Introduction: Warfarin, aspirin, and the combination of these, have all proven to be efficacious in preventing future events after myocardial infarction. The accompanying bleeding tendency is a concern. The aim of the present study was to compare the occurrence of occult bleeding and iron deficiency during these treatment modalities.
Methods: The 267 patients who had survived a myocardial infarction were randomly assigned in the Warfarin Aspirin Reinfarction Study to treatment with aspirin 160 mg/day, or warfarin (INR 2.8-4.2), or aspirin 75 mg/day plus warfarin (INR 2.0-2.5). The patients were screened for the occurrence of occult bleeding in faeces and urine after 3 months. Haemoglobin and iron metabolism parameters were measured at baseline, after 3 months, and at the end of the 4 years follow-up.
Results: The number of occult bleeding in faeces was 19 (7.1%) and in urine 29 (10.9%). There were no intergroup differences (p=0.45 and 0.39, respectively). In the occult bleeders, a second test showed 3 (1.1%) positive samples in faeces and 9 (3.4%) in urine. Further investigation revealed 2 cases of malignant disease. Haemoglobin and iron status variables were all within normal limits after 3 months and after 4 years in all treatment groups.
Conclusions: Long-term treatment with aspirin, warfarin, or both, in the present doses and levels of anticoagulation did not lead to anemia or iron deficiency. The occurrence of occult bleeding in faeces and urine was a temporary phenomenon in most patients. Only macroscopic bleedings during these treatment modalities were of clinical importance, and screening for occult bleeding was of limit value.