The Effects of Angiotensin II Signaling Blockade on Platelet Activity in Subjects with Hypertension

Background: To investigate the effects of Angiotensin II receptor blockade (ARB) and angiotensin converting enzyme (ACE) inhibition on platelet reactivity in patients with mild to moderate hypertension. PFA-100 evaluates platelet function (expressed in seconds as closure time, CT) in anti-coagulated whole blood in vitro at high shear rates. The test cartridge is impregnated with either collagen and epinephrine (Col/Epi) or collagen and ADP (Col/ADP). Methods: 33 patients were randomized to perindopril 4mg (n = 9), valsartan 80mg/d (n = 9) and for lifestyle modification (n = 15) for 4 weeks. Platelet reactivity was measured at baseline and after 4 weeks by PFA-100. Normotensive controls (n = 11) were also tested at baseline to standardize PFA-100 CT. Haematocrit, platelet count and plasma vWF antigen levels were measured. Results: There was no difference in baseline haematocrit, platelet count or vWF antigen level between the groups. The vWF antigen levels measured after 4 weeks showed no significant difference either. Significant blood pressure reduction was seen in the treated group (SBP P = 0.002 and DBP P = 0.005) when compared to the life style modification group (SBP P = 0.06 and DBP P = 0.04) after 4 weeks. There was no significant statistical difference in Col/ADP CT in treated and non-treated groups but increase in CT (P = 0.05) in treated group with Col/Epi seen after 4 weeks. Conclusion: In patients with mild to moderate hypertension, valsartan and perindopril compared to life style modification demonstrate a significant decrease in platelet reactivity.