Hemolytic effect of deformed intra-arterial stents and stent grafts in vitro

Our objective was to evaluate the hemolytic effect of stents and stent grafts in an in vitro flow model. The model consisted of silicone tubings. Pulsatile flow was delivered at 1170 ml/min. Diluted packed erythrocytes were used (hematocrit of 33%). The Palmaz, MegaLink stents or Passager, Hemobahn stent grafts were placed in the middle portion of the model; control experiments contained no implant ( n=10 each). Concentric stenosis of the implant was achieved by constricting the implant to 25, 50, or 70% (area, n=10 each). Samples were drawn at minute 1, 2, 4, 6, 8, 10, 15, and every 10 min up to 1 h. Hemolytic parameters were evaluated. All implants produced hemolysis, increasing in the course of time. Without deformation (0%) the Hemobahn stent causes less hemolysis compared with the other prostheses. At 25% no significant difference could be shown between all devices. At 50% constriction the Palmaz stent caused more hemolysis than the other grafts, and at 70% stenosis the Palmaz and Hemobahn caused more hemolysis than Passager or Megalink. A hemolytic effect was evaluable, probably due to mechanical stress and sheer forces, induced by turbulences in the proximity of the deformed stent. The stent grafts did not perform better than the stents. Differences in the design of a prosthesis and in the degree of stent deformation seem to have an influence on the hemolysis caused.