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TAVI is eligible for the all-risk severe symptomatic aortic stenosis patient population

Introduction

Aortic stenosis (AS) is the most common valvular heart disease in developed countries.1 It presents in 1.3% of the population aged ≥65 years,2 which rises to 4.1-5.2% in the population aged ≥75 years.3

By 2050, the prevalence of AS is expected to have doubled,2 and the impact of AS on health institutions is expected to increase due to the progressive ageing of the population.4

The only currently accepted treatment for symptomatic patients with severe AS (ssAS) is aortic valve replacement (AVR), and without treatment, prognosis is poor with a 3-year survival rate <30%.5 However, it is estimated that 33% of patients aged ≥75 years are declined for treatment, even when indicated.5 Moreover, many older patients are deemed to be of prohibitive risk for surgical aortic valve replacement (SAVR).1

Instead, patients with ssAS could be considered for transcatheter aortic valve implantation (TAVI).1

All-risk patients for TAVI

After the first successful TAVI procedure in 2002,6 >300,000 TAVI procedures have since taken place,7 and numerous prospective trials and observational studies have reported improved survival of TAVI compared with SAVR in prohibitive,8 high,9 intermediate10 and low surgical risk11 patients with ssAS.

In 2010, the first PARTNER trial enrolled patients with ssAS who were not considered candidates for surgical replacement of the aortic valve and found that, compared with standard therapy, TAVI significantly reduced the rates of death from any cause.8

This was followed by a non-inferiority trial that found similar rates of survival at 1 year in high-risk patients with ssAS who were still considered to be candidates for surgery who were assigned to undergo either SAVR or TAVI.9

By 2015, TAVI for inoperable or high-risk patients with ssAS was well established, but real-world evidence showed that 94% of patients with ssAS fall into the low- (80%) or intermediate-risk (14%) categories for whom TAVI was an option, despite a paucity of data.12 Clinical trial validation was provided by the PARTNER trial investigators in 2016, where intermediate-risk patients with ssAS were assigned to undergo either TAVI or SAVR, and no significant difference was reported in the primary end point of death or disabling stroke between TAVI and SAVR.10 This was supported by data from a propensity score analysis in intermediate-risk patients with ssAS that indicated significant superiority of TAVI compared with surgery for the composite outcome of all-cause death, all strokes and moderate to severe aortic regurgitation, suggesting that TAVI might be the preferred treatment alternative in intermediate-risk patients.13

In 2019, the PARTNER 3 trial was designed to address whether TAVI was a viable treatment alternative to SAVR in patients with ssAS of low risk. Patients were randomised to undergo either TAVI or SAVR and the primary endpoint was a composite outcome of death from any cause, stroke or rehospitalisation at 12 months. The rate of the primary endpoint was reported to be significantly lower in the TAVI group than the SAVR group.11

As TAVI moves into the low-risk patient population, an important consideration should be the increased life expectancy of this group, and therefore, the long-term valve durability needs to be understood.14 Long-term data on the function of TAVI valves post-procedure are just emerging but one study reported at a median follow-up of 5.8 years and a maximum of 10 years, long-term function is excellent with 91% of patients not experiencing any structural valve deterioration.14

Expanding population and resource planning

It has been reported that there are 115,000 eligible ssAS candidates for TAVI who are deemed inoperable or of high- and intermediate-risk across the EU. With an ever-increasing ssAS population becoming eligible for TAVI, the expansion into young, low-risk patients as well as promising long-term outcome data, the uptake of TAVI across the EU is expected to increase to as much as 177,000 with major implications for healthcare resource planning.15

The ongoing COVID-19 pandemic is undoubtedly adding to the increasing ssAS patient population who are eligible for TAVI: it has been reported that during the peak of the pandemic, ssAS patients who were previously accepted for SAVR were being reconsidered for TAVI. In a pandemic setting, TAVI has some unique organisational advantages over SAVR such as reduced resourcing needs. However, patients should be risk stratified to ensure that the risk of exposure to COVID-19 is balanced with a definitive need to treat their ssAS, allowing those with poor short-term or intermediate-term outcomes to be treated.16


References

  1. Osnabrugge RLJ, Mylotte D, Head SJ, et al. Aortic Stenosis in the Elderly: Disease Prevalence and Number of Candidates for Transcatheter Aortic Valve Replacement: A Meta-Analysis and Modeling Study. J Am Coll Cardiol. 2013;62:1002-1012.
  2. d’Arcy J, et al. Large-scale community echocardiographic screening reveals major burden of undiagnosed valvular heart disease in older people: the OxVALVE Population Cohort Study. Eur Heart J 2016;37:3515–22.  
  3. Nkomo V, et al. Burden of valvular heart disease: a population-based study. Lancet 2006;368:1005–11.  
  4. Yazdanyar A, et al. The burden of cardiovascular disease in the elderly: Morbidity, Mortality, and Costs. Clin Geriatr Med. 2009;25:563–vii. Doi:10.1016/j.cger.2009.07.007. 
  5. Spaccarotella C, et al. Pathophysiology of Aortic Stenosis and Approach to Treatment With Percutaneous Valve Implantation. Circ J 2011;75:11–9.  
  6. Cribier A, et al. Percutaneous transcatheter implantation of an aortic valve prosthesis for calcific aortic stenosis: first human case description. Circulation 2002;106:3006–3008.
  7. Cahill TJ, et al. Transcatheter aortic valve implantation: current status and future perspectives. Eur Heart J. 2018;39:2625-34
  8. Leon, MB, et al. Transcatheter Aortic-Valve Implantation for Aortic Stenosis in Patients Who Cannot Undergo Surgery. N Engl J Med 2010;363:1597–1607.
  9. Smith CR, et al. Transcatheter versus surgical aortic-valve replacement in high-risk patients. N Engl J Med 2011;364:2187–98. 
  10. Leon MB, et al. Transcatheter or surgical aortic-valve replacement in intermediate-risk patients. N Engl J Med 2016;374:1609–20.  
  11. Mack MJ, et al. Transcatheter aortic-valve replacement with a balloon-expandable valve in low-risk patientsN Engl J Med 2019;380:1695–705.  
  12. Thourani VH, et al. Contemporary real-world outcomes of surgical aortic valve replacement in 141,905 low-risk, intermediate-risk and high-risk patients. Ann Thoracic Surg 2015;99:55-61.
  13. Thourani VH, et al. Transcatheter aortic valve replacement versus surgical valve replacement in intermediate-risk patients: a propensity score analysis. Lancet 2016;2218–25 
  14. Blackman DJ, et al. Long-Term Durability of Transcatheter Aortic Valve Prostheses. J Am Coll Cardiol. 2019;73:537-45
  15. Durko AP, et al. Annual number of candidates for transcatheter aortic valve implantation per country: current estimates and future projectionsEur Heart J 2018;0:1–8. 
  16. Harky A, et al. COVID-19 and its implications on patient selection for TAVI and SAVR: are we heading into a new era. Available from: https://onlinelibrary.wiley.com/doi/10.1111/jocs.15181.

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