Reframing Optimal Implantation of the Sapien 3 Transcatheter Heart Valve

Abstract

Objectives. To define the optimal implantation of the Sapien 3 (Edwards Lifesciences) transcatheter heart valve (THV), this study systematically analyzed the predeployment fluoroscopic THV position and correlated this to clinical outcomes. Methods. This was an observational study of 279 patients treated with the Sapien 3 THV. Fluoroscopic imaging was used to categorize patients into low (n = 147), intermediate (n = 86), and high (n = 46) implantation zones. These zones were based on the relationship of the balloon marker and radiolucent line of the valve frame (line of lucency) to the annular plane at deployment. The primary outcome was the rate of permanent pacemaker implantation (PPI) at 30 days. The secondary outcomes were the rates of new left bundle-branch block (LBBB) in-hospital and all-cause mortality at 1 year. Results. In the high, intermediate, and low groups, 30-day PPI rates were 4.3%, 8.1%, and 8.8% (P=.62); in-hospital LBBB rates were 10.9%, 26.7%, and 32.0% (P=.02); and all-cause mortality rates at 1 year were 3.1%, 7.3%, and 12.5% (P=.14), respectively. No differences were observed with respect to procedural success/complications or THV performance between the groups. Conclusion. This study demonstrates fewer conduction abnormalities for Sapien 3 valves positioned within a higher zone defined fluoroscopically by the line of lucency and balloon marker.

J INVASIVE CARDIOL 2022;34(5):E380-E389. Epub 2022 April 8.

Key words: balloon-expandable valve, conduction abnormalities, high deployment, implantation depth, line of lucency, transcatheter aortic valve replacement

Transcatheter aortic valve implantation (TAVI) has become an integral part of clinical practice. TAVI has been shown to be noninferior to surgical aortic valve replacement (SAVR) in patients at intermediate to high surgical risk.^1-3 The PARTNER 3 study demonstrated the superiority of TAVI, using the Sapien 3 (S3) valve (Edwards Lifesciences) with respect to a composite of death, stroke, or rehospitalization at 1 year.⁴ The 2020 American College of Cardiology/American Heart Association valvular heart disease guidelines consider transfemoral TAVI preferable to SAVR if anatomically suitable for patients older than 80 years and state that it may be considered for patients aged 65 to 80 years.⁵ The movement toward transfemoral TAVI as a treatment in lower-risk patients has intensified interest in the optimization of transcatheter heart valve (THV) implantation techniques.

In the PARTNER 3 trial, TAVI was inferior to the incidence of both mild paravalvular leak and new conduction abnormalities. While the rate of permanent pacemaker implantation (PPI) at 30 days was similar (6.6% vs 4.1%; hazard ratio [HR], 1.65; 95% CI, 0.92-2.95), left bundle-branch block (LBBB) was more frequent following TAVI (22.0% vs 8.0%; HR, 1.65; 95% CI, 2.13-4.72).⁴ This finding is not unique to balloon-expandable THVs, and has been observed in low-risk self-expanding THV trials, with 30-day PPI rates as high as 17.4% with TAVI.⁶

LBBB and chronic right ventricular pacing are known markers of poor long-term survival.^7-10 LBBB produces an intraventricular dyssynchrony that can result in deterioration of left ventricular (LV) systolic and diastolic function.¹¹ A large review and meta-analysis demonstrated that new-onset LBBB post TAVI is not only associated with an increased risk of PPI at 1 year, but also an independent predictor of cardiac death.¹²

There are a variety of clinical, anatomical, and procedural factors that predict the need for PPI following TAVI.¹³ Some of these factors are nonmodifiable (preexisting conduction abnormalities, diabetes mellitus, previous coronary bypass surgery, membranous septal length [MSL], and severity of valvular/subvalvular calcification). However, some are potentially modifiable during the procedure (implantation depth, THV type, and sizing).

The conventional recommendation from Edwards Lifesciences is that the S3 THV should be deployed in a 3-sinus view. The THV is positioned relative to the aortic annulus using the 3-mm central balloon marker. It is advised that the optimal implant positions the inferior aspect of this marker at the annular plane, with a 6-mm target zone. This zone allows for the balloon marker to be positioned half a center marker length superior or inferior to the annular plane (Figure 1). This technique typically results in between a 70:30 and 80:20 ratio of the valve in the aorta:left ventricular outflow tract (LVOT).

