Incidence of atrial fibrillation among patients with an embolic stroke of undetermined source: Insights from insertable cardiac monitors

Background: Prophylactic use of direct oral anticoagulants for recurrent stroke prevention in patients with embolic strokes of undetermined source is currently being investigated. It is uncertain whether the bleeding risks associated with prophylactic direct oral anticoagulants use will outweigh any stroke prevention benefit in embolic strokes of undetermined source patients who lack underlying atrial fibrillation. Methods: We determined the proportion of cryptogenic stroke patients in the CRYSTAL atrial fibrillation trial who met inclusion criteria for the NAVIGATE embolic stroke of undetermined source and RE-SPECT embolic stroke of undetermined source trials and their atrial fibrillation incidence. Both embolic strokes of undetermined source trials impose requirements on age, modified Rankin Score, antiplatelet use, and type of infarction. Insertable cardiac monitors were used to determine the atrial fibrillation detection rates at 30 days and 3 years using Kaplan–Meier’s estimates. Results: Among 441 patients enrolled in the CRYSTAL atrial fibrillation trial, 189 (42.9%) and 236 (53.5%) met the inclusion criteria of the NAVIGATE embolic stroke of undetermined source and RE-SPECT embolic stroke of undetermined source trials, respectively. Atrial fibrillation detection rates at 3 years among insertable cardiac monitors patients eligible for the NAVIGATE embolic stroke of undetermined source and RE-SPECT embolic stroke of undetermined source trials were 35.8% and 33.6% while detection rates at 30 days were 5.6% and 3.5%, respectively. Conclusion: Only half of cryptogenic stroke patients in CRYSTAL atrial fibrillation met the inclusion criteria for the ongoing embolic strokes of undetermined source trials. Approximately, two-thirds of patients with embolic strokes of undetermined source do not have any atrial fibrillation despite continuous rhythm monitoring for up to three years. The benefits of prophylactic use of direct oral anticoagulants in the absence of atrial fibrillation is unknown and therefore embolic strokes of undetermined source patients could benefit from prolonged atrial fibrillation monitoring until more robust data are available. ClinicalTrials.gov Registration: NCT00924638. https://clinicaltrials.gov/ct2/show/NCT00924638.