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.

A landmark environmental law looks ahead.

In late December 1973, the United States enacted what some would come to call "the pitbull of environmental laws." In the 50 years since, the formidable regulatory teeth of the Endangered Species Act (ESA) have been credited with considerable successes, obliging agencies to draw upon the best available science to protect species and habitats. Yet human pressures continue to push the planet toward extinctions on a massive scale. With that prospect looming, and with scientific understanding ever changing, Science invited experts to discuss how the ESA has evolved and what its future might hold. -Brad Wible.

Impact of a refined advanced design for left atrial appendage exclusion.

OBJECTIVES: Exclusion of the left atrial appendage has been proposed to reduce the risk of stroke in patients with atrial fibrillation. The aim of this study was to evaluate the feasibility and efficacy of the AtriClip PRO·V device (AOD2), now in development, for left atrial appendage exclusion in a canine model. METHODS: The newest AtriClip design comprises a dual-spring mechanism that allows the clip to open into a 'V' shape while still providing equivalent force along the length of the beam. The AOD2's hallmark is a distal tip closure to help retain the appendage during clip closure. Six dogs were implanted via thoracotomy with the clinically available AtriClip device (AOD1) on the right atrial appendage and the AOD2 on the left. At 90 days after implantation, all devices were evaluated by epicardial echocardiography, computed tomography, gross pathology and histology. System performance at the initial surgery was evaluated as well. RESULTS: The ease of use of the clinically available AtriClip device (AOD1) and AOD2 was deemed comparable in all cases. All animals survived for the planned 90-day duration without complications. The atrial appendages were fully occluded in all cases without device migration. On histology, all AtriClip devices demonstrated an acceptable biocompatibility response. CONCLUSIONS: The AOD2 achieved easy, reliable and safe exclusion of the left atrial appendage, with favourable histologic findings. Once approved for clinical application, the AOD2 could provide a new therapeutic option to lower the risks of stroke in patients with atrial fibrillation.