The introduction of the S3 THV resulted in a reduction in vascular complications and paravalvular leak; however, the valve was associated with increased rates of conduction disturbances compared with the Sapien XT valve (Edwards Lifesciences). Previous studies highlighted the importance of THV implantation depth as a predictor of PPI rate.^14-19 In a 2020 study, Ramanathan et al reported a modified method for the implantation of balloon-expandable THVs to reduce PPI rate, characterized as the “line of lucency” technique.²⁰ Shortly following this publication, another study compared a conventional deployment technique with a high deployment technique, reporting a significant reduction in 30-day PPI rate (5.5% vs 13.1%; P<.001).²¹ Both of the techniques described in these studies use the visible radiolucent line on the stent of the THV, herein referred to as the line of lucency. The objective of both techniques is a reduction in implantation depth and thus less impact on the native conduction system. These studies reported no detriment regarding immediate procedural complications or valve performance.

The line of lucency and high deployment techniques recommend a strict implantation landmark rather than the conventional zone around the balloon marker. The challenge in trying to achieve such a precise target is the inevitable degree of variation that will occur. Therefore, we hypothesize that establishing a target zone would be preferable. To define the optimal predeployment THV position, we evaluated implantation depth using the traditional balloon marker and more novel line of lucency landmarks. We characterize the impact of a variety of clinical factors on short- and long-term outcomes following TAVI, with an emphasis on describing the impact of implantation depth on the rate of new conduction abnormalities, procedural success, and all-cause mortality following TAVI using the Edwards S3 and S3 Ultra THVs.

Methods

Patient selection. This was a single-center observational study. Informed consent for data collection was obtained from all patients. Our TAVI database was used to identify patients who had previously undergone implantation of an S3 or S3 Ultra THV.

Between August 2013 and November 2020, a total of 310 consecutive patients were identified. Thirty-one patients were excluded from the study; 26 had PPI at baseline (8.4% of the total population); 3 had fluoroscopic imaging that prevented identification of the required anatomical and THV landmarks; and 2 had previously undergone SAVR. Baseline demographics, procedural information, and clinical outcomes from the remaining 279 patients were collated from national electronic health care records and procedural logs. Patients with bicuspid aortic valves (3.6% of the total population) were included in the analysis.

Evaluating THV deployment depth. All fluoroscopic imaging was reviewed by an operator independent of the index procedure (JM) and blinded to clinical outcomes. Images were calibrated with the graduated pigtail catheter used for aortography. The distance from the bottom of the THV balloon marker to the top of the line of lucency on the stent frame was measured. The annular plane was then annotated immediately prior to THV deployment. Figure 2 and  Figure 3 demonstrate the relevant landmarks used to evaluate THV predeployment depth relative to the annular plane in a 3-sinus fluoroscopic view.

Patients were divided into groups based on the proportion of the balloon marker to line of lucency distance that lay above the annular plane prior to deployment, which was derived from the following formula:

Implantation depth was defined as low if the balloon marker to annular distance was less than 25% of the total distance from balloon marker to the line of lucency, intermediate if this measurement was between 25% and 50%, and high if it was greater than 50%. There were no implants that positioned the line of lucency superior to the annular plane at the point of THV deployment.

A high implant therefore positioned the line of lucency closer to the annular plane at the point of deployment and a low-intermediate implant positioned the balloon marker closer to the annular plane. Figure 4 depicts the classification of predeployment depth in relation to both balloon marker and the line of lucency. Following deployment, the final implantation depth was measured. This was then expressed as the percentage of the implanted THV stent frame that lay on the aortic aspect of the annular plane.

Protocol for computed tomography (CT) analysis. Measurements of aortic annular diameter, area, and perimeter were performed before each procedure by the operating structural interventional cardiologist. Aortic valvular and LVOT degrees of calcification were graded semiquantitatively. MSL was measured in a dedicated coronal view, and defined as the perpendicular distance from the annular plane to the beginning of the muscular septum (Figure 5).

Assessing procedural success and postimplantation THV performance. Procedural success was defined as the absence of periprocedural death, conversion to open surgery, emergency valve-in-valve (ViV) implantation, valve embolization, annular rupture, aortic dissection, coronary obstruction, or ventricular perforation. THV hemodynamic performance was assessed by baseline echocardiographic parameters of peak/mean gradient, valve area, and severity of aortic regurgitation. Grading of bioprosthetic valve function was in line with British Society of Echocardiography recommendations.²²

Study endpoints. The primary endpoint was the rate of new PPI at 30 days. Secondary endpoints included the rate of new LBBB in-hospital and all-cause mortality at 1 year. The rates of LBBB and other conduction abnormalities were assessed following a retrospective review of postprocedure electrocardiograms.

