal to date for early degeneration of transcatheter valves, and that the totality of data so far suggest that TAVI valves are as durable as SAVR valves.
The 10-year follow-up of the low-risk trials (Evolut Low Risk and PARTNER 3) will provide definitive information regarding durability of both transcatheter valves and surgical bioprostheses, the authors claim, adding, however, that they do not believe that patients and physicians will wait for 10 years before offering TAVI to young patients, “so interim looks into the data will be invaluable to inform patient discussions”.
Other challenges considered in the paper include surgical explantation of transcatheter valves. The authors describe this as a “significant clinical problem”, adding that early evidence suggests that these surgical valve explantation procedures should be performed at experienced aortic centres.
The authors also consider lifetime management of severe aortic stenosis in young patients. Until now, they write, most TAVI patients have been older, and one transcatheter valve is likely to last the rest of their lives. However, if bioprosthetic valves are implanted in younger patients with surgery or TAVI, “many are predicted to require more than one aortic valve intervention”.
In conclusion, the study’s authors write that pivotal TAVI trials in low-risk patients have, so far, demonstrated excellent clinical outcomes, but advise that these results should be extrapolated to younger patients with caution.
“Strategies for the lifetime management of patients with aortic stenosis should be balanced within the heart team and tailored to individual patients. Until unanswered questions are addressed with further evidence, these issues should be discussed with patients, taking into consideration their priorities and expectations,” they state.
Commenting on the study’s message, co-author Waksman told Cardiovascular News: “The future of TAVI in the young will be depend on valve durability and the feasibility and safety of TAVI in TAVI.”