Responses of systemic and pulmonary veins to the presence of an intravascular stent in a swine model

The outcome of stent implantation for children with pulmonary venous obstruction has been characterized by late reocclusion associated with a marked vessel neointimal proliferation. The purpose of this study was to compare the responses of the systemic vein and pulmonary vein to the presence of an intravascular stent, using a Yorkshire swine (N = 10) model. Under cardiopulmonary bypass, a single Palmaz stent was placed in the inferior vena cava (IVC) and right lower pulmonary vein (PV) with sacrifice at 4.9-6.1 months. Angiography and hemodynamic data were determined at 1 and 3 months post-stent implant and prior to euthanasia. All stents were found to be patent, with no difference in degree of thrombosis or neointimal formation. No statistical difference was found in the initial and final stent diameter for both inferior vena cava and pulmonary vein stents (PV initial 6.8 +/- 0.9; final 7.1 +/- 0.6) (IVC initial 10.4 +/- 1.2; final 10.4 +/- 1.2). Electron microscopy demonstrated smooth endothelialization of both pulmonary and systemic venous stent devices. No thrombosis was found on gross morphology. The data indicate that there is no intrinsic difference in the response of the pulmonary vein to the presence of a stent device. The clinical experience of restenosis following stent implantation for pulmonary vein stenosis appears to be more related to variables of final stent diameter combined with the marked intrinsic abnormal vessel architecture, as seen with this condition.