Effect of heart failure exacerbations on anticoagulation: a prospective, observational, pilot cohort study

Effect of diseases on response to vitamin K antagonists

INTRODUCTION

The purpose of this review article is to summarize the literature on diseases that are documented to have an effect on response to warfarin and other VKAs.

METHODS

We searched the English literature from 1946 to September 2015 via PubMed, EMBASE, and Scopus for the effect of diseases on response vitamin K antagonists including warfarin, acenocoumarol, phenprocoumon, and fluindione.

DISCUSSION

Among many factors modifying response to VKAs, several disease states are clinically relevant. Liver disease, hyperthyroidism, and CKD are well documented to increase response to VKAs. Decompensated heart failure, fever, and diarrhea may also elevate response to VKAs, but more study is needed. Hypothyroidism is associated with decreased effect of VKAs, and obese patients will likely require higher initial doses of VKAs.

CONCLUSION

In order to minimize risks with VKAs while ensuring efficacy, clinicians must be aware of the effect of disease states when prescribing these oral anticoagulants.

Changes in Warfarin Sensitivity During Decompensated Heart Failure and Chronic Obstructive Pulmonary Disease

Background: Heart failure (HF) has been associated with an elevated international normalized ratio (INR) in patients on warfarin. Objectives: Compare warfarin sensitivity during hospital admission for HF exacerbation and chronic obstructive pulmonary disease (COPD) exacerbation with admissions unrelated to HF or COPD (controls) as well as during disease stability. Methods: We conducted a case-controlled observational study. Patients admitted to a tertiary teaching hospital for HF exacerbation (n = 37), COPD exacerbation (n = 26), and admissions unrelated to HF or COPD (controls, n = 60) were included. Warfarin sensitivity (INR per daily mg dose of warfarin) at admission was compared to periods of disease stability and also compared between the 3 groups. Results: The increase in warfarin sensitivity at admission was 94% for HF patients ( P < 0.0001), 59% for COPD ( P = 0.003) patients, and 24% for controls ( P = 0.002). HF patients with New York Heart Association (NYHA) class 3 and 4 and NYHA class 1 and 2 experienced changes in warfarin sensitivity of 125% ( P = 0.006) and 50% ( P = 0.13) at admission. HF patients had higher warfarin sensitivity at admission (mean = 1.62 [SD = 1.27]) compared to the control group (0.91 [0.52], P < 0.0001) and COPD group (1.03 [0.79], P = 0.04). and required greater intervention with vitamin K than controls (14% vs 0%, P = 0.007). Conclusion: HF and COPD patients were more sensitive to warfarin during disease exacerbation, with HF exacerbation having the largest impact, resulting in clinically significant management implications.

Effect of oral diuretics on chronic warfarin therapy: a retrospective study

BACKGROUND

Limited clinical documentation is suggestive of a drug interaction between warfarin and diuretics.

OBJECTIVE

To evaluate the effect on international normalized ratio (INR) when a daily oral diuretic is started or increased in patients on chronic stable warfarin therapy.

METHODS

The medical records of all active patients of two hospital-based anticoagulation clinics were retrospectively reviewed to identify patients who were started on or received a dose increase of a daily oral diuretic while on stable warfarin therapy. The primary endpoint was the mean difference between an INR recorded within 30 days prior to the diuretic initiation (pre-INR) and an INR recorded within 30 days after diuretic initiation (post-INR).

RESULTS

A total of 1254 patient charts were screened and a total of 123 patients met the study criteria. The mean difference in pre-INR and post-INR was 0.09 (95% CI -0.03 to 0.21, p = 0.12). Post-INR values were outside of the patient's therapeutic range in 39 patients (32%), but no major bleeding or thromboembolic events were reported.

CONCLUSION

Based on this retrospective study, diuretics did not result in a significant change in the INR in patients on stable warfarin therapy.