[Placing an endoprosthesis to maintain arterial canal permeability in lamb neonates]

Placing an endoprosthesis in the arterial canal in order to maintain permeability is a possible alternative to performing a modified Blalock-Taussig type surgical systemico-pulmonary anastomosis. This was studied in an animal model. Twelve newborn lambs, weighing from 1.8 to 3.5 kg, were catheterised in the neonatal period in order to place a stent. Three had a partial ligature of the pulmonary artery in utero. During the initial angiography, the canal was occluded in ten of them. Different types of coronary endoprosthesis were used: Multi link tetra TM and RX Herculink TM (Guidant Europe SA), Niroyal (Boston Scientific International), Bx Velocity (Cordis, Johnson and Johnson), Jostent (Jomed). The length of the endoprostheses varied from 12 to 18 mm and the diameter from 3.5 to 6 mm. Implantation was successful 10 out of 12 times: in one case, implantation was complicated by a fatal haemopericardium, and in another by pulmonary artery embolism. Nine animals out of 10 were followed up for 1 to 2 months. At autopsy verification, the canal was permeable in 7 cases with the development of a neointima and zones of moderate stenosis with intimal hyperplasia. In 2 animals the canal was occluded at the aortic level in a zone not covered by the endoprosthesis. Three animals died after implantation: the 2 implantation failures. A third animal with a well inserted prosthesis and a permeable canal died on day 1 from an unknown cause. Placing a stent in the arterial canal is a possible alternative to performing an aorto-pulmonary shunt. Coronary stents seem well adapted and this study does not allow any conclusions to be made at this time on the best type of stent. Further studies will be necessary in order to validate this concept before its use in congenital cardiopathies.