Influence of statin use on the incidence of recurrent venous thromboembolism and major bleeding in patients receiving rivaroxaban or standard anticoagulant therapy

Statins Effects on Blood Clotting: A Review

Statins are powerful lipid-lowering drugs that inhibit cholesterol biosynthesis via downregulation of hydroxymethylglutaryl coenzyme-A reductase, which are largely used in patients with or at risk of cardiovascular disease. Available data on thromboembolic disease include primary and secondary prevention as well as bleeding and mortality rates in statin users during anticoagulation for VTE. Experimental studies indicate that statins alter blood clotting at various levels. Statins produce anticoagulant effects via downregulation of tissue factor expression and enhanced endothelial thrombomodulin expression resulting in reduced thrombin generation. Statins impair fibrinogen cleavage and reduce thrombin generation. A reduction of factor V and factor XIII activation has been observed in patients treated with statins. It is postulated that the mechanisms involved are downregulation of factor V and activated factor V, modulation of the protein C pathway and alteration of the tissue factor pathway inhibitor. Clinical and experimental studies have shown that statins exert antiplatelet effects through early and delayed inhibition of platelet activation, adhesion and aggregation. It has been postulated that statin-induced anticoagulant effects can explain, at least partially, a reduction in primary and secondary VTE and death. Evidence supporting the use of statins for prevention of arterial thrombosis-related cardiovascular events is robust, but their role in VTE remains to be further elucidated. In this review, we present biological evidence and experimental data supporting the ability of statins to directly interfere with the clotting system.

Effect of statins on the risk of recurrent venous thromboembolism: A systematic review and meta-analysis

BACKGROUND

Recent studies have suggested that statins may be associated with a lower risk of recurrent venous thromboembolism (VTE).

METHODS

We systematically searched PubMed, Web of Science and Cochrane Library from inception until May 2020 to identify any eligible studies that reported the association between statin use and the risk of recurrent VTE, and conducted a comprehensive systematic review and meta-analysis (PROSPERO registration number: CRD42020190169) on this matter.

RESULTS

A total of 14 observational studies were included for qualitative review and 12 of them qualified for meta-analyses. The main meta-analysis found that statin use was associated with a lower risk of disease recurrence among patients with VTE (pooled adjusted HR: 0.76, 95% CI: 0.69-0.83), which was robust in sensitivity analyses and free of significant publication bias. Additionally, such association was present when restricting to periods after anticoagulation withdrawal (pooled adjusted HR: 0.78, 95% CI: 0.70-0.88) and when separately analyzing recurrent deep vein thrombosis (pooled adjusted HR: 0.71, 95% CI: 0.62-0.81) and recurrent pulmonary embolism (pooled adjusted HR: 0.80, 95% CI: 0.66-0.97; P = 0.027). Furthermore, statin use in patients with VTE was also found to be associated with a lower risk of all-cause mortality (adjusted HR: 0.65, 95% CI: 0.56-0.77), and possibly an even lower risk of bleeding (adjusted HR: 0.88, 95% CI: 0.73-1.07), albeit not statistically significant.

CONCLUSION

Statins have the potential to reduce recurrent events among patient with VTE. Randomized clinical trials to better explore the effect of statins in secondary prevention of VTE are warranted.

The Safety and Efficacy of Rivaroxaban Compared with Warfarin in Patients with Atrial Fibrillation and Diabetes: A Systematic Review and Meta-analysis

AIMS

This meta-analysis was conducted to compare the efficacy and safety of rivaroxaban with warfarin in patients with atrial fibrillation (AF) and diabetes mellitus.

METHODS

PubMed, Embase, Cochrane Library, and Web of Science databases were systematically searched from the establishment of databases up to 15 October 2019. Studies on efficacy and safety outcomes of rivaroxaban and warfarin were included. Efficacy and safety outcomes, including stroke, ischemic stroke, stroke or systemic embolism, myocardial infarction, major adverse cardiac events, major bleeding, intracranial hemorrhage, and major gastrointestinal bleeding were collected for meta-analysis.

RESULTS

Compared with warfarin, rivaroxaban could significantly reduce stroke (risk ratio [RR] 0.77; 95% confidence interval [CI] 0.63-0.95; P = 0.01), ischemic stroke (RR 0.74; 95% CI 0.63-0.87; P = 0.0004), stroke or systemic embolism (RR 0.73; 95% CI 0.60-0.89; P = 0.002), myocardial infarction (RR 0.68; 95% CI 0.56-0.82; P < 0.0001), and major adverse cardiac events (RR 0.71; 95% CI 0.53-0.94; P = 0.02) in patients with AF and diabetes. Moreover, rivaroxaban was associated with a lower risk of major bleeding (RR 0.79; 95% CI 0.65-0.96; P = 0.02), intracranial hemorrhage (RR 0.52; 95% CI 0.39-0.69; P < 0.00001), and major gastrointestinal bleeding (RR 0.74; 95% CI 0.56-0.98; P = 0.04). Similar results were obtained in stratified meta-analysis of cohort studies.

