Restoration Of Endogenous Tissue In 4yr Explant Of The Xeltis PV Conduit: Promising Results
David L. Morales1, Zsolt Prodán2, Gerardus Bennink3, Renu Virmani4.
1Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA, 2Gottsegen György Hungarian Institute of Cardiology, Budapest, Hungary, 3Heart Center of the University of Cologne, Cologne, Germany, 4CVPath Institute, Gaithersburg, MD, USA.
OBJECTIVE: The Xeltis Pulmonary Valve conduit (XPV) is composed of a restorative absorbable polymer designed to enable cell infiltration and neotissue formation, resulting in functional restoration of endogenous tissue.
METHODS: A 16-year-old male patient with a diagnosis of Tetralogy of Fallot was initially repaired at 2yo with a transannular patch. At age 12, an 18mm XPV was surgically implanted. By age 16, after a significant amount of growth, there was an increased gradient of 51mmHg across the XPV for which it was explanted at 46 months and subjected to histopathologic examination.
RESULTS: No relevant calcification, no thrombus formation and no excessive inflammation was seen. Sub- and supravalvular conduit sections revealed no conduit stenosis. The conduit polymer was 80-90% absorbed and replaced by collagen-rich tissue with few scattered lymphocytes and macrophages with interspersed neovascularization including thick-walled neo-arterioles. The valve polymer did not show significant absorption nor inflammation. Neotissue ingrowth was ongoing, predominantly at base and near commissures.
CONCLUSIONS: These findings suggest that in humans, endogenous tissue infiltrated the Xeltis polymer structure, eventually replacing it with viable tissue. The reported findings are very consistent with previously reported preclinical data on XPVs suggesting that preclinical learnings can be translated to the clinical situation. The reported case was part of a Eurasian clinical feasibility trial (n=12 patients). An improved version of the XPV was investigated in a US EFS study (n=6 patients) with promising results. All of this data has led to the FDA approving the XPLORE2/Pivotal Study which includes 16 centers worldwide and 50 additional patients.
Left: sub-valvular conduit cross-section (Movat-Pentachrome) staining collagen in green to yellow, scaffold fragments (off-white) with ongoing absorption (purple). Right: longitudinal cross-section ( HE) at valve level showing ingoing tissue ingrowth from base of leaflet.
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