How to Monitor Patients Receiving Direct Oral Anticoagulants for Stroke Prevention in Atrial Fibrillation: A Practice Tool Endorsed by Thrombosis Canada, the Canadian Stroke Consortium, the Canadian Cardiovascular Pharmacists Network, and the Canadian Cardiovascular Society

Initiation of anticoagulation in atrial fibrillation by primary care physicians: Results of a telephone survey

BACKGROUND

Direct oral anticoagulants (DOACs) are prescribed for over 80% of patients who start anticoagulant therapy for a new diagnosis of atrial fibrillation (AF). Inappropriate DOAC prescriptions are associated with increased mortality. However, limited data exist as to what proportion of primary care physicians (PCPs) initiate anticoagulation in patients with new AF and the extent of their DOAC knowledge.

MATERIAL AND METHODS

We conducted a telephone survey of randomly selected PCPs in Ontario, Canada. Our primary objective was to determine the percentage of PCPs who initiate anticoagulation in new AF patients and the proportion of patients they initiate on DOACs. Our secondary objectives were to assess PCPs' knowledge about DOACs and to identify educational opportunities to address any knowledge gaps.

RESULTS

Our survey included 50 respondents. After making a new AF diagnosis, 66% of PCPs stated that they usually initiate anticoagulation themselves and 84% prescribed a DOAC at least 75% of the time. Potential DOAC knowledge gaps included: administration considerations, off-label dosing, concomitant use of acetylsalicylic acid (ASA) in stable coronary artery disease (CAD) and use in valvular AF.

CONCLUSION

Most PCPs initiate anticoagulants for AF and prescribe DOACs for the vast majority of new patients. PCPs were well versed in certain aspects of DOAC prescribing, however, a number of knowledge gaps were identified. PCPs may benefit from targeted education in these areas to improve patient outcomes in AF.

Assessment of a Pharmacist-Led Direct Oral Anticoagulant Monitoring Clinic

BACKGROUND

Direct oral anticoagulants (DOACs) are recommended as first-line therapy for treatment and prevention of venous thromboembolism (VTE) and prevention of stroke related to nonvalvular atrial fibrillation. Recent publications have suggested incorporating DOAC monitoring into anticoagulant management clinics. The Eastern Health Adult Outpatient Thrombosis Service (Newfoundland and Labrador) includes a pharmacist-led DOAC monitoring clinic that uses standardized evidence-based care processes.

OBJECTIVES

To describe a new pharmacist-led DOAC monitoring clinic and to assess patients' adherence to medication therapy, adherence to guideline-recommended frequencies for blood work, and adverse and non-adverse events.

METHODS

This retrospective chart review involved patients who attended their first visit to the DOAC clinic between October 10, 2017, and May 31, 2018. Patients were followed until November 30, 2018. Data were abstracted from electronic hospital records and the provincial pharmacy network. Descriptive statistics were used to analyze the data: categorical variables were presented as frequencies and percentages; continuous variables were analyzed and presented as means with standard deviations and, where applicable, as medians with interquartile ranges.

RESULTS

Forty-seven patients, who attended a total of 74 clinic visits, were included. Twenty-eight patients (60%) were adherent to their DOAC therapy. All patients had blood work completed before each clinic appointment. The mean time between the first and second sets of blood tests was 6.2 (standard deviation [SD] 1.4) months and between the second and third sets of blood tests was 5.1 (SD 1.0) months. There were no episodes of VTE or major bleeding. There was 1 cerebrovascular accident (3.2 events per 100 person-years, 95% confidence interval [CI] 0.2-15.7) and 5 episodes of clinically relevant non-major bleeding (12.8 events per 100 person-years, 95% CI 4.1-30.1). Pharmacists identified 51 issues at the clinic appointments, of which 48 were medication-related. Referral to the Thrombosis Service physician was required to resolve 8 (16%) of the issues identified. A brief discussion between the Thrombosis Service physician and pharmacist was required to resolve 30 (59%) of the issues, with 13 (25%) resolved by the pharmacist alone.