CONCLUSION

Our study suggests a favorable risk-benefit profile of rivaroxaban, with superior efficacy and safety over warfarin in patients with AF and diabetes.

Statins and the risk of bleeding in patients taking dabigatran

OBJECTIVES

Dabigatran etexilate is a direct thrombin inhibitor that clinicians increasingly prescribe to prevent stroke in patients with non-valvular atrial fibrillation (NVAF). Clinicians also commonly prescribe statins for primary and secondary prevention of cardiovascular diseases. Little is known about the bleeding risk in patients taking a statin and dabigatran together. The aim of this study was to evaluate the safety and persistence of dabigatran after co-medication with statins.

MATERIALS AND METHODS

We performed a prospective, multicenter registry study of stroke patients with NVAF who initiated dabigatran therapy within 3 months after a clinically evident ischemic cerebrovascular event between 2013 and 2017. The main outcome measure was symptomatic bleeding after 90, 180, and 360 days.

RESULTS

In total, 652 patients (336 statin users, 316 non-users) were followed for 1 year after dabigatran therapy. Cox multivariate analysis demonstrated that male sex, prior use of aspirin, and concurrent use of an antiarrhythmic drug were associated with a higher risk of bleeding at 360 days. After adjusting time-dependent covariates, statin users had a significantly lower bleeding risk (adjusted hazard ratio: 0.11, P < 0.001) than non-users. Kaplan-Meier analysis indicated that patients prescribed with statins had a higher rate of bleeding-free survival (P = 0.028).

CONCLUSION

For secondary prevention of stroke in patients with NVAF who are taking dabigatran etexilate, co-prescription with a statin was associated with a lower risk of bleeding complications. Future research is needed to determine the pharmacological mechanism underlying this effect.

Methods for time-varying exposure related problems in pharmacoepidemiology: An overview

Purpose

Lack of control for time‐varying exposures can lead to substantial bias in estimates of treatment effects. The aim of this study is to provide an overview and guidance on some of the available methodologies used to address problems related to time‐varying exposure and confounding in pharmacoepidemiology and other observational studies. The methods are explored from a conceptual rather than an analytical perspective.

Methods

The methods described in this study have been identified exploring the literature concerning to the time‐varying exposure concept and basing the search on four fundamental pharmacoepidemiological problems, construction of treatment episodes, time‐varying confounders, cumulative exposure and latency, and treatment switching.

Results

A correct treatment episodes construction is fundamental to avoid bias in treatment effect estimates. Several methods exist to address time‐varying covariates, but the complexity of the most advanced approaches—eg, marginal structural models or structural nested failure time models—and the lack of user‐friendly statistical packages have prevented broader adoption of these methods. Consequently, simpler methods are most commonly used, including, for example, methods without any adjustment strategy and models with time‐varying covariates. The magnitude of exposure needs to be considered and properly modelled.

Conclusions

Further research on the application and implementation of the most complex methods is needed. Because different methods can lead to substantial differences in the treatment effect estimates, the application of several methods and comparison of the results is recommended. Treatment episodes estimation and exposure quantification are key parts in the estimation of treatment effects or associations of interest.

Secondary prevention of recurrent venous thromboembolism after initial oral anticoagulation therapy in patients with unprovoked venous thromboembolism

BACKGROUND

Currently, little evidence is available on the length and type of anticoagulation used for extended treatment for prevention of recurrent venous thromboembolism (VTE) in patients with unprovoked VTE who have completed initial oral anticoagulation therapy.

OBJECTIVES

To compare the efficacy and safety of available oral therapeutic options (aspirin, warfarin, direct oral anticoagulants (DOACs)) for extended thromboprophylaxis in adults with a first unprovoked VTE, to prevent VTE recurrence after completion of an acceptable initial oral anticoagulant treatment period, as defined in individual studies.

SEARCH METHODS

For this review, the Cochrane Vascular Information Specialist (CIS) searched the Specialised Register (March 2017) as well as the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 2). We also searched trials registries (March 2017) and reference lists of relevant articles.

