Dual arterial cannulation for aortic surgical procedures in adult sheep.

BACKGROUND/AIMS: Preclinical site-specific placement of valvular prostheses is highly recommended to fully appreciate hemodynamics. An ovine model is commonly used for preclinical prosthetic mitral valve evaluation; however, the ideal animal model for prosthetic aortic valve evaluation has yet to be determined. Past studies have utilized adult sheep for prosthetic aortic valve replacement; however, an anatomically short length of the ascending aorta can present a surgical challenge during implantation. Due to this anatomically short length of the ascending aorta, we designed an arterial cannulation technique for cardiopulmonary bypass (CPB) to provide a more ideal operative setting. METHODS: Dual arterial cannulation for CPB was used in adult Polypay sheep (n = 15) subjected to an aortic root/valve surgical procedure. RESULTS: The arterial cannulation technique described in this paper was successful in performing aortic root/valve surgical procedures in adult sheep. All animals survived the operative procedure without complications. Postoperatively, all animals were alert, neurologically intact and assumed normal daily functions following extubation, which continued throughout their survival. CONCLUSIONS: The use of this arterial cannulation technique was safe, provided better visualization of the aortic root/valve area, less difficulty in performing the aortic root/valve surgical procedure, and less observed tissue tension while closing the aortotomy.

Chronic orthotopic aortic valve implantation model.

BACKGROUND AND AIM OF THE STUDY: The ideal animal model to assess implanted prosthetic aortic valves has yet to be universally accepted. The majority of mechanical valves are used for aortic valve replacement (AVR), yet historically animal models have provided data mainly after mitral valve implantation, due to the poor survival of animals undergoing AVR. Proposed regulations will require data from site-specific models. Thus, we modified previously reported chronic ovine models used for orthotopic implantation of aortic valves, to conduct preclinical aortic valve evaluation and to establish a predictive animal model needed for safety, hemodynamics, pathology and handling. METHODS: Fourteen sheep underwent AVR with 19 mm mechanical valves. Each animal was placed on cardiopulmonary bypass and the prosthetic valve implanted using a complete transverse ascending aortic transection. Hemodynamic data and aortography were obtained intraoperatively and again after 20 weeks, at which time hemodynamic studies, aortography, and pathological examination were performed. RESULTS: There were two operative deaths, but no significant complications in the other 12 sheep, 11 of which survived for 20 weeks. One animal died two weeks before sacrifice due to valve thrombosis. Chronic hemodynamic and aortographic data were within normal limits for all 11 sheep, and gross pathology of the implanted valve revealed no abnormalities. CONCLUSION: This study demonstrated the feasibility of the ovine model for orthotopic AVR, thus allowing greater confidence in the predictive value of in vivo hemodynamic and angiographic data gathered before clinical trials. Compared with other species, this ovine model provided improved rates of morbidity and mortality, reproducibility, ease of postoperative care, availability and acceptable anatomical similarities to humans. Future aortic valve studies at Medtronic will build on this knowledge base, making ovines - with this surgical technique - our animal model of choice.

A colorimetric sensor array for odour visualization.

Array-based vapour-sensing devices are used to detect and differentiate between chemically diverse analytes. These systems--based on cross-responsive sensor elements--aim to mimic the mammalian olfactory system by producing composite responses unique to each odorant. Previous work has concentrated on a variety of non-specific chemical interactions to detect non-coordinating organic vapours. But the most odiferous, toxic compounds often bind readily to metal ions. Here we report a simple optical chemical sensing method that utilizes the colour change induced in an array of metalloporphyrin dyes upon ligand binding while minimizing the need for extensive signal transduction hardware. The chemoselective response of a library of immobilized vapour-sensing metalloporphyrin dyes permits the visual identification of a wide range of ligating (alcohols, amines, ethers, phosphines, phosphites, thioethers and thiols) and even weakly ligating (arenes, halocarbons and ketones) vapours. Water vapour does not affect the performance of the device, which shows a good linear response to single analytes, and interpretable responses to analyte mixtures. Unique colour fingerprints can be obtained at analyte concentrations below 2 parts per million, and responses to below 100 parts per billion have been observed. We expect that this type of sensing array will be of practical importance for general-purpose vapour dosimeters and analyte-specific detectors (for insecticides, drugs or neurotoxins, for example).