Introduction
Transcatheter aortic valve replacement (TAVR) is a well-established treatment for older adults with severe aortic stenosis, and its indications are expanding to include patients with low surgical risk [
1,
2]. Technological developments of the devices, such as smaller device profiles and the evolution of the outer skirt, as well as technical refinements of the procedure have reduced the periprocedural complication rate and improved in-hospital and long-term outcomes [
3‐
5].
Among several transcatheter heart valves (THVs), the SAPIEN series of intra-annular balloon-expandable (BE) valves (Edwards Lifesciences, Irvine, CA, USA) and the EVOLUT series of supra-annular self-expandable valves (Medtronic, Minneapolis, MN, USA) have been used most widely since publication of the excellent results obtained in several randomized controlled trials. Supra-annular THVs reportedly provide better hemodynamic performance with a lower transvalvular pressure gradient, larger effective orifice area (EOA), and lower incidence of patient–prosthesis mismatch (PPM) compared with intra-annular BE THVs [
6‐
8]. Whichever type of valve is used, however, ensuring the optimal THV implantation depth is an important factor to obtain excellent hemodynamic outcomes and avoid pacemaker implantation after TAVR [
9,
10]. Deep THV implantation increases the risk of permanent pacemaker implantation (PPI) and more severe paravalvular leak (PVL). Several studies have demonstrated that a higher implantation technique using newer-generation devices is associated with high efficacy and safety and a low incidence of PPI [
11,
12]. By contrast, excessively high valve implantation may increase the difficulty of coronary access and TAV-in-TAV procedures.
A previous study investigating the implantation depth for a BE THV demonstrated that the implant position was deeper in patients with severe PPM than in those with no PPM (4.0 vs. 3.5 mm, respectively;
p = 0.028), suggesting that the implantation depth is associated with the hemodynamic performance of THVs [
13]. By contrast, a study of a newer-generation BE THV used in a higher implantation technique with a mean depth of 1.5 mm did not show beneficial effects on hemodynamic performance compared with the conventional technique with a depth of 3.5 mm [
12]. However, few reports have focused on the relationship between the implantation depth and hemodynamic performance, especially when using BE THVs. Moreover, the effects and safety of much higher THV deployment techniques are unclear.
We, therefore, investigated the feasibility and hemodynamic performance of BE-TAVR using a supra-annular position.
Discussion
The three main findings of this study are as follows. First, the iEOA and DVI after TAVR were significantly higher in the supra-annular BE-TAVR group. Second, THV diameter was significantly lager in supra-annular BE-TAVR. Third, supra-annular BE-TAVR is an independent predictor of favorable THV function (iEOA of > 0.85).
Few reports have focused on the implantation depth and valve function of TAVR, particularly in BE valves such as the SAPIEN 3. In contrast to our data, a recent report by Sammour et al. [
12] showed no hemodynamic advantage when performing high implantation of the SAPIEN 3 valve. By contrast, a retrospective analysis of the implanted device position in 969 patients with the SAPIEN 3 valve showed that no severe PPM occurred in the high implantation position, whereas the rate was 13.8% in the correct position and 21.9% in the low position (
p = 0.049) [
13]. Our depth-control implantation technique also lowers the implantation depth, showing that 85% of patients had the SAPIEN 3 valve implanted in the supra-annular position. The mean THV depth in the supra-annular implantation group was 1.1 mm, which represents much higher implantation than in a previous report (1.5–2.6 mm) [
11,
13,
19]. In our population, the distribution of THV deployment depth was as follows: 21 (11.3%) patients had the THV deployed above the annular line, 33 (17.8%) at 0.0–1.0 mm, 34 (18.9%) at 1.0–2.0 mm, 26 (14.0%) at 2.0–3.0 mm, 22 (11.9%) at 3.0–4.0 mm, and 48 (26.0%) at > 4.0 mm. Among these, the THV depth above the annular line had the best hemodynamic performance with respect to the iEOA, and the > 4-mm depth had the worst hemodynamic result. Our data indicate that the THV position is associated with hemodynamic performance, and implantation above the annular line may provide the best hemodynamic performance. It is reported that supra-annular design THV could gain more EOA than intra-annular design THV [
6‐
8]. Similar to this mechanism, we believe that greater EOA can be obtained in the SAPIEN series with an intra-annular design by having the valve function in the supra-annular position.
We found that the THV frame expansion was greater in the supra-annular group for the 23-, 26-, and 29-mm valves. In a recent experimental study of the valve-in-valve technique, Simonato et al. [
20] evaluated valve function according to the THV implantation depth. The implantation depth was positively correlated with the mean gradient and negatively correlated with the EOA. Notably, supra-annular implantation had a low mean gradient of 3.7% with better leaflet motion and a better EOA. Although valve-in-valve procedures involve different pathologies and conditions, it is reasonable to consider that a higher THV position has less impact on THV under-expansion and leaflet immobility.
