Anticoagulants are different from antiplatelet agents. One acts on coagulation cascade , while the other acts on platelet aggregation. That’s what ,we have been taught for over a century.The reality is , there is a huge functional overlap between these two .
Some of the questions which struggle to get a clear answer ( Atleast for me !)
What will be the bleeding time in patients who are on oral anticoagulants ?
Ans : Since it affects only clotting mechanism bleeding time will be normal or near normal .(Is this reasoning correct ?) But ,we clearly know , Warfarin increases systemic bleeding risk : Does this risk occur without affecting the platelet function ?
If bleeing and clotting are two different phenomenon how warfarin increases bleeding risk ? If warfarin alone increases bleeding risk heavily why Warfarin – Aspirin combination is used in many patients with prosthetic valve ?
In a patient who is receiving full intensity heparin( say in Acute coronary syndrome ) can we afford to withhold aspirin or clopidogrel ?
Heparin is given for preventing recurrent STEMI and antiplatelets are given for preventing recurrent NSTEMI ! Is that the answer ? How solid is the concept of white clots in Unstable angina and red clots in STEMI ? Can a blood really clot without help from platelets ? Can a person really bleed with intact platelet function ?
Final message
We are far . . . far away from fully understanding science of human coagulation and bleeding ! Meanwhile it is a common sight to prescribe all in one cocktail (A LMW Heparin* , an aspirin, clopidogrel ) to most of our ACS patients believing at least one of them will take care !
* Remember the original caution message when LMWH was introduced said , LMWH should not be used along with Aspirin !
Dr.S.Venkatesan MD 