Atrial fibrillation is the most common sustained arrhythmia encountered in clinical practice. The global prevalence of atrial fibrillation is rising due to ageing populations and concomitant conditions. In Australia, atrial fibrillation is thought to affect 3.8% of adults aged 60 years and over.
Atrial fibrillation is a condition where the atria beat irregularly and chaotically. This may lead to pooling of blood as the heart is no longer able to move blood through the atria efficiently. For some people, atrial fibrillation is a silent condition that does not impact their quality of life. For other people, symptoms may be experienced including shortness of breath, palpitations, and fatigue. One of the most serious complications of atrial fibrillation is an increased susceptibility to thromboembolic events.
Stroke is a recognised consequence of atrial fibrillation and anticoagulation is an important preventative measure. Historically, evidence to support the use of anticoagulation in this population has been generated with vitamin-K antagonists (VKA). Four non-VKA oral anticoagulants (NOAC, also known as novel oral anticoagulants) have been found to be at least as effective and safer than VKAs in this setting. These agents include rivaroxaban, apixaban, dabigatran, and edoxaban (not currently available in Australia). Additional evidence on the effectiveness of NOACs is gathering in the form of additional clinical trials and retrospective registries.
The XANTUS trial is the first large-scale prospective observational study of a NOAC in patients with non-valvular atrial fibrillation. It involved over 6,700 rivaroxaban-treated patients in Europe, Canada, and Israel, with a mean CHADS2-score of 2.0. This compares to a score of 3.5 in the original pivotal Rocket-AF trial for rivaroxaban. At the end of the one-year observational period in XANTUS, the rate of major bleeding was 2.1% (compared to 3.6% in Rocket-AF). XANTUS also demonstrated effective stroke and systemic embolism prevention in the real-world setting, with an annual stroke rate of 0.7% (compared to an annual stroke risk of 4% for untreated patients with a CHADS2 score of 2.0).
Medication compliance is also a major concern in stroke prevention as discontinuation of anticoagulants could potentially leave patients unprotected from the risk of embolic strokes. This is true even for patients who do not experience symptoms of atrial fibrillation. Recent data demonstrates a discontinuation rate of 32% at six months and 38% at 12 months for patients taking VKAs for atrial fibrillation. In comparison, discontinuation of rivaroxaban was found to occur in only 20% of patients at 12 months.
For further information on this topic, please ask your HPS Pharmacies Pharmacist about the new Lecture Series topic ‘Treatment and Management of Atrial Fibrillation.’
- Ball J, Thompson DR, Ski CF, Carrington MJ, Gerber T, Stewart S. Estimating the current and future prevalence of atrial fibrillation in the Australian adult population. Med J Aust. 2015; 202(1): 32-5.
- Camm AJ, Amarenco P, Haas S, Hess S, Kirchhof P, Kuhls S, et al. XANTUS: a real-world, prospective, observational study of patients treated with rivaroxaban for stroke prevention in atrial fibrillation. Eur Heart J. 2016; 37(14): 1145-53.