Efficacy and safety of oral anticoagulants versus aspirin for patients with atrial fibrillation: a meta-analysis

Carbonization of quercetin into nanogels: a leap in anticoagulant development

Quercetin, a flavonoid abundantly found in onions, fruits, and vegetables, is recognized for its pharmacological potential, especially for its anticoagulant properties that work by inhibiting thrombin and coagulation factor Xa. However, its clinical application is limited due to poor water solubility and bioavailability. To address these limitations, we engineered carbonized nanogels derived from quercetin (CNGsQur) using controlled pyrolysis and polymerization techniques. This led to substantial improvements in its anticoagulation efficacy, water solubility, and biocompatibility. We generated a range of CNGsQur by subjecting quercetin to varying pyrolytic temperatures and then assessed their anticoagulation capacities both in vitro and in vivo. Coagulation metrics, including thrombin clotting time (TCT), activated partial thromboplastin time (aPTT), and prothrombin time (PT), along with a rat tail bleeding assay, were utilized to gauge the efficacy. CNGsQur showed a pronounced extension of coagulation time compared to uncarbonized quercetin. Specifically, CNGsQur synthesized at 270 °C (CNGsQur270) exhibited the most significant enhancement in TCT, with a binding affinity to thrombin exceeding 400 times that of quercetin. Moreover, variants synthesized at 310 °C (CNGsQur310) and 290 °C (CNGsQur290) showed the most substantial delays in PT and aPTT, respectively. Our findings indicate that the degree of carbonization significantly influences the transformation of quercetin into various CNGsQur forms, each affecting distinct coagulation pathways. Additionally, both intravenous and oral administrations of CNGsQur were found to extend rat tail bleeding times by up to fivefold. Our studies also demonstrate that CNGsQur270 effectively delays and even prevents FeCl3-induced vascular occlusion in a dose-dependent manner in mice. Thus, controlled pyrolysis offers an innovative approach for generating quercetin-derived CNGs with enhanced anticoagulation properties and water solubility, revealing the potential for synthesizing self-functional carbonized nanomaterials from other flavonoids for diverse biomedical applications.

Country and health expenditure are major predictors of withholding anticoagulation in atrial fibrillation patients at high risk of stroke

BACKGROUND

Guidelines for patients with atrial fibrillation (AF) at high thromboembolic risk recommend oral anticoagulants (OACs) for preventing stroke and systemic embolism (SE). The reasons for guideline non-adherence are still unclear.

AIM

The aim is to identify clinical, demographic and non-patient characteristics associated with withholding OAC in patients with AF at high stroke risk.

METHODS

Patients in the Global Anticoagulant Registry in the FIELD-AF, newly diagnosed with AF between March 2010 and August 2016, and with CHA2DS2-VASc Score≥2 (excluding sex), were grouped by OAC treatment at enrolment. Factors associated with OAC non-use were analysed by multivariable logistic regression.

RESULTS

Of 40 416 eligible patients, 12 126 (30.0%) did not receive OACs at baseline. Globally, OAC prescription increased over time, from 60.4% in 2010-2011 to 74.7% in 2015-2016. Country of enrolment was the major predictor for OAC withholding (χ2-df=2576). Clinical predictors of OAC non-use included type of AF (χ2-df=404), history of bleeding (χ2-df=263) and vascular disease (χ2-df=99). OACs were used most frequently around the age of 75 years and decreasingly with younger as well as older age beyond 75 years (χ2-df=148). Non-cardiologists (χ2-df=201) and emergency room physicians (χ2-df=14) were less likely to prescribe OACs. OAC prescription correlated positively with country health expenditure.

CONCLUSIONS

Approximately one out of three AF patients did not receive OAC, while eligible according to the guidelines. Country of enrolment was the major determinant of anticoagulation strategy, while higher country health expenditure was associated with lower likelihood of withholding anticoagulation.

The Budget Impact Analysis of Adopting Direct Oral Anticoagulants for Stroke Prevention in Nonvalvular Atrial Fibrillation Patients in Malawi

OBJECTIVES

This study aimed to estimate the budget impact of adopting direct oral anticoagulants (DOACs) for stroke prevention in patients with nonvalvular atrial fibrillation in Malawi after the inclusion of DOACs in the World Health Organization's essential medicine list.

