Melody Valve Implantation Into the Branch Pulmonary Arteries for Treatment of Pulmonary Insufficiency in an Ovine Model of Right Ventricular Outflow Tract Dysfunction Following Tetralogy of Fallot Repair

Abstract

Transannular patch (TAP) repair of tetralogy of Fallot often results in significant right ventricular outflow tract (RVOT) dilation and distortion. We hypothesized that insertion of Melody valves into the proximal right and left branch pulmonary arteries (PAs) would reduce pulmonary regurgitation fraction (PRF) in an ovine model of pulmonary insufficiency and dilated RVOT. Ten sheep underwent baseline cardiac catheterization, surgical pulmonary valvectomy, and TAP placement. A subset (n=5) had Melody valves (2 devices per animal) inserted into the proximal right and left PAs during the surgical procedure. Melody valves were placed distal to the right-upper-lobe (RUL) artery branch, leaving the RUL "unprotected." Preoperative MRIs (n=5) were used to determine baseline RV ejection fraction (RVEF) and left ventricular (LV) EF. All surviving animals (n=9) underwent MRI and catheterization 6 weeks postsurgery. Mean PRF was lower in the Melody valve group (15±6% versus 37±3%; P=0.014). The unprotected RUL was responsible for 64% of the PRF measured in the Melody valve group. In the non-Melody group, the RVEF was lower than baseline (P=0.003) and than in the Melody group (P=0.05). The LVEF was also lower in the non-Melody group versus baseline (P=0.004) and versus Melody (P=0.01). Bilateral branch PA Melody valve implantation significantly reduced PRF and altered RV and LV function favorably in a model of TAP for tetralogy of Fallot. This novel intervention may offer potential benefit in treating patients with anatomically heterogeneous disease of the RVOT.