Statistical analysis. Statistical analysis was performed using IBM SPSS Statistics, version 26 (SPSS Inc). Continuous variables were expressed as mean ± standard deviation and were compared using the 1-way analysis of variance (ANOVA) test. Categorical variables were compared using the Chi-square test or Fisher’s exact test. Survival was estimated using Kaplan-Meier estimates and associated log rank test. The 30-day PPI rates based on implantation depth were assessed using Cox regression. Logistic regressions were used to estimate the effect of multiple independent variables on 30-day PPI rate.

Results

Baseline demographics. All 279 patients were followed up for a minimum of 30 days. Mean follow-up was 3.3 ± 1.9 years (range, 35 days to 7.1 years). Mean EuroSCORE II was 6.86 ± 5.85%. There were significantly more patients in the low group (n = 147) and intermediate group (n = 86) compared with the high group (n = 46), reflective of a temporal trend in implantation depth over the study period. The baseline characteristics were well balanced across the groups (Table 1). The only variable that statistically differed between the groups was EuroSCORE II, with a post hoc analysis revealing the difference arose between the low and intermediate groups (P=.01).

Successful THV implantation was achieved in 99.3% of patients, with no difference between the groups (low 99.3%, intermediate 98.8%, and high 100%; P>.99). A total of 2 patients (0.7%) required conversion to open surgery (1 due to annular disruption and 1 due to LV perforation). There were no cases of device embolization or emergency ViV implantation. Two patients (0.7%) required emergency percutaneous coronary intervention following THV implantation. Both of these cases were the result of embolization of material from the native valve during THV implantation and not due to either ostial coronary occlusion or THV migration following deployment.

There was no difference between groups in preprocedural conduction abnormalities or aortic valve hemodynamics as assessed by echocardiography. Annular measurements obtained by CT did differ between the groups, with larger annular measurements in the low vs intermediate and high groups (Table 2). As expected, given the difference in  CT annular measurements, a higher number of patients in the low vs intermediate or high groups underwent TAVI using a 29-mm valve (40.1% vs 22.1% vs 17.4%, respectively; P<.01). A post hoc analysis demonstrated no significant difference in valve size between the intermediate and high groups (Table 2). Mean MSL measured by CT did not differ between the groups (low 9.4 ± 1.5 mm vs intermediate 9.5 ± 1.7 mm vs high 9.6 ± 1.7 mm; P=.70). There was no difference between groups in the degree of aortic valve calcification, presence of LVOT calcification, or location of LVOT calcium relating to the left, right, and noncoronary cusps (Table 2).

There were 2 implants (1 low and 1 high) that resulted in a final THV position that was supra-annular. Neither of these cases resulted in device embolization or any subsequent adverse periprocedural or postprocedural complications as the THV position remained stable within the calcified native leaflets.

Postdeployment THV depth was assessed by review of the final aortogram of the deployed THV. The percentage of the frame that lay on the aortic side superior to the annulus was measured. As expected, final postdeployment THV depth decreased sequentially across the groups. The mean percentage of the THV stent frame that lay above the annular plane postimplant was 78.3 ± 9.8% in the low group, 83.7 ± 7.3% in the intermediate group, and 87.5 ± 6.3% in the high group (P<.001).

The differences in postprocedure THV hemodynamics as assessed by echocardiography are shown in Table 3. The gradients observed were significantly influenced by THV size. There was no significant difference in gradient comparing the groups separated by THV size. The degree of aortic regurgitation did not differ between the groups.

The impact of nonmodifiable ­variables on clinical outcomes

Membranous septal length. Mean MSL across all patients was 9.5 ± 1.6 mm (range, 4.8-14.3 mm). A point-biserial correlation demonstrated a significant association of MSL with 30-day PPI (r_pb(38) = -0.46; P<.001). Mean MSL in patients requiring PPI within 30 days was 7.0 ± 1.1 mm and 9.7 ± 1.4 mm in those who did not require PPI (P<.001). The difference in the rate of PPI in patients with an MSL <8 mm vs those ≥8 mm was statistically significant (48.6% vs 1.7%, respectively; P<.001).

In patients with MSL <8 mm, the 30-day PPI rate was 22.2% in the high group, 54.5% in the intermediate group, and 58.8% in the low group (P=.21). No difference was observed in the rate of new LBBB in patients with MSL <8 mm compared with those ≥8 mm (27.0% vs 26.9%; P=.98).

Preexisting conduction abnormalities. Of the 279 study patients, 11 (3.9%) had right bundle-branch block (RBBB) and 25 (9.0%) had first-degree atrioventricular (AV) block at baseline. Both of these findings conferred an increased PPI risk to all patients. The 30-day PPI rate in those with baseline RBBB was 13.6% vs 3.1% in those without (P=.04), whereas preexisting first-degree AV block conferred nearly a 5-fold increase in PPI rate (31.8% vs 7.0%; P<.01).