METHODS

A model was developed in Microsoft Excel. An eligible population of 201 491 was adjusted with 0.05 % incidence rate and mortality rates yearly according to the treatments. The model estimated the implication of supplementing rivaroxaban or apixaban to the standard treatment mix (also the comparator), thus warfarin and aspirin. The current market share of 43% aspirin and 57% warfarin was adjusted proportionally with 10% DOAC uptake in the first year and 5% annually over the subsequent 4 years. Clinical events of stroke and major bleeding from the ROCKET-AF and ARISTOTLE trials were used because health outcome indicators affect resource utilization. The analysis was conducted solely from the Malawi Ministry of Health perspective and it considered direct costs over 5 years. The sensitivity analysis involved varying drug costs, population, and care costs from both public and private sectors.

RESULTS

The research suggests that despite potential savings of $6 644 141 to $6 930 812 in stroke care because of fewer stroke events, the total Ministry of Health healthcare budget (approximately $260 400 000) may increase by between $42 488 342 to $101 633 644 in 5 years because drug acquisition costs are greater than savings.

CONCLUSIONS

With a fixed budget and current DOACs prices, Malawi can consider using DOACs in patients at the highest risk while waiting for cheaper generic versions.

Thromboembolic and haemorrhagic events in patients with atrial fibrillation: a prospective cohort study in UK primary and secondary care

BACKGROUND

Strong evidence on the long-term safety and efficacy of different types of anticoagulants would help clinicians to prevent thromboembolic events among patients with atrial fibrillation (AF) while minimising the risk of haemorrhages.

AIM

To estimate the risk of thromboembolic and haemorrhagic events for patients with AF on antiplatelets or anticoagulants.

DESIGN AND SETTING

This was a cohort study using routinely collected UK primary and secondary care clinical data from patients with AF, aged ≥18 years, and with an indication to receive anticoagulation before April 2012.

METHOD

The risk of ischaemic stroke or transient ischaemic attack (TIA), coronary heart disease (CHD), peripheral artery disease (PAD), or gastrointestinal (GI) haemorrhage, between 1 April 2012 and 1 April 2017, was estimated using multivariate Cox regression models for patients on antiplatelets only, a combination of antiplatelets and vitamin K antagonists (VKAs), or novel oral anticoagulants (NOACs), and compared with those on VKAs only.

RESULTS

Compared with VKAs, antiplatelets were associated with a higher risk of stroke or TIA, hazard ratio (HR) 1.51, 95% confidence interval (CI) = 1.09 to 2.09, and GI haemorrhage, HR 1.79, 95% CI = 1.01 to 3.18. The risk of thromboembolic and haemorrhagic events was similar for those on a combination of antiplatelets and VKAs, or those on VKAs only. The risk was also similar for those on NOACs or VKAs, except for CHD, where it was higher for patients on NOACs, HR 2.07, 95% CI = 1.35 to 3.19.

CONCLUSION

Anticoagulants are associated with lower risk of thromboembolic and haemorrhagic events among patients with AF than antiplatelets. More research is required on the risk associated with VKAs or NOACs.

INR Control of Patients with Mechanical Heart Valve on Long-Term Warfarin Therapy

BACKGROUND

Warfarin is an anticoagulant indicated for patients who had undergone mechanical heart valve(s) replacement (MHVR). In these patients, time in therapeutic range (TTR) is important in predicting the bleeding and thrombotic risks.

OBJECTIVE

This study aimed to describe the anticoagulation control of warfarin using TTR in patients with MHVR in a tertiary health care referral Center.

METHODS

Data were collected retrospectively by reviewing clinical notes of outpatients who attended international normalized ratio (INR) clinics in November 2015. Patients who had MHVR and who took warfarin were included. The data collected were demographics, relevant laboratory investigations, and patients' prior medical history. TTR was calculated using Rosendaal and traditional methods.

