CRT 2012: Second-generation TAVR valves target paravalvular leakage, repositioning, and procedural control improvements

on February 17, 2012  |  Permalink

Topics: Clinical Technology, Service Lines, Cardiovascular

Haley David

The Cardiovascular Research Technologies (CRT) conference concluded last week in Washington, D.C. On the heels of President Clinton’s keynote address advocating for an Innovation Commission to facilitate U.S. medical device advancement, CRT’s Cardiovascular Innovations session offered a glimpse into pipeline technologies. The session emphasized transcatheter aortic valve innovations, presenting five second-generation devices that strive to address some of the key concerns of first-generation devices, namely paravalvular insufficiency, valve positioning, and ease of use. The devices presented included the Direct Flow Medical Valve, Sadra’s Lotus Device, Medtronic’s Engager Valve, the JenaValve, and the Valve Xchange Solution.

CRT 2012: Pipeline Transcatheter Aortic Valves

Direct Flow Medical’s valve advanced positioning improve placement; inflation media provides extra valve support

The Direct Flow Medical (DFM) percutaneous aortic valve is a non-metallic, bovine pericardial leaflet valve, mounted on a balloon frame covered with polyester fabric. The inflatable polyester fabric cuff conforms to the native aortic valve annulus to form a seal, which minimizes paravalvular leakage.

The device has independently inflatable ventricular and aortic rings, which encircle the annulus to provide stable anchoring. Single inflation opens both rings using a saline, contrast solution that renders the valve functional and permits fluoroscopic visualization. The valve, sized at 25 and 27 Fr (with a 29 Fr device in development), is attached to three wires used to position the valve precisely as each wire moves independently.

Before final deployment, a solidifying inflation media hardens to form the permanent support structure. The valve has the ability to be repositioned and completely retrieved if necessary. Early experience in 31 patients—22 implanted—demonstrates a 69% two-year survival rate with 73% of patients presenting no aortic insufficiency.

Adaptive seal conforms to irregular valve anatomy, reducing the Lotus device’s paravalvular leak risk

Sadra’s Lotus valve is a bovine tissue tri-leaflet bioprosthetic aortic valve supported by a self-expanding nitinol frame and the Lotus Delivery Catheter. The valve is pre-attached to the delivery system, providing easy device preparation. The valve is intended for placement over the native aortic valve using a retrograde approach.

In addition to its repositionable and self-centering features, which facilitate optimal positioning, the device's unique ability to be resheathed and completely retrieved provides greater procedural control. The Lotus Valve does not require balloon inflation or rapid pacing of heart. The Lotus Valve features Sadra’s Adaptive Seal, which is designed to conform to irregular, anatomical surfaces minimizing paravalvular leakage. The valve functions early in deployment with complete assessment performed while the valve is fully locked.

Early experience in 10 patients—6 implanted—shows procedure time at less than 20 minutes with minimal paravalvular leak. The REPRISE I feasibility study and REPRISE II clinical trial are also underway.

Engager valve’s minimized pericardial thickness decreases surgical cut down, crimping forces

Medtronic’s Engager transapical valve, comprised of bovine, pericardial tissue leaflets, uses a self-expanding nitinol frame with self-positioning technology to facilitate accuracy and stability. The procedure, which begins with a minimized surgical cut down, involves placing the valve arms over the native aortic leaflets, providing true commissure to commissure alignment.

The valve, which is equal in pericardial thickness to a surgical valve, is partially repositionable and retrievable. The major advantages of the valve include fixation of the native leaflets with accurate alignment, supra annular valve positioning, less crimping forces due to pericardial thickness, less turbulent and guided bloodflow, and greater ease of use offering self-orientation with good tactile feedback. The Engager System was evaluated successfully in Europe in a feasibility trial in 2011.

JenaValve’s aortic clip structure provides active fixation, resistance to migration

The JenaValve is a porcine root valve fitted with an outer pericardial skirt sewn onto a nitinol self-expanding frame. Using an aortic clip concept, the frame has three feelers, enabling accurate, anatomical positioning with commissure to commissure alignment onto the native valve.

The JenaValve, available in three sizes, 23mm, 25mm and 27mm, is intended for transapical implantation using the Cathlete delivery system. Rapid pacing is not required during valve positioning and release, and hemodynamic flow is maintained during placement. With shealthless delivery the JenaValve system is fully repositionable and partially retrievable. After the feelers have been placed in the correct position in the native valve, the lower part of the device is released and the patient’s native valve leaflets are clipped between the feelers and the device base, providing active fixation and resistance to migration.

Early experience in 67 patients shows 7.6% mortality and 3% stroke rates at 30 days. The transfemoral system is in development with completion expected later this year.

Valve Xchange Solution uses two-part valve platform, increased visibility with demonstrated durability

The Valve Xchange procedure is performed using a range of approaches, from open surgical to off-pump transapical procedures. The system uses an exchangeable bovine, pericardial leaflet set, and a valve docking station, either for surgical or transapical placement. The system has three tools that work in concert with each other: the valve stabilizer, valve removal tool, and valve insertion tool. All three tools nest within each other coaxially so once one tool is aligned, all others are aligned.

The Vanguard transapically-implanted docking station, which consists of a solid, collapsible metal ring, provides flexible stent posts to cushion closing leaflets, central gap for leaflet extension, and geometrical precision of 120-degree symmetry. The procedure includes a two-part valve platform in which the valve base is implanted separately from the leaflets. The leaflets remain safely in a surgical bath, and do not obscure visibility below the valve cuff during the valve base implantation. Shields retract the aortonomy and ready base for final valve assembly. Researchers demonstrated significant valve durability, minimizing the need for reinterventions and offering a potential lifetime tissue valve for TAVR patients.

Durability, size remain focus areas for future TAVR devices

Despite these advances in valve design, CRT’s panel discussion analyzed focus areas for future valve development. Those concerned about valve size projected that improved closure devices will be a major factor in reducing femoral access site infection.

In addition, manufacturers will need to minimize valve leaflet thickness, with potential to decrease valve size to 14 Fr. As stroke remains a top concern with these devices, experts expressed a need to remove the native calcified leaflets from patients, while others advocated improvement of embolus protection devices.

The panel also debated the need for device durability. While some experts hope to apply durability improvements seen in surgical valves and reduce the prevalence of reinterventions, other experts argued that durability is not a concern with the TAVR patient population. Instead, paravalvular leakage should be the primary focus before TAVR can be applied to a younger population.

These debates will continue to evolve as TAVR devices permeate the market, with future devices able to address the diverse challenges of this highly complex patient population.