Blood Clots

Having chronic atrial fibrillation, I am on Coumadin and Aspirin. For medical procedures such as esophagial dilation I was advised to come off Coumadin and Aspirin and take Plavix for 6 days prior to the procedure. Many people refer to the above drugs as 'blood thinners'. My questions are:

1.) Do any of the above drugs lower the effective blood viscosity (thereby increasing the blood throughput through the blood vessels) or are they strictly anticoagulants?

2.) Please explain briefly the differences in the action of these drugs.

3.) Is regular vigorous exercise effective for AF patients in reducing the probability of blood clot formation in the atria?

Thanks for your time!

[Cleveland Clinic, MD]

1.) Do any of the above drugs lower the effective blood viscosity (thereby increasing the blood throughput through
     the blood vessels) or are they strictly anticoagulants?
A: Strictly anticoagulants;  "blood thinners" is somewhat of a misnomer.

     2.) Please explain briefly the differences in the action of these drugs.
A: Coumadin - inhibits vit K dependent clotting cascade
ASpirin - inhibits cyclooxygenase
Plavix - blocks the ADP receptor

     3.) Is regular vigorous exercise effective for AF patients in reducing the probability of blood clot formation in the
     atria?
A: No.