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.
Keywords: ACE, ARB, hypertension, PFA-100, platelets, platelet reactivity.
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