Page 11 - Journal of Structural Heart Disease Volume 4, Issue 1

Original Scienti c Article
2
lation [9]. tPVR is categorized as a class II American Heart Association recommendation for conduits with moderate-to-severe stenosis or regurgitation, provid- ed the patient meets inclusion and exclusion criteria for the available valves [10]. However, only ~15-20% of potential patients with RVOT dysfunction are suit- able for currently approved implantable valves [11]. The design and approval of currently available valves (i.e., Melody valve and Edwards Sapien valves) are for patients with a conduit or bioprosthetic valve be- tween the right ventricle (RV) and pulmonary artery (PA), leaving most patients without a percutaneous interventional option after transannular patch repair.
Limitation of Currently Available Devices
Presently, two commercial transcatheter heart valves systems exist: the Melody valve (Medtronic Inc., Minneapolis, Minnesota, USA) and the Edwards Sapi- en XT valve (Edwards Lifesciences, Irvine, California, USA). The maximum diameter is 22 mm for the Melo- dy valve and 26 mm for the Sapien XT valve [12]. The Edwards valve has evolved over recent years, with an increased range of sizes including the 29-mm Sapien XT and, more recently, the Sapien S3 valve. Both valves are mounted on a balloon-expandable stent platform and require pre-stenting to create an optimal land- ing zone and reduce the chances of stent fracture or stenosis (for the Melody valve) of the framework after valve implantation [11-13]. For RVOT diameters >26–27 mm or patients with native RVOT post-tran- sannular patch or very expansile RVOT, pre-stenting followed by implantation of these valves is very chal- lenging. Despite these limitations, in the absence of a larger diameter valve, operators have achieved some success of implanting the presently available valves in patients with a native/patched RVOT. Meadows et al. [14] reported on 31 patients with RVOT patch repair who underwent implantation of the Melody valve; at a median follow-up of 15 months, no patient had greater than mild pulmonary regurgitation (PR). Eight patients developed more than mild pulmonary valve obstruction, six of whom experienced stent fractures. Boudjemline et al. described successful implantation of the Melody valve in 13 patients with patched RVOT using technical variations such as implantation of multiple coaxial stents to reduce the diameter (i.e.,
“Russian doll technique”) or anchoring multiple over- lapping stents in one PA branch to allow implantation of the valve into the meshwork protruding into the main PA (thereby jailing the opposite PA) [15]. Similar results were reported for the Sapien valve [16]. The 29-mm Sapien XT was recently used successfully for large native or patched RVOT with excellent results [17]. Although several reports of other challenging techniques using the two approved valves describe good immediate hemodynamic results, no data on long-term follow-up are available. Therefore, more recent e orts have concentrated on designing a self-expanding system to provide valve competence despite signi cant dilation of the native RVOT [18, 19].
Self-Expanding Platform Design (The Venus P-Valve)
The Venus P-valve (Venus Medtech, Shanghai, Chi- na) is a recently developed self-expanding transcath- eter heart valve designed to adapt to a dilated RVOT [20].
Valve and Delivery System
The Venus P-valve consists of a stent using a Niti- nol frame. The valve leaflets are made of porcine peri- cardium preserved in low-concentration solutions of bu ered gluteraldehyde that are hand-sewn to the multi-level self-expanding Nitinol frame. The frame has proximal and distal flares to anchor the valve in the RVOT and PA bifurcation, respectively. The proxi- mal flare is completely covered by pericardial tissue, whereas the distal flare is an open cell wire frame al- lowing access into the PA branches. The middle part is tubular and straight, fully houses the valve, and is intended to be expanded in the main PA. For ease of identification, there are two radiopaque platinum markers at the proximal and distal are junctions with the straight segment. The valve is located ap- proximately 5 mm distal to the proximal marker. The diameters and lengths of the straight segment range from 18 to 34 mm (in 2-mm increments) and from 20 to 35 mm (in 5-mm increments), respectively. After cardiac magnetic resonance (CMR) and angiographic evaluation, the valve length can be selected to match the length of the main PA to reduce the possibility of obstruction of the RV body or PA branches and to
Journal of Structural Heart Disease, February 2018
Volume 4, Issue 1:1-8