Biologically engineered valved conduits for right ventricular outflow tract repair evaluated for 52 weeks in growing lambs

Abstract

Aims Replacement heart valves that grow with children remain an unmet need. We previously reported valves fabricated from tubes of fibroblast-derived collagenous matrix increased in size while functioning with low systolic gradients and less than moderate regurgitation over 52 weeks in most cases, when implanted as interpositional grafts in the pulmonary artery of lambs. Here, we evaluated valved conduits fabricated by including an inflow segment to the tri-tube valve allowing for myocardial anastomosis as done in a typical right ventricular outflow tract (RVOT) surgical repair, in the same growing lamb model. Methods and results In this pilot study, 19 mm valved conduits fabricated from resorbable suture were implanted into Dorset lambs (n = 3), sutured to the pulmonary annulus and distal pulmonary artery with resorbable suture after dissection of the pulmonary valve leaflets and resection of an arterial segment. Valve function and dimensions were measured with longitudinal transthoracic echocardiography. All animals exhibited an increase in valve diameter (18.2 ± 1.8 mm at 1 week to 25.1 ± 2.4 mm at 52 weeks) and leaflet free-edge length (21.1 ± 2.4 mm at 1 week to 26.2 ± 3.9 mm at 52 weeks) while functioning with at most mild regurgitation over 52 weeks. The inflow segment of the conduit grew somatically based on its unchanged thickness and increased diameter (38%) and collagen content (128%). In all three explanted conduits, the leaflets contained interstitial cells, new collagen and elastin primarily around the base, a developing endothelium on the surfaces, and they remained thin and pliable without macroscopic calcification. There was interdigitating integration of the conduit with the myocardium at the pulmonary annulus. Further, a stent was successfully placed in a valved conduit at term to evaluate feasibility of a prospective clinical intervention. Conclusion This valved conduit grows in lambs based on this pilot study and thus has clinical potential for RVOT reconstruction and long-term valve growth in children.