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.