CONCLUSIONS

This study described the implementation and outcomes of a novel pharmacist-led DOAC clinic. Clinic patients underwent blood work at recommended intervals and received guidance on adherence and adverse events; as such, patients had follow-up that aligned with guideline recommendations.

Insights Into Direct Oral Anticoagulant Therapy Implementation of Stroke Survivors with Atrial Fibrillation in an Ambulatory Setting

OBJECTIVES

To describe how stroke survivors with atrial fibrillation implement direct oral anticoagulant treatment and propose appropriate metrics to describe adherence.

MATERIALS AND METHODS

Stroke patients with atrial fibrillation electronically recorded their self-administered direct oral anticoagulants (apixaban, dabigatran, edoxaban, rivaroxaban) during a 6-month observation phase after hospitalisation for ischemic stroke. Taking and timing adherence, correct dosing days, drug holidays, time of the day and day of the week subsets, dose-to-dose intervals and longest intervals between two consecutive doses were calculated from electronic monitoring data to describe and discuss the implementation phase of adherence.

RESULTS

Data from 41 patients were analysed. Median age was 77 (IQR = 69-84), 63.4% were male and the majority suffered a mild stroke (median NIHSS: 1). Mean taking and timing adherence exceeded 90%. Correct dosing occurred in 86.6% of the days. Seven patients (17.1%) had intake pauses of three or more consecutive days. Patients with twice-daily regimen (70.7%) had higher taking adherence in the morning than in the evening (94.4% versus 89.9%; p = 0.001). No therapy- or anamneses-related characteristic was associated with taking adherence.

CONCLUSIONS

Although adherence to direct oral anticoagulants of stroke patients with atrial fibrillation exceeded 90%, deviant intake patterns such as drug holidays and missed evening doses were common and raise concerns. Appropriate adherence metrics calculated from electronic monitoring data may guide healthcare professionals elucidating patient-tailored adherence-enhancing interventions. ClinicalTrials.gov registration number: NCT03344146.

Creatinine monitoring patterns in the setting of direct oral anticoagulant therapy for non-valvular atrial fibrillation

Guidelines and experts note that patients with atrial fibrillation require regular renal function monitoring to ensure safe use of direct oral anticoagulants (DOACs). Insufficient monitoring could lead to inappropriate dosing and adverse events. Our objective was to describe the frequency of insufficient creatinine monitoring among patients on DOACs, and to describe clinical factors associated with insufficient monitoring. We hypothesized that renal impairment would be associated with insufficient monitoring. A retrospective cohort study was performed with data from the Michigan Anticoagulant Quality Improvement Initiative. Patients were included if they initiated DOAC therapy for stroke prevention related to atrial fibrillation, remained on therapy for ≥ 1 year, and had baseline creatinine and weight measurements. Creatinine clearance (CrCl) was calculated via Cockcroft-Gault equation. Our outcome was the presence of insufficient creatinine monitoring, defined as: < 1 creatinine level/year for patients with CrCl > 50, or < 2 creatinine levels/year for patients with CrCl ≤ 50. Multivariable analysis was done via logistic regression. Study population included 511 patients. In overall, 14.0% of patients received insufficient monitoring. Among patients with CrCl > 50, 11.5% had < 1 creatinine level/year. Among patients with CrCl ≤ 50, 27.1% received < 2 creatinine levels/year. Baseline renal dysfunction was associated with a higher likelihood of insufficient creatinine monitoring (adjusted odds ratio 3.64, 95% confidence interval 1.81-7.29). This shows a significant gap in the monitoring of patients on DOACs-patients with renal impairment are already at higher risk for adverse events. Future studies are needed to describe the barriers in monitoring these patients and to identify how to optimally address them.

Practical use of Direct Oral Anti Coagulants (DOACs) in the older persons with atrial fibrillation

Direct Oral Anticoagulants (DOACs) consistently demonstrated a greater net clinical benefit compared to Vitamin K Antagonists (VKAs) also in persons aged 75 years and over, who account for the largest proportion of AF patients; however, major uncertainties in DOACs prescription have to do with this age group. In this review, persistent uncertainties and implications of frailty and geriatric syndromes on DOACs prescription, and practical use of DOACs in real-world older persons, and will be discussed.

