Subclinical atrial fibrillation: how hard should we look?

More than three decades ago, an analysis from the Framingham Heart Study revealed that atrial fibrillation (AF) increases the risk of stroke by a factor of five in non-rheumatic AF and by a factor of 17 in rheumatic AF.1 Since then, it has convincingly been shown that anticoagulation is one of the most effective secondary stroke prophylactic treatment options, which reduces the risk of stroke by 2/3,2 even in an older population.3 AF may occur in different types and in an individual patient often starts with paroxysmal AF, but later becomes persistent or permanent AF.4 Interestingly, the risk of stroke or systemic embolism is influenced by cardiovascular risk factors such as hypertension, diabetes or history of stroke, but not by type of AF.5 Most patients with paroxysmal AF had never reported typical clinical symptoms, which supports the argument of a clinically silent disease, especially during the earlier stages.6 Within the last few years, research interest has grown in the clinical relevance of AF at an even earlier stage, before the clinical detection of AF. It has now convincingly been shown that the first manifestation of clinical AF is often preceded by short episodes of ‘subclinical’ or ‘undiagnosed' AF. These data are mostly derived from patients with implantable pacemaker devices which allow a continuous monitoring of cardiac rhythm and are often able to record changes in it.7 ,8 Earlier this year, the Asymptomatic Atrial Fibrillation and Stroke Evaluation in Pacemaker Patients and the Atrial Fibrillation Reduction Atrial Pacing Trial (ASSERT) investigators reported data on 2580 hypertensive older pacemaker patients.9 These patients were aged 65 years or older and had recently been implanted with a pacemaker or defibrillator. Patients with a history of AF or atrial flutter and patients on oral anticoagulation with a …