REACTION TO INJURY FOLLOWING BALLOON ANGIOPLASTY AND INTRAVASCULAR STENT PLACEMENT IN THE CANINE FEMORAL-ARTERY

Intravascular stents are used clinically as an adjunct to coronary and iliac angioplasty. This study was performed to evaluate the thromboge nicity and intimal hyperplasia incited by stents deployed in non-injur ed and in balloon-injured femoral arteries in the canine model. Medinv ent stents (4 mm) were placed in the femoral arteries bilaterally in f ive mongrel dogs via cut down. This was preceded by balloon catheter a ngioplasty of the stent site on one side. Platelet deposition was meas ured at 30,60, and 90 minutes and at 24 and 48 hours after stent place ment, using gamma camera imaging of Indium-111 platelets. The animals were killed after 2 months using a pressure perfusion technique, and t he stents harvested. All vessels were patent at the time of harvest. N eointimal thickness was measured by computer image analysis. Platelet deposition was significantly increased on the angioplastied side compa red to the non-angioplastied side at 60 minutes (5.67 x 10(9) +/- 1.4 versus 2.17 x 10(9) +/- 0.5 platelets/cm; P < 0.05), at 90 minutes (8. 13 x 10(9) +/- 1.8 versus 2.33 x 10(9) +/- 0.6 platelets/cm; P < 0.05) , and at 24 hours (stent-to-blood ratio = 15.86 +/- 6.3 versus 3.75 +/ - 1.5; P < 0.05). Neointimal thickness was also significantly greater on the side of combined angioplasty and stent placement (0.45 +/- 0.21 mm versus 0.33 +/- 0.09 mm; P < 0.05). These results demonstrate that placement of intravascular stents in normal arteries is associated wi th a certain degree of thrombogenicity and formation of neointimal hyp erplasia. Combining balloon angioplasty with stent placement significa ntly augments both thrombogenicity and production of intimal hyperplas ia. This can limit the clinical application of such devices in small c aliber blood vessels.