Warfarin use and the risks of stroke and bleeding in hemodialysis patients with atrial fibrillation: A systematic review and a meta-analysis

Antithrombotic Therapy With Ticagrelor in Atrial Fibrillation Subjects After Percutaneous Coronary Intervention

Background: Warfarin, along with aspirin and clopidogrel, has long been recommended for patients with atrial fibrillation (AF) who are undergoing percutaneous coronary intervention with a drug-eluting stent (PCI-DES). However, this triple therapy has been known to increase the risk of bleeding complications. Meanwhile, there is no evidence from prospective trials on the use of ticagrelor in a dual therapy. We here aimed to compare the antiplatelet drug ticagrelor as a dual antithrombotic agent to aspirin and clopidogrel in bleeding events.

Methods: In this multicenter, active-controlled, open-label, randomized trial, patients with AF taking warfarin who had undergone PCI-DES were randomly assigned to the ticagrelor therapy group (Dual group) or the clopidogrel plus aspirin therapy group (Triple group). The primary and secondary endpoints were overall bleeding events and major bleeding events, respectively, according to the Thrombolysis in Myocardial Infarction (TIMI) criteria at 6 months. Cardiovascular events [re-PCI, surgical bypass, myocardial infarction (MI), heart failure, rehospitalization due to angina pectoris, stent thrombosis and death due to cardiovascular causes] at 6 months were also recorded.

Results: A total of 296 patients from 12 medical centers in China were randomized after PCI-DES to either the Dual therapy group (n = 148) or the Triple group (n = 146) for 6 months. The overall incidence of bleeding events at 6 months was 36.49% in the Dual therapy group and 35.62% in the Triple group [hazard ratio, 0.930; 95% confidence interval (CI), 0.635 to 1.361; P = 0.7088]. The incidence of the secondary endpoint over 6 months was 4.73% in the Dual therapy group and 1.37% in the Triple group (hazard ratio, 0.273; 95% CI, 0.057 to 1.315; P = 0.1056). Cardiovascular event occurrence was also comparable in both groups at 6 months (18.24 vs. 16.44%; hazard ratio, 0.845; 95% CI, 0.488 to 1.465; P = 0.5484).

Conclusions: The incidence of total bleeding events in AF patients treated with ticagrelor was comparable to that in patients treated with clopidogrel plus aspirin at 6 month; Meanwhile, the incidence of cardiovascular events were also comparable between the groups.

Clinical Trial Registration: MANJUSRI, ClinicalTrials.gov# NCT02206815, 2014, August 1^st

Retention and molecular-recognition mechanisms of molecularly imprinted polymers for warfarin derivatives and their application for the determination of warfarin in human serum

Monodisperse molecularly imprinted polymers (MIPs) for warfarin (WF), 4'-chlorowarfarin (CWF), 4'-bromowarfarin (BWF), 4'-nitrowarfarin (NWF) and 4'-methylwarfarin (MWF) (MIP_WF, MIP_CWF, MIP_BWF, MIP_NWF and MIP_MWF, respectively) were prepared using 4-vinylpyridine (4-VPY) and ethylene glycol dimethacrylate as a functional monomer and crosslinker, respectively, by multi-step swelling and polymerization. The retention and molecular-recognition properties of those MIPs were evaluated in HILIC, and reversed- and normal-phase modes. According to ¹H NMR studies, one-to-three complex formation of one WF or CWF molecule with three 4-VPY molecules occurred. Via computational approaches, the intermolecular interaction modes and energies between WF derivatives and 4-VPYs were evaluated by semi-empirical quantum chemistry methods and density functional theory calculations. Three major possible hydrogen bonding interaction modes were identified: the interactions between the 4-hydroxy group, α-proton (methylene C-H) and α-proton (methyl C-H) of the WF derivative and the nitrogen atoms of 4-VPYs. In HILIC and normal-phase modes, the interaction energies showed satisfactory correlations with the retention factors of the WF derivatives. In reversed-phase mode, the retention factors of the WF derivatives were described by the hydrophobicity and the acidity of the 4-hydroxy groups of the WF derivatives. These results demonstrate that three hydrogen bonding interactions in HILIC and normal-phase modes, and hydrogen bonding or ionic interactions and hydrophobic interactions in reversed-phase mode play important roles in the retention and molecular-recognition of the WF derivatives on MIPs. Furthermore, MIP_BWF was successfully applied to the determination of WF in human serum by column-switching LC with high accuracy, precision and selectivity and without template-leakage problems.

Warfarin Dosing and Outcomes in Chronic Kidney Disease: A Closer Look at Warfarin Disposition

BACKGROUND

Chronic Kidney Disease (CKD) is a prevalent worldwide health problem. Patients with CKD are more prone to developing cardiovascular complications such as atrial fibrillation and stroke. This warrants the use of oral anticoagulants, such as warfarin, in this population. While the efficacy and safety of warfarin in this setting remain controversial, a growing body of evidence emphasizes that warfarin use in CKD can be problematic. This review discusses 1) warfarin use, dosing and outcomes in CKD patients; and 2) possible pharmacokinetic mechanisms for altered warfarin dosing and response in CKD.

METHODS

Structured search and review of literature articles evaluating warfarin dosing and outcomes in CKD. Data and information about warfarin metabolism, transport, and pharmacokinetics in CKD were also analyzed and summarized.

RESULTS

The literature data suggest that changes in warfarin pharmacokinetics such as protein binding, nonrenal clearance, the disposition of warfarin metabolites may partially contribute to altered warfarin dosing and response in CKD.

CONCLUSION

Although the evidence to support warfarin use in advanced CKD is still unclear, this synthesis of previous findings may help in improving optimized warfarin therapy in CKD settings.

Warfarin use and the risk of stroke, bleeding, and mortality in older adults on dialysis with incident atrial fibrillation

AIM

There is conflicting evidence regarding the safety and effectiveness of warfarin for atrial fibrillation (AF) treatment among older end-stage renal disease (ESRD) patients, and differences among subgroups are unclear.

METHODS

Older dialysis patients who were newly diagnosed with AF (7/2007-12/2011) were identified in the United States Renal Data System. The adjusted hazard ratios (HR) of the outcomes (any stroke, ischaemic stroke, major bleeding, severe gastrointestinal bleeding, and death) by time-varying warfarin use were estimated using Cox regression accounting for the inverse probability of treatment weight.

RESULTS

Among 5765 older dialysis patients with incident AF, warfarin was associated with significantly increased risk of major bleeding (HR = 1.50, 95% CI 1.33-1.68), but was not statistically associated with any stroke (HR = 0.92, 95% CI 0.75-1.12), ischaemic stroke (HR = 0.88, 95%CI 0.70-1.11) or gastrointestinal bleeding (HR = 1.03, 95% CI 0.80-1.32). Warfarin use was associated with a reduced risk of mortality (HR = 0.72, 95%CI 0.65-0.80). The association between warfarin and major bleeding differed by sex (male: HR = 1.29; 95%CI 1.08-1.55; female: HR = 1.67; 95%CI 1.44-1.93; P-value for interaction = 0.03).

CONCLUSION

Older ESRD patients with AF who were treated with warfarin had a no difference in stroke risk, lower mortality risk, but increased major bleeding risk. The bleeding risk associated with warfarin was greater among women than men. The risk/benefit ratio of warfarin may be less favourable among older women.

Warfarin and the Risk of Death, Stroke, and Major Bleeding in Patients With Atrial Fibrillation Receiving Hemodialysis: A Systematic Review and Meta-Analysis

Background: Up to date, the efficacy and safety of warfarin treatment in atrial fibrillation patients receiving hemodialysis remain controversial. So we performed this meta-analysis to try to offer recommendations regarding warfarin management in this population.

Methods: We searched Pubmed, Embase, and Cochrane library and reviewed relevant reference lists from 1980 to March 2018. Studies were included if they described the risks of mortality, stroke, and bleeding events with or without warfarin in atrial fibrillation patients receiving hemodialysis.

Results: Overall, the use of warfarin was not associated with mortality (OR = 0.95, 95%CI = 0.89–1.02), stroke (OR = 1.06, 95% CI = 0.87–1.30) and ischemic stroke (OR = 0.85, 95% CI = 0.68–1.05), but its use could increase the risks of hemorrhagic stroke (OR = 1.34, 95% CI = 1.13–1.59) and major bleeding (OR = 1.24, 95% CI = 1.14, 1.35). In subgroup analyses, when analyses were mainly restricted to atrial fibrillation patients who were undergoing hemodialysis and taking other anticoagulation agents, warfarin therapy didn't reduce the risks for mortality (OR = 0.98, 95% CI = 0.68–1.42) and ischemic stroke (OR = 1.03, 95% CI = 0.89–1.19), but significantly increased the risks of stroke (OR:1.14, 95% CI = 1.01–1.29) and bleeding events such as hemorrhagic stroke (OR = 1.42, 95% CI = 1.14–1.77) and major bleeding (OR = 1.24, 95% CI = 1.14–1.35). While in patients who didn't take other anticoagulation agents or aspirin, warfarin use was not associated with all-cause mortality (OR = 0.90, 95% CI = 0.78–1.04), or any stroke (OR = 1.00, 95% CI = 0.71–1.40). Its use was associated with significantly decreased risk of ischemic stroke (OR = 0.71, 95% CI = 0.60–0.85), but not associated with hemorrhagic stroke (OR = 1.45, 95% CI = 0.83–2.55). Besides, another subgroup analysis showed that warfarin therapy didn't exert a protective role in patients with normal serum lipid levels (OR = 1.04, 95% CI = 0.85–1.26), but seemed to decrease the risk of ischemic stroke in patients with hyperlipidemia (OR = 0.38, 95% CI = 0.11–1.29).

Conclusion: Our results suggested that it was necessary to prescribe warfarin for the prevention of ischemic events in hemodialysis patients with atrial fibrillation, but if these patients were already prescribed with other anticoagulants for the treatment of other co-existing diseases, then warfarin was not recommended.

Mortality due to bleeding, myocardial infarction and stroke in dialysis patients

Essentials Mortality due to bleeding vs. arterial thrombosis in dialysis patients is unknown. We compared death causes of 201 918 dialysis patients with the general population. Dialysis was associated with increased mortality risks of bleeding and arterial thrombosis. Clinicians should be aware of the increased bleeding and thrombosis risks.

SUMMARY

Background Dialysis has been associated with both bleeding and thrombotic events. However, there is limited information on bleeding as a cause of death versus arterial thrombosis as a cause of death. Objectives To investigate the occurrence of bleeding, myocardial infarction and stroke as causes of death in the dialysis population as compared with the general population. Methods We included 201 918 patients from 11 countries providing data to the ERA-EDTA Registry who started dialysis treatment between 1994 and 2011, and followed them for 3 years. Age-standardized and sex-standardized mortality rate ratios for bleeding, myocardial infarction and stroke as causes of death were calculated in dialysis patients as compared with the European general population. Associations between potential risk factors and these causes of death in dialysis patients were investigated by calculating hazard ratios (HRs) with 95% confidence intervals (CIs) by the use of Cox proportional-hazards regression. Results As compared with the general population, the age-standardized and sex-standardized mortality rate ratios in dialysis patients were 12.8 (95% CI 11.9-13.7) for bleeding as a cause of death (6.2 per 1000 person-years among dialysis patients versus 0.3 per 1000 person-years in the general population), 13.4 (95% CI 13.0-13.9) for myocardial infarction (22.5 versus 0.9 per 1000 person-years), and 12.4 (95% CI 11.9-12.9) for stroke (14.3 versus 0.7 per 1000 person-years). Conclusion Dialysis patients have highly increased risks of death caused by bleeding and arterial thrombosis as compared with the general population. Clinicians should be aware of the increased mortality risks caused by these conditions.

Safety and effectiveness of apixaban compared to warfarin in dialysis patients

Background: The use of apixaban for stroke prophylaxis or for the treatment of venous thromboembolism in end stage renal disease (ESRD) patients maintained on dialysis is based on one single-dose pharmacokinetic study. There is a deficiency of clinical evidence supporting safety in this population.Objective: The purpose of this study was to determine the safety and efficacy of apixaban compared with warfarin in dialysis patients.Patients/methods: This is a retrospective cohort study conducted at the University of Virginia Medical Center. A total of 124 ESRD patients maintained on dialysis who either received apixaban (n = 74) or warfarin (n = 50) between January 1, 2014 and October 31, 2016 were included in the study. We used multivariable logistic regression to compare the likelihood of patients experiencing a bleeding event based on anticoagulant therapy.Results: The apixaban group experienced fewer overall bleeding events than the warfarin group (18.9% vs 42.0%; P = .01); this significant difference persisted in adjusted analysis (OR = 0.15; 95% CI = 0.05-0.46; P = .001). Major bleeding events were less frequent in the apixaban group compared with patients on warfarin (5.4% vs 22.0%; P = .01). There were no recurrent ischemic strokes in either groups. A lower, non-significant, incidence of recurrent VTE was found in patients on apixaban compared with warfarin (4.4% vs 28.6%; P = .99).Conclusion: Compared to warfarin, our findings suggest that apixaban is a safe and effective alternative in patients with ESRD maintained on dialysis, with apixaban patients experiencing fewer bleeding events than warfarin patients.

Long-term prognostic impact of anticoagulation on patients with atrial fibrillation undergoing hemodialysis

INTRODUCTION AND OBJECTIVES

Evidence for the efficacy and safety of oral anticoagulation with dicumarines in patients with atrial fibrillation (AF) on hemodialysis is controversial. The aim of our study is to evaluate the long-term prognostic implications of anticoagulation with dicumarines in a cohort of patients with non-valvular AF on a hemodialysis program due to end-stage renal disease.

METHODS

Retrospective, observational study with consecutive inclusion of 74 patients with AF on hemodialysis. The inclusion period was from January 2005 to October 2016. The primary variables were all-cause mortality, non-scheduled readmissions and bleeding during follow-up.

RESULTS

Mean age was 75±10 years; 66.2% were men and 43 patients (58.1%) received acenocoumarol. During a median follow-up of 2.40 years (IQR=0.88-4.15), acenocoumarol showed no survival benefit [HR=0.76, 95% CI (0.35-1.66), p=0.494]. However, anticoagulated patients were at increased risk of recurrent cardiovascular hospitalizations [IRR=3.94, 95% CI (1.06-14.69), p=0.041]. There was a trend towards an increase in repeated hospitalizations of ischemic cause in anticoagulated patients [IRR=5.80, 95% CI (0.86-39.0), p=0.071]. There was a statistical trend towards a higher risk of recurrent total bleeding in patients treated with acenocoumarol [IRR=4.43, 95% CI (0.94-20.81), p=0.059].

CONCLUSIONS

In this study, oral anticoagulation with acenocoumarol in patients with AF on hemodialysis did not increase survival. However, it was associated with an increased risk of hospitalizations of cardiovascular causes and a tendency to an increased risk of total bleeding.

Chronic kidney disease and bleeding risk in patients at high cardiovascular risk: a cohort study

Essentials The association between chronic kidney disease and bleeding is unknown. We followed 10 347 subjects at high cardiovascular risk for bleeding events. Chronic kidney disease was associated with a 1.5-fold increased bleeding risk. Especially albuminuria rather than decreased kidney function was associated with bleeding events.

SUMMARY

Background There are indications that patients with chronic kidney disease have an increased bleeding risk. Objectives To investigate the association between chronic kidney disease and bleeding in patients at high cardiovascular risk. Methods We included 10 347 subjects referred to the University Medical Center Utrecht (the Netherlands) from September 1996 to February 2015 for an outpatient visit with classic risk factors for arterial disease or with symptomatic arterial disease (Second Manifestation of Arterial disease [SMART] cohort). Patients were staged according to the KDIGO guidelines, on the basis of estimated glomerular filtration rate (eGFR) and albuminuria, and were followed for the occurrence of major hemorrhagic events until March 2015. Hazard ratios (HRs) with 95% confidence intervals (CIs) for bleeding were calculated with Cox proportional hazards analyses. Results The incidence rate for bleeding in subjects with chronic kidney disease was 8.0 per 1000 person-years and that for subjects without chronic kidney disease was 3.5 per 1000 person-years. Patients with chronic kidney disease (n = 2443) had a 1.5-fold (95% CI 1.2-1.9) increased risk of bleeding as compared with subjects without chronic kidney disease (n = 7904) after adjustment. Subjects with an eGFR of < 45 mL min-1  1.73 m-2 with albuminuria had a 3.5-fold (95% CI 2.3-5.3) increased bleeding risk, whereas an eGFR of < 45 mL min-1  1.73 m-2 without albuminuria was not associated with an increased bleeding risk (HR 1.3, 95% CI 0.7-2.5). Conclusion Chronic kidney disease is a risk factor for bleeding in patients with classic risk factors for arterial disease or with symptomatic arterial disease, especially in the presence of albuminuria.

Treatment of atrial fibrillation with warfarin among older adults with end stage renal disease

BACKGROUND

There is increasing evidence questioning the use of warfarin for atrial fibrillation (AF) among older adults with end stage renal disease (ESRD). We assessed the patterns and determinants of warfarin utilization among these patients in the US.

METHODS

We assembled a cohort of older adults (age ≥65) undergoing dialysis with incident AF from July 2007 to November 2011 from the US Renal Data System (USRDS). We used descriptive statistics to characterize warfarin utilization within 30 days of AF discharge, and logistic regression to quantify patient characteristics associated with warfarin initiation.

RESULTS

Among 5730 older adults undergoing dialysis with incident AF, 15.5% initiated warfarin. Among 2906 patients with high risk of bleeding, 12.7% initiated warfarin; whereas 14.9% initiated warfarin among 4824 patients with high risk of stroke. After adjustment for patient characteristics, warfarin initiation was lower among patients who were older [odds ratio (OR) = 0.74 per 10-year increase, 95% confidence interval (CI) 0.66-0.83] and those with a history of diabetes (OR = 0.75, 95% CI 0.63-0.90), myocardial infarction (OR = 0.64, 95% CI 0.50-0.80), or bleeding (OR = 0.63, 95% CI 0.50-0.80). There was no association between sex, race, or dialysis modality and warfarin initiation. Among patients who initiated warfarin, 46.8% discontinued warfarin use after a median treatment length of 8.6 months.

CONCLUSION

Despite the unclear benefit and increased bleeding risk of warfarin treatment in patients with ESRD, 1 in 8 older adults undergoing dialysis with incident AF in the US who had high risk of bleeding used warfarin. Changes to warfarin therapy due to discontinuation were common after initiation.

Warfarin Use in Hemodialysis Patients With Atrial Fibrillation: A Systematic Review of Stroke and Bleeding Outcomes

Background:

Given the lack of clear indications for the use of warfarin in the treatment of atrial fibrillation (AF) in patients on hemodialysis and the potential risks that accompany warfarin use in these patients, we systematically reviewed stroke and bleeding outcomes in hemodialysis patients treated with warfarin for AF.

Objective:

To systematically review the stroke and bleeding outcomes associated with warfarin use in the hemodialysis population to treat AF.

Design:

Systematic review.

Setting:

All adult hemodialysis patients.

Patients:

Patients on hemodialysis receiving warfarin for the management of AF.

Measurements:

Any type of stroke and/or bleeding outcomes.

Methods:

MEDLINE(R) In-Process & Other Non-Indexed Citations and MEDLINE(R) via OVID (1946 to January 11, 2017), and EMBASE via OVID (1974 to January 11, 2017) were searched for relevant literature. Inclusion criteria were randomized controlled trials, observational studies, and case series in English that examined stroke and bleeding outcomes in adult population of patients (over 18 years old) who are on hemodialysis and taking warfarin for AF. Studies with less than 10 subjects, case reports, review articles, and editorials were excluded. Quality of selected articles was assessed using Newcastle-Ottawa Scale (NOS).

Results:

Of the 2340 titles and abstracts screened, 7 met the inclusion criteria. Two studies showed an association between warfarin use and an increased risk of stroke (Hazard Ratio: 1.93-3.36) but no association with an increased risk of bleed (HR: 0.85-1.04), while 4 studies showed no association between warfarin and stroke outcomes (HR: 0.12-1.17) but identified an association between warfarin and increased bleeding outcome (HR: 1.41-3.96). And 1 study reported neither beneficial nor harmful effects associated with warfarin use.

Limitations:

The major limitation to this review is that the 7 included studies were observational cohort studies, and thus the outcome measures were not specified and predetermined in a research protocol.

Conclusion:

Our systematic review demonstrated that for patients with AF who are on hemodialysis, warfarin was not associated with reduced outcomes of stroke but was rather associated with increased bleeding events.

Nonvitamin K-dependent oral anticoagulants (NOACs) in chronic kidney disease patients with atrial fibrillation

Atrial fibrillation (AF) represents the most common arrhythmia in patients with chronic kidney disease (CKD). As in the general population, in CKD patients AF is associated with an increased risk of thromboembolism and stroke. However, CKD patients, especially those on renal replacement therapy (RRT), also exhibit an increased risk of bleeding, especially from the gastrointestinal tract. Oral anticoagulation is the most effective form of thromboprophylaxis in patients with AF presenting increased risk of stroke. Limited evidence on efficacy, the increased risk of bleeding as well as some concern regarding the use of warfarin in CKD, has often resulted in the underuse of anticoagulation CKD patients. A large body of evidence suggests that non-vitamin K-dependent oral anticoagulant agents (NOACs) significantly reduce the risk of stroke, intracranial hemorrhage, and mortality, with lower to similar major bleeding rates compared with vitamin K antagonist such as warfarin in normal renal function subjects. Hence, they are currently recommended for patients with atrial fibrillation at risk for stroke. However, NOACs metabolism is largely dependent on the kidneys for elimination and little is known in patients with creatinine clearance <25ml/min who were excluded from all pivotal phase 3 NOACs trials. This review focuses on the current pharmacokinetic, observational, and prospective data on NOACs in patients with moderate to advanced chronic kidney disease (creatinine clearance 15-49ml/min) and those on dialysis.

Emerging therapeutic uses of direct-acting oral anticoagulants: An evidence-based perspective

Direct-acting oral anticoagulants (DOACs) were claimed to cause a potential paradigm shift in the therapeutic scenario of patients requiring short- and long-term anticoagulation, by virtue of their pharmacological properties, perceived as innovative. The evidence gathered so far (from pre-approval pivotal trials to real-world post-marketing observational data) consistently confirmed that DOACs are overall comparable to vitamin-K antagonists (VKAs) in terms of safety, efficacy and effectiveness and unequivocally documented a consistent and clinically relevant reduced risk of intracranial bleeding in the settings of non-valvular atrial fibrillation (NVAF) and venous thromboembolism (VTE). Interestingly, two parallel paths can be identified in the current research scenario: A) in the aforementioned consolidated therapeutic indications, an innovative approach is directed towards tailored treatment strategies, to identify patients most likely to benefit from one of the different anticoagulant drugs, in particular subpopulations at increased risk of adverse events (e.g., bleeding); B) in unconventional settings, DOACs are gaining interest for potential use in emerging diseases characterized by arterial and venous thromboembolic risk. In these scenarios, the risk-benefit profile of DOACs, as compared to VKAs or heparins, is less defined. The aim of this review is to critically assess the body of evidence underlying emerging therapeutic uses of DOACs (e.g., heparin-induced thrombocytopenia, anti-phospholipid antibody syndrome), including evolving issues in special populations (e.g., patients with VTE and cancer or cirrhosis). This will be achieved by analyzing the strength (i.e., systematic reviews, randomized clinical trials, observational studies, case report/series) and consistency (i.e., concordance) of both published and unpublished evidence registered in major public repositories.

Vitamin K antagonists for stroke prevention in hemodialysis patients with atrial fibrillation: A systematic review and meta-analysis

BACKGROUND

The use of vitamin K antagonists (VKAs) in hemodialysis patients with atrial fibrillation (AF) is controversial. No randomized trials are available and observational studies have yielded conflicting results, engendering a large clinical practice variability and physician uncertainty. An unresolved but highly relevant question is whether AF poses a true risk of ischemic stroke in hemodialysis and whether any form of oral anticoagulation is therefore warranted.

METHODS

We conducted a systematic review of studies that compared the incidence of ischemic stroke and bleeding in hemodialysis patients with AF taking VKA and those not taking VKA. When hemodialysis patients had been pooled with peritoneal dialysis, kidney transplant, or stage V chronic kidney disease patients, unpublished outcome data of the hemodialysis subgroup were obtained through personal communication. The main outcome measures were ischemic stroke/thromboembolic events, all-cause mortality, major bleeding, and hemorrhagic stroke. Combined hazard ratios (HRs) and 95% CIs were calculated using a random-effects model.

RESULTS

Twelve prospective or retrospective cohort studies were included in the meta-analysis, totaling 17,380 hemodialysis patients of whom 4,010 (23.1%) received VKA. In VKA-treated patients, mean CHADS₂ or CHA₂DS₂VASc score was low (range 1.7-2.75) or a sizeable proportion of patients had scores <2 (range 2%-23%). Time in the therapeutic range or mean international normalized ratio was generally low. Treatment with VKA was associated with a nonsignificant 26% reduction of the risk of ischemic stroke (HR 0.74; 0.51-1.06), a 21% increase in total bleeding risk (HR 1.21; 1.03-1.43), and no effect on mortality (HR 1.00; 0.92-1.09). Vitamin K antagonist almost doubled the risk of hemorrhagic stroke, but this did not reach the limit of statistical significance (4 studies, n = 16.365; HR 1.93; 0.93-3.98).

CONCLUSION

Our meta-analysis revealed a trend for a reduction of the risk of ischemic stroke in hemodialysis patients with AF treated with VKA. The true protective effect may have been underestimated, owing to inclusion of low-risk patients not expected to benefit from anticoagulation and to suboptimal anticoagulation. However, assessment of the overall effect of VKA in hemodialysis patients should also take into account the increased risk of bleeding, in particular of hemorrhagic stroke. Whether new oral anticoagulants provide a better benefit-risk ratio in hemodialysis patients should be the subject of future trials.

Warfarin use and stroke, bleeding and mortality risk in patients with end stage renal disease and atrial fibrillation: a systematic review and meta-analysis

Background

Patients with end stage renal disease (ESRD), including stage 5 chronic kidney disease (CKD), hemodialysis (HD) and peritoneal dialysis (PD), are at high risk for stroke-related morbidity, mortality and bleeding. The overall risk/benefit balance of warfarin treatment among patients with ESRD and AF remains unclear.

Methods

We systematically reviewed the associations of warfarin use and stroke outcome, bleeding outcome or mortality in patients with ESRD and AF. We conducted a comprehensive literature search in Feb 2016 using key words related to ESRD, AF and warfarin in PubMed, Embase and Cochrane Library without language restriction. We searched for randomized trials and observational studies that compared the use of warfarin with no treatment, aspirin or direct oral anticoagulants (DOACs), and reported quantitative risk estimates on these outcomes. Paired reviewers screened articles, collected data and performed qualitative assessment using the Cochrane Risk of Bias Assessment Tool for Non-randomized Studies of Interventions. We conducted meta-analyses using the random-effects model with the DerSimonian - Laird estimator and the Knapp-Hartung methods as appropriate.

Results

We identified 2709 references and included 20 observational cohort studies that examined stroke outcome, bleeding outcome and mortality associated with warfarin use in 56,146 patients with ESRD and AF. The pooled estimates from meta-analysis for the stroke outcome suggested that warfarin use was not associated with all-cause stroke (HR = 0.92, 95 % CI 0.74–1.16) or any stroke (HR = 1.01, 95 % CI 0.81–1.26), or ischemic stroke (HR = 0.80, 95 % CI 0.58–1.11) among patients with ESRD and AF. In contrast, warfarin use was associated with significantly increased risk of all-cause bleeding (HR = 1.21, 95 % CI 1.01–1.44), but not associated with major bleeding (HR = 1.18, 95 % CI 0.82–1.69) or gastrointestinal bleeding (HR = 1.19, 95 % CI 0.81–1.76) or any bleeding (HR = 1.21, 95 % CI 0.99–1.48). There was insufficient evidence to evaluate the association between warfarin use and mortality in this population (pooled risk estimate not calculated due to high heterogeneity). Results on DOACs were inconclusive due to limited relevant studies.

Conclusions

Given the absence of efficacy and an increased bleeding risk, these findings call into question the use of warfarin for AF treatment among patients with ESRD.

The Active Metabolite of Warfarin (3'-Hydroxywarfarin) and Correlation with INR, Warfarin and Drug Weekly Dosage in Patients under Oral Anticoagulant Therapy: A Pharmacogenetics Study

Objectives

Warfarin oral anticoagulant therapy (OAT) requires regular and frequent drug adjustment monitored by INR. Interindividual variability, drug and diet interferences, and genetics (VKORC1 and CYP2C9) make the maintenance/reaching of stable INR a not so easy task. HPLC assessment of warfarin/enantiomers was suggested as a valid monitoring-tool along with INR, but definite results are still lacking. We evaluated possible correlations between INR, warfarin/3’-hydroxywarfarin, and drug weekly dosage aimed at searching novel alternatives to OAT monitoring. VKORC1/CYP2C9 pharmacogenetics investigation was performed to account for the known influence on warfarin homeostasis.

Methods

133 OAT patients were recruited and assessed for warfarin/3’-hydroxywarfarin serum levels (HPLC), INR, and VKORC1 and CYP2C9 genotypes. A subgroup of 52 patients were monitored in detail (5 consecutive controls; c0-c4) till the target INR was reached. Correlation analyses were performed in both groups

Results

In the whole OAT group both warfarin and 3’-hydroxywarfarin correlate with INR at comparable degree (r² = 0.0388 and 0.0362 respectively). Conversely, warfarin weekly dosage better correlates with warfarin than with 3’-hydroxywarfarin (r² = 0.0975 and r² = 0.0381 respectively), but considering together warfarin plus 3’-hydroxywarfarin the correlation strongly increased (r² = 0.1114; p<0.0001). Interestingly, 3’-hydroxywarfarin reached a strong correlation at c4 respect to warfarin (r² = 0.2157 and r² = 0.0549; p = 0.0005 and p = 0.0944 respectively) seeming less affected by drug adjustments in the subgroup of 52 patients who started OAT. The multivariate analyses aimed at estimating the true contribution of 3’-hydroxywarfarin on INR value ascribed it the unique significant value (p = 0.0021) in spite of warfarin who lost association. The pharmacogenetics studies confirmed that patients carrying the VKORC1 variant-allele required lower warfarin maintenance dosage and that the combination of VKORC1 and CYP2C9 yielded a warfarin responsive index (WRI) inversely related to the number variant alleles

Conclusion

Our results overall suggest that 3’-hydroxywarfarin monitoring could be of great advantage in INR monitoring respect to classical warfarin assessment showing significant contribution also in multivariate analysis. Therefore, additional active metabolites should be recognized and investigated as novel useful indicators.

Efficacy and safety of warfarin in dialysis patients with atrial fibrillation: a systematic review and meta-analysis

Objective

To systematically review and meta-analyse the risk–benefit ratio of warfarin users compared with non-warfarin users in patients with atrial fibrillation (AF), who are undergoing dialysis.

Methods

We searched PubMed/MEDLINE, EMBASE, SCOPUS, Web of Science, Cochrane Library, grey literature, conference proceedings, trial registrations and also did handsearch. Cohort studies without language restrictions were included. Two investigators independently conducted a full abstraction of data, risk of bias and graded evidence. Effect estimates were pooled using random-effect models.

Main outcome measure

All-cause mortality, total stroke/thromboembolism and bleeding complications.

Results

14 studies included 37 349 dialysis patients with AF, of whom 12 529 (33.5%) were warfarin users. For all-cause mortality: adjusted HR=0.99 (95% CI 0.89 to 1.10; p=0.825), unadjusted risk ratio (RR)=1.00 (95% CI 0.96 to 1.04; p=0.847). For stroke/thromboembolism: adjusted HR=1.06 (95% CI 0.82 to 1.36; p=0.676), unadjusted incidence rate ratio (IRR)=1.23 (95% CI 0.94 to 1.61; p=0.133). For ischaemic stroke/transient ischaemic attack, adjusted HR=0.91 (95% CI 0.57 to 1.45; p=0.698), unadjusted IRR=1.16 (95% CI 0.84 to 1.62; p=0.370). For haemorrhagic stroke, adjusted HR=1.60 (95% CI 0.91 to 2.81; p=0.100), unadjusted IRR=1.48 (95% CI 0.92 to 2.36; p=0.102). Major bleeding was increased among warfarin users; adjusted HR=1.35 (95% CI 1.11 to 1.64; p=0.003) and unadjusted IRR=1.22 (95% CI 1.07 to 1.40; p=0.003).

Conclusions

Among dialysis patients with AF, warfarin therapy was not associated with mortality and stroke/thromboembolism, but significantly increased the risk of major bleeding. More rigorous studies are essential to demonstrate the effect of warfarin for stroke prophylaxis in dialysis patients with AF.

Atrial fibrillation in dialysis patients: time to abandon warfarin?

Atrial fibrillation (AF) is a frequent clinical complication in dialysis patients, and warfarin therapy represents the most common approach for reducing the risk of stroke in this population. However, current evidence based on observational studies, offer conflicting results, whereas no randomized controlled trials have been carried out so far. Additionally, many clinicians are wary of the possible role of warfarin as vascular calcification inducer and its potential to increase the high risk of bleeding among patients on dialysis. Ideally the most promising therapy would be based on direct inhibitors of factor IIa or Xa; however, at the moment, none of these drugs can be safely prescribed in dialysis patients, because of their potentially dangerous accumulation, and the lack of sufficient experience with apixaban or rivaroxaban, two drugs showing a favorable pharmacokinetic profile in end-stage renal disease. Hence, the use of vitamin K inhibitors is currently the only pharmacological option for stroke prevention in dialysis patients with atrial fibrillation, leaving the clinicians in a management conundrum.This review discusses the trade-offs implicated in warfarin use for this population, the promises of newly developed drugs, the role of dialysis as atrial fibrillation trigger, as well as potential non-pharmacological management options suitable in selected clinical situations.

The atrial fibrillation conundrum in dialysis patients

The burden of atrial fibrillation (AF) and the risk of stroke are high in dialysis patients. The decision to use anticoagulation rests heavily on effective risk stratification. Because both the pathophysiology of the disease and the response to therapy differ in dialysis, data from the general population cannot be extrapolated. The effect of vitamin K antagonists (VKAs) on the risk of stroke in dialysis patients with AF has not been studied in randomized trials. The available observational data provide contradictory results, reflecting differences in the degree of residual confounding, quality of international normalized ratio control, and stroke characterization. Dialysis patients have a high baseline bleeding risk. It remains unclear to what extent VKAs affect the overall bleeding propensity, but they may significantly increase the risk of intracerebral hemorrhage. Vascular calcifications are extremely prevalent in dialysis patients and independently associated with an adverse outcome. Vitamin K antagonists inhibit the activity of key anticalcifying proteins and may thus compound the risk of vascular calcification progression in dialysis. In the absence of evidence-based guidelines for anticoagulation in dialysis patients with AF, we provide recommendations to assist clinicians in individualized risk stratification. We further propose that new oral anticoagulants may have a better benefit-risk profile in dialysis patients than VKA, provided appropriate dose reductions are made. New oral anticoagulant may yield more on-target anticoagulation, reduce the risk of intracerebral bleeding, and not interfere with vascular calcification biology. Clinical trials with new oral anticoagulant in dialysis patients are eagerly awaited, to reveal whether these assumptions can be confirmed.

Effectiveness and Safety of Warfarin in Dialysis Patients With Atrial Fibrillation: A Meta-Analysis of Observational Studies

In routine practice, warfarin is widely used in dialysis patients with atrial fibrillation (AF) for stroke prevention though the ratio of risks to benefits remains unclear. Recent cohort studies investigating the association between warfarin use and the risks of stroke and bleeding in dialysis patients with AF present conflicting results. The objective of this study was to assess the effectiveness and safety of warfarin use in patients with AF undergoing dialysis. Three databases PubMed, EMBASE, and OVID were searched from their inception to August 2015. Observational studies which assessed the ischemic stroke or bleeding risk of warfarin use in dialysis patients with AF were included. Two reviewers independently extracted data and assessed methodological quality based on the Newcastle-Ottawa Scale score. Combined hazard ratios (HRs) and 95% con&filig;dence intervals (CIs) were calculated using the random-effects model and heterogeneity was assessed based on the Cochrane Q-statistic test and the I statistic. Metaregression analyses were performed to explore the source of heterogeneity. A total of 11 eligible studies with 25,407 patients were included in the analysis. Warfarin use, in comparison with no-warfarin use, was not associated with a lower risk for ischemic stroke (HR 0.95, 95% CI 0.66-1.35). Sensitivity analyses found results to be robust. Metaregression analysis showed that demographic feature, clinical characteristics, or study-level variable had no impact of warfarin use on stroke risk. In addition, warfarin use was associated with a 27% higher risk for bleeding (95% CI 1.04-1.54). Overall, warfarin use did not have a significant association with reduced mortality (95% CI 0.96-1.11). It appears that warfarin use is not beneficial in reducing stroke risk, but with a high risk for bleeding in dialysis patients with AF. Randomized trials are needed to determine the risk-benefit ratio of warfarin in dialysis patients with AF.