As senior investigator Dr. Frits R. Rosendaal told, this study of a very large number of Dutch patients, who were monitored closely in an anticoagulant clinic, shows the way to finding the optimal dose for clot prevention without a high risk of bleeding.

Dr. Rosendaal of Leiden University Medical Center and team investigated 4202 patients who were followed for 7788 patient-years. Of all, patients who were hospitalized because of major thromboembolism or major hemorrhage were 306.

Overall, there was nearly 4% incidence of such events a year. Patients with mechanical heart valve prostheses or with atrial fibrillation had the proportion of 4.3%. The annual rate for patients treated after a myocardial infarction was 3.6%.

The INR-specific incidence rates were calculated for these untoward events. The optimal intensity of anticoagulation for patients with mechanical heart valve prostheses was an INR of 2.5 to 2.9. For patients with atrial fibrillation, the value was 3.0 to 3.4, and following myocardial infarction, the optimal INR was 3.5 to 3.9.

By carefully monitoring patients (and maintaining) the right INR, Dr. Rosendaal suggests the risk of clot formation and bleeding can be substantially reduced, which can save people’s lives.

Dr. Rosendaal and his colleagues conclude that having defined the presumed optimal intensity of oral anticoagulation for patients with mechanical heart valve prostheses, atrial fibrillation, and after myocardial infarction, testing these ranges in new clinical trials should be considered.