An assay to measure levels of factor Xa inhibitors in blood and plasma

Essentials Direct oral anticoagulants (DOAC) are used for stroke and venous thromboembolism prevention. We report a new assay that measures anti-factor Xa DOAC levels in plasma and whole blood. Rivaroxaban and apixaban can be accurately quantified below trough levels. The ease and accuracy of the assay demonstrate its potential for point-of-care applications.

BACKGROUND

Rivaroxaban and apixaban are the most commonly used anti-factor (F) Xa direct oral anticoagulants (DOAC), with indications for prevention of stroke in nonvalvular atrial fibrillation as well as treatment and prevention of venous thromboembolism. However, lacking is accessibility to a detection method that is able to quantify low levels of anti-FXa DOACs.

OBJECTIVE

We report a new assay that measures anti-FXa DOAC levels in plasma and whole blood.

METHODS

This is achieved by the use of a prothrombin derivative that is labeled with a fluorescent probe (Flu-II), which then acts as the macromolecular substrate to measure residual FXa activity. The Flu-II cleavage is then initiated by the addition of a solution containing FXa, FVa, and phospholipid vesicles composed of 75% PC and 25% PS (PCPS) vesicles with calcium, in the presence of hirudin to prevent feedback activity by the native thrombin generated. The Flu-II cleavage is monitored by fluorescence in real time where the initial rate of fluorescence change is inversely proportional to DOAC levels.

RESULTS

In plasma systems, the assay demonstrates dose-response between 0 and 5 nmol/L rivaroxaban and between 0 and 10 nmol/L apixaban. Corn trypsin inhibitor did not affect this assay. With individual plasma samples, the assay showed excellent consistency and reproducibility. From 2 μL of whole blood, the assay showed dose-response between 0 and 2 nmol/L of DOACs in the final mixture of 100 μL, thus representing up to 100 nmol/L in circulating blood.

CONCLUSION

The assay is ideal for rapidly and accurately measuring DOAC levels in plasma and blood, demonstrating its potential for point-of-care applications.

Excessive Prolongation of Coagulation Time During Treatment With Direct Oral Anticoagulants in Patients With Nonvalvular Atrial Fibrillation

BACKGROUND

Conventional coagulation assays have poor sensitivity and specificity for assessing the anticoagulant effect of direct oral anticoagulants (DOACs). This study aimed to evaluate the causes and consequences of the excessive prolongation of coagulation time in patients with nonvalvular atrial fibrillation who receive DOACs.

METHODS

We retrospectively analysed 1521 patients (age, 66 ± 12 years). The prothrombin time (PT) and activated partial thromboplastin time (APTT) were averaged if they were measured more than twice depending on the respective DOAC and dosage across individuals. Excessive coagulation time prolongation was defined as PT or APTT of >2 standard deviations over the median for each DOAC.

RESULTS

In all, 1913 DOAC cases were found. Excessive prolongation (EP), which was noted in 88 patients (5.8%), was found to be significantly associated with inappropriately high DOAC dosage and body weight (≤ 60 kg). During follow-up (median, 8.9 months), thromboembolisms developed in 10 patients (0.66%) and bleeding events in 85 (5.6%). Bleeding events were significantly higher in patients with excessive prolongation (EP group) than in those without (P = 0.013). Of the 53 patients in the EP group, 15 (28%) were positive for antiphospholipid antibodies, 6 (11%) had inappropriately high prescription dosages, 4 (8%) had coagulation factor deficiencies, and 3 (6%) had severe liver dysfunction.

CONCLUSIONS

Bleeding event rates were remarkably higher in patients receiving DOACs that caused EP of PT or APTT. Thus, following the current guidelines and administering the recommended dose of DOACs are fundamentally important. Patients with the body weight of <60 kg should be considered for dosage reduction or DOAC withdrawal.

