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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.

For people with severe symptomatic aortic stenosis, implanting an aortic valve by guiding it into place through the blood vessels rather than by open heart surgery improves survival at two years.

This review pooled data from four major trials of different catheter-based devices in people who were eligible for either treatment. It found the less invasive approach improved survival compared to open heart surgery at two years, when the results for all surgical risk categories were combined. The less invasive approach is already an option for people who are at high surgical risk or cannot have open heart surgery because of the risk.

The less invasive technique caused fewer initial complications, like heart irregularities or blood transfusion, but more major complications, such as the need for a pacemaker and leaking around the valve later in the trials. This study provides welcome news of the overall effectiveness of the less invasive approach, but implies there is a trade- off between outcomes that will require clinical judgment and an understanding of patient circumstances and preferences. Five-year outcomes will be further tested in an NIHR-funded HTA trial in progress.

Why was this study needed?

Narrowing, or stenosis, of the aortic valve restricts blood flow to the body and causes worsening shortness of breath and chest pain on exertion, leading to heart failure if left untreated. Replacement of the aortic valve is often performed once a person has significant symptoms.

The risk of dying from surgery for an aortic valve replacement is around 1 to 3% although this risk is much smaller than if severe aortic valve problems are left untreated.

Traditionally aortic valve replace has needed open heart surgery with the heart stopped and a heart lung bypass machine supplying blood, with oxygen, to essential organs. Transcatheter aortic valve implantation (TAVI) involves inserting a new artificial heart valve inside the old tight valve. The valve is folded up so it can be inserted, via a large artery or through a small chest incision, without stopping the heart. The artificial valve is then positioned before unfolding it.

This review aimed to include trials that directly compared the two techniques in people at any level of surgical risk.

What did this study do?

This was a meta-analysis which combined the results of four randomised trials of 3,806 participants comparing the two procedures for people with severe aortic stenosis. Half the participants received TAVI and the other half received open surgery. The average age was 82.

The trials were all multi-centre which increases the generalisability of the results. They were all from the US and Scandinavia and two early generation devices were used. These and newer devices are available in the UK.

The risk of bias in the included trials was low so the results are reliable. However, subgroup analysis of different access routes or devices was hampered by the small number of studies.

What did it find?

  • By two years there were fewer deaths from any cause in the TAVI group; 19.8% compared to 21.3% in the open surgery group (hazard ratio [HR] 0.87, 95% confidence interval [CI] 0.76 to 0.99).
  • In the subgroup analysis, compared to open surgery, fewer deaths occurred when TAVI was performed through the transfemoral route (HR 0.80, 95% CI 0.69 to 0.93) but not the transthoracic route (HR 1.17, 95% CI 0.88 to 1.56). Females were also likely to benefit from TAVI compared to open surgery (HR 0.68, 95% CI 0.50 to 0.91) but not males (HR 0.99, 95% CI 0.77 to 1.28).
  • There were lower rates of early complications around the TAVI procedure compared to open surgery. This included reduced kidney injury (4.3% vs 7.2%), new-onset atrial fibrillation (13.5% vs 28.6%) and need for blood transfusion (19.4% vs 39%).
  • TAVI was associated with higher risks of major complications including major vascular complications (8.5% vs 4.1%), incidence of permanent pacemaker implantation (15.2% versus 8.7%) and leakage around the valve (7.9% vs 1.5%).
  • There were no differences in rates of cerebrovascular events, stroke, heart attack and valve endocarditis (infection) between open surgery and TAVI.

What does current guidance say on this issue?

NICE guidance from 2012 on TAVI for aortic stenosis states that TAVI is recommended for people with aortic stenosis who are unsuitable for open surgery.

When open surgery is considered suitable they recommend that TAVI should be used under special arrangements for consent and clinical governance in high risk patients and for research purposes in non-high risk patients. It recommends inclusion of patients into the NIHR funded UK TAVI randomised controlled trial which commenced in 2013 and is due to be published in 2018.

The guidance states TAVI is a technically challenging procedure that should be performed only by experienced clinicians with specialist training in complex endovascular cardiac interventions.

What are the implications?

Compared to open surgery, TAVI is associated with a significant survival benefit for people with severe symptomatic aortic stenosis at two years irrespective of heart valve device used and risk status. It is important to note that failure of implanted valves may increase with time and longer term results will be needed before any change in clinical decisions.

There were mixed findings across safety data for TAVI versus open surgery. There were fewer immediate complications around the TAVI procedure but more major medium term complications compared to open surgery. The analysis only covered two years of follow up, so longer term data are needed, particularly on the likelihood of late failure of the different types of valve. Cost and resource implications were also not assessed in this review.

It is worth noting that improvements have been made to TAVI devices since those used in the included trials, and they have been associated with reduced complications.

Citation and Funding

Siontis GC, Praz F, Pilgrim T, et al. Transcatheter aortic valve implantation vs. surgical aortic valve replacement for treatment of severe aortic stenosis: a meta-analysis of randomized trials. Eur Heart J. 2016;37(47):3503–3512.

This project was funded by the Department of Cardiology, Bern University Hospital, Bern Switzerland.


NICE. Transcatheter aortic implantation for aortic stenosis. IPG421. London: National Institute for Health and Care Excellence; 2012.

NHS Choices. Aortic valve replacement. London: Department of Health; 2016.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre

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