RESULTS

A total of 103 patients with MHVR were recruited. The mean age was 51.72 ± 13.97 years and 46.6% were male. A total of 54.4% had mitral valve replacement (MVR), whereas 26.2% had aortic valve replacement (AVR). The mean TTR calculated using the Rosendaal method was 57.1%. There was no significant difference among patients with AVR, MVR, and both valves (AMVR) in terms of TTR (AVR vs. MVR vs. AMVR, 62.94 ± 23.08, 54.12 ± 21.62, 57.63 ± 17.47; p = 0.213). The average dose of warfarin for all groups was approximately 3 mg/day. Moreover, MVR, AVR, and AMVR patients who had TTR (Rosendaal method) ≤60% were 58.9%, 37.0%, and 45.0%, respectively. Only 4.8% had minor bleeding, whereas none had stroke in the period of TTR determination.

CONCLUSIONS

Despite a majority of patients having <60% TTR, there were low incidences of bleeding and stroke events in this center. There were no factors found to be associated with INR control in this study.

Association between antithrombotic treatment and hemorrhagic stroke in patients with atrial fibrillation-a cohort study in primary care

Objective

The objective of this study was to study the association between antithrombotic treatment and risk of hemorrhagic stroke (HS) in patients with atrial fibrillation (AF) treated in primary health care.

Methods

Study population included all adults (n = 12,215) 45 years and older diagnosed with AF at 75 primary care centers in Sweden 2001–2007. Outcome was defined as a first hospital episode with a discharge episode of HS after the AF diagnosis. Association between HS and persistent treatment with antithrombotic agents (warfarin, acetylsalicylic acid (ASA), clopidogrel) was explored using Cox regression analysis, with hazard ratios (HRs) and 95 % CIs. Adjustment was made for age, socioeconomic status, and co-morbid cardiovascular conditions.

Results

During a mean of 5.8 years (SD 2.4) of follow-up, 162 patients (1.3 %; 67 women and 95 men) with HS were recorded. The adjusted risk associated with persistent warfarin treatment compared to no antithrombotic treatment consistently showed no increased HS risk, HR for women 0.53 (95 % CI 0.23–1.27) and for men 0.55 (95 % CI 0.29–1.04); corresponding HRs for ASA were, for women, 0.45 (95 % CI 0.14–1.44) and, for men, 0.56 (95 % CI 0.24–1.29).

Conclusions

In this clinical setting, we found no evidence pointing to an increased risk of HS with antithrombotic treatment.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-016-2152-8) contains supplementary material, which is available to authorized users.

Warfarin treatment and risk of stroke among primary care patients with atrial fibrillation

OBJECTIVE

Our aim was to study the risk of a first ischaemic stroke (IS) in patients with atrial fibrillation (AF) treated in primary healthcare.

DESIGN

The study population included all adults (n = 11,517), 45 years and older diagnosed with AF, from 75 primary care centres in Sweden between 2001 and 2007. IS was defined as a hospital care event of stroke between 2001 and 2010. Association between incident stroke and warfarin treatment was explored using Cox regression analysis, with hazard ratios (HRs), and 95% confidence intervals (95%CIs). Adjustment was made for age, socioeconomic factors and co-morbidity.

RESULTS

Persistent treatment with warfarin was present among 33.7% of women and 40.0% among men. Persistent warfarin treatment, compared to no persistent treatment, was associated with a stroke preventing effect with fully adjusted HRs of 0.25 (95%CI 0.18-0.36) in women, and 0.25 (95%CI 0.19-0.32) in men. A CHA₂DS₂-VASc score of at least two among women, and three among men, was associated with a stroke risk exceeding 18% during a mean follow-up of 5.4 years. Risk of haemorrhagic stroke was not increased.

CONCLUSIONS

Warfarin is effective in preventing stroke in AF patients in primary healthcare.

Warfarin treatment and risk of myocardial infarction - A cohort study of patients with atrial fibrillation treated in primary health care

OBJECTIVE

To study the risk of myocardial infarction (MI) in patients with atrial fibrillation (AF) treated in primary health care with warfarin or acetylsalicylic acid (ASA, aspirin).