Morphologic valve type. When comparing bicuspid and tricuspid valves, there was no statistically significant difference observed in the rates of either in-hospital new LBBB (20.0% vs 27.1%, respectively; P>.99) or 30-day PPI (10.0% vs 7.8%, respectively; P=.57). Given the small proportion of patients (3.6%) with bicuspid valves in this study, conclusions that can be drawn from this finding are limited.

The impact of modifiable variables on outcomes

THV sizing. All THVs were sized according to the sizing chart provided by Edwards Lifesciences. THVs were deemed to be oversized if the CT measurement of the annular area was lower than the nominal area of the THV that was implanted. The percentage of oversizing was calculated using the following formula:

[1 – CT measurement of annular area/THV nominal area] x 100

A total of 202 THVs (72.4%) were oversized based on the CT measurement of annular area. The mean percentage of oversizing was 9.8 ± 5.4% in the low group, 10.8 ± 6.2% in the intermediate group, and 9.2 ± 6.0% in the high group (P=.39). Oversizing resulted in a trend toward increased 30-day PPI rate (9.4% vs 3.9%; P=.13). A point-biserial correlation, however, did not suggest a statistically significant correlation of the extent of THV oversizing with either PPI at 30 days (r_pb(38) = -0.04; P=.60) or new LBBB in-hospital (r_pb(38) = 0.05; P=.51).

Balloon aortic valvuloplasty (BAV). Pre-THV deployment BAV was performed in 122 patients (43.7%). Patients who underwent BAV were numerically more likely to develop new LBBB (31.1% vs 23.6%; P=.16) and require PPI within 30 days (9.0% vs 7.0%; P=.54). Neither of these findings met statistical significance.

THV type (S3 vs S3 Ultra). There was a significant difference in the number of patients in the high vs low cohort receiving an S3 Ultra (2.7% vs 26.2%; P<.001) rather than an S3 THV. This raises the hypothesis that the difference in clinical outcomes may be due to THV selection rather than implantation depth.  Post hoc analysis, however, revealed no significant difference in the valve type used between the intermediate and high groups, yet a difference in outcomes was observed between these groups. This is consistent with the predominant factor influencing outcomes being implantation depth and not THV type.

Multivariable analysis. The results of a multivariable model generated to predict the need for new PPI at 30 days are shown in Table 4. At univariable analysis, MSL <8 mm, presence of LVOT calcification under the left coronary cusp, and a baseline electrocardiogram with either first-degree AV block or RBBB were predictive of PPI at 30 days post TAVI. In a multivariable model including these variables, only first-degree AV block (odds ratio [OR], 4.940; 95% confidence interval [CI], 1.17-20.78; P=.03) and MSL <8 mm (OR, 49.658; 95% CI, 14.44-170.75; P<.001) were found to be independent predictors of PPI.

Primary outcome. A total of 22 patients (7.9%) underwent PPI within 30 days. All of these events occurred within 11 days of the procedure. The rate of new PPI at 30 days was 8.9% in the low group, 8.1% in the intermediate group, and 4.3% in the high group (P=.62). The hazard ratio was 0.48 (95% CI, 0.11-2.14) for the high vs low groups (Figure 6).

Secondary outcomes. A total of 75 patients (26.9%) developed new LBBB on the first 12-lead electrocardiogram post procedure. The incidence of new LBBB significantly differed between the groups, with a rate of 10.9% in the high group, 26.7% in the intermediate group, and 32.0% in the low group (P=.02). Although no statistically significant difference was observed between rates of immediate temporary pacing wire dependence, first-degree AV block, or second-degree AV block; there was a trend toward reduction in these variables in the high group (Table 5).

A total of 25 patients (9.0%) died of any cause within 1 year of TAVI. A trend toward reduction in death from any cause was observed between the groups. However, this did not meet statistical significance (low 12.5% vs intermediate 7.3% vs high 3.1%; P=.14) (Figure 7).

Discussion

Reducing the incidence of new conduction abnormalities following TAVI has become more pertinent as guidelines change and lower-risk patients are considered for treatment. Evidence from recent studies suggests that the conventional deployment technique of the S3 THV can be improved upon.^20,21 We, along with others clinicians, have observed a temporal relationship in our implantation depth using the S3 THV. This has undoubtedly been influenced by emerging evidence suggesting the safety and efficacy of reducing implantation depth.^14-19 While this potential benefit has been clearly demonstrated, the need to define a safe upper limit to implantation depth using this THV type persists.

