Discussion
Since currently established guidelines do not recommend the use of TAVI
in low-risk surgical patients AS, our study aimed to evaluate the
efficacy and effectiveness of TAVI in this patient subset by comparing
the clinical outcomes of TAVI and SAVR at 30-day, 1-year, and 2-year
follow-up time frames. This study included 3 RCTs, comprising 2633
patients, and used a meta-analysis to compare the aforementioned
outcomes. Kolte et al. reported that TAVI was associated with a lower
risk of cardiovascular and all-cause mortality at 1
year.[21]. Our 1-year follow-up had similar
results; however, their study did not report outcomes at other follow-up
time intervals. In reviewing the 2-year results of the newly released
PARTNER III trial, we found that the low-risk patients who underwent
TAVI at the 30-day and 1-year follow-up outperformed those who underwent
SAVR in cardiovascular mortality, acute kidney injury (stage 2 or 3),
NAF, and life-threatening or significant bleeding. However, TAVI
resulted in a higher risk of PPI during the same time period. Compared
with SAVR at the 2-year follow-up, there was no significant difference
in cardiovascular and all-cause mortality for patients who underwent
TAVI. Therefore, TAVI can reduce mortality and complications at the
30-day and 1-year follow-up, but at the 2-year follow-up, most of the
results demonstrated no significant difference. Most notably, the 5-year
follow-up of the PARTNER Ⅱ trial noted patients who underwent TAVI with
a higher risk of death or disabling
strokes.[22,23] Furthermore, Barili et al.
performed time-interval modelling, incorporating 3 RCTs (including the
PARTNER Ⅱ trial), and found that TAVI was associated with better
survival in the first few months after implantation and was a risk
factor for all-cause mortality after 40
months.[24] Although these trials were conducted
with patients at intermediate and high risk, the results still have
important significance to our research conclusions. It reminds us that
over time, the risk of mortality and complications after TAVI may
increase rapidly, which corresponds to our discovery in the 2-year
clinical results.
The PARTNER III trial using the SAPIEN 3 valve has achieved superior
results. According to the analysis of Deharo, the design of SAPIEN 3 is
easier to fit the Landing Zone, which reduces the risk of cardiovascular
complications after TAVI.[25,26]This may also be
the reason for the large heterogeneity of TIA and PPI in our finding.
Different valves used in various experiments affect the heterogeneity of
the analysis. Although the new generation of the valve reduces the
incidence of PPI, compared to SAVR, the incidence of PPI after TAVI is
still higher. Recent studies have shown that PPI is associated with late
all-cause mortality and increased risk of hospitalisation due to cardiac
failure[27] Therefore, reducing the incidence of
PPI after TAVI is an important issue to be considered and an interesting
area for valve improvement.
Valve degeneration is another TAVI-associated complication that should
be considered. Once it occurs, valve-in-valve implantation is
indicated[28,29], and it is a complex operative
procedure. Postoperatively, device malposition and ostial coronary
obstruction are also common TAVI-associated complications. Only the
NOTION trial reports data on valve conditions in low-risk surgical
patients with AS undergoing TAVI for more than 5
years[30]; therefore, there is insufficient data
to analyse this problem. Moreover, most of the patients undergoing TAVI
in the current RCTs are over 75 years old; therefore, their life
expectancy is much less than the expected valve use time, hindering the
valve durability study. RCTs need to be conducted among relatively
younger patients to assess long-term follow-up, providing more effective
data for future meta-analyses.
Finally, based on the optimal performance of TAVI at the 30-day and the
1-year clinical follow-up and the continuous replacement of the
operative valve, TAVI appears to be a very promising procedure in
low-risk surgical patients with AS. The eventual use of TAVI in older
patients with a shortened life expectancy is reasonable. However, we
should also note the changes at the 2-year TAVI follow-up and the
potential clinical complications of PPI and valve degeneration. In lieu
of these results, the decision to use TAVI in patients with a longer
life expectancy has yet to be recommended.
There were several limitations of this study. First, study omissions
occurred due to their absence from the search database, resulting in
eventual publication bias. Second, some inevitable differences in
baseline characteristics between studies affect the accuracy of the
results. Third, there is significant variability in the literature of
the definitions for valve type, surgical risk, and outcomes, leading to
possible discrepancies in the results.