The Journal of Thoracic and Cardiovascular Surgery, Vol 94, 251-255, Copyright © 1987 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Low-dose aspirin protects against lipid accumulation in primate vein bypass grafts
LE Boerboom, GN Olinger, AH Kissebah and RR Montgomery
Platelet inhibition with high-dose aspirin combined with dipyridamole
reduces lipid accumulation and improves early patency of coronary artery
bypass grafts. However, recent evidence suggests that platelet inhibition
can be achieved with substantially lower aspirin doses than have been
conventionally prescribed. To evaluate whether low-dose aspirin protects
against lipid accumulation in bypass grafts, we studied 15 stump-tailed
macaque monkeys in which autologous cephalic veins were grafted into the
femoral arteries. A control group received no treatment, a second group was
treated with a low, single daily dose of aspirin (12 mg), and a third group
was given a higher dosage of aspirin (80 mg/day) combined with dipyridamole
(50 mg/day) divided into two daily doses. A special diet was fed that
resulted in plasma cholesterol levels (224 +/- 50 mg/dl, mean +/- standard
deviation) and plasma lipoprotein distributions that mimic the profile in
humans. Cholesterol concentration in grafts removed 3 months after
insertion was 0.47 +/- 0.12 mg/100 mg tissue in the control group; it was
reduced to 0.23 +/- 0.04 mg/100 mg (p less than 0.001) by low-dose aspirin
and to 0.17 +/- 0.05 mg/100 mg (p less than 0.001) by combined aspirin and
dipyridamole therapy. Graft apolipoprotein B concentration was 66 +/- 19
micrograms/100 mg in control group; it was reduced to 40 +/- 8
micrograms/100 mg (p less than 0.05) by low-dose aspirin and to 23 +/- 7
micrograms/100 mg (p less than 0.001) with the combination treatment. There
were no differences between groups in either cholesterol concentration
(0.09 +/- 0.02 mg/100 mg) or apolipoprotein B concentration (10 +/- 3
micrograms/100 mg) in normal ungrafted vein. Platelet function tests
demonstrated platelet aggregation in all control monkeys, in none of the
combined therapy group, and in two of five monkeys receiving low-dose
aspirin. This study indicates that low- dose aspirin is protective against
graft lipid accumulation in monkeys. The mechanism of this antilipid effect
and its relation to any antithrombotic effect remain to be elucidated.
