The Effect of Implantation of Aortic Stents on Compliance and Blood Flow. An Experimental Study in Pigs

Balloon dilation of coarctation of the aorta has been found to be an effective modality for treatment. Recently, in the older child and adult, implantation of endovascular stents has been considered a clinical alternative to dilation alone. Little is known, however, of the effect of implantation of stents on aortic compliance. To investigate this impact of implantation, we studied 18 piglets, divided into experimental and control groups. At median weight of 14 kg, 2 pairs of ultrasonic crystals were implanted on the aortic wall. After 1 week, all animals underwent catheterization. In the experimental group, a 3 cm long balloon expandable stent was implanted in the descending thoracic aorta between the pairs of crystals. Measurements of arterial pressure and dimensions were performed before implantation and immediately thereafter, and at follow-up catheterization. The index of stiffness, beta, and the the elastic modulus of aortic pressure-strain, were calculated as indexes of arterial compliance. The change in compliance during the period of study was not different between groups. At follow-up, no difference was observed between groups in the velocity of the aortic pulse wave, the augmentation index, or the maximum velocity of flow of blood. The stents remained patent and did not affect aortic growth or medial wall thickness. There was no difference between groups in levels of plasma renin activity and serum aldosterone. In this animal model studied over the short term, therefore, implantation of stents does not affect aortic compliance. Further studies are required to elucidate the long term effects of stents on the hemodynamics affecting the aortic wall and local flow dynamics.