Asymptomatic Atrial Fibrillation After Cryptogenetic Stroke: Incidence, Clinical Significance, and Therapeutic Implications

A. Raviele
2015 Circulation: Arrhythmia and Electrophysiology  
A trial fibrillation (AF) is the most common sustained cardiac arrhythmia, with a prevalence of 1% to 2% in the general population; this increases with age, reaching >8% in subjects over 80 years of age. 1,2 The arrhythmia is independently associated with an increased risk of stroke, which is about 5-fold higher in AF-affected patients than in controls. 3 AF is considered to be the cause of ischemic stroke in 15% to 17% of cases. 3,4 Interestingly, AF-related strokes cause higher mortality and
more » ... isability than strokes unrelated to AF 4,5 and stroke risk is independent of the type of AF (paroxysmal, persistent, or permanent). 6,7 The rate of stroke caused by AF can be significantly reduced (by 60% to 70%) by the use of warfarin or novel oral anticoagulants. 8, 9 Article see p 263 AF is usually symptomatic, causing symptoms, such as palpitations, dyspnea, fatigue, angina, dizziness, and syncope. 10 Not rarely, however, the arrhythmia is not perceived at all by the patient and, in this case, is defined as asymptomatic, silent, undetected, occult, or subclinical AF. According to the EURObservational Research Programme-AF (EORP-AF) Pilot General Registry, almost 40% of the AF patients who are seen in daily cardiology practice are completely asymptomatic, and another 30% have only mild symptoms. 11 The prevalence of silent AF varies in different clinical settings, ranging from 0% to 31% in postablation patients 12, 13 to 16% to 25% as incidental finding at standard ECG, 2,14 54% to 70% in patients treated with antiarrhythmic drugs, and 15,16 up to 51% to 74% in pacemaker/implantable cardioverterdefibrillator recipients. 17, 18 Stroke is the leading cause of long-term adult disability and mortality in the developed world. Approximately, 30% to 40% of all strokes are cryptogenetic or caused by unknown causes. 19,20 A possible explanation for these strokes is occult or subclinical AF. Several studies have shown that the incidence of silent AF after an undiagnosed stroke may be as high as 5% to 20%. 21 In daily clinical practice, it is important after cryptogenetic stroke to detect episodes of silent AF to start appropriate anticoagulation therapy and reduce the risk of future events. In this issue of Circulation: Arrhythmia and Electro physiology, Dussault et al 22 report a systematic review and meta-analysis of electrocardiographic monitoring to detect AF after undiagnosed ischemic stroke or transient ischemic attack. The main purpose of the meta-analysis was to assess the relationship between the duration of ECG monitoring and the proportion of newly diagnosed AF. A total of 31 studies met the inclusion criteria (including 3 randomized controlled trials). The overall proportion of newly detected AF was 7.4%: 5.1% on short (<3 days) and 15% on long (>7 days) ECG monitoring. Extending ECG monitoring from 24 hours to 30 and 180 days increased the detection of AF from 4.2% to 15.2% and 29.15%, respectively. In the 3 randomized controlled trials, 23-25 long-term monitoring was associated with 7.26 odds of detecting AF in comparison with traditional short-term monitoring. These results clearly show that more is better than less with regard to monitoring for the detection of asymptomatic AF after cryptogenetic stroke and support the recent guideline recommendation of at least 30 days of ECG monitoring after a stroke with undiagnosed cause. 26 The main limitation of this article is the significant degree of heterogeneity observed among studies and the inability to detect the potential sources of this heterogeneity, despite subgroup analyses performed by the authors on prespecified variables. Indeed, many other factors, besides the length of monitoring, can influence the detection rates of AF in patients with cryptogenetic stroke. These include the definition of AF duration that constitutes an episode (>30 seconds, >2 minutes, > 6 minutes, etc), the interval from the index stroke to the start of monitoring (from hours to days or months), and patient characteristics and selection (age and sex of patients, presence of comorbidities, type and burden of AF, value of CHADS 2 or CHA 2 DS 2 -VASc risk score systems, etc). Despite this limitation, it is evident that silent AF is a common finding in patients with cryptogenetic stroke if prolonged electrocardiographic monitoring is performed soon after the index event, reaching ≤30% at 3 months if an implantable loop recorder is used. 22 But what is the clinical and prognostic significance of silent AF after cryptogenetic stroke? At present, the literature is lacking in data on this issue; the only information we have is indirect and comes from patients treated with implantable electronic devices (pacemaker, implantable cardioverter-defibrillator, or CRT device) for an arrhythmic problem. 17, 18, [27] [28] [29] [30] [31] In these patients, detection of silent AF by the device is associated with an increased risk of thrombo-embolic events, with a hazard ratio ranging from 2.2 to 9.4. 32 According to a (Circ Arrhythm Electrophysiol. 2015;8:249-251.
doi:10.1161/circep.115.002835 pmid:25900985 fatcat:5zycilokorhsljkixtqm26i2au