Low occult bleeding levels with aspirin, warfarin use in post-MI patients

5 September 2006

The use of aspirin, warfarin, or both drugs by patients after myocardial infarction (MI) does not appear to result in significant levels of occult bleeding with anemia or iron deficiency, researchers claim.

The use of warfarin, aspirin, or a combination of these agents has proven efficacious in preventing future events in patients who have suffered MI. However, the risk of bleeding and iron deficiency remains a concern, explain the authors in the journal Thrombosis Research.

To investigate this issue, the scientists enrolled 267 patients with MI into the Warfarin Aspirin Reinfarction Study (WARIS-II) and randomly assigned them to receive 160 mg/kg aspirin per day, daily warfarin to an international normalized ratio (INR) value of 2.8–4.2, or a combination of aspirin 75 mg/kg and daily warfarin to an INR of 2.0–2.5.

Screening for occult bleeding after 3 months revealed that there was comparable levels in the patients regardless of type of anticoagulant treatment received, with 19 (7.1%) patients reporting bleeding in feces and 29 (10.9%) reporting bleeding in urine.

Moreover, at the second follow-up at 4 years, testing revealed normal hemoglobin and iron status variables in all patients.

The latter finding implies that during this time "there was no decompensated, chronic blood loss in either treatment group," Mette Hurlen and co-workers, from Ullevål University Hospital, Norway, comment.

"We conclude that, in general, only macroscopic bleedings during treatment with these antithrombotic drugs are of clinical relevance, and that screening for occult bleeding yields limited further information," they add.

In an accompanying editorial, Gregory Lip and Chetan Varma, from City Hospital in Birmingham, UK, said that these findings perhaps go "some way to allay anxieties over bleeding with the use (or abuse) of anticoagulant and antiplatelet therapies post-MI."

Thromb Res 2006; 118: 433-438