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Silent Atrial Fibrillation and Cryptogenic Strokes

Published:October 15, 2016DOI:https://doi.org/10.1016/j.amjmed.2016.09.027

      Abstract

      A new suspected cause of cryptic strokes is “silent atrial fibrillation.” Pacemakers and other implanted devices allow continuous recording of cardiac rhythm for months or years. They have discovered that short periods of atrial fibrillation lasting minutes or hours are frequent and usually are asymptomatic. A meta-analysis of 50 studies involving more than 10,000 patients with a recent stroke found that 7.7% had new atrial fibrillation on their admitting electrocardiogram. In 3 weeks during and after hospitalization, another 16.9% were diagnosed. A total of 23.7% of these stroke patients had silent atrial fibrillation; that is, atrial fibrillation diagnosed after hospital admission. Silent atrial fibrillation is also frequent in patients with pacemakers who do not have a recent stroke. In a pooled analysis of 3 studies involving more than 10,000 patients monitored for 24 months, 43% had at least 1 day with atrial fibrillation lasting more than 5 minutes. Ten percent had atrial fibrillation lasting at least 12 hours. Despite the frequency of silent atrial fibrillation in these patients with multiple risk factors for stroke, the annual incidence of stroke was only 0.23%. When silent atrial fibrillation is detected in patients with recent cryptogenic stroke, anticoagulation is indicated. In patients without stroke, silent atrial fibrillation should lead to further monitoring for clinical atrial fibrillation rather than immediate anticoagulation, as some have advocated.

