Atrial Fibrillation: Atrial High-Rate Events (AHRES): Look and You Will Find-Then What?

The article by Halcox et al 1 describes the REHEARSE-AF study (Assessment of Remote Heart Rhythm Sampling Using the AliveCor Heart Monitor to Screen for Atrial Fibrillation), a randomized trial of screening for atrial fibrillation (AF) with a smartphone-based single-lead electrocardiographic capture system in 1001 patients ≥65 years of age with a CHA2DS2-VASc score of ≥ 2 and without a history of AF. Patients were randomized either to biweekly electrocardiographic recordings with the iPhone device (iECG group; n=500) or to routine care (control group; n=501) over a 12-month period. Not surprisingly, more patients with AF were identified in the iECG group (n=19) than in the control group (n=5). The data from this study confirm results from studies with implanted pacemakers, cardioverter-defibrillators, and loop recorders2–9 and other AF screening studies10,11 that, in patients unknown to have AF, particularly those with cardiovascular comorbidities, the more we look for AF, the more we will find it. As Sophocles mused more generally, “Look and you will find–what is unsought will go undetected.” But is there a need to know about asymptomatic episodes of so-called subclinical AF (SCAF)? What are the implications of such a finding? Clinical AF is associated with increased rates of stroke, heart failure, mortality, hospitalization, and cognitive decline, much of which may present suddenly and constitute irretrievable harm.12 Therefore, there is a strong prima facie argument that it would help to know the onset of AF as soon as possible, but that is true only if we have therapeutic strategies that can prevent the adverse consequences of AF both safely and effectively. Anticoagulation for AF leads to a reduction in stroke and mortality and perhaps halts the decline of cognitive function and the onset of dementia. It seems that a solid case might be made to look for AF and to react to its discovery by recommending anticoagulation. But is it that simple? The AF detected by continuous monitoring with implanted devices, or frequent electrocardiographic sampling as in the REHEARSE-AF study, may not have the same adverse consequences as in patients who present with clinically symptomatic AF. We have learned that paroxysmal and perhaps persistent forms of AF may have less risk of stroke than permanent AF.13,14 There also seems to be a direct relationship between stroke and the duration of episodes of AF or the overall burden of AF. Do the possibly short and infrequent bouts of atrial high-rate events (AHREs), or SCAF, imply a clinically significant incidence of adverse consequences? Several studies of patients with implantable devices have tried to quantify the duration of AF that would merit oral anticoagulation on the basis of the incidence of stroke or systemic embolism. They all showed an increased rate of stroke associated with AHREs. Representative data from these studies indicate that the duration of the AF is of particular importance. The MOST study (Atrial Diagnostics Ancillary Study of the Mode Selection Trial; a retrospective study) found that AF as short as 5 Atrial Fibrillation Atrial High-Rate Events (AHRES): Look and You Will Find–Then What?