METHODS

The study population included subjects (n=12,283) 45years or older diagnosed with AF who were treated in 75 primary care centres in Sweden between 2001 and 2007. MI was defined as a hospital stay for MI during 2001 through 2010 registered in the Swedish Patient Register. Associations between warfarin or ASA treatment and incident MI were explored using Cox regression analysis, by estimating hazard ratios (HRs) and 95% confidence intervals (95% CIs). Adjustment was made for age, socio-economic factors and cardio-vascular co-morbidity.

RESULTS

Persistent treatment ("per protocol" treatment) with warfarin alone was present among 32.4% of women and 37.4% of men, and with ASA alone among 30.0% of women and 28.1% of men. The fully adjusted HRs for MI, compared to those with no antithrombotic treatment, with warfarin treatment for women were 0.26 (95% CI 0.16-0.41) and for men 0.28 (95% CI 0.20-0.39); and the corresponding HRs for those treated with ASA were for women 0.57 (95% CI 0.37-0.87), and for men 0.44 95% CI (0.31-0.63). The fully adjusted HR for MI when comparing patients with warfarin treatment to those with ASA treatment was for women 0.46 (95% CI 0.27-0.80), and for men 0.58 (95% CI 0.38-0.89).

CONCLUSIONS

Warfarin seems to prevent MI among AF patients in a primary healthcare setting, which emphasizes the importance of persistent anticoagulant treatment in those patients.

Efficacy, safety and tolerability of rivaroxaban for the secondary prevention of stroke in patients with atrial fibrillation in clinical practice

Aim: To evaluate the efficacy, safety and tolerability of rivaroxaban for the secondary prevention of stroke in patients with atrial fibrillation in clinical practice. Methods: Patients treated with rivaroxaban for secondary prevention of stroke/transient ischemic attack attended at a cerebrovascular disease unit were consecutively included in a noninterventional and prospective study. Results: 89 patients (median age 77 years, CHADS2 = 4, HAS-BLED = 3, follow-up = 15 months) were included. Rivaroxaban was started early after the cerebrovascular event (median 5 days for stroke and 3 days for transient ischemic attack). Stroke recurrence occurred in only one patient (annual rate, 0.82%). Eight cases of clinically significant bleeding were recorded (annual rate, 6.58%), of which two were major (annual rate, 1.64%) and one intracranial (annual rate, 0.82%). Medication persistence was very good. Conclusion: Our data show that the early treatment with rivaroxaban is well tolerated, efficacious and safe for secondary prevention of real-life atrial fibrillation patients.

Neighborhood deprivation and warfarin, aspirin and statin prescription - A cohort study of men and women treated for atrial fibrillation in Swedish primary care

BACKGROUND

We aimed to study differences in the prescribing of warfarin, aspirin and statins to patients with atrial fibrillation (AF) in socio-economically diverse neighborhoods. We also aimed to explore the effects of neighborhood deprivation on the relationship between CHADS2 risk score and warfarin prescription.

METHODS

Data were obtained from primary health care records that contained individual clinical data that were linked to national data on neighborhood of residence and a deprivation index for different neighborhoods. Logistic regression was used to estimate the potential neighborhood differences in prescribed warfarin, aspirin and statins, and the association between the CHADS2 score and prescribed warfarin treatment, in neighborhoods with high, middle (referent) and low socio-economic (SES).

RESULTS

After adjustment for age, socio-economic factors, co-morbidities and moves to neighborhoods with different SES during follow-up, adults with AF living in high SES neighborhoods were more often prescribed warfarin (men odds ratio (OR) (95% confidence interval (CI): 1.44 (1.27-1.62); and women OR (95% CI): 1.19 (1.05-1.36)) and statins (men OR (95% CI): 1.23 (1.07-1.41); women OR (95% CI): 1.23 (1.05-1.44)) compared to their counterparts residing in middle SES. Prescription of aspirin was lower in men from high SES neighborhoods (OR (95% CI): 0.75 (0.65-0.86)) than in those from middle SES neighborhoods. Higher CHADS2 risk scores were associated with higher warfarin prescription which remained after adjustment for neighborhood SES.

CONCLUSIONS

The apparent inequalities in pharmacotherapy seen in the present study call for resource allocation to primary care in neighborhoods with low and middle socio-economic status.