Warfarin for stroke prevention in atrial fibrillation: time to switch?

Monitoring of dabigatran therapy using Hemoclot(®) Thrombin Inhibitor assay in patients with atrial fibrillation

Dabigatran, a new direct thrombin inhibitor, achieves strong anticoagulation that is more predictable than warfarin. Nevertheless, a patient on dabigatran therapy (DT) may suffer from thrombotic or bleeding events. The routine monitoring of DT is not recommended, and standard coagulation tests are not sensitive enough for the assessment of DT activity. The aim of this study was to examine the clinical usefulness of the Hemoclot(®) Thrombin Inhibitor (HTI) assay in the assessment of dabigatran plasma levels in patients with non-valvular AF. Nineteen patients (12 men, 7 women) on DT were included in this preliminary prospective observational study. Dabigatran was administrated twice daily in a two dose regimens: 150 mg (5 patients) and 110 mg (14 patients). Blood samples were taken for the assessment of trough and peak levels of dabigatran. Dabigatran concentrations were measured with the HTI assay. The average dabigatran trough level was 69.3 ± 55.5 ng/ml and the average dabigatran peak level was 112.7 ± 66.6 ng/ml. The dabigatran trough plasma concentration was in the established reference range in 15 patients and the dabigatran peak plasma concentration was in the established reference range in 9 patients, respectively. Despite the fact that the activated partial thromboplastin and thrombin times were generally changed (prolonged), these tests failed to identify the patients with too low or too high dabigatran concentrations. The study confirmed the high sensitivity of the HTI assay for the assessment of dabigatran plasma levels. When compared to standard coagulation tests, the HTI is a more suitable assay for the monitoring of patients treated with dabigatran. Monitoring of DT may be beneficial in selected patients; however, further studies will be needed for the final clarification of this issue.

Underutilization of warfarin for stroke prophylaxis in patients with atrial fibrillation or atrial flutter in Korea

OBJECTIVE

Anticoagulation therapy with warfarin is recommended for stroke prevention in patients with atrial fibrillation (AF) or atrial flutter (AFL) whose risks for stroke are high. However, previous studies suggest that warfarin is markedly underused. This study aims to investigate the incidence and risk factors of warfarin underutilization in patients with high risk of stroke in Korea.

METHODS

This was a cross-sectional study using the data of 2009 from National Patients Sample compiled by the Health Insurance Review and Assessment Service. Patients with high risk of thromboembolism were identified with congestive heart failure, hypertension, age ≥75 years, diabetes, and prior stroke (CHADS2) score ≥2. High-risk patients of bleeding were excluded using Anticoagulation and Risk Factors in Atrial Fibrillation (ATRIA) score >4. Warfarin and antithrombotic therapy underutilization were defined and estimated in high-risk patients. Any demographic and clinical factors associated with warfarin and antithrombotic therapy underutilization were explored using a logistic regression model.

RESULTS

Of the national patient sample, 15,885 patients were identified with AF or AFL. Among them, a total of 8475 patients who had an admission history, CHADS2 ≥2, and ATRIA score ≤4 were included in the analysis. From the study sample, warfarin underutilization and antithrombotic therapy underutilization were estimated to be 64.0% and 20.4%, respectively. Predictors of warfarin underutilization include female sex, age ≥80 years, lower CHADS2 score, and insurance type (Medical Aid program).

CONCLUSIONS

A high portion of AF/AFL patients with CHADS2 score ≥2 were undertreated with warfarin. As ischemic stroke is one of the leading causes of death in Korea, a more aggressive approach to prevent stroke in patients with AF/AFL is required.

The place of newer oral anticoagulants in the treatment of patients with non-valvular atrial fibrillation and coronary artery disease

With the arrival of the newer oral anticoagulants (NOACs), we now have a more convenient means of providing anticoagulation for patients with non-valvular atrial fibrillation (AF). Are there any particular considerations for the many patients who also have coronary artery disease? For many patients there is an obvious need to use the newer agents but for others, such as those who simply refuse to consider using a vitamin K antagonist (VKA) such as warfarin, the decision may be more problematical.