How I manage anticoagulant therapy in older individuals with atrial fibrillation or venous thromboembolism

Anticoagulant therapy is the most effective strategy to prevent arterial and venous thromboembolism, but treating older individuals is challenging, because increasing age, comorbidities, and polypharmacy increase the risk of both thrombosis and bleeding. Warfarin and non-vitamin K antagonist oral anticoagulants are underused and often underdosed in the prevention of stroke in older patients with atrial fibrillation because of concerns about the risk of bleeding. Poor adherence to anticoagulant therapy is also an issue for older patients with atrial fibrillation and those at risk of recurrent pulmonary embolism. In this review, we present 5 clinical cases to illustrate common challenges with anticoagulant use in older patients and discuss our approach to institute safe and effective antithrombotic therapy.

Factors That Determine the Prothrombin Time in Patients With Atrial Fibrillation Receiving Rivaroxaban

Rivaroxaban, a direct factor Xa inhibitor, is widely used to reduce the chance of stroke in patients with atrial fibrillation (AF). It is not clear why the prothrombin time (PT) of the international normalized ratio (INR) fails to correlate with treatment using rivaroxaban in patients with AF. In this study, patient characteristics, the rivaroxaban dosage, AF type, drug history, biochemical properties, and hematological profiles were assessed in patients treated with rivaroxaban. In 69 patients with AF receiving rivaroxaban, 27 (39.1%) patients had a normal INR (≤1.1, group 1), 27 (39.1%) patients had a slightly prolonged INR (1.1∼1.5, group 2), and 15 (21.7%) patients had a significantly prolonged INR (>1.5, group 3). Group 1 patients had a higher incidence of a stroke history than did patients in group 2 (P = .026) and group 3 (P = .032). We scored patients with a persistent AF pattern (1 point), paroxysmal AF pattern (0 point), renal function (ie, the creatinine clearance rate in mL/min/1.73 m² of >60 as 0 points, of 30∼60 as 1 point, and of <30 as 2 points), and no history of stroke (1 point), and we found that group 3 had a higher score than groups 2 or 1 (2.9 ± 0.8, 2.4 ± 0.7, and 2 ± 0.7, respectively; P < .05). There were similar incidences of bleeding, stroke, and unexpected hospitalizations among the 3 groups. The PT of the INR is determined by multiple variables in patients with AF receiving rivaroxaban. Rivaroxaban-treated patients with AF having different INR values may have similar clinical outcomes.

Preventability of serious thromboembolic and bleeding events related to the use of oral anticoagulants: a prospective study

AIMS

To determine the preventability of serious adverse drug reactions (ADRs) related to the use of direct oral anticoagulants (DOACs), and to explore contributing factors to preventable ADRs. Results were compared with vitamin K antagonists (VKAs).

METHODS

We conducted a prospective observational study in the emergency departments of two teaching hospitals from July 2015 to January 2016. Patients admitted with a thrombotic or bleeding event while under DOAC or VKA were included. Four independent reviewers assessed causality, seriousness and preventability of ADRs using pilot-tested scales. For cases of serious and potentially preventable ADRs, we performed semi-structured interviews with general practitioners to identify contributing factors to ADRs. The primary outcome was the proportion of serious ADRs that were potentially preventable.

RESULTS

The analysis included 46 DOAC and 43 VKA patients (median age 79 years). Gastrointestinal (n = 34) and intracranial (n = 16) bleedings were the most frequent ADRs. Results were that 53% of DOAC- and 61% of VKA-related serious ADRs were deemed potentially preventable. Prescribing issues and inadequate monitoring were frequent for DOAC and VKA respectively. We identified many causes of preventable ADRs that applied to all oral anticoagulants, such as pharmacodynamic drug interactions and lack of communication.

CONCLUSIONS

More than half of serious ADRs were potentially preventable for both DOACs and VKAs. Interventions focusing on prescribing, patient education and continuity of care should help improve the use of DOACs in practice.

