The Hancock® Valved Conduit for Right Ventricular Outflow Tract Reconstruction in Sheep for Assessing New Devices

BACKGROUND AND AIM OF THE STUDY: Xenograft conduits have been used successfully to repair congenital heart defects, but are prone to failure over time. Hence, in order to improve patient outcomes, better xenografts are being developed. When evaluating a conduit's performance and safety it must first be compared against a clinically available control in a large animal model. The study aim was to evaluate a clinically available xenograft conduit used in right ventricular outflow tract (RVOT) reconstruction in a sheep model.

METHODS: RVOT reconstruction was performed in 13 adult and juvenile sheep, using the Medtronic Hancock® Bioprosthetic Valved Conduit (Hancock conduit). The method had previously been used on patients, and a newly modified variant termed 'RVOT Extraction' was employed to facilitate the surgical procedure. Animals were monitored over predetermined terms of 70 to 140 days. Serial transthoracic echocardiography, intracardiac pressure measurements and angiography were performed. On study completion the animals were euthanized and necropsies performed.

RESULTS: Two animals died prior to their designated study term due to severe valvular stenosis and distal conduit narrowing, respectively. Thus, 11 animals survived the study term, with few or no complications. Generally, maximal and mean transvalvular pressure gradients across the implanted conduits were increased throughout the postoperative course. Among 11 full-term animals, seven conduits were patent with mild or no pseudointimal proliferation and with flexible leaflets maintaining the hemodynamic integrity of the valve.

CONCLUSIONS: RVOT reconstruction using the Hancock conduit was shown to be successful in sheep, with durable and efficient performances. With its extensive clinical use in patients, and ability for long-term use in sheep (as described in the present study) it can be concluded that the Hancock conduit is an excellent control device for the evaluation of new xenografts in future preclinical studies.