      Keywords

      Clinical Significance
      • Silent atrial fibrillation is very frequent in patients with recent cryptogenic stroke. Anticoagulation is indicated in these patients if atrial fibrillation is diagnosed.
      • Silent atrial fibrillation is also very frequent in patients without a history of recent stroke.
      • Stroke is uncommon in patients with silent atrial fibrillation who do not have a history of recent stroke. If silent atrial fibrillation is detected in these patients, further electrocardiographic monitoring rather than anticoagulation is indicated.
      More than 25% of ischemic strokes per year in the US are classified as cryptogenic: that is, after extensive evaluation, no cause is determined.
      • Saver J.L.
      Cryptogenic stroke.
      Some
      • Mas J.L.
      • Arquizan C.
      • Lamy C.
      • et al.
      Recurrent cerebrovascular events associated with patent foramen ovale, atrial septal aneurysm, or both.
      • Di Tullio M.R.
      • Sacco R.L.
      • Sciacca R.R.
      • et al.
      Patent foramen ovale and the risk of ischemic stroke in a multiethnic population.
      have suggested that cryptogenic strokes may be due to paradoxical embolism of venous thrombi across a patent foramen ovale. This led to surgical closure of patent foramen ovales in some patients, and then patent foramen ovale closure by a transvenous device in thousands of patients.
      • Dalen J.E.
      Are patients with a patent foramen ovale at increased risk of stroke? A billion dollar question.
      However, 3 randomized clinical trials failed to find a benefit of patent foramen ovale closure.
      • Dalen J.E.
      • Alpert J.S.
      Cryptogenic strokes and PFOs: what's the right treatment?.
      Paradoxical embolism is a rare cause of ischemic strokes.
      • Dalen J.E.
      • Alpert J.S.
      Cryptogenic strokes and PFOs: what's the right treatment?.
      Cardioembolism is the commonest cause of ischemic stroke,
      • Grau A.J.
      • Weimar C.
      • Buggle F.
      • et al.
      Risk factors, outcome and treatment in subtypes of ischemic stroke. The German stroke data bank.
      and atrial fibrillation is the commonest cause of cardioembolism.
      • Dalen J.E.
      Prevention of embolic strokes. The role of the American College of Chest Physicians.
      The percentage of ischemic strokes due to cardioembolism increases with age; in one series it accounted for <5% of strokes in patients younger than 45 years of age and 53% in patients older than 70 years. This parallels the increasing prevalence of atrial fibrillation with increasing age.
      • Tsang T.S.
      • Petty G.W.
      • Barnes M.E.
      • et al.
      The prevalence of atrial fibrillation in incident stroke cases and matched population controls in Rochester, Minnesota.
      The risk of stroke in patients with atrial fibrillation can be determined by a score based on the presence or absence of congestive heart failure, hypertension, diabetes, history of stroke or transient ischemic attack (TIA), vascular disease, age >75 years, sex (CHA2DS2-VASc).
      • Lip G.Y.
      • Nieuwlaat R.
      • Pisters R.
      • et al.
      Refining clinical risk stratification for predicting stroke and thromboembolism in atrial fibrillation using a novel risk factor-based approach.
      Multiple randomized clinical trials have shown that anticoagulation with warfarin or one of the newer oral anticoagulants reduces the rate of stroke in patients with atrial fibrillation by at least two-thirds and reduces death by 25%.
      • Kirchhof P.
      • Benussi S.
      • Kotecha D.
      • et al.
      2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS: the Task Force for the management of atrial fibrillation of the European Society of Cardiology (ESC) developed with the special contribution of the European Heart Rhythm Association (EHRA) of the ESC endorsed by the European Stroke Organisation (ESO).
      Anticoagulation is effective in patients with paroxysmal atrial fibrillation as well as patients with chronic atrial fibrillation. Hohnloser et al
      • Hohnloser S.H.
      • Pajitnev D.
      • Pogue J.
      • et al.
      Incidence of stroke in paroxysmal versus sustained atrial fibrillation in patients taking oral anticoagulation or combined antiplatelet therapy.
      randomized 6706 patients with atrial fibrillation to treatment with oral anticoagulants or aspirin plus clopidogrel to prevent strokes. Twelve hundred two of these patients had paroxysmal atrial fibrillation defined as sinus rhythm at randomization, but atrial fibrillation by electrocardiogram (ECG) on 2 separate occasions, at least 2 weeks apart in the 6 months prior to randomization. The other 5495 patients had chronic atrial fibrillation. The incidence of stroke during follow-up in those with paroxysmal atrial fibrillation (2.0%/y) was not significantly different from those with chronic atrial fibrillation (2.2%/y).
      Hart et al
      • Hart R.G.
      • Pearce L.A.
      • Rothbart R.M.
      • et al.
      Stroke with intermittent atrial fibrillation: incidence and predictors during aspirin therapy.
      compared the rate of stroke in patients treated with aspirin in 1126 patients with permanent atrial fibrillation with 460 patients with intermittent atrial fibrillation on admission, but sinus rhythm documented within the prior 6 months. The rates of stroke during 2-year follow-up was nearly the same: 3.2% vs 3.3%.
      • Hart R.G.
      • Pearce L.A.
      • Rothbart R.M.
      • et al.
      Stroke with intermittent atrial fibrillation: incidence and predictors during aspirin therapy.

      Detection of Silent Atrial Fibrillation

      The ability of modern dual-chamber pacemakers to function as permanently implanted cardiac monitors has led to the observation that transient atrial fibrillation lasting minutes or hours is frequent in patients with pacemakers. The vast majority of these episodes are asymptomatic and are termed “silent atrial fibrillation.”
      • Boriani G.
      • Glotzer T.V.
      • Santini M.
      • et al.
      Device-detected atrial fibrillation and risk for stroke: an analysis of >10,000 patients from the SOS AF project (stroke prevention on strategies based on atrial fibrillation information from implanted devices).
      These observations lead to many important questions. Are patients with episodes of silent atrial fibrillation at increased risk of stroke? Is silent atrial fibrillation a major cause of cryptic stroke? How long must these episodes last to increase the incidence of left atrial thrombi? Would oral anticoagulants prevent strokes in these patients? Which patients with silent atrial fibrillation should be anticoagulated?

