Optimising the Use of Thromboprophylaxis in Atrial Fibrillation (AF): Exploring Factors Affecting Decision-Making
- Publication Type:
- Thesis
- Issue Date:
- 2017
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The risk of stroke is five-folds higher among patients with atrial fibrillation (AF) in comparison to those without AF. In fact, thromboembolic strokes occurring in AF patients are more disabling and fatal than in patients without AF. This increase in morbidity and mortality due to stroke in patients with atrial fibrillation has become a major global healthcare burden, and for this reason stroke prevention (using antithrombotic agents as the mainstay therapy) has been a critical feature of AF management. Although warfarin (an oral vitamin K antagonist) has been traditionally used for preventing stroke in AF patients, its complex pharmacology (i.e., narrow therapeutic index requiring regular therapeutic monitoring, its interactions with food, alcohol, and other medications), and prescribers’ concerns regarding patients’ nonadherence to the therapy make the decision-making around the initiation of therapy quite complicated. Consequently, anticoagulants are underutilised in many ‘at-risk’ patients, exposing them to an increased risk of a preventable stroke. Our research in a hospital-based study that used decision-making support tool i.e., a computerised antithrombotic risk assessment tool (CARAT- a tool developed based on local and international guidelines assists in therapy selection based on patients’ individualised risk versus benefit assessment) observed a marginal increase in anticoagulation prescription among eligible patients (57.8% vs 64.7%, P=0.35) in comparison to the baseline prescription. However, many at-risk patients were still not prescribed anticoagulants as recommended by CARAT, and the clinicians’ agreement with CARAT recommendation was low. This might have been due to clinicians’ perceived fears of risk such as falls, bleeding, and patients’ nonadherence to the therapy. To increase clinicians’ acceptance for CARAT tool, studies should further explore its validity in predicting clinical outcomes.
Recently, the direct oral anticoagulants (DOACs) have become available for thromboprophylaxis in patients with AF. These agents have safety and efficacy (in stroke prevention) profiles comparable to warfarin therapy. They also offer some practical advantages over warfarin in terms of not requiring regular therapeutic drug monitoring, plus their interactions with food, alcohol and other medications is limited. However, the DOACs are not completely devoid of risks or challenges to their use. These challenges include: a) the lack of specific drug monitoring tests; b) complicated management of renally-impaired patients; c) limited access to and/or unavailability of antidotes for the management of DOAC-related acute bleeding; d) high ‘out-of-pocket’ costs for patients in some countries; and e) the potential for patient nonadherence (due to the more frequent dosing required with dabigatran and apixaban). Such conditions present specific challenges for clinicians when prescribing these medications for long-term stroke prophylaxis in patients with AF. In 2014 following the listing of DOACs on the pharmaceutical benefits scheme (PBS) (which subsidises DOACs for stroke prevention in AF), it was important to report their utilisation of anticoagulant prescription in local Australian settings. It was also necessary to updated CARAT 2.0 in assessing whether the prescriptions were based on these revised guidelines. Our study (in a hospital setting in Sydney) found that 52.0% of the people were prescribed anticoagulants. Warfarin was the first-choice anticoagulant prescribed for two-thirds of patients, while the remaining one-third were on DOCAs. However, most of the patients eligible for anticoagulants were not prescribed it but were either prescribed antiplatelets or kept on nil therapy.
In this thesis a structured literature review explored factors influencing patients’ preference and adherence for warfarin versus DOACs. This is because research suggests that patients have an important role in the decision-making process for antithrombotic therapy selection in AF. This review discussed patients’ perspectives on medications. Here the findings were synthesised to present a framework depicting the five interacting dimensions of adherence: 1) therapy-related factors; 2) patient-related factors; 3) condition-related factors; 4) social–economic factors; and 5) health system factors. From this study, it was clear that patients’ views about treatment must be incorporated into the decision-making process to facilitate a) treatment; b) adherence; and c) achieve good clinical outcomes. In line with this study, another study then evaluated the information within web-based resources designed to educate patients on thromboprophylaxis in AF. The content and thematic analysis were conducted on these resources. It was found that the information provided in these resources were varied. It was found that implied bias of some resources towards specific anticoagulant therapies and their imbalanced information on the importance of anticoagulation in AF might misinform or confuse patients. Therefore, patients’ engagement in shared decision-making and adherence to medicines might be undermined by the suboptimal quality of information provided in these resources.
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