Atrial fibrillation in patients with cryptogenic stroke.

N Engl J Med 2014 Jun;370(26):2467-77

From the Division of Neurology (D.J.G.), Department of Medicine (D.J.G., P.D., A.L., M.S., J.A.B., L.K.C., D.S., M. Mehdiratta, K.B., M.K.K.), and Dalla Lana School of Public Health (K.E.T.), University of Toronto, the University of Toronto Stroke Program (D.J.G.), Division of Neurology, Department of Medicine, and Brain Sciences Program, Sunnybrook Health Sciences Centre and Sunnybrook Research Institute (D.J.G., R.A.), the Heart and Stroke Foundation Canadian Partnership for Stroke Recovery (D.J.G.), and the Applied Health Research Centre, Li Ka Shing Knowledge Institute of St. Michael's Hospital (V.P., K.E.T., J.H., H.V., A.L., M. Mamdani), Toronto, McMaster University, Hamilton, ON (M.S., D.J.S.), McGill University, Montreal (R.C.), University of Alberta, Edmonton (A.S., B.B.), Western University, London, ON (V.H., J.D.S.), Department of Clinical Neurosciences and Radiology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB (S.B.C.), University of British Columbia, Vancouver (P.T., S.Y.), Queen's University, Kingston, ON (A.J.), Thunder Bay Regional Health Sciences Centre, Thunder Bay, ON (D.H.), Université Laval, Quebec City (S.V.), and Vancouver Island Health Research Centre, Victoria, BC (A.P.) - all in Canada; and the National University of Ireland, Galway (M.O.).

Background: Atrial fibrillation is a leading preventable cause of recurrent stroke for which early detection and treatment are critical. However, paroxysmal atrial fibrillation is often asymptomatic and likely to go undetected and untreated in the routine care of patients with ischemic stroke or transient ischemic attack (TIA).

Methods: We randomly assigned 572 patients 55 years of age or older, without known atrial fibrillation, who had had a cryptogenic ischemic stroke or TIA within the previous 6 months (cause undetermined after standard tests, including 24-hour electrocardiography [ECG]), to undergo additional noninvasive ambulatory ECG monitoring with either a 30-day event-triggered recorder (intervention group) or a conventional 24-hour monitor (control group). The primary outcome was newly detected atrial fibrillation lasting 30 seconds or longer within 90 days after randomization. Secondary outcomes included episodes of atrial fibrillation lasting 2.5 minutes or longer and anticoagulation status at 90 days.

Results: Atrial fibrillation lasting 30 seconds or longer was detected in 45 of 280 patients (16.1%) in the intervention group, as compared with 9 of 277 (3.2%) in the control group (absolute difference, 12.9 percentage points; 95% confidence interval [CI], 8.0 to 17.6; P<0.001; number needed to screen, 8). Atrial fibrillation lasting 2.5 minutes or longer was present in 28 of 284 patients (9.9%) in the intervention group, as compared with 7 of 277 (2.5%) in the control group (absolute difference, 7.4 percentage points; 95% CI, 3.4 to 11.3; P<0.001). By 90 days, oral anticoagulant therapy had been prescribed for more patients in the intervention group than in the control group (52 of 280 patients [18.6%] vs. 31 of 279 [11.1%]; absolute difference, 7.5 percentage points; 95% CI, 1.6 to 13.3; P=0.01).

Conclusions: Among patients with a recent cryptogenic stroke or TIA who were 55 years of age or older, paroxysmal atrial fibrillation was common. Noninvasive ambulatory ECG monitoring for a target of 30 days significantly improved the detection of atrial fibrillation by a factor of more than five and nearly doubled the rate of anticoagulant treatment, as compared with the standard practice of short-duration ECG monitoring. (Funded by the Canadian Stroke Network and others; EMBRACE number, NCT00846924.).

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