      Incidence of Clinical Atrial Fibrillation and Silent Atrial Fibrillation in Patients with Ischemic Stroke

      Approximately 20% of patients presenting with ischemic stroke are known to have atrial fibrillation prior to the stroke.
      • Sposato L.A.
      • Cipriano L.E.
      • Saposnik G.
      • et al.
      Diagnosis of atrial fibrillation after stroke and transient ischaemic attack: a systematic review and meta-analysis.
      Atrial fibrillation first detected AT or after admission for stroke is termed silent atrial fibrillation. Silent atrial fibrillation during the admission for stroke can be detected by serial ECGs, Holter monitoring, continuous telemetry, or continuous ECG monitoring. After discharge, external Loop Event monitors
      • Higgins P.
      • MacFarlane P.W.
      • Dawson J.
      • et al.
      Non-invasive cardiac event monitoring to detect atrial fibrillation after ischemic stroke.
      and implantable loop recorders
      • Seet R.C.S.
      • Friedman P.A.
      • Rabinstein A.A.
      Prolonged rhythm monitoring for the detection of occult paroxysmal atrial fibrillation in ischemic stroke of unknown cause.
      and outpatient telemetry can be utilized for long-term monitoring.
      Sposato et al
      • Sposato L.A.
      • Cipriano L.E.
      • Saposnik G.
      • et al.
      Diagnosis of atrial fibrillation after stroke and transient ischaemic attack: a systematic review and meta-analysis.
      performed a meta-analysis of 50 studies comprising 11,658 patients with ischemic stroke from 1980 until 2014 who were assessed for silent atrial fibrillation.
      As shown in the Table, the ECG on admission detected new atrial fibrillation in 7.7%. During the hospital admission, new atrial fibrillation was documented in another 5.1%. After discharge, serial Holter monitors detected 10.7% with atrial fibrillation. Additional postdischarge testing with mobile telemetry and external or implantable loop recording detected an additional 16.9%. Of note, the percentage detected was essentially the same with mobile telemetry or external or implantable loop recorders. The total percentage of patients with new (or silent) atrial fibrillation was 23.7%
      • Sposato L.A.
      • Cipriano L.E.
      • Saposnik G.
      • et al.
      Diagnosis of atrial fibrillation after stroke and transient ischaemic attack: a systematic review and meta-analysis.
      (Table).
      TableDetection of New AF in Patients with Recent Stroke or TIA
      • Sposato L.A.
      • Cipriano L.E.
      • Saposnik G.
      • et al.
      Diagnosis of atrial fibrillation after stroke and transient ischaemic attack: a systematic review and meta-analysis.
      Detected# Tested% New AF
      Admission ECG28967.7%
      In-hospital monitoring46185.1%
      Postdischarge, serial Holters10.7%
      Postdischarge additional tests172316.9%
       Mobile telemetry41715.3%
       External loop recording82916.2%
       Implant loop recording47716.9%
      Overall proportion of patients with new (silent) AF = 23.7%
      AF = atrial fibrillation; ECG = electrocardiogram; TIA = transient ischemic attack.

      Incidence of Silent Atrial Fibrillation in Pacemaker Patients Without a Recent Stroke