Canadian stroke best practice recommendations: Secondary prevention of stroke, sixth edition practice guidelines, update 2017

The 2017 update of The Canadian Stroke Best Practice Recommendations for the Secondary Prevention of Stroke is a collection of current evidence-based recommendations intended for use by clinicians across a wide range of settings. The goal is to provide guidance for the prevention of ischemic stroke recurrence through the identification and management of modifiable vascular risk factors. Recommendations include those related to diagnostic testing, diet and lifestyle, smoking, hypertension, hyperlipidemia, diabetes, antiplatelet and anticoagulant therapies, carotid artery disease, atrial fibrillation, and other cardiac conditions. Notable changes in this sixth edition include the development of core elements for delivering secondary stroke prevention services, the addition of a section on cervical artery dissection, new recommendations regarding the management of patent foramen ovale, and the removal of the recommendations on management of sleep apnea. The Canadian Stroke Best Practice Recommendations include a range of supporting materials such as implementation resources to facilitate the adoption of evidence to practice, and related performance measures to enable monitoring of uptake and effectiveness of the recommendations. The guidelines further emphasize the need for a systems approach to stroke care, involving an interprofessional team, with access to specialists regardless of patient location, and the need to overcome geographic barriers to ensure equity in access within a universal health care system.

Oral anticoagulant therapy for older patients with atrial fibrillation: a review of current evidence

Atrial fibrillation is more frequent in older patients, who have a higher risk of cardioembolic stroke and thromboembolism. Oral anticoagulant therapy is the standard of treatment for stroke prevention; however, under-prescription is still very common in older patients. The reasons underlying this phenomenon have not been systematically investigated, and true contraindications only partially account for it. An intimate skepticism on the real benefit-risk balance of oral anticoagulant therapy in the oldest patients seems to derive from the fact that most studies supporting it were conducted decades ago and included younger patients, with overall better functional and clinical status. In this review we will focus on the main barriers to anticoagulant therapy prescription in older patients and summarize the available evidences on the efficacy and safety of vitamin K antagonists and direct oral anticoagulants in this population. The encouraging evidence of a higher net clinical benefit of direct oral anticoagulants compared with warfarin should hopefully widen the treatment options also for frail individuals, thereby allowing a greater number of patients to be treated according to current international guidelines.

Evolving Treatments for Arterial and Venous Thrombosis: Role of the Direct Oral Anticoagulants

The direct oral anticoagulants (DOACs) represent a major advance in oral anticoagulant therapy and have replaced the vitamin K antagonists as the preferred treatment for many indications. By simplifying long-term anticoagulant therapy and improving its safety, the DOACs have the potential to reduce the global burden of thrombosis. Postmarketing studies suggest that the favorable results achieved with DOACs in the randomized controlled trials can be readily translated into practice, but highlight the need for appropriate patient, drug and dose selection, and careful follow-up. Leveraging on their success to date, ongoing studies are assessing the utility of DOACs for the prevention of thrombosis in patients with embolic stroke of unknown source, heart failure, coronary artery disease, peripheral artery disease, antiphospholipid syndrome, and cancer. The purpose of this article is to (1) review the pharmacology of the DOACs, (2) describe the advantages of the DOACs over vitamin K antagonists, (3) summarize the experience with the DOACs in established indications, (4) highlight current challenges and limitations, (5) highlight potential new indications; and (6) identify future directions for anticoagulant therapy.

Direct oral anticoagulant use and the incidence of bleeding in the very elderly with atrial fibrillation

Atrial fibrillation (AF) is a major risk factor for stroke in the elderly population. The use of anticoagulation in patients with AF greatly reduces the risk for stroke, but results in an increased risk of bleeding. Over the past several years, direct oral anticoagulants (DOACs, dabigatran, rivaroxaban, and apixaban) have been used in place of warfarin for stroke prevention in AF. We conducted a retrospective cohort study to assess the safety of DOACs in very elderly patients (75+) managed in a health care system encompassing both community and academic settings. We found that 36 % of patients had moderate to severe renal failure (estimated glomerular filtration rate <59 ml/min/1.73 m(2)) at the time of DOAC initiation. 142 patients were followed for a mean of 2.56 years, and five experienced a major bleeding episode while on anticoagulation, for a rate of 1.37 per 100 person years. All major bleeding episodes were associated with a decline in GFR compared to baseline. There were 12 non-major bleeding episodes reported. HAS-BLED scores were similar for those patients who experienced bleeding complications compared to those who did not. 21 % of patients were prescribed an inappropriately low dose of DOAC based on approved recommendations. DOACs appear to be a safe form of anticoagulation in very elderly patients with AF. However, the decline in GFR among patients with major bleeding highlights the importance of routine renal function monitoring.