SELECTION CRITERIA

We included randomised controlled trials in which patients with a first, symptomatic, objectively confirmed, unprovoked VTE, who had been initially treated with anticoagulants, were randomised to extended prophylaxis (vitamin K antagonists (VKAs), antiplatelet agents, or DOACs) versus no prophylaxis or placebo. We also included trials that compared one type of extended prophylaxis versus another type of extended prophylaxis.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, assessed quality, and extracted data. We resolved disagreements by discussion.

MAIN RESULTS

Six studies with a combined total of 3436 participants met the inclusion criteria. Five studies compared extended prophylaxis versus placebo: three compared warfarin versus placebo, and two compared aspirin versus placebo. One study compared one type of extended prophylaxis (rivaroxaban) versus another type of extended prophylaxis (aspirin). For extended prophylaxis versus placebo, we downgraded the quality of the evidence for recurrent VTE and all-cause mortality to moderate owing to concerns arising from risks of selection and performance bias in individual studies. For all other outcomes in this review, we downgraded the quality of the evidence to low owing to concerns arising from risk of bias for the studies stated above, combined with concerns over imprecision. For extended prophylaxis versus other extended prophylaxis, we downgraded the quality of the evidence for recurrent VTE and major bleeding to moderate owing to concerns over imprecision. Risk of bias in the individual study was low.Meta-analysis showed that extended prophylaxis was no more effective than placebo in preventing VTE-related mortality (odds ratio (OR) 0.98, 95% confidence interval (CI) 0.14 to 6.98; 1862 participants; 4 studies; P = 0.98; low-quality evidence), recurrent VTE (OR 0.63, 95% CI 0.38 to 1.03; 2043 participants; 5 studies; P = 0.07; moderate-quality evidence), major bleeding (OR 1.84, 95% CI 0.87 to 3.85; 2043 participants; 5 studies; P = 0.86; low-quality evidence), all-cause mortality (OR 1.00, 95% CI 0.63 to 1.57; 2043 participants; 5 studies; P = 0.99; moderate-quality evidence), clinically relevant non-major bleeding (OR 1.78, 95% CI 0.59 to 5.33; 1672 participants; 4 studies; P = 0.30; low-quality evidence), stroke (OR 1.15, 95% CI 0.39 to 3.46; 1224 participants; 2 studies; P = 0.80; low-quality evidence), or myocardial infarction (OR 1.00, 95% CI 0.35 to 2.87; 1495 participants; 3 studies; P = 1.00; low-quality evidence).One study showed that the novel oral anticoagulant rivaroxaban was associated with fewer recurrent VTEs than aspirin (OR 0.28, 95% CI 0.15 to 0.54; 1389 participants; P = 0.0001; moderate-quality evidence). Data show no clear differences in the incidence of major bleeding between rivaroxaban and aspirin (OR 3.06, 95% CI 0.37 to 25.51; 1389 participants; P = 0.30; moderate-quality evidence) nor in the incidence of clinically relevant non-major bleeding (OR 0.84, 95% CI 0.37 to 1.94; 1389 participants; 1 study; P = 0.69; moderate-quality evidence). Data on VTE-related mortality, all-cause mortality, stroke, and myocardial infarction were not yet available for participants with unprovoked VTE and will be incorporated in future versions of the review.

AUTHORS' CONCLUSIONS

Evidence is currently insufficient to permit definitive conclusions concerning the effectiveness and safety of extended thromboprophylaxis in prevention of recurrent VTE after initial oral anticoagulation therapy among participants with unprovoked VTE. Additional good-quality large-scale randomised controlled trials are required before firm conclusions can be reached.

Statins as a preventative therapy for venous thromboembolism

The anti-inflammatory effects of statins have likely not been used to their fullest extent, particularly in reducing venous thromboembolic events. Current therapy for thrombotic events hinges on anticoagulation via heparin, warfarin or new oral anticoagulants. Interventional procedures with thrombectomy may also play a critical role. Unfortunately, thrombotic events can occur and recur despite meticulous anticoagulation therapy. Venous thromboembolism (VTE) includes both deep vein thrombosis (DVT) and pulmonary embolism (PE), two complicated and prevalent diseases that can cause chronic disease states such as post-thrombotic syndrome (PTS). In 2009 the JUPITER trial demonstrated that rosuvastatin may be effective when dealing with vascular inflammation by providing an anti-inflammatory effect. Multiple subsequent studies have looked at this association with some promising findings. The mechanism of action for statins is not entirely understood but there has been a variety of proposals and subsequent testing of inflammatory biomarkers. Additional prospective trials are needed to confirm the possible benefit of VTE reduction through an anti-inflammatory effect, but if this can be shown then statins may become a safe adjunctive therapy for VTE prevention.

