Transcatheter aortic valve implantation vs. surgical aortic valve replacement for treatment of symptomatic severe aortic stenosis: an updated meta-analysis

Selected in the European Heart Journal by E. Asher

Owing to new evidence from randomized controlled trials in low-risk patients with severe aortic stenosis, the authors compared the collective safety and efficacy of TAVI vs. SAVR across the entire spectrum of surgical risk patients...

Reviewer

Elad Asher

@AsherElad

Interventional cardiologist / Cardiologist

Jerusalem, Israel

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My Comment

Why this study – the rationale/objective?

Transcatheter aortic valve replacement implantation (TAVI) has become an alternative to surgical aortic valve replacement (SAVR) in high-risk patients, and continues to develop as an alternative procedure in intermediate- and low-risk patients with severe symptomatic aortic stenosis (AS). Furthermore, several trials demonstrated a signal for the superiority of TAVI over SAVR when performed via transfemoral approach.

Due to new evidence from randomized controlled trials (RCTs) in low-risk patients with severe AS, the aim of the current trial was to compare the collective safety and efficacy of TAVI vs. SAVR across the entire spectrum of surgical risk patients.

How was it executed – the methodology?

In this meta-analysis, all RCTs comparing TAVI vs. SAVR in patients with severe symptomatic AS and with outcomes reported over a period of at least 1 year or longer of follow-up were considered.

Exclusion criteria: 1) non-arterial (transthoracic) access for TAVI, 2) head-to-head trials of different transcatheter heart valve systems, 3) trials that compared TAVI with medical therapy, and 4) observational studies.

Data extraction: The authors extracted trial, patient, intervention, and outcome characteristics following predefined criteria.

Primary outcome: All-cause mortality up to 2 years for the main analysis (and for the longest available follow-up period in each individual trial).
Secondary outcomes: stroke and disabling stroke, cardiovascular death, myocardial infarction (MI), acute kidney injury (AKI), new onset atrial fibrillation (NOAF), major bleeding (as defined by individual studies), major vascular complications, valve endocarditis, and permanent
pacemaker implantation, up to 2-year follow-up.
Stratified meta-analyses were also performed for the primary outcome according to surgical risk (high, intermediate, or low), access route (transfemoral or transthoracic), and transcatheter heart valve (THV) system (balloon or self-expandable).

What is the main result?

In total, 14 articles reporting on 7 trials (PARTNER 1A, US CoreValve High Risk, NOTION, PARTNER 2A, SURTAVI, PARTNER 3, and Evolut Low Risk) were deemed eligible and included in the meta-analysis.

• Across the 7 trials, 8020 participants were enrolled (4014 TAVI patients and 4006 SAVR patients).
• Two trials recruited patients at high surgical risk, two at intermediate, and three at low surgical risk.
• Men were predominantly enrolled (TAVI: 59%, 2361/4014 patients; SAVR: 61%, 2404/4006 patients). The combined mean STS score for the TAVI arm across the trials was 9.4% for high-risk trials, 5.1% for intermediate-risk, and 2.0% for low-risk trials.

Primary outcome:

• Transcatheter aortic valve implantation was associated with reduced mortality compared to SAVR [HR 0.88 (95% CI 0.78–0.99), P= 0.030]. 
• Survival benefit was particularly evident in patients undergoing transfemoral TAVI, with a 17% relative reduction in the risk of all-cause mortality [HR 0.83 (95% CI 0.72–0.94)]; whereas there was no advantage of transthoracic TAVI over SAVR [HR 1.17 (95% CI 0.88–1.55)]. p-for-interaction= 0.032 for both.
• There was no difference between the two THV systems used in the trials (P-for-interaction=0.674). Moreover, there was also no difference between TAVI and SAVR when considering the longest available follow-up period for each trial [HR 0.96 (95% CI 0.87–1.06)], P= 0.402.

Secondary outcomes:

• TAVI was associated with a significant reduction in stroke [HR 0.81 (95% CI 0.68–0.98), P=0.028], but not disabling stroke [HR 0.78 (95% CI 0.53–1.14), P = 0.192].
• TAVI was associated with reduced risk of AKI, atrial fibrillation, or major bleeding (all P<0.01) but not cardiovascular death, MI, or valve endocarditis. 
• Conversely, SAVR was associated with reduced risk of major vascular complications [HR 1.99 (95% CI 1.34–2.93), P= 0.001] and need for permanent pacemaker implantation [HR 2.27 (95% CI 1.47–3.64), P<0.001], and there was a higher risk of permanent pacemaker requirement after self-expandable valve implantation compared with other THV systems (P-for-interaction <0.001).

Critical reading and the relevance for clinical practice

This meta-analysis highlights several findings:

1. All-cause mortality was lower after TAVI (12% relative risk reduction up to 2 years compared with SAVR).
2. Mortality was even lower when TAVI was performed via the transfemoral route (17% RRR up to 2 years compared with SAVR).
3. The mortality benefits of TAVI were consistent across the entire spectrum of baseline surgical risk and irrespective of THV systems.
4. Risk of stroke was lower after TAVI (19% RRR up to 2 years compared with SAVR).
5. TAVI was linked to a higher risk of permanent pacemaker implantation and major vascular complications, but a reduced risk of major bleeding, new onset AF, and AKI.

The individual studies in the meta-analysis were not powered to compare mortality in patients randomized to TAVI or SAVR, and only the US CoreValve High-Risk trial has previously demonstrated a survival benefit of TAVI. Hence, the present analysis is the first to demonstrate a statistically significant in survival associated with TAVI over 2-year follow-up across the entire spectrum of surgical risk, especially via the transfemoral route.

Another very interesting key finding was a significant reduction in the risk of stroke in patients undergoing TAVI compared with SAVR. The authors suggest that this finding will probably have critical implications for decision-making in lower-risk, younger patients who may be suitable for either TAVI or SAVR.

Should the guidelines be changed and, in contrast to the past, recommend TAVI as the first-line treatment for all surgical risk (high, intermediate, or low) patients with severe symptomatic AS?

The authors suggest that the mortality benefits of TAVI across all risk categories indicates that there is no longer a requirement for surgical risk stratification among patients considered to undergo TAVI. Instead, TAVI should be considered as the first line interventional strategy for isolated AS in patients aged greater than 65 years. Moreover, to their approach, SAVR should be reserved for patients with complex anatomy precluding a good outcome from TAVI, concomitant conditions warranting surgery (e.g. aortic root aneurysm or complex coronary artery disease) or active infective endocarditis.

Nevertheless, this meta-analysis had several limitations: 1) the definitions of low, intermediate, and high risk based on STS score used in the included trials were poorly predictive and overestimate procedural risk; 2) there has been important improvement in valve design and technical aspects of both TAVI and SAVR procedures over the time period of study; 3) the duration of follow-up was limited up to 2 years.

So is this the final meta-analysis comparing TAVI and SAVR? Would it change your state of mind/practice so that TAVI would be considered as the first line interventional strategy for isolated AS in patients aged greater than 65 years?