Our study showed that an implantation technique that positions the annular plane closer to the line of lucency rather than the balloon marker on the S3 THV results in a statistically significant reduction in final implantation depth, the rate of new-onset LBBB, and a favorable trend toward reduction in 30-day PPI. A reduction in THV implantation depth did not result in detrimental valve performance (gradients or regurgitation) or immediate procedural complications (THV embolization, conversion to sternotomy, or coronary occlusion).

In this study, the main determinants of conduction disturbance post TAVI were MSL, the presence of LVOT calcification under the left coronary cusp, and baseline conduction abnormalities (RBBB or first-degree AV block). Although it must be acknowledged that implantation depth was not the strongest predictor of conduction disturbance, it was the most important modifiable predictor of PPI. High implantation techniques resulted in a 50% relative risk reduction in 30-day PPI compared with low and intermediate depth implantation techniques. MSL was the strongest independent predictor of PPI and we observed a near 3-fold reduction in PPI in patients with an MSL <8 mm using a high vs low implantation technique (58.8% vs 22.6%; P=.21). Therefore, striving to improve implantation technique remains crucial, even in patients with nonmodifiable anatomical risk factors for conduction disease.

Our findings, alongside the studies that described the line of lucency²⁰ and the high deployment²¹ techniques, have highlighted the utility of the line of lucency on the THV to impact predeployment depth and assist valve positioning. We have validated using this in combination with the conventional balloon marker to define a zone for safe predeployment position. This zone affords the prospect of an overall reduction in conduction disturbances, while enabling implantation depth to be tailored to the individual characteristics of the patient as influenced by factors such as age (hence life expectancy and the prospect of future ViV procedure), coronary height, MSL, and preexisting conduction abnormalities. Figure 8 demonstrates our proposed approach to integrate relevant patient factors when considering implantation depth using the S3 THV. We recommend that THV deployment within the low to intermediate zones should be reserved for patients who are pacing dependent prior to TAVI, or in a small subgroup with low coronary heights and/or narrow sinus of Valsalva widths in the absence of high-risk features for PPI (RBBB, first-degree AV block, MSL <8 mm, or extensive LVOT calcification).^23,24 In all other patients, a high THV implantation zone is preferable. This allows for depth to be safely varied depending on relevant clinical factors known to predict PPI.

THV implantation depth is ideally optimized in a fluoroscopic view that is both perpendicular to the virtual annular plane and removes all parallax from the valve frame. This is rarely possible in a conventional 3-sinus view, and is most often achieved in a right anterior oblique-caudal projection. This topic has been predominantly investigated with self-expanding THVs, leading to recommendations to use a 2-cusp overlap technique. This has potential merit using the S3 THV to remove valve parallax and enable easy identification of the line of lucency while remaining perpendicular to the annulus.

The benefit to conduction disturbances and long-term outcomes from techniques to reduce final deployment depths of THVs must be carefully weighed against potential adverse outcomes. High deployment techniques may have a detrimental effect on coronary reaccess and future ViV implantation if required. Although not observed in this study, theoretically a reduction in deployment depth may also increase serious procedural complications such as coronary obstruction and device embolization. It seems prudent to identify an upper limit to implantation depth. Our study supports this being defined fluoroscopically by the line of lucency.

Study limitations. This is a retrospective, observational study from a single center. The review of fluoroscopic imaging was performed by one of the authors rather than a core lab assessment. However, analysis was performed with no knowledge of patient outcomes in an effort to prevent bias. The cohorts analyzed were not equal in size, impacting the power of the study to detect the clinical outcomes evaluated. Grading implantation depth was based on fluoroscopic imaging and not CT measurements. In view of the retrospective nature of data collected, the rates of new-LBBB and AV block were assessed in-hospital and not at 30 days or 1 year post procedure. Whereas PPI as an outcome is indicative of procedural impact on native conduction, the degree of pacing dependency was not available.

Conclusion

This study demonstrates improved clinical outcomes for S3 THVs positioned within a zone targeting a reduced implantation depth that is easily identified fluoroscopically using the combination of the line of lucency on the inferior portion of the stented THV and the conventional balloon marker.

Affiliations and DIsclosures

From the Royal Victoria Hospital, Belfast, United Kingdom.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Spence and Dr Jeganathan have received consulting fees from Edwards Lifesciences. The remaining authors report no conflicts of interest regarding the content herein.

Manuscript accepted July 9, 2021.

Address for correspondence: Dr Jonathan Andrew Mailey, Royal Victoria Hospital, 274 Grosvenor Road, Belfast, BT12 6BA United Kingdom. Email: jonathan.mailey@belfasttrust.hscni.net

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