Statin use and venous thromboembolism in cancer: A large, active comparator, propensity score matched cohort study

BACKGROUND

Statins have been shown to have a protective effect for venous thromboembolism (VTE) in the general population. This study sought to assess the association between statins and the risk for cancer-associated deep vein thrombosis (DVT) and pulmonary embolism (PE).

METHODS

Patients with newly diagnosed cancer were followed for up to one year in a healthcare claims database (2010-2013). Three treatment groups included statin users, non-statin cholesterol lowering medication users, and an untreated group with pre-existing indications for statin therapy (hyperlipidemia, diabetes, or heart disease). Propensity score matched groups were compared using competing risks survival models for DVT and PE outcomes reporting the hazard ratios (HR) between the treatment groups. Sensitivity analyses assessed the influence of age and individual medications.

RESULTS

The total cohort included 170,459 patients, which, after matching, were similar on baseline characteristics. The overall model showed a statistically significant protective effect for statins compared to no treatment attributed only to leukemia for DVT (HR=0.77, 95% CI 0.61-0.99) and colorectal cancers for PE (HR=0.80, 95% CI 0.64-0.99) in stratified analyses. There were generally no differences in outcomes between statins and non-statins and no individual statin use showed results different from the class effect.

CONCLUSIONS

In this propensity score matched sample of patients with cancer, statins were shown to have a small protective effect in some cancers for DVT or PE compared to no treatment and little difference compared to an active control group. The lack of effect was consistent across statins and was also not found for any of the sensitivity analyses included.

Statins and secondary prevention of venous thromboembolism: pooled analysis of published observational cohort studies

AIMS

There have been suggestions that statins may have a potential role in secondary prevention of venous thromboembolism (VTE) [which includes deep vein thrombosis (DVT) and pulmonary embolism (PE)], but the evidence is inconsistent. We aimed to evaluate the association between statin use and risk of recurrent VTE.

METHODS AND RESULTS

We conducted a systematic review and meta-analysis of observational cohort studies. All relevant studies which reported associations between statin use and recurrent VTE outcomes were identified from MEDLINE, EMBASE, Web of Science, and manual search of bibliographies from inception to January 2017. Study specific relative risks (RRs) with 95% confidence intervals were aggregated using random effects models. Eight eligible studies comprising of 103 576 participants and 13 168 recurrent VTE outcomes were included in the pooled analysis. In pooled analysis of 7 studies, the RR for recurrent VTE was 0.73 (0.68-0.79) when comparing statin use with no use. There was no evidence of heterogeneity between contributing studies (I2=0%, 0-71%; P = 0.93). The RRs for recurrent PE (three studies) and DVT (two studies) comparing statin use with no statin use were 0.75 (95% CI: 0.58-0.96) and 0.66 (95% CI: 0.60-0.71) respectively.

CONCLUSION

Available evidence from observational cohort studies suggests a beneficial effect of statin use on VTE recurrence. Well-designed intervention studies are needed to corroborate these findings.

Influence of statin therapy at time of stroke onset on functional outcome among patients with atrial fibrillation

BACKGROUND

Statin pretreatment has been associated with reduced infarct volume in nonlacunar strokes. The effect of statins on functional outcomes of strokes related to atrial fibrillation (AF) is unknown. We aimed to define the influence of prestroke statin use on functional outcome in AF.

METHODS

We assembled a cohort of consecutive ischemic stroke patients from 2006 to 2010. All patients underwent CT or MRI and were adjudicated by site investigators. AF was confirmed by electrocardiogram in 100% of patients. Site neurologists blinded to the study hypothesis affirmed the type of stroke and assessed the severity of disability at the time of hospital discharge. The frequency of death at 30-days was calculated.

RESULTS

Ischemic stroke (n=1030) resulted in a severe neurological deficit or death (modified Rankin scale ≥4) at 30days in 711 patients (69%). Using multivariable logistic regression models adjusting for factors associated with statin treatment and factors associated with functional outcome, prestroke statin use was associated with a 32% reduction in frequency of severe stroke (odds ratio [OR], 0.68; 95% confidence interval [CI], 0.50-0.92; P=0.011). Other independent factors associated with severe stroke included older age, female sex, non-White race, diabetes mellitus, prior ischemic stroke, prior venous thromboembolism, and dementia.

CONCLUSION

Ischemic strokes in AF are associated with high mortality and morbidity. Statin use at time of stroke onset among patients with AF was associated in this study with less severe stroke and warrant validation.