The influence of the pulsatility of the blood flow on the extent of platelet adhesion.

A new improved flow system was developed to study the influence of blood flow pulsatility on platelet adhesion on adhesive proteins and bio-medical materials. The pulsatility was introduced by changing the shear rate every 15 s in blood that was aspirated through a perfusion chamber by a syringe pump. The advantage of this new system is that it avoids system related platelet activation. At steady low shear rate (300/s) after 5 min a collagen type III surface was covered for 24.2+/-3.8% with platelets. At steady high shear rate (1300/s) platelet coverage to collagen was 48.8+/-6.8%. When pulsatility was introduced by changing the shear rate was every 15 s form 300/s to 1300/s and vice-versa, platelet coverage after 5 min was increased to 60.4+/-4.0% (p<0.001). After 5 min perfusion samples were taken from the perfusate and the extent of platelet activation was measured. The significant difference in surface expression of P-selectin on platelets is only seen when comparing pulse flow with control (no flow). We concluded that a significant increase in platelet activation during blood pulsatile flow compared with steady flow, which results in an increased platelet adhesion to collagen.