      Healey et al
      • Healey J.S.
      • Connolly S.J.
      • Gold M.R.
      • et al.
      Subclinical atrial fibrillation and the risk of stroke.
      monitored 2580 patients with pacemakers or other implanted devices for 3 months. None had a recent stroke, but 7% had a past history of stroke. The average age was 77 years; none had a history of atrial fibrillation. They defined silent atrial fibrillation as an atrial rate >190/min lasting >6 minutes. During the first 3 months, 10.1% had silent atrial fibrillation. During an additional 2.5 years of follow-up, an additional 24.5% had one or more episodes of silent atrial fibrillation.
      • Healey J.S.
      • Connolly S.J.
      • Gold M.R.
      • et al.
      Subclinical atrial fibrillation and the risk of stroke.
      Connolly et al
      • Connolly S.J.
      • Kerr C.R.
      • Gent M.
      • et al.
      Effects of physiologic pacing versus ventricular pacing on the risk of stroke and death due to cardiovascular causes.
      followed 2568 patients for 3 years after placement of a ventricular or a dual-chamber pacemaker. None had a recent stroke. The average age was 70 years; 20% had a history of intermittent atrial fibrillation. Less than 10% had a past history of stroke or TIA. During 3 years of follow-up, the incidence of new atrial fibrillation was 6.6% with a ventricular pacemaker, compared with 5.3% with a dual-chamber pacemaker.
      • Connolly S.J.
      • Kerr C.R.
      • Gent M.
      • et al.
      Effects of physiologic pacing versus ventricular pacing on the risk of stroke and death due to cardiovascular causes.
      The largest series of pacemaker patients without a recent ischemic stroke who were monitored for silent atrial fibrillation was reported by Boriani et al.
      • Boriani G.
      • Glotzer T.V.
      • Santini M.
      • et al.
      Device-detected atrial fibrillation and risk for stroke: an analysis of >10,000 patients from the SOS AF project (stroke prevention on strategies based on atrial fibrillation information from implanted devices).
      They pooled the results of 3 prospective trials totaling 10,016 patients. The median age was 70 years. Five percent had persistent atrial fibrillation and 19% had a history of paroxysmal atrial fibrillation. Six percent had a past history of stroke; none had a recent ischemic stroke. Atrial fibrillation was defined as an atrial rate of >175/min lasting 5 minutes or longer.
      During 3 months of monitoring, 24% had at least 1 day of atrial fibrillation lasting more than 5 minutes, 18% at least 1 hour, and 6% had an episode of atrial fibrillation lasting more than 1 day.
      • Boriani G.
      • Glotzer T.V.
      • Santini M.
      • et al.
      Device-detected atrial fibrillation and risk for stroke: an analysis of >10,000 patients from the SOS AF project (stroke prevention on strategies based on atrial fibrillation information from implanted devices).
      During 24 months of monitoring, 43% had an episode of silent atrial fibrillation lasting 5 minutes or longer.
      • Boriani G.
      • Glotzer T.V.
      • Santini M.
      • et al.
      Device-detected atrial fibrillation and risk for stroke: an analysis of >10,000 patients from the SOS AF project (stroke prevention on strategies based on atrial fibrillation information from implanted devices).

      Incidence of Strokes in Patients with Silent Atrial Fibrillation

      In the report by Healey et al,
      • Healey J.S.
      • Connolly S.J.
      • Gold M.R.
      • et al.
      Subclinical atrial fibrillation and the risk of stroke.
      during 2.5 years of follow-up, the incidence of ischemic stroke or systemic embolism was 1.54%/y in those with silent atrial fibrillation during the first 3 months, compared with 0.62% in those without silent atrial fibrillation (hazard ratio 2.52, P = .01).
      In the study by Connolly et al,
      • Connolly S.J.
      • Kerr C.R.
      • Gent M.
      • et al.
      Effects of physiologic pacing versus ventricular pacing on the risk of stroke and death due to cardiovascular causes.
      the annual incidence of stroke was essentially the same in the 2 types of pacemakers: 1.1% and 1.0%. The incidence of stroke in those with or without silent atrial fibrillation was not reported.
      During 24 months of follow-up in a meta-analysis involving more than 10,000 patients by Boriani et al,
      • Boriani G.
      • Glotzer T.V.
      • Santini M.
      • et al.
      Device-detected atrial fibrillation and risk for stroke: an analysis of >10,000 patients from the SOS AF project (stroke prevention on strategies based on atrial fibrillation information from implanted devices).
      there were 57 ischemic strokes, an incidence of 0.23%/year. Of those with strokes, 46% had at least 5 minutes of atrial fibrillation prior to the stroke. The incidence of stroke was 0.27%/y for those without atrial fibrillation and 0.30%/y for those with atrial fibrillation of 23 hours or more. This very low incidence of strokes occurred in a population with many risk factors for stroke: median age 70 years, hypertension 59%, diabetes 25%. Nearly 70% had a CHADS2 score of 2 or more.

