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Articles: Robert J. Glynn, Paul M Ridker, Samuel Z. Goldhaber, and Julie E. Buring Effect of Low-Dose Aspirin on the Occurrence of Venous Thromboembolism: A Randomized Trial Ann Intern Med 2007; 147: 525-533 [Abstract] [Full text] [PDF]

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Treating the Right Clot: Red vs White Thrombi

Akashdeep Singh   (1 November 2007)

Treating the Right Clot: Red vs White Thrombi 1 November 2007
Akashdeep Singh, MD, DM Christian Medical College and Hospital Ludhiana,India Send rapid response to journal: Re: Treating the Right Clot: Red vs White Thrombi drsinghakashdeep{at}gmail.com Akashdeep Singh	Aspirin and other antiplatelet drugs are highly effective at reducing major vascular events in patients who are at risk for or who have established atherosclerotic disease.1 Evidence suggests that antiplatelet agents can lower the risk for venous thromboembolism (VTE) in high-risk patients.2 Why aspirin is not effective for primary prevention of VTE in women at low to moderate risk as seen in the present study? Part of the answer to this question may be found in the differences in thrombus formation between the arterial and venous systems. The low-flow and low- pressure venous system is susceptible to reduced blood flow (stasis) and systemic activation of the coagulation cascade, as Virchow described more than 150 years ago, which predisposes to a thrombus even in a nonstenotic vessel. Most venous thrombi consist predominantly of red cells enmeshed in fibrin and contain relatively few platelets; hence, they have been described pathologically as “red thrombi.” In contrast, in the high-flow and high-pressure arterial system, thrombi form under the influence of local shear forces, platelet activation, and exposure to thrombogenic substances on damaged vascular surfaces. Arterial thrombi, referred to as “white thrombi,” typically are composed predominantly of platelets with relatively little fibrin or red-cell accumulation. Thus, it is plausible to expect that an anticoagulant would be used to prevent venous thromboemboli, whereas an antiplatelet agent would be used to prevent arterial thrombosis.3 References 1. Antiplatelet Trialists’ Collaboration. Collaborative overview of randomised trials of antiplatelet therapy: III. Reduction in venous thrombosis and pulmonary embolism by antiplatelet prophylaxis among surgical and medical patients. BMJ 1994; 308:235–246 2. Pulmonary Embolism Prevention (PEP) Trial Collaborative Group. Prevention of pulmonary embolism and deep vein thrombosis with low dose aspirin: Pulmonary Embolism Prevention (PEP) Trial. Lancet 2000; 355:1295–1302 3. Richard N. Mitchell : Hemodynamic Disorders, Thromboembolic Disease, and Shock in Robbins and Cotran Pathologic Basis Of Disease 7th Ed. Saunders. 2004 pp119-144 Conflict of Interest: None declared