WATCH AFib: smartwatches for detection of atrial fibrillation in secondary prevention of cryptogenic stroke-protocol for a prospective, intraindividual-controlled, multicentre clinical study.

Rationale: Detection of atrial fibrillation (AFib) and subsequent anticoagulation therapy reduce the risk of recurrent stroke, while prolonged rhythm monitoring significantly increases AFib detection. Thus, prolonged smartwatch-based ECG monitoring after cryptogenic ischemic stroke or transient ischemic attack (TIA) could lead to a reduction of recurrent stroke by prompting adequate anticoagulation therapy. Aim: WATCH AFib investigates the accuracy of smartwatches for AFib detection in patients with cryptogenic TIA or ischemic stroke compared to an implantable event recorder. Sample size: 40 cases of AFib are required to estimate the sensitivity for AFib detection per patient with a precision of about 10%. As AFib is observed in 9%-16% of cryptogenic strokes, we intend to enroll 400 patients. Methods: WATCH AFib is a prospective, intraindividual-controlled, multicentre clinical study in patients with cryptogenic ischemic stroke or TIA. ECG-data from smartwatches and event recorders is continuously monitored by two independent cardiologists for a follow-up period of 6 months. If AFib is detected, therapeutic options are discussed at the including center. Primary outcome: To compare smartwatch- and event recorder- based sensitivity and specificity of AFib detection per patient after 6 months. Discussion: Prolonged AFib screening after stroke is currently suboptimal. Smartwatches might be a non-invasive, cost-effective, widely available alternative for prolonged rhythm monitoring. Usability in severely affected patients and patients with persisting neurological deficits might be limited. Trial registration: The study is registered on clinicaltrials.gov. Registration number: 20230726.