In this study, most patients in the supra-annular group underwent balloon post-dilatation (BPD), which is reportedly associated with greater THV expansion and better hemodynamics [
21,
22]. On sub-analysis for BPD, 20 mm valves are used less frequently and 29 mm valve are used more frequently in patent with BPD (supplemental Table
1). There was no significant difference in baseline BSA, annulus area and oversizing ratio. However, our sub-analysis showed no association between the iEOA or DVI with or without BPD (iEOA: 1.07 with BPD vs. 1.04 without BPD,
p = 0.14; DVI: 0.51 with BPD vs. 0.50 without BPD,
p = 0.88, respectively). Beside PBD, inflation volume may also have a post-operative hemodynamic performance. Inflation volume at THV deployment was significantly lower in supra-annular group compared with intra-annular group. Additionally, the final inflation volume was significantly lower in supra-annular grope. Nevertheless, THV expansion, iEOA and DVI were significantly higher in supra-annular group. Comparison of inflation volume showed no significant differences between the underfill, nominal and overfill groups for iEOA.
By contrast, supra-annular implantation had significantly better hemodynamic performance than intra-annular implantation (DVI: 0.51 vs. 0.47, p < 0.05). Only the supra-annular position was an independent factor for favorable valve function (iEOA of > 0.85 cm2/m2 and DVI of > 0.5) in the multivariate analyses including BPD and inflation volume. These results suggest that supra-annular implantation is a more important factor for better THV hemodynamic function than is BPD.
Several studies using an iEOA of < 0.65 cm
2/m
2 to indicate severe PPM have reported an incidence of 0.7% to 1.8% after TAVR. The prognostic impact of PPM after TAVR has been variously reported and remains controversial [
17,
23,
24]. In our study, when an iEOA of < 0.65 cm
2/m
2 was defined as severe PPM and 0.65–0.85 cm
2/m
2 was defined as moderate PPM, severe PPM occurred in 2 (1.0%) patients and moderate PPM in 32 (17.5%) patients. The incidence of PPM was significantly lower in the supra-annular implantation group, with no cases of severe PPM in this group. Several factors may be associated with PPM, including age, BSA, a small annulus, and BPD [
23,
25]. Our multivariate analysis for avoiding PPM (iEOA > 0.85 cm
2/m
2) showed that supra-annular implantation was a stronger predictor than BMI and BPD. To avoid miscalculation of the EOA caused by the left ventricular outflow tract or annular diameter, we added a hemodynamic assessment based on the DVI using a > 0.5 for no PPM, and the results were similar to those of the iEOA. However, this threshold remains uncertain. A recent report of the PARTNER trial investigating normal THV function showed that the expected DVI for the SAPIEN 3 valve is > 0.43 [
26]. Our multivariate analysis for an acceptable DVI with a cut-off of 0.43 similarly showed that supra-annular implantation was the independent factor. A small annulus is a predictor of hemodynamic valve dysfunction and PPM. For such patients, a supra-annular self-expandable valve is often used to provide a larger EOA. In fact, a recent randomized controlled trial involving patients with a small annulus (< 430 mm
2) confirmed hemodynamic structural valve dysfunction in 32.8% of the BE valves but in only 3.5% of the self-expandable valves [
8]. Therefore, supra-annular implantation might be particularly useful when these patients are treated with a BE valve.
Although supra-annular implantation of the SAPIEN 3 provides a low PPI rate and better hemodynamic function, it is associated with a risk of THV embolization, PVL, and coronary occlusion. However, there was no difference between the two groups in our study with regard to valve embolization and the need for a second valve within the first THV. Despite the performance of extremely high implantation with a mean implantation depth of 1.1 mm, mild PVL occurred in only two (1.6%) patients. We believe it is possible to implant the SAPIEN 3 in a supra-annular position, leading to better hemodynamic outcomes without an increase in the risk of valve embolization or PVL. It is important to note that the risk plane was significantly higher in the supra-annular BE-TAVR group with 63% of patents having a risk plane above STJ. When performing high THV implantation, the clinician must consider the difficulty of coronary re-access or the need for a TAV-in-TAV procedure following TAVR based on the anatomical assessment by pre-procedural CT.
Study limitations
Important limitations of this study are the small sample size and the retrospective, single-center design. The THV frame diameter and depth were calculated by fluoroscopy; however, co-axiality between the annular plane and the THV plane was not always maintained. Although additional CT assessment might have been ideal, post-TAVR CT analysis could not be performed because data were lacking in the conventional implantation group. Additionally, few patients with a smaller annulus were included, possibly leading to PPM bias. PPM is more likely to occur in patients with a small annulus, and a self-expanding THV is often used for these patients. Further investigation is needed to determine the effect of the implantation depth on patients with a small annulus. In this study, a larger EOA and lower incidence of PPM were confirmed in supra-annular implantation, whereas peak velocity and mean PG showed no significant difference. Several factor, such as in-stent flow acceleration or a greater pressure recovery within the aorta, may affect the hemodynamic parameters of echocardiography. To validate the hemodynamic efficacy of supra-annular implantation, it is important to evaluate its prognostic value. In the present study, supra-annular implantation did not show a significant impact on one-year hospitalization and mortality. However, PPM may have a prognostic impact in long-term. Follow-up echocardiographic data and information on long-term clinical outcomes might be necessary to evaluate the prognostic impact of supra-annular implantation.
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