This study aims to determine if treatment with apixaban, compared with aspirin, will reduce the risk of ischemic stroke and systemic embolism in patients with device-detected sub-clinical atrial fibrillation and additional risk factors for stroke.
Device-detected sub-clinical atrial fibrillation (SCAF) is a new disorder that has been recognized since the availability of implantable devices capable of long term continuous heart rhythm monitoring. It is characterized by one or more runs of rapid atrial arrhythmia detected by the device without symptoms and without any clinical atrial fibrillation (AF) detected by the usual methods, (i.e. electrocardiogram, Holter monitor, etc.). In the ASSERT trial, SCAF was detected by a pacemaker or implantable cardioverter defibrillator (ICD) in nearly 40% of patients during 2 and a half years of follow up. The presence of SCAF increased stroke risk by 2.5-fold (1). The risk of stroke or systemic embolism among patients with SCAF and a CHADS2 score ≥ 4 was 2.75% per year. Oral anticoagulation is effective and safe for stroke prevention in patients with clinical atrial fibrillation, but it is unknown if the same risk benefit ratio exists for anticoagulation therapy in patients with SCAF (2;3). SCAF differs from clinical AF in being of shorter duration, being asymptomatic, and often have a more regular rhythm in the right atrium where it is typically detected. Data ASSERT suggest that the increase in stroke risk with SCAF may be less than the increase with clinical AF. Therefore opinion leaders have written that the role of oral anticoagulation for the treatment of SCAF is uncertain and that randomized trials of anticoagulation are needed (4;5). Recent surveys of pacemaker clinic practice indicate that only 25% of patients with SCAF are treated with oral anticoagulation (6;7). Thus there is clinical equipoise for a trial of oral anticoagulation compared to aspirin in higher risk patients with SCAF.
Apixaban is a Factor Xa inhibitor that is an effective and safe anticoagulant. It has been shown to have an excellent risk benefit profile for stroke prevention in clinical AF (14, 15). It is highly suitable to test if oral anticoagulation therapy will reduce the risk of stroke or systemic embolism in SCAF.
Patients will be randomized double-blind to receive apixaban or aspirin. Apixaban dose will be 5 mg twice daily (2.5 mg twice daily if 2 or more of: age > 80, weight ≤ 60 kg or serum creatinine ≥ 133 mmol/L). Those assigned to aspirin will receive a dose of 81 mg daily. The study will be event driven and will continue until 248 patients have experienced a primary outcome event.
- Atrial Fibrillation
- Atrial Tachyarrhythmia
- Stroke Risk
- Pacemaker, Artificial
- Defibrillators, Implantable
- Aspirin Drug
Intervention Desc: aspirin 81 mg once daily ARM 1: Kind: Experimental Label: Control Description: Aspirin 80-100 mg once daily
- Apixaban Drug
Intervention Desc: apixaban at a dose of 5 mg twice daily (2.5 mg twice daily if 2 or more of: age > 80, weight ≤ 60 kg or serum creatinine ≥ 133 mmol/L) ARM 1: Kind: Experimental Label: Intervention Description: Apixaban, 5 mg twice daily (or 2.5 mg twice daily if 2 or more of: age > 80, weight ≤ 60 kg or serum creatinine ≥ 133 mmol/L)
- Allocation: Randomized
- Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor)
- Purpose: Prevention
- Endpoint: Safety/Efficacy Study
- Intervention: Parallel Assignment
|Type||Measure||Time Frame||Safety Issue|
|Primary||Composite of ischemic stroke and systemic embolism||event driven duration - mean follow-up time anticipated: 3 years||No|
|Secondary||Major bleeding||event driven duration - mean follow-up time anticipated: 3 years||Yes|
|Primary||Major Bleed||duration of follow-up||Yes|
|Secondary||Ischemic Stroke||Duration of Follow-up||No|
|Secondary||Myocardial Infarction||Duration of follow-up||No|
|Secondary||Cardiovascular Death||Duration of follow-up||No|
|Secondary||All-cause Death||Duration of follow-up||No|
|Secondary||Composite of stroke, MI, SE and death||Duration of follow-up||No|
|Secondary||Composite of stroke, MI, SE, death and major bleeding||Duration of follow-up||No|