Atrial Fibrillation (AFib) Support Group
Atrial fibrillation (AF or afib) is an abnormal heart rhythm (cardiac arrhythmia) which involves the two small, upper heart chambers (the atria). Heart beats in a normal heart begin after electricity generated in the atria by the sinoatrial node spread through the heart and cause contraction of the heart muscle and pumping of blood.
I had a question I was curious about and wondered if maybe someone knows the answer. I had blood work completed a few weeks ago while I was taking Pradaxa and my INR result was 1.3 and my PT time was 14.1 sec. The doctor completed bloodwork prior to my switching from Pradaxa to Warfarin. I was taking Pradaxa since January. Am I correct in thinking that Pradaxa does not have an effect on INR and PT values? I am assuming its action is on different components of the clotting process which INR and PT test do not measure. While I understand that routine blood tests are not required for Pradaxa, I was curious on what component of the blood clotting factors its action is effective on. Based on the numbers received from the lab work, the doctor has me taking a 5 mg tablet and a 2.5 mg tablet that I am supposed to alternate every day. (5mg one day, 2.5mg the next, 5mg the next day, etc). I had my PT/INR done again today (7 days after starting Warfarin and 4 days after stopping Pradaxa). I should have the results tomorrow AM. Thanks for any education or advice anyone could provide. Carrie
Dabigatran works by binding to thrombin in the clotting process above and blocking its action. This stops the formation of fibrin, the essential component of blood clots. Dabigatran can therefore prevent blood clots from developing.
TESTS (cut and paste):
Prothrombin time (PT/INR) is NOT sensitive to dabigatran. Patients can have a normal/ near normal PT/INR and still have considerable dabigatran concentrations. This test SHOULD NOT be used for patients on dabigatran.
o Activated Partial Thromboplastin Time (aPTT) can be used, but is relatively insensitive to the effects of direct thrombin inhibitors. The expected median peak aPTT level is approximately 2x control values and median trough aPTT is approximately 1.5x control values. The utility of aPTT assessment is primarily for its negative predictive value, i.e. a NORMAL aPTT suggests little anticoagulant activity is present; importantly, even a mildly elevated aPTT can still be associated with clinically important levels of dabigatran and aPTT becomes increasingly insensitive at higher dabigatran levels as could be seen in an overdose.
o Thrombin Time for Direct Thrombin Inhibitors (TTDTI) can be ordered STAT to qualitatively assess anticoagulation status of patients taking direct thrombin inhibitors. This test is sensitive to the effects of therapeutic dabigatran levels and a normal TTDTI excludes the presence of significant dabigatran levels. In cases of drug overdose/excess anticoagulation, the TTDTI is less useful. The TTDTI is best used as a sensitive test to ensure no presence of dabigatran. Of note, the TTDTI can also be influenced by the concomitant administration of other anticoagulants.
petey
"are" not "is"
petey