Thrombosis, Hypercoagulable States, and Anticoagulants

Patients with derangements of secondary hemostasis resulting from inherited or acquired thrombophilias are at increased risk of venous thromboemboli (VTE). Evaluation of a patient with suspected VTE proceeds via evidence-based algorithms that involve computing a pretest probability based on the history and physical examination; this guides subsequent work-up, which can include D dimer and/or imaging. Testing for hypercoagulable disorders should be pursued only in patients with VTE with an increased risk for an underlying thrombophilia. Direct oral anticoagulants are first-line VTE therapies, but they should be avoided in patients who are pregnant, have active cancer, antiphospholipid antibody syndrome, severe renal insufficiency, or prosthetic heart valves.

Overcoming global challenges in stroke prophylaxis in atrial fibrillation: The role of non-vitamin K antagonist oral anticoagulants

Atrial fibrillation is the world's most common sustained cardiac arrhythmia and is associated with a significantly increased risk of stroke. The global burden of atrial fibrillation is rising, commensurate with the ageing population. Well-controlled vitamin K antagonist-based anticoagulation has been shown to reduce the risk of stroke secondary to atrial fibrillation by two-thirds. However, patients with atrial fibrillation have frequently been denied anticoagulation because of a variety of perceived risks related to bleeding, falls, chronological age, and poor compliance. Even when vitamin K antagonists are used, maximum benefit and safety are only delivered when high quality control of therapy (TTR > 70%) is achieved, which has proven remarkably difficult in many health-care systems and amongst many patient groups. The non-vitamin K antagonist oral anticoagulants (NOACs) offer solutions to many of the challenges of achieving widespread, safe, and effective anticoagulation for stroke prophylaxis in atrial fibrillation, yet their uptake into routine clinical practice remains variable. The evidence supporting their more widespread use to overcome the challenges of stroke prophylaxis for atrial fibrillation is reviewed in this article.

Practical Guide to Direct New Oral Anticoagulant Use for Secondary Stroke Prevention in Atrial Fibrillation

OPINION STATEMENT

Anticoagulation remains the optimal treatment choice for secondary stroke prevention of AF. The vitamin K antagonists (VKAs) have been the choice of treatment for the last 60 years, but the new oral anticoagulants are now a safe option for treatment of non-valvular AF (NVAF) in the right patient population, taking into account age, renal function, bleeding risk, cardiovascular comorbidities, cost, and drug interactions.

Management of antithrombotic therapy during cardiac implantable device surgery

Anticoagulants are commonly used drugs that are frequently encountered during device placement. Deciding when to halt or continue the use of anticoagulants is a balance between the risks of thromboembolism versus bleeding. Patients taking warfarin with a high risk of thromboembolism should continue to take their warfarin without interruption during device placement while ensuring their international normalized ratio remains below 3. For patients who are taking warfarin and have low risk of thromboembolism, either interrupted or continued warfarin may be used, with no evidence to clearly support either strategy. There is little evidence to support continuing direct acting oral anticoagulants (DOACs) for device implantation. The timing of halting these medications depends largely on renal function. If bleeding occurs, warfarin׳s anticoagulation effect is reversible with vitamin K and activated prothrombin complex concentrate. There are no DOAC reversal agents currently available, but some are under development. Regarding antiplatelet agents, aspirin alone can be safely continued while clopidogrel alone may also be continued, but with a slightly higher bleeding risk. Dual antiplatelet therapy for bare-metal stent/drug-eluting stent implanted within 4 weeks/6 months, respectively, should be continued due to high risk of stent thrombosis; however, if they are implanted after this period, then clopidogrel can be halted 5 days before the procedure and resumed soon after, while aspirin is continued. If the patient is taking both aspirin and warfarin, aspirin should be halted 5 days prior to the procedure, while warfarin is continued.