Stroke risk similar in paroxysmal and sustained AF
Most clinicians are aware of the risk of stroke in patients with permanent or persistent atrial fibrillation (AF) and the need for thromboprophylaxis. This study looked at an often neglected group: those with paroxysmal AF.
Current guidelines advise treating paroxysmal AF in the same way as sustained AF but the evidence is weak, with only one retrospective analysis comparing the risk of stroke in patients with paroxysmal AF vs chronic AF (analysis of the SPAF trials, performed 15 years ago and limited to patients treated with aspirin).
The ACTIVE W trial showed that warfarin is more effective than aspirin plus clopidogrel for the prevention of vascular events (stroke, embolism, MI and vascular death) in patients with AF.
A recent substudy of this trial looked at the risk of stroke in 1,202 patients with paroxysmal AF compared with 5,495 with sustained AF, and the effectiveness of thromboprophylaxis in these patients.
There was no significant difference in the risk of stroke or non-CNS systemic embolism for patients with paroxysmal AF compared with sustained AF. The risk for the combined end point was 2.0 and 2.2 per 100 patient-years respectively.
The incidence of stroke and non-CNS embolism was lower for patients treated with oral anticoagulation therapy, irrespective of the type of AF.
This substudy has shown that the risk of stroke is similar, irrespective of whether AF is paroxysmal or sustained, and that anticoagulation therapy is equally effective in both groups. Other factors, such as age and cardiovascular comorbidity, remain central to the ultimate choice of thromboprophylaxis in these patients.
The other pertinent question is what degree of paroxysmal AF should be considered harmful. The ACTIVE W study did not provide the answer. However, the forthcoming ASSERT trial will use pacemaker memory to determine the number of episodes and the duration of paroxysmal AF, which will then be linked to stroke risk and should shed light on this issue.
Hohnloser SH, Pajitnev D, Pogue J et al. Incidence of Stroke in Paroxysmal Versus Sustained Atrial Fibrillation in Patients Taking Oral Anticoagulation or Combined Antiplatelet Therapy. An ACTIVE W substudy. J Am Coll Cardiol 2007;50:2156-61Table 1: QOF2 AF indicators Reviewer
Dr Peter Savill
GPwSI Cardiology, Southampton