Abstract 3513: Randomized Trial of Outpatient Cardiac Monitoring After Cryptogenic Stroke

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Background: Diagnosis of atrial fibrillation (AF) as a cause of stroke or TIA is important because it identifies patients who may benefit from anticoagulation. Observational studies indicate that outpatient cardiac monitoring detects previously undiagnosed AF in 5-20% of patients with stroke, but these studies may overestimate the rate of AF if selection bias prompts analysis and publication. It is also unknown whether the yield of cardiac monitoring is higher than that of routine clinical follow-up. Methods: In a pilot trial, we randomly assigned consecutive patients with cryptogenic ischemic stroke or high-risk TIA (ABCD 2 score ≥ 4) to wear a Cardionet mobile cardiac outpatient telemetry monitor for 21 days after discharge, or to not wear a monitor. We excluded patients with a known history of AF, AF detected by inpatient cardiac telemetry (at least 24 hours required), a definite small-vessel etiology, a source found by vascular imaging or echocardiography, an obvious culpable systemic illness such as endocarditis, or inability to provide written, informed consent. All patients received routine clinical follow-up from their primary care physician and neurologist. We contacted patients and their physicians 3 months after discharge and used validated questionnaires to inquire about clinical diagnoses of AF and recurrent stroke or TIA. Results: The target enrollment of 40 patients was completed over 18 months. The mean age was 67 years (± 13), 23 (58%) were men, and 32 (80%) had at least one vascular risk factor; the baseline characteristics of our cohort were broadly similar to those in prior observational studies of cardiac monitoring after stroke. Our prespecified feasibility criteria were met, with full follow-up on 38 patients (95%) and successful completion of monitoring in 15 of the 20 patients (75%) randomized to monitoring. Overall, patients wore monitors for 64% of the assigned days. No patient in either study arm received a diagnosis of AF. Cardiac monitoring revealed AF in zero patients (0%, 95% CI 0-17%), brief episodes (< 10 seconds) of atrial tachycardia in two patients (10%, 95% CI 1-32%) and nonsustained ventricular tachycardia in two patients (10%, 95% CI 1-32%). There were no recurrent strokes; recurrent TIAs occurred in two patients assigned to the control group. Conclusions: The results of our pilot trial indicate that randomizing patients to outpatient cardiac monitoring after stroke is feasible. However, rates of AF detection were lower than expected, which may be due to publication bias in prior observational studies or selection of lower risk patients in our trial. Furthermore, 25% of patients assigned to undergo monitoring were not compliant. These results suggest that an adequately powered randomized trial of cardiac monitoring after stroke may require large numbers of participants.