Circulation, Vol 89, 630-634, Copyright © 1994 by American Heart Association
L L-Lacoste, JY Lam, J Hung and D Waters
BACKGROUND: Calcium antagonists such as verapamil are potent coronary and
systemic vasodilators that are used in the treatment of coronary disease.
They have also been shown to inhibit platelet aggregation in vitro, but
whether they have beneficial antithrombotic effects in humans is unclear,
and whether they can potentiate the antithrombotic effects of aspirin is
unknown. METHODS AND RESULTS: Platelet thrombus formation and whole blood
platelet aggregation were measured in 18 stable coronary patients on three
separate occasions: at baseline when receiving no active medications, after
7 days of receiving oral verapamil SR (240 mg/d), and after 7 days of
receiving a combination of oral verapamil SR and aspirin (325 mg/d).
Thrombus formation on porcine aortic media that were placed into
cylindrical flow chambers and exposed to flowing antecubital venous blood
for 3 minutes was assessed morphometrically at a shear rate of 2546 s-1,
which is typical of arterial flow at sites of stenoses. Thrombus formation
under basal conditions was 7.0 +/- 1.6 microns 2, and this was decreased to
3.1 +/- 0.5 microns 2 (P < .05) after 7 days of treatment with oral
verapamil SR and to 2.6 +/- 0.5 microns 2 (P < .05) after 7 days of
treatment with oral verapamil and aspirin. Whole blood platelet aggregation
levels in response to 0.050 and 0.075 U of thrombin at baseline were 10.8
+/- 1.0 and 11.9 +/- 1.0 omega; aggregation was inhibited after 7 days of
treatment with verapamil to 6.5 +/- 1.1 and 7.8 +/- 0.9 omega (P < .05
versus baseline) and after 7 days of treatment with verapamil and aspirin
to 6.1 +/- 1.1 and 7.2 +/- 1.0 omega (P < .05), respectively.
CONCLUSIONS: The present study demonstrates that part of the benefit of
verapamil in ischemic heart disease may occur by inhibition of platelet
aggregation and thrombus formation. This beneficial antithrombotic effect
may be important in preventing acute coronary ischemic events resulting
from thrombus formation at sites of plaque rupture.
ARTICLES
Oral verapamil inhibits platelet thrombus formation in humans
Department of Medicine, Montreal Heart Institute, Quebec, Canada.
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