Transcatheter Aortic Valve Implantation in Patients With Longer Life Expectancy

What Measures Are Needed?

Lars Sondergaard

Disclosures

Eur Heart J. 2019;40(17):1331-1333. 

During the last decade, transcatheter aortic valve implantation (TAVI) has provided an evidence-based paradigm shift in the treatment of patients with symptomatic severe aortic stenosis (AS) and increased surgical risk. Thus, randomized clinical trials across surgical risk scores have shown that TAVI is at least non-inferior to surgical aortic valve replacement (SAVR) with regards to safety and efficacy profiles.[1–6] An additional two trials comparing TAVI and SAVR in patients at low surgical risk are expected to be presented during 2019 (NCT02675114 and NCT02701283).

In this context, the large study from the German registry GARY presented by Bekeredjian and co-authors in this issue of the European Heart Journal adds to the weight of evidence on TAVI vs. SAVR in patients at low surgical risk.[7] In a propensity score model including traditional risk factors, TAVI was associated with a higher survival rate at 30 days (98.1% vs. 97.1%; P = 0.014) and a similar rate at 1 year (90.0% vs. 91.2%; P = 0.158) as compared with SAVR.

What do these measures actually mean and how relevant are they for the future for TAVI? A simplified interpretation is that the 30-day mortality reflects the safety of the procedure, whereas the 1-year mortality is related mainly to the characteristics of the treated patient cohort. For TAVI, the combination of increasing implanter experience and device iterations have led to a high procedural safety profile even in old patients with a high co-morbidity burden. The age, frailty, and co-morbidity characteristics of the patients, on the other hand, are the main drivers of mortality after the peri-procedural period. The data from the GARY confirm these aspects—TAVI is safe, but 1-year mortality is 10% in patients with a mean age of ~80 years.

Will these data impact clinical practice? Probably not! The 2017 ESC/EACTS Guidelines for the management of valvular heart disease recommend TAVI in patients 75 years of age or older, particularly if it can be performed by a transfemoral approach.[8] So, what is needed for potential further expansion of TAVI in patients with severe AS? The answer is randomized clinical trials comparing TAVI and SAVR in patients with longer life expectancy!

Patients at low surgical risk, but high age do not necessarily have long life expectancy, as demonstrated by the results from the GARY and the NOTION trial,[6,7] and the long-term issues related to TAVI may therefore not be relevant for these patients. However, the surgical community has, during the last decades, used bioprosthetic aortic valves in younger and younger patients.[9] One reason for not using mechanical valves is patient preference of omitting anticoagulation therapy. Therefore, exploring whether TAVI is a valid alternative to SAVR in this patient cohort is of utmost interest for the community. Also, the term 'patients with longer life expectancy' is more relevant than just 'low-risk patients'. Importantly, the use of TAVI in patients with longer life expectancy raises new questions, which are not answered by the 30-day and 1-year mortality rates.

Paravalvular leakage (PVL) and need for a new permanent pacemaker have been the Achilles heels for TAVI. The adaptation of computed tomography in order to determine the aortic annulus dimensions and the correct size of the transcatheter heart valve (THV) more accurately, as well as next-generation THVs, have substantially reduced the rate of moderate and severe PVL. However, a significant proportion of patients treated with TAVI still have mild PVL, and the long-term impact of this on left ventricular function, symptoms, and mortality is unknown. Similarly, the higher rate of conduction abnormalities and need for a permanent pacemaker after TAVI as compared with SAVR may also impact the outcomes for the patients. Although a pacemaker may even be beneficial for patients in the immediate post-procedural period after TAVI due to the risk of late atrioventricular block and sudden cardiac death, the long-term impact of ventricular pacing may be harmful for the patient.

Another important aspect is the durability of bioprosthetic aortic valves. Currently, with mainly elderly patients treated with TAVI, the longevity of a THV probably exceeds the life expectancy of patients (Figure 1, top). However, patients with longer life expectancy may survive one or even more bioprosthetic aortic valves. As an example, assume that a 60-year-old patient with a remaining 25-year life expectancy undergoes TAVI. If the durability of the THV is 10 years, then the patient will need a new bioprosthetic valve at 70 and 80 years of age (Figure 1, bottom). Although TAVI-in-TAVI is feasible, it will reduce the effective orifice area of the valve with risk of patient–prosthesis mismatch, and—importantly—make it difficult or even impossible to access the coronary arteries, particularly for THVs with a supra-annular position of the leaflets.[10] This may become a major issue if the patient—who at 70 years of age had a TAVI-in-TAVI and still had a life expectancy of 15 years—later on is admitted with acute coronary syndrome.

Figure 1.

In a patient who undergoes TAVI at 80 years of age, the longevity of the THV is likely to exceed the remaining life expectancy of the patient (top). However, a patient who is 60 years at the time of TAVI may need one or more TAVI-in-TAVI during their remaining lifetime (bottom). THV, transcatheter heart valve; TAVI, transcatheter aortic valve implantation.

These issues highlight the major differences in expanding TAVI to elderly patients with low surgical risk and to patients with longer life expectancy. Although the next logical step is to explore TAVI in younger patients, who today undergo SAVR with a bioprosthetic aortic valve, new measures are needed in order to support this change in treatment strategy. Thus, the traditionally used safety endpoints of mortality and stroke are not applicable, but should be replaced by new measures including the long-term impact of PVL, permanent pacemaker, durability issues, etc. On the other hand, SAVR also has limitations such as a higher rate of new-onset atrial fibrillation, acute kidney injury, and patient–prosthesis mismatch, which all impact the patient outcome. Randomized clinical trials between TAVI and SAVR including these complex measures are necessary in order to evaluate the best long-term solution for patients with severe AS and longer life expectancy.

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