Rationale: A standard work-up of stroke patients to identify a cause of stroke consists of Computed Tomography (CT), CT angiography of head and neck arteries, transthoracic echocardiography, 12-lead 10-seconds electrocardiogram (ECG), blood tests and 24-hour ECG monitoring. A stroke is called "cryptogenic" if no cause can be determined after standard work-up. Current detection of atrial fibrillation (AF) after stroke is 2.0%. Recent studies revealed that prolonