Alterra Adaptive Prestent and SAPIEN 3 THV for Congenital Pulmonic Valve Dysfunction: An Early Feasibility Study.

Shahanavaz S, Balzer D, Babaliaros V, Kim D, Dimas V, Veeram Reddy SR, Leipsic J, Blanke P, Shirali G, Parthiban A, Gorelick J, Zahn EM.JACC Cardiovasc Interv. 2020 Nov 9;13(21):2510-2524. doi: 10.1016/j.jcin.2020.06.039. Epub 2020 Oct 14.PMID: 33069657

Take Home Points:

• The Alterra Adaptive Prestent is a self- expanding Nitinol device, partially covered with expanded polytetrafluoroethylene, that serves as a landing zone for implantation of the SAPIEN 3 THV
• The screening process is comprehensive, including MRI and contrast-enhanced CTA, as well as virtual and physical simulation in patient-specific models.
• There was 100% successful device and valve implantation at the index catheterization, and no THV dysfunction nor RVOT reinterventions at 6-month follow-up.

Commentary from Dr. Arash Salavitabar (Ann Arbor MI, USA), catheterization section editor of Pediatric Cardiology Journal Watch: The authors reports on this early feasibility study designed to determine the safety and functionality of the Alterra Adaptive Prestent in patients with dysfunctional right ventricular outflow tracts (RVOT) or pulmonary valves (PV). The Alterra Adaptive Prestent is a self- expanding Nitinol device, partially covered with expanded polytetrafluoroethylene, in a self-sheathed delivery system. This serves as a landing zone for implantation of the SAPIEN 3 THV.

The primary outcome was a 5-item, nonhierarchical composite measure of post-procedural device success and the secondary outcome was a 3-item composite measure of freedom from valve dysfunction at 30 days and 6 months. Patients considered suitable candidates for implantation had proximal and distal landing zone diameters of 27-38 mm and a minimum of 35 mm from contractile tissue to lowest pulmonary artery (PA) takeoff immediately before Alterra Adaptive Prestent insertion. Patients were first evaluated by cMRI and 2D phase contrast MRA, and if met initial criteria for valve implantation, were followed with contrast-enhanced CTA. Perimeter plots of each patient’s RVOT (Figure B), in both systole and diastole, were created and analyzed in relation to the diameter and perimeter of the unconstrained device. Virtual implants were then performed, followed by 3D printed models at peak systole and diastole for each patient (Figures C and D)

Over nearly 10 months, 4 investigational sites performed this study on 15 patients, out of 29 patients initially screened, with a median age of 29 years and most common underlying cardiac anatomy of tetralogy of Fallot. Anatomic unsuitability was the primary reason for exclusion. All patients met the composite endpoints of device success. There were no major adverse events through 180 day follow-up, including no deaths, RVOT reintervention, device embolism, endocarditis, or coronary compression. No THV dysfunction nor RVOT reinterventions were reported at 6 months. All patients had trivial-to-mild PR and median RVOT Doppler gradient of 9mmHg.

There were several adverse events, including likely TV chordal rupture, self-limited transient ventricular tachycardia, and small pericardial effusion. One patient had an incidental thrombus noted by TTE attached to the inflow of the Alterra Adaptive Prestent and without valve-related thrombus, however the RVOT gradient continued to increase (mildly so) over the following 6 months. Echocardiography showed prominent native valve leaflet tissue that was not entirely captured by the Alterra Prestent, resulting in in-folding of the native leaflet proximal to the Alterra Prestent, causing subvalvular obstruction. Adjustments were made to the pre-procedural imaging to prevent similar episodes from occurring. Another patient had progressive RVOT obstruction secondary to an acute angulation of the RVOT causing the inferomedial aspect of the Alterra Adaptive Prestent to project into the RVOT.

This early feasibility study demonstrates the importance of patient-specific pre-procedural imaging and simulation, as well as the thoughtful determination of the interactions between the present and the dynamic, heterogeneous RVOTs in this patient population. The relatively high screening acceptance rate, procedural success rate, and freedom of valve dysfunction at 6-month follow-up make the Alterra Adaptive Prestent a promising and attractive option for patients with dysfunctional RVOTs based on this preliminary experience.