      Discussion

      The incidence of silent atrial fibrillation in patients with a recent stroke is significant, nearly 25% in the report of more than 11,000 patients by Sposato et al.
      • Sposato L.A.
      • Cipriano L.E.
      • Saposnik G.
      • et al.
      Diagnosis of atrial fibrillation after stroke and transient ischaemic attack: a systematic review and meta-analysis.
      However, the incidence of silent atrial fibrillation is even higher in patients without a recent stroke who have continuous monitoring by an implanted pacemaker. In the more than 10,000 patients without a recent stroke in the meta-analysis by Boriani et al
      • Boriani G.
      • Glotzer T.V.
      • Santini M.
      • et al.
      Device-detected atrial fibrillation and risk for stroke: an analysis of >10,000 patients from the SOS AF project (stroke prevention on strategies based on atrial fibrillation information from implanted devices).
      who were monitored by a pacemaker, 43% had an episode of atrial fibrillation lasting more than 5 minutes during 24 months of monitoring.
      The incidence of strokes is much lower than the incidence of silent atrial fibrillation in these reports.
      • Boriani G.
      • Glotzer T.V.
      • Santini M.
      • et al.
      Device-detected atrial fibrillation and risk for stroke: an analysis of >10,000 patients from the SOS AF project (stroke prevention on strategies based on atrial fibrillation information from implanted devices).
      • Healey J.S.
      • Connolly S.J.
      • Gold M.R.
      • et al.
      Subclinical atrial fibrillation and the risk of stroke.
      • Connolly S.J.
      • Kerr C.R.
      • Gent M.
      • et al.
      Effects of physiologic pacing versus ventricular pacing on the risk of stroke and death due to cardiovascular causes.
      The annual risk of stroke in those without a recent stroke was 1.0% to 1.1% in the series reported by Connolly et al
      • Connolly S.J.
      • Kerr C.R.
      • Gent M.
      • et al.
      Effects of physiologic pacing versus ventricular pacing on the risk of stroke and death due to cardiovascular causes.
      and 0.71 in the series reported by Healey et al.
      • Healey J.S.
      • Connolly S.J.
      • Gold M.R.
      • et al.
      Subclinical atrial fibrillation and the risk of stroke.
      In the series by Healey et al,
      • Healey J.S.
      • Connolly S.J.
      • Gold M.R.
      • et al.
      Subclinical atrial fibrillation and the risk of stroke.
      silent atrial fibrillation was detected in 10.1% during 3 months of observation. The incidence of stroke during follow-up was 0.71%/y. The incidence of stroke was greater in those with silent atrial fibrillation: 1.54/y vs 0.62/y without atrial fibrillation (hazard ratio 2.52, P < .01). The total number of strokes in the 2580 patients followed for 2.5 years was 46.
      • Saver J.L.
      Cryptogenic stroke.
      Boriani et al
      • Boriani G.
      • Glotzer T.V.
      • Santini M.
      • et al.
      Device-detected atrial fibrillation and risk for stroke: an analysis of >10,000 patients from the SOS AF project (stroke prevention on strategies based on atrial fibrillation information from implanted devices).
      reported an incidence of recurrent stroke of 0.23%/y. In 4287 patients with an episode of silent atrial fibrillation lasting 5 minutes or longer, the incidence was 0.31%/y, compared with 0.24%/y for 5729 patients without silent atrial fibrillation.
      The percentage of strokes that were cryptic in these 3 reports was not reported; as a result, the incidence of silent atrial fibrillation in patients with cryptic stroke vs all ischemic strokes could not be determined.
      Several studies have reported that the risk of recurrent stroke in patients with cryptogenic stroke is lower than in all patients with other ischemic strokes.
      • Saver J.L.
      Cryptogenic stroke.
      • Kishore A.
      • Vail A.
      • Majid A.
      • et al.
      Detection of atrial fibrillation after ischemic stroke or transient ischemic attack. A systematic review and meta-analysis.
      • Kent D.M.
      • Dahabreh I.J.
      • Ruthazer R.
      • et al.
      Device closure of patent foramen ovale after stroke.
      Kent et al
      • Kent D.M.
      • Dahabreh I.J.
      • Ruthazer R.
      • et al.
      Device closure of patent foramen ovale after stroke.
      reported an annual recurrence of ischemic stroke of 0.98%/y in 2303 patients with cryptic stroke treated with medical therapy or transvenous closure of a patent foramen ovale plus medical therapy.
      The indication for anticoagulation in patients with silent atrial fibrillation is not clear, because the shortest duration of atrial fibrillation necessary for a left atrial thrombus to form and result in stroke is unknown.
      • Kirchhof P.
      • Benussi S.
      • Kotecha D.
      • et al.
      2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS: the Task Force for the management of atrial fibrillation of the European Society of Cardiology (ESC) developed with the special contribution of the European Heart Rhythm Association (EHRA) of the ESC endorsed by the European Stroke Organisation (ESO).
      There is some indirect evidence that suggests that it may take more than 48 hours of atrial fibrillation for a left atrial thrombus to form.
      Clinical guidelines recommend anticoagulation prior to and after cardioversion for patients with atrial fibrillation present longer than 48 hours, but not for patients with atrial fibrillation known to be <48 hours in duration.
      • Kirchhof P.
      • Benussi S.
      • Kotecha D.
      • et al.
      2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS: the Task Force for the management of atrial fibrillation of the European Society of Cardiology (ESC) developed with the special contribution of the European Heart Rhythm Association (EHRA) of the ESC endorsed by the European Stroke Organisation (ESO).
      • You J.J.
      • Singer D.E.
      • Howard P.A.
      • et al.
      Antithrombotic therapy for atrial fibrillation: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.
      This recommendation is consistent with reports of embolic stroke after cardioversion. Airaksinen et al
      • Airaksinen K.E.J.
      • Gronberg T.
      • Nuotio L.
      • et al.
      Thromboembolic complications after cardioversion of acute atrial fibrillation: the FinCV (Finnish Cardioversion) Study.
      reported the results of cardioversion of 3143 patients with atrial fibrillation lasting <48 hours. None received anticoagulation prior to or after cardioversion; there were 38 (0.7%) strokes within 30 days of cardioversion. This suggests it may take more than 48 hours of atrial fibrillation for a thrombus to form in the left atrium.
      Hansen et al
      • Hansen M.L.
      • Jepsen R.M.H.G.
      • Olesen J.B.
      • et al.
      Thromboembolic risk in 16,274 atrial fibrillation patients undergoing direct current cardioversion with and without oral anticoagulant therapy.
      reported the results of cardioversion with or without anticoagulation in 16,274 patients. The incidence of stroke, TIA, or systemic embolism was 4.0% in those who received anticoagulation and 10.3% in those without anticoagulation. The duration of atrial fibrillation in these patients was not reported. These 2 studies
      • Airaksinen K.E.J.
      • Gronberg T.
      • Nuotio L.
      • et al.
      Thromboembolic complications after cardioversion of acute atrial fibrillation: the FinCV (Finnish Cardioversion) Study.
      • Hansen M.L.
      • Jepsen R.M.H.G.
      • Olesen J.B.
      • et al.
      Thromboembolic risk in 16,274 atrial fibrillation patients undergoing direct current cardioversion with and without oral anticoagulant therapy.
      make it clear that cardioversion can result in embolic stroke, and the risk is less in those with atrial fibrillation lasting <48 hours and is less in those who are treated with anticoagulation. This suggests that left atrial thrombi are most likely to be formed after 48 hours of atrial fibrillation. It also implies that it is unlikely that silent atrial fibrillation lasting minutes or hours will cause the formation of a left atrial thrombus.
      Many recommend that patients with cryptic strokes should be monitored for the presence of silent atrial fibrillation.
      • Dobreanu D.
      • Svendsen J.H.
      • Lewalter T.
      • et al.
      Current practice for diagnosis and management of silent atrial fibrillation: results of the European Heart Rhythm Association survey.
      • Gladstone D.J.
      • Spring M.
      • Dorian P.
      • et al.
      Atrial fibrillation in patients with cryptogenic stroke.
      • Grond M.
      • Jauss M.
      • Hamann G.
      • et al.
      Improved detection of silent atrial fibrillation using 72 hour Holter ECG in patients with ischemic stroke. A prospective Multicenter cohort study.
      Given the current knowledge of silent atrial fibrillation, what are the indications for anticoagulation if silent atrial fibrillation is detected? If silent atrial fibrillation is documented in a patient with a recent cryptic stroke, anticoagulation would be indicated in the absence of contraindications.
      Is anticoagulation indicated if silent atrial fibrillation is detected in patients without a history of stroke? In a survey of electrophysiologists by the European Heart Rhythm Association in 2013, the overwhelming majority considered that a single episode of silent atrial fibrillation is an indication for anticoagulation without further tests in patients with a CHADS2 score of 1 or more.
      • Dobreanu D.
      • Svendsen J.H.
      • Lewalter T.
      • et al.
      Current practice for diagnosis and management of silent atrial fibrillation: results of the European Heart Rhythm Association survey.
      The 2016 European Society of Cardiology guidelines for the management of atrial fibrillation note that the shortest duration of atrial fibrillation conveying a stroke risk is unknown, and it is unknown if patients with silent atrial fibrillation will benefit from anticoagulation.
      • Kirchhof P.
      • Benussi S.
      • Kotecha D.
      • et al.
      2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS: the Task Force for the management of atrial fibrillation of the European Society of Cardiology (ESC) developed with the special contribution of the European Heart Rhythm Association (EHRA) of the ESC endorsed by the European Stroke Organisation (ESO).
      An ongoing clinical trial will address these uncertainties.
      • Kirchhof P.
      • Benussi S.
      • Kotecha D.
      • et al.
      2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS: the Task Force for the management of atrial fibrillation of the European Society of Cardiology (ESC) developed with the special contribution of the European Heart Rhythm Association (EHRA) of the ESC endorsed by the European Stroke Organisation (ESO).
      Given the very low incidence of stroke in patients with silent atrial fibrillation who do not have a history of recent stroke
      • Boriani G.
      • Glotzer T.V.
      • Santini M.
      • et al.
      Device-detected atrial fibrillation and risk for stroke: an analysis of >10,000 patients from the SOS AF project (stroke prevention on strategies based on atrial fibrillation information from implanted devices).
      • Healey J.S.
      • Connolly S.J.
      • Gold M.R.
      • et al.
      Subclinical atrial fibrillation and the risk of stroke.
      • Connolly S.J.
      • Kerr C.R.
      • Gent M.
      • et al.
      Effects of physiologic pacing versus ventricular pacing on the risk of stroke and death due to cardiovascular causes.
      and an annual risk of major bleeding of 2% with anticoagulation,
      • DiMarco J.P.
      • Flaker G.
      • Waldo A.L.
      • et al.
      Factors affecting bleeding risk during anticoagulant therapy in patients with atrial fibrillation: observations from the atrial fibrillation follow-up investigation of rhythm management (AFFIRM) study.
      many
      • Kirchhof P.
      • Benussi S.
      • Kotecha D.
      • et al.
      2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS: the Task Force for the management of atrial fibrillation of the European Society of Cardiology (ESC) developed with the special contribution of the European Heart Rhythm Association (EHRA) of the ESC endorsed by the European Stroke Organisation (ESO).
      • Lamas G.
      How much atrial fibrillation is too much atrial fibrillation?.
      (including the authors) would recommend further monitoring to detect clinical atrial fibrillation prior to initiating anticoagulation when silent atrial fibrillation is detected in patients without a history of stroke.

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      Linked Article

      • Selective Reporting: Silent Atrial Fibrillation and Cryptogenic Strokes
        The American Journal of MedicineVol. 130Issue 9
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          I read with interest the article by Dalen and Alpert.1 Bothersome to me was the selectiveness of the data reported and the somewhat biased resultant interpretation. Consider: they did not mention the pivotal Cryptogenic Stroke and Underlying AF trial,2 in which the unmonitored control group had atrial fibrillation detected in 3% by 36 months, versus 3.7%, 8.9%, 12.4%, and 30.0% at 1, 6, 12, and 36 months, respectively, in the implanted monitor group. Notably, not only was the detection rate frequent with the implanted monitor but also greater than could have occurred with any external monitoring.
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