Sclerotic aortic valve disease affects approximately 29% of the United States adult population who are older than 65 years and 37% of patients older than 75 years,1 while the prevalence of moderate aortic stenosis patients who are 70 to 80 years of age is estimated to be 2%.2 Surgical aortic valve replacement (SAVR) was developed almost half a century ago.3 Techniques and valves have been refined, but such procedures can carry up to a 10% risk of death in patients older than 80 years perioperatively.4 Mortality rates can be threefold higher than in younger patients in such a population.5 In patients older than 90 years, mortality rates can be as high as 20% at 1 year.5 However, outcomes in the average population of those 65 years of age or older who undergo surgical aortic valve replacement are relatively robust, with operative mortality rates in the 4% range, as reported from the Society of Thoracic Surgeons Adult Cardiac Surgery Database.6 The development and subsequent approval of transcatheter aortic valve replacement (TAVR) has been a major advancement in the treatment of severe aortic stenosis. The first-in-human implantation took place in 2002.7 Conservative estimates indicate that since 2007, more than 750 centers have treated nearly 100,000 aortic stenosis patients using TAVR technologies.8

Since the Sapien device (Edwards Lifesciences) was approved by the US Food and Drug Administration in 2012,9 TAVR devices have undergone numerous design changes. The initial study10 evaluating the CoreValve system (Medtronic) principally involved patients with severe aortic stenosis who were deemed to be at extreme risk for SAVR with New York Heart Association class II or greater symptoms and suitable aortic annular diameters (18–29 mm). TAVR was performed in 486 patients at 41 clinical sites. The primary endpoint of all-cause mortality or major stroke at 12 months was lower with CoreValve (26% vs 43%; P < .0001) compared to a prespecified objective performance goal based on previous and contemporary studies at that time. A cohort of patients deemed to be at high risk for SAVR were randomized to SAVR or CoreValve. At 1 year, mortality was lower with TAVR (14.2% vs 19.1%; P = .04). These data from the pivotal trials supported the US Food and Drug Administration’s decision to approve the device without an advisory panel.11

The newest iteration of the self-expanding CoreValve is the Evolut R system. The CoreValve Evolut R CE Mark clinical study12 evaluated safety and clinical performance of the CoreValve Evolut R system. The study evaluated 60 patients with a 26- or 29-mm Evolut valve in a single-arm, multicenter study of high- or extreme-risk patients with a mean Society of Thoracic Surgeons (STS) score of 7% ± 3.7% with symptomatic aortic stenosis. The results showed that overall Valve Academic Research Consortium-2 device success rate was 78.6%, and paravalvular regurgitation after TAVR was mild or less in 96.6%, moderate in 3.4%, and severe in 0% at 30 days. Major vascular complications were seen in 8.3%, and permanent pacemaker implantation was required in 11.7% of patients. The 1-year follow-up of this study13 was presented at the Transcatheter Cardiovascular Therapeutics (TCT) annual meeting in October 2015 and reported a survival rate of 93.3% and a stroke rate of 3.4%. Paravalvular regurgitation after TAVR was mild or less in 95.7%, moderate in 4.3%, and severe in 0%, and the permanent pacemaker implantation rate was 15.2%. The Evolut R device was approved in mid-2015 for use in patients with severe native calcific aortic stenosis or failure of a surgical bioprosthetic aortic valve who are judged by a heart team, including a cardiac surgeon, to be at high or greater risk for open surgical therapy (ie, STS predicted risk of operative mortality score ≥ 8% or a ≥ 15% risk of mortality at 30 days).

EVOLUT R DESIGN FEATURES

The valve comes in 23-, 26-, and 29-mm sizes to treat annular diameters of 18 to 26 mm. The more ergonomic EnVeo delivery system replaced the less responsive AccuTrak delivery system used for the initial CoreValve, and the device profile was reduced substantially from 18 F (22-F outer diameter) to 14 F (18-F outer diameter). The reduced profile was, in part, accomplished through utilization of an inline sheath (Figure 1).

With the capsule covering the valve flares during deployment, coupled with the flexible shaft, the device is able to self-center within the aortic annulus better than its predecessor. After initial deployment and before the valve is released from the delivery mechanism, the device can be completely recaptured and repositioned if the operator is not satisfied with the position of the valve (Figure 2). Ease of positioning, extension of the sealing skirt, and enhanced conformability below the annulus improved fit and reduced incidence of moderate-to-severe paravalvular leak to 3.4% at 30 days in the CE Mark study. The retention hooks were also redesigned to allow easier and more reproducible release of the valve from the delivery catheter.

TECHNIQUE

A standard preprocedure workup is performed and, if transfemoral access is selected, standard femoral arterial access procedures are performed. When using the CoreValve’s InLine sheath, predilation may be performed by a 14-F sheath or an 18-F dilator before inserting the loading catheter. Next, the InLine sheath is maintained flush against the capsule while it is inserted into the vessel. It is important to position the handle so that it conforms to the patient’s anatomy as it is advanced. Aortic valvuloplasty may be performed, particularly if the valves are heavily calcified.

Fluoroscopic examination of the prosthesis loading system should always be performed. Because the CoreValve EnVeo R delivery system does not allow direct visual inspection of the loaded valve, fluoroscopic examination is necessary. Fluoroscopy can be performed in an anteroposterior view holding the loading system parallel to the patient or table and rotating in a circumferential manner. The paddle positions are carefully checked to ensure that they are properly seated at the same height within the pockets and equidistant from paddle attachment. The outflow crowns should be straight and parallel to the distal end of the paddle attachment. The capsule should be straight and free of any bends or curves, with node bands appearing straight and uniform (Figures 3 and 4).

While advancing the valve delivery system, the radiopaque marker band line is positioned below this plane at an implant depth of 3 to 5 mm for the Evolut R valve versus 4 to 6 mm for CoreValve. Due to valve frame length differences, the implant depth should be calculated from the inflow edge if this edge is not at the same level as the marker band (Figure 5).

The first one-third of the valve is slowly deployed, allowing for release of any stored tension in the system. Ventricular pacing at 90 to 130 bpm may be considered. Because the valve occludes the cardiac output between one-third and two-thirds deployment positions, deployment of this portion of the valve proceeds quickly. At approximately two-thirds deployment, the operator will feel a tactile cue. This so-called rumble strip alerts the operator that deployment is nearing the point of no recapture. The valve is deployed a few more millimeters to seven-eighths of the valve height, and positioning is assessed.

If the valve requires repositioning, it can be fully or partially recaptured three times (third time for removal from the body only) at any point until the paddles lose contact with the delivery system. Typically, a recapture can be done safely at one-third deployment or just prior to the point of no capture. During final release, to prevent valve movement, it is important to retract the guidewire, and detachment of the paddles is confirmed on fluoroscopy. The delivery system also has a safety feature: a component connects the tip retrieval system with the delivery system handle and is held in place with two plastic tabs and slots. Any maneuver causing excessive deployment forces may cause a separation of the two components. Although a valve can still be retrieved if this were to occur, deployment should not be attempted. The nose cone is reapposed to the capsule and withdrawn to the InLine sheath. The sheath and delivery system are removed while maintaining the wire in the body. A 14-F sheath is reinserted, and final hemodynamic measurements are made. Adjunctive balloon valvuloplasty is performed if necessary.

IMPACT ON PRACTICE

The Evolut R valve, like other contemporary TAVR valves, is approved for high- and extreme-risk patients with severe aortic stenosis involving native and failed surgical bioprosthetic aortic valves. The ability to reposition the valve represents an improvement in accurate deployment, and the lower profile expands the number of patients who can be treated transfemorally. Coupled with ease of use, these changes represent significant improvements for the operator, as well as several advantages in streamlining the procedural and postprocedural care of the patient.

FUTURE PERSPECTIVES

The design improvements implanted in the CoreValve Evolut R device represent significant technological advances in TAVR. Many challenges remain as this technology evolves, including the need to further reduce the delivery profile to accommodate patients with poor iliofemoral vessels and to reduce the incidence of vascular complications. There is still a need to reduce periprocedural stroke rates, the incidence of paravalvular leak, and the need for permanent pacemakers. Presently, an Evolut R system does not exist for annulae that require a valve larger than 29 mm; however, a 34-mm Evolut R valve is in development to address this issue. As this exciting technology moves into intermediate- and low-risk populations, issues such as durability, coronary access, and leaflet thrombosis will require further investigation. 

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7. Cribier A, Eltchaninoff H, Bash A, et al. Percutaneous transcatheter implantation of an aortic valve prosthesis for calcific aortic stenosis: first human case description. Circulation. 2002;106:3006-3008.

8. Leon MB, Gada H, Fontana GP. Challenges and future opportunities for transcatheter aortic valve therapy. Prog Cardiovasc Dis. 2014;56:635-645.

9. Dvir D, Barbash IM, Ben-Dor I, et al. The development of transcatheter aortic valve replacement in the USA. Arch Cardiovasc Dis. 2012;105:160-164.

10. Popma JJ, Adams DH, Reardon MJ, et al. Transcatheter aortic valve replacement using a self-expanding bioprosthesis in patients with severe aortic stenosis at extreme risk for surgery. J Am Coll Cardiol. 2014;63:1972-1981.

11. US Food and Drug Administration. Medtronic CoreValve System—P130021/S010/. http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/DeviceApprovalsandClearances/Recently-ApprovedDevices/ucm441181.htm. Accessed December 31, 2015.

12. Manoharan G, Walton AS, Brecker SJ, et al. Treatment of symptomatic severe aortic stenosis with a novel resheathable supra-annular self-expanding transcatheter aortic valve system. JACC Cardiovasc Interv. 2015;8:1359-1367.

13. Medtronic. CoreValve Evolut R CE study 1-year results. http://www.corevalve.com/wcm/groups/mdtcom_sg/@mdt/@cardio/documents/documents/evolut-r-1-year-databook-us.pdf. Accessed January 4, 2015.

Abdul Moiz Hafiz, MD
Clinical and Research Fellow
Division of Interventional Cardiology
Beth Israel Deaconess Medical Center
Boston, Massachusetts
Disclosures: None.

Duane Pinto, MD, MPH
Associate Professor of Medicine
Harvard Medical School
Associate Director, Interventional Cardiology Section
Director, Cardiac Intensive Care Unit
Beth Israel Deaconess Medical Center
Boston, Massachusetts
(617) 632-9210; dpinto@bidmc.harvard.edu
Disclosures: Proctor for Medtronic.