Treatment with aspirin and dipyridamole is more effective than aspirin in reducing low shear blood viscosity.
OBJECTIVE
Investigate effects of aspirin/dipyridamole and aspirin on blood viscosity (BV) in subjects with hyperhomocystememia (>14 micromol/L) and stable cardiovascular disease (CVD) or >or= 20% risk for CVD were the aims of this study.


METHODS
Forty-seven subjects were treated with 14 days of either aspirin/dipyridamole (25 mg/200 mg twice-daily) or aspirin (81 mg daily). BV was measured from fasting specimens at 37 degrees C from whole blood at shear rates ranging from 1,000 to 1s(-1) by using a scanning capillary viscometer (Rheolog; Rheologics Inc., Exton, Pennsylvania, USA).


RESULTS
Aspirin/dipyridamole was more effective than aspirin therapy in reducing BV at shear rates of 1 s(-1) (-3.03 [-3.88, -2.17] mPas vs. -0.07 [-1.06, 0.92] mPas; P<0.0001) and 2 s(-1) (-1.86 [-2.72, -1.01] mPas vs. -0.21 [-1.20, 0.79] mPas; P=0.0136); however, there were no significant differences in blood viscosity at shear rates of 5 s(-1) to 1000 s(-1). Changes in hematocrit, a major determinant of whole BV, were greater in the aspirin/dipyridamole group than the aspirin group (P=0.043). After hematocrit adjustment, differences in BV between aspirin/dipyridamole and aspirin remained significant at 1s(-1) (-2.78 [-3.68, -1.88] mPas vs. -0.04 [-1.05, 0.98] mPas; P<0.0001) and 2 s(-1) (-1.62 [-2.52, -0.72] mPas vs. -0.17 [-1.19, 0.85] mPas; P=0.0315).


CONCLUSIONS
These findings may have important clinical benefits in the CVD prevention and treatment due to the contribution of BV in tissue perfusion and thrombus formation.
Rosenson
Robert S
RS
Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan 48106, USA. rrosenson@umich.edu
D000328:Adult; D000368:Aged; D001241:Aspirin / Q000008:administration & dosage*; D001809:Blood Viscosity / Q000187:drug effects*; D002318:Cardiovascular Diseases / Q000209:etiology / Q000517:prevention & control; D004176:Dipyridamole / Q000008:administration & dosage*; D005260:Female; D006400:Hematocrit; D006801:Humans; D020138:Hyperhomocysteinemia / Q000097:blood* / Q000150:complications / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage*
D010975:Platelet Aggregation Inhibitors; D004176:Dipyridamole; D001241:Aspirin