Second Copenhagen Atrial Fibrillation, Aspirin, and Anticoagulant Therapy Study (AFASAK 2): Methods and Design

Influence of sex on risk of bleeding in anticoagulated patients: a systematic review and meta-analysis

BACKGROUND

The risk of bleeding on anticoagulation varies between patients. It is uncertain whether sex influences this risk.

OBJECTIVES

To determine if the risk of major bleeding differs between men and women receiving anticoagulation for atrial fibrillation or venous thromboembolism(VTE).

METHODS

We searched MEDLINE, EMBASE, and Cochrane databases, and relevant conference proceedings, until February 2013. We included randomized controlled trials and prospective cohort studies of patients on therapeutic anticoagulation for atrial fibrillation or VTE. Two reviewers independently extracted data. The relative risk of bleeding in men compared to women was pooled using a random-effects model.

RESULTS

Forty-two studies including 94 293 patients were eligible; 78 044 patients (83%) had atrial fibrillation; 16 156 patients (17%) had VTE; 37 250 patients were women (40%); and there were 4147 major bleeds. The relative risk of major bleeding for men vs. women was 1.02(95% CI 0.95–1.10; P = 0.27 for heterogeniety). The relative risk was 1.02 (95% CI 0.95–1.09) in patients with atrial fibrillation and 0.80 (95% CI 0.65–0.98) in patients with VTE (P = 0.03 for subgroup effect). Type of anticoagulant,intensity of anticoagulation, and whether patients began or were already established on anticoagulants at enrollment did not influence the relative risk of major bleeding in men compared to women.

CONCLUSIONS

The risk of major bleeding on anticoagulation appears to be the same in men and women, particularly if patients have atrial fibrillation. This finding is less certain for patients with VTE, in whom the risk of bleeding may be marginally lower in men compared to in women.

Influence of CYP2C9 and VKORC1 on patient response to warfarin: a systematic review and meta-analysis

Background

Warfarin is a highly effective anticoagulant however its effectiveness relies on maintaining INR in therapeutic range. Finding the correct dose is difficult due to large inter-individual variability. Two genes, CYP2C9 and VKORC1, have been associated with this variability, leading to genotype-guided dosing tables in warfarin labeling. Nonetheless, it remains unclear how genotypic information should be used in practice. Navigating the literature to determine how genotype will influence warfarin response in a particular patient is difficult, due to significant variation in patient ethnicity, outcomes investigated, study design, and methodological rigor. Our systematic review was conducted to enable fair and accurate interpretation of which variants affect which outcomes, in which patients, and to what extent.

Methodology/Principal Findings

A comprehensive search strategy was applied and 117 studies included. Primary outcomes were stable dose, time to stable dose and bleeding events. Methodological quality was assessed using criteria of Jorgensen and Williamson and data synthesized in meta-analyses using advanced methods. Pooled effect estimates were significant in most ethnic groups for CYP2C9*3 and stable dose (mutant types requiring between 1.1(0.7–1.5) and 2.3 (1.6–3.0)mg/day). Effect estimates were also significant for VKORC1 and stable dose for most ethnicities, although direction differed between asians and non-asians (mutant types requiring between 0.8(0.4–1.3) and 1.5(1.1–1.8)mg/day more in asians and between 1.5(0.7–2.2) and 3.1(2.7–3.6)mg/day less in non-asians). Several studies were excluded due to inadequate data reporting. Assessing study quality highlighted significant variability in methodological rigor. Notably, there was significant evidence of selective reporting, of outcomes and analysis approaches.

Conclusions/Significance

Genetic associations with warfarin response vary between ethnicities. In order to achieve unbiased estimates in different populations, a high level of methodological rigor must be maintained and studies should report sufficient data to enable inclusion in meta-analyses. We propose minimum reporting requirements, suggest methodological guidelines and provide recommendations for reducing the risk of selective reporting.

Risk of Intracerebral Hemorrhage in Patients With Arterial Versus Cardiac Origin of Cerebral Ischemia on Aspirin or Placebo

Background and Purpose— Patients who are anticoagulated after cerebral ischemia have a 19-fold-higher risk of intracerebral hemorrhage (ICH) if they had an arterial rather than a cardiac source. To determine whether this excess risk of ICH was due to the underlying disease (cerebral ischemia of arterial versus cardiac origin) or whether it depended on the antithrombotic regimen, we studied the risk of ICH in arterial versus cardiac origin of cerebral ischemia in patients who received aspirin or no antithrombotic drugs.

Methods— Individual patient data of patients who received aspirin or placebo after cerebral ischemia were obtained from 9 clinical trials. Presence of atrial fibrillation was considered evidence of a cardiac source. Otherwise, events were considered of arterial origin. Cox proportional-hazards modeling was used for univariate and multivariate analyses.

Results— Fifty-four ICHs occurred in 16 625 patient-years in the aspirin-treated patients, and 7 ICHs occurred in 4317 patient-years in those on placebo. After multivariate adjustment for age, sex, current smoking, history of hypertension and diabetes, and aspirin dose (aspirin-treated patients only), the hazard ratio for ICH in patients with an arterial versus a cardiac source was 0.74 (95% confidence interval, 0.30 to 1.82) for aspirin-treated patients and 4.34 (95% confidence interval, 0.35 to 54) for placebo-randomized patients.

Conclusions— Our findings do not confirm the previous finding of an excess risk of ICH in patients with cerebral ischemia of arterial origin. Therefore, it seems that having cerebral ischemia of arterial origin by itself is not associated with an increased risk of ICH, but only in combination with high-intensity anticoagulation.

Oral anticoagulation in nonvalvular atrial fibrillation

Chronic nonvalvular atrial fibrillation is associated with an overall risk of thromboembolic complications of 4.5% per year. Advancing age, prior stroke or transient cerebral ischaemia, diabetes, hypertension, and impaired function of the left ventricle are known risk factors. Placebo-controlled trials have demonstrated that oral anticoagulant therapy with warfarin is effective for primary and secondary prevention of ischaemic stroke, reducing the risk by 68%. The effect of aspirin is still controversial, reducing the risk by 18-44%. Recent clinical trials have investigated the effect of warfarin given at a very low intensity alone or combined with aspirin. The results from the SPAF III study demonstrated that a combination of mini-intensity warfarin plus aspirin was insufficient for stroke prevention in atrial fibrillation. More trials have now confirmed that oral anticoagulation at INR-values below 2.0 is not effective for prevention of thromboembolic events in these patients. It is currently recommended that patients at a high risk of stroke are treated with warfarin at an intensity of INR 2.0-3.0. Patients younger than 65 years without other risk factors can be given aspirin 325 mg day-1.