Hemodynamic Performance of Self-Expandable Transcatheter Aortic Valve Replacement Systems During Valve Deployment

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Objectives. Little is known about valve hemodynamic performance during the Evolut and ACURATE Neo deployment course.  We aimed to evaluate transvalvular mean and peak-to-peak gradients over several intraprocedural timepoints during TAVR with Evolut PRO+ (Medtronic) and ACURATE Neo (Boston Scientific) systems.

Methods. This was a single-center pilot sub-study from the SavvyWire EFficacy and SafEty in Transcatheter Aortic Valve Implantation Procedures (SAFE-TAVI) trial. Participants received either the Evolut PRO+ or ACURATE Neo for native valve severe aortic stenosis and the SavvyWire (OpSens Medical) was used for device delivery, pacing, and continuous left ventricular and aortic pressure measurements. For the Evolut, evaluation was done for baseline, two-thirds of valve deployment (still recapturable), 90% of valve deployment (no longer recapturable), and post-deployment hemodynamics. For the Neo, analysis was done at baseline, after the first step (top-crown deployment), and at final status.

Results. Nineteen patients were included (Evolut = 15; Neo = 4). There were no statistically significant changes in peak-to-peak gradients (44 mm Hg [IQR:33-69] vs 43 mm Hg [IQR:26-62], P = .41) between baseline and two-thirds of valve deployment in the Evolut patients. There was a significant decrease in mean (40 mm Hg [IQR:32-54] vs 14 mm Hg [IQR:10-18], P < .001) and peak-to-peak (43 mmHg [IQRS:26-62] vs 9 mm Hg [IQR:8-13], P < .001) transvalvular gradients between two-thirds and 90% of valve deployment for Evolut. Neo patients exhibited a decrease in transvalvular gradients after top-crown deployment (42.5 mm Hg baseline vs 13 mm Hg).

Conclusions. Transvalvular gradients did not vary between the point of “no-recapture” compared to baseline values in patients receiving the Evolut, whereas a significant reduction in transvalvular gradients was observed when the valve was deployed at 90% and fully deployed. The Neo valve was slightly obstructive after the first step of deployment.

Transcatheter aortic valve replacement (TAVR) has become a first-line therapy for treating severe symptomatic aortic stenosis, and current clinical practice guidelines recommend TAVR even for low-risk and relatively young patients up to 75 years old.¹ Moreover, the number of TAVR procedures performed worldwide has increased exponentially over the last decade,² mainly fueled by the favorable outcomes of TAVR in intermediate- and low-risk patients.^3-5 However, as TAVR implantations shift towards younger individuals with greater life expectancy, avoiding procedural-related complications that may impact long-term outcomes has gained relevance. Recently, a new valve implantation technique that aims to decrease the rates of pacemaker implantation and conduction disturbances has been proposed for the self-expandable (SE) Evolut system (Medtronic).⁶ For this approach, both implantation depth and valve positioning are closely monitored during valve deployment. The Evolut system allows for full recapture and repositioning of the device up to a certain point of unsheathing, which enables comprehensive fluoroscopic evaluation before the device is fully released. The ACURATE Neo (Boston Scientific) is a supra-annular SE device characterized by the presence of self-aligning stabilization arches and a top-down deployment in 2 separate steps. This device is no longer recapturable once the first step of deployment (upper crown with stabilization arches) has been performed.

However, little is known about valve performance along the deployment course of SE devices, as left ventricular pressure monitoring has never been possible until the valve is fully deployed. Hence, the timing for height and positioning assessment remains controversial, as it may lead to hemodynamic deterioration and instability when too prolonged. Recently, a new high-support guidewire system purposely designed for structural procedures has been developed. This system, the SavvyWire (OpSens Medical), implements a distal pressure sensor that provides continuous left ventricular monitoring. In this study, we aimed to evaluate the hemodynamic performance of 2 self-expandable systems (Evolut and ACURATE Neo) during several timepoints of valve implantation in a real-life scenario.

Patient selection. This single-center pilot study included 19 consecutive patients undergoing TAVR for native valve severe aortic stenosis with the use of SE transcatheter heart valve (THV) systems (Evolut PRO + for 15 patients, and ACURATE Neo for 4 patients) in whom the SavvyWire guidewire system was used for valve delivery, pacing, and pressure monitoring.

All participants were part of a single-arm clinical trial (SAFE-TAVI: SavvyWire EFficacy and SafEty in Transcatheter Aortic Valve Implantation Procedures), which aimed to assess the effectiveness of rapid-pacing and the safety of the SavvyWire system in the TAVR setting (NCT05492383).

Exclusion criteria for the trial included extremely horizontal aortas (aortic root angle ≥ 70°), extreme tortuosity at the level of the femoral arteries, and prohibitive surgical risk preventing conversion to open heart surgery, if necessary. Patients with previous aortic valve replacement (valve-in-valve procedures) were also excluded in our investigation.

The local Heart Team determined which patients would undergo TAVR. All patients provided written informed consent for participation in the trial and for data gathering and reporting. Data regarding previous medical history, procedural details, echocardiographic features, and clinical outcomes were recorded prospectively in a dedicated database.

Guidewire pressure monitoring system. The SavvyWire guidewire system consists of a stainless-steel guidewire with an optical pressure sensor located immediately proximal to a pre-shaped spiral tip. The guidewire has a diameter of 0.035 inches and a length of 280 cm. It is available in 2 sizes: extra-small (spiral tip of 29 mm in length and 32 mm in width) and small (spiral tip of 36 mm in length and 42 mm in width). The SavvyWire is supplied with a tip insertion tube attached to a hemostasis valve to flush, insert the guidewire, and equalize the pressure sensor. A polytetrafluoroethylene sleeve covers the whole length of the guidewire shaft except for a zone left exposed (100 cm distal from the proximal guidewire tip), which allows for connection of pacing cables. The proximal zone also allows connection of the SavvyWire to the Fiber Optical Interface Cable handle. The SavvyWire was used in combination with OpSens’ OptoMonitor system for blood pressure measurement and digital display. The accuracy of the SavvyWire has been previously validated for pressure monitoring in human TAVR procedures.^7,8

TAVR procedure. All procedures were performed under local anesthesia and conscious sedation. Transfemoral access was guided by echography and the cusp overlap fluoroscopic projection was utilized in all cases.

In the Evolut cases, rapid pacing was transiently used during early valve deployment until the system was expanded and in full contact with the aortic annulus but was yet recapturable (referred to as two-thirds of valve deployment). At this point, height and position were newly assessed by fluoroscopy. If device positioning was considered satisfactory, a gradual valve release without rapid pacing followed, and a new halt was performed when the device was no longer recapturable but the paddles were still within the capsule (referred to as 90% of valve deployment). Subsequently, slow valve release followed until the system was fully deployed.

In the ACURATE Neo cases, the usual two-step top-down deployment approach was performed. After the top-crown deployment (first step), a halt was performed and transvalvular gradients were assessed. Then, the lower-crown deployment (second step) was performed under rapid pacing to ensure optimal valve positioning.

Pressure monitoring during valve deployment. Left ventricular pressure was obtained utilizing the SavvyWire, whereas systemic aortic pressure was monitored by a 6-French pigtail catheter located at the level of the ascending aorta. Zero-pressure level and equalization between the pigtail catheter and the left ventricular guidewire were performed at the beginning of the procedure. The pigtail catheter was cleansed with fluid saline before every pressure measurement to avoid biased pressure waveforms due to contrast media.

The measures taken were the following: left ventricular systolic and end-diastolic pressure; aortic systolic, diastolic, and mean pressure; and both mean and peak-to-peak gradients between the left ventricle and the aorta.

A total of 4 timepoints were selected for hemodynamic valve performance monitoring in patients receiving the Evolut system:

• Baseline: the aortic valve was crossed and the SavvyWire positioned but no other intervention was performed (Figure 1A and B)
• Two-thirds of valve deployment (67%-VD): immediately below the threshold allowing for system recapture (Figure 1C and D).
• 90% of valve deployment (90%-VD): unsheathing above the recapture point but before any of the Evolut THV paddles were released from the capsule (Figure 1E and F).
• End-procedure: once the device was fully deployed

For ACURATE Neo patients, on top of baseline and end-procedural gradients, an analysis between the first and second steps of deployment was performed. At this point, the top-crown was opened and the system stabilized, but the lower-crown was not yet expanded (Figure 2).

Study endpoints. The primary endpoint of the study were the changes in mean and peak-to-peak gradients between the left ventricle and the aorta over the timepoints previously specified.

Clinical in-hospital outcomes (death, stroke, new permanent pacemaker, major vascular complication, and major bleeding) were defined according to Valve Academic Research Consortium-3 criteria.⁹ 

Statistical analysis. Continuous variables were presented as median (interquartile range [IQR]), and categorical variables as absolute numbers and percentages. Wilcoxon rank test was used for analyzing changes in paired continuous data over the different timepoints of valve deployment. Box plots were used for the graphical display of the study results. All analyses were performed using STATA version 14.0 software (STATA Corp).

A total of 15 Evolut and 4 ACURATE Neo patients fulfilled inclusion/exclusion criteria and were included in the study. Main baseline characteristics for both Evolut and Neo patients are shown in Table 1. Median age was 83.8 (IQR: 80.9-87.1) years, and 6 (40%) patients were female among the Evolut recipients. The median Society of Thoracic Surgeons score was 3.4 (IQR: 1.9-5.8). The main baseline echocardiographic and tomographic features are summarized in Table 1. The Evolut population exhibited a median aortic valve calcification score of 2858 Agatston Units (IQR: 2038-4139), whereas the score was 2643 (IQR: 2113-3098) for Neo receivers. The median aortic valve annular perimeter was 75 mm (IQR: 68-82) and 77 mm (IQR: 73-79.5) for Evolut and Neo patients, respectively.

For Evolut patients, the PRO+ system was used in all cases. No 23-mm valve size was implanted, whereas 5 (33.3%), 6 (40%), and 4 (26.7%) patients received the 26-mm, 29-mm, and 34-mm valve sizes, respectively. For Neo patients, there were 2 Neo M (25 mm) and 2 Neo L (27 mm) implants. Other procedural details are shown in Table 2.

Hemodynamic data along the different timepoints during valve deployment in Evolut cases are summarized in Table 3. There were no statistically significant changes either in the mean aortic gradient (41 mm Hg [IQR: 38-65] vs 40 mm Hg [32-54], P = .34) or in the peak-to-peak gradient (44 mm Hg [IQR:33-69] vs 43 mm Hg [IQR:26-62], P = .41) between baseline values and two-thirds of valve deployment.

There was a significant decrease in the mean (40 mm Hg [IQR: 32-54] vs 14 mm Hg [IQR: 10-18], P < .001) and peak-to-peak (43 mm Hg [IQR: 26-62] vs 9 mm Hg [IQR: 8-13], P < .001) transvalvular gradients between two-thirds and 90% of valve deployment. There was also a statistically significant decrease in transvalvular gradients between 90% of valve deployment and full deployment (mean gradient: 14 mm Hg [IQR: 10-18] vs 4 mm Hg [IQR: 3-6], P < .001; peak-to-peak gradient: 9 mm Hg [IQR: 8-13] vs 2 mm Hg [IQR: 1-4] final, P < .001).

Box plots for both mean and peak-to-peak transvalvular gradients across the different timepoints specified during valve deployment are displayed in Figure 1G and H.

Among the Neo subgroup, there was a significant reduction in transvalvular peak-to-peak gradients after the first step for deployment: 42.5 (42-48.5) mm Hg baseline vs 13 (10-16) mm Hg after the first step. After full deployment, residual transvalvular gradients were insignificant (mean and peak-to-peak gradients of 3 mm Hg) (Table 4).

The median length of stay was 2 days (IQR: 2-4). There were no cases of in-hospital death. Stroke, new pacemaker implantation, and major and minor vascular complications were presented in 1 patient each for the Evolut subgroup, whereas 2 cases of new pacemaker implantation were observed among Neo patients (Table 5).

The main findings of our study can be summarized as follows: (1) mean and peak-to-peak transvalvular (left ventricle to aorta) gradients did not vary significantly between the baseline value and the point of “no-recapture” (67% of valve deployment) in patients receiving the Evolut PRO + THV; (2) valve performance improved notably at 90% of valve deployment with this device, with a significant decrease in both mean and peak-to-peak gradients; and (3) among ACURATE Neo receivers, the transvalvular gradient significantly decreased already after the first step for valve deployment.

Late technological iterations and procedural aspects have led to a continuous improvement in clinical outcomes for patients receiving the SE Evolut THV system.^10,11The Evolut PRO, in comparison with the prior generation Evolut R, has incorporated an outer porcine pericardial wrap to reduce residual perivalvular leakage after TAVR.¹²In regards to procedural aspects, the use of the cusp overlap technique for device deployment has led to a decline in the rates of permanent pacemaker implantation in Evolut patients.^6,13 This is explained by a decrease in implantation depth, further translating into a lower interaction between the valve itself and the conduction system. It has also been hypothesized that these higher implants, in combination with the supra-annular design of the Evolut THV system, might also provide better hemodynamic performance that leads to lower post-implantation gradients and, possibly, greater valve durability. Some unique features of the Evolut THV are of utmost importance when attempting implantations with minimal depth, such as the possibility for recapturing and repositioning. Mainly, the relationship between the distal prosthetic nitinol frame and the hinge point of the non-coronary cusp should be closely monitored before the valve is unsheathed above the point of no-return (when the system is no longer recapturable). However, valve performance during these timepoints remained elusive. Rapid valve recapture or early complete deployment could be necessary when the patient's hemodynamic status worsens rapidly during deployment.

To our knowledge, this is the first study to report how the Evolut PRO + performs over several valve deployment timepoints in real-life TAVR cases for native valve AS. In our study, the Evolut PRO + system is still partially obstructive when deployed at its two-thirds, as it maintains a significant gradient between the left ventricle and the aorta, which is almost like baseline conditions. This fact, in addition to a probable increase in aortic regurgitation before moving on to the final steps of device deployment, might explain the poorer hemodynamic tolerance observed in some cases when the two-thirds of valve opening are transiently maintained. On the other hand, the Evolut THV system is greatly functional at its 90% deployment, with just slightly higher mean and peak-to-peak gradients compared to the full-deployment phase. This favors the adoption of slow-motion and closely controlled final device expansion, preventing unexpected tilting or changes in valve positioning when the paddles are expanded and the tension within the system is ultimately released.

The Evolut is the most widely used SE-THV, its adoption boosted by the remarkable clinical outcomes observed across the whole range of surgical-risk strata when this device was compared to surgical aortic valve replacement.^4,14 Moreover, excellent results have been demonstrated for this device in regard to valve performance, with larger effective orifice areas and reduced transvalvular gradients compared to the surgical approach¹⁵ and to balloon-expandable devices.¹⁶ These results might favor the use of this device system in clinical settings where an important risk for patient-prosthesis mismatch exists, such as in patients exhibiting small annuli or for valve-in-valve procedures. Therefore, greater knowledge about device hemodynamic performance and procedural aspects is necessary to improve clinical outcomes with this THV. In this regard, continuous left ventricular pressure assessment might facilitate the adoption of prompt decision-making during the implant. Additionally, a relatively poor correlation between invasive and echocardiographic-driven hemodynamic gradients has been demonstrated, highlighting the importance for immediate and catheter-based assessment of valve performance.¹⁷

The ACURATE Neo 2 system incorporates a new distal radiopaque marker that aims at greater device positioning, and the key procedural aspects are the top-down deployment, the low radial strength, and the wide cells´ design facilitating coronary access post-TAVR.¹⁸ Importantly, we have observed that this device system is almost non-obstructive within the aortic apparatus after the first step for valve deployment is completed. In this setting, operators do not have to speed up to complete the implantation, as patients´ hemodynamics stay better compared to baseline conditions. However, it should be noted that, on the contrary to the Evolut platform, the Neo system is no longer recapturable after the first step of its top-down deployment, and only fine adjustment of the position is enabled at that point before final release (second step). Therefore, despite allowing for smooth fine adjustment between the first and second steps of deployment given the benign valve hemodynamics, marked mispositioning during the second part of valve positioning would be difficult to overcome.

Limitations. Although the number of cases seems adequate to demonstrate the trends that exist in valve hemodynamics during implantation for the Evolut device, our sample size was small (especially for the Neo cohort), and further multicentric studies with larger cohorts will help validate our findings. We did not evaluate commissural alignment after TAVR. We performed the technique leading to the lower rate of commissural misalignment (flush port at 3 o´clock and capsule hat oriented towards the outer aortic edge),^19,20 but our rate of potential commissural misalignment was unknown as we performed no systematic computed tomography after TAVR.

Mean and peak-to-peak transvalvular gradients did not vary between the point of “no-recapture” (two-thirds of valve deployment) compared to baseline values in patients receiving the Evolut PRO + THV, whereas a significant reduction in transvalvular gradients was observed when the valve was deployed at 90%. For patients receiving ACURATE Neo 2, the system was just slightly obstructive after the first step of valve deployment.

From the ¹University Hospital of Asturias, Oviedo, Asturias, Spain; ²Instituto de Investigación Sanitaria del Principado de Asturias, Spain; ³University of Oviedo, Asturias, Spain; ⁴Quebec Heart & Lung Institute, Laval University, Quebec City, Quebec, Canada; ⁵Centro de Investigación en Red de Enfermedades Cardiovasculares (CIBERCV).

Disclosures: The authors report no financial relationships or conflicts of interest regarding the content herein.

Address for correspondence: Pablo Avanzas, MD, PhD, University Hospital of Asturias, Avenida de Roma s/n, 33011, Oviedo, Asturias, Spain. Email: avanzas@secardiologia.es; avanzaspablo@uniovi.es; avanzas@gmail.com; X: @HUCA

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