Blood flow and thrombus formation determine the development of stent neointima

To establish a relationship between flow, acute thrombus formation, and lat e intimal formation in implanted arterial stents, canine femoral arteries w ith normal blood flow were compared to contralateral femoral arteries with restricted blood flow. Thrombocyte activity over the stent segment was eval uated for 3 h after stent placement with nuclear scanning, following admini stration of In-(111) labeled platelets. To evaluate long-term stent patency in relationship to arterial flow, an additional group of dogs were subject ed to long-term observation. Matched, symmetrically implanted femoral stent s with normal and restricted flow were explanted at 1, 12, and 24 weeks for histological analysis and comparative measurement of neointimal thickness. Angiographic studies were performed before and after nuclear scan in the a cute animals and before explant in the chronic animals. Acutely, hepariniza tion prevented subocclusive or occlusive thrombus, regardless of flow. In t he absence of heparinization, normal arterial blood flow did not prevent th rombus formation on stents. Chronically, stents with flow restriction had s ignificantly greater neointimal formation in comparison with unrestricted s tents. Histological studies suggested that the stent neointima resulted fro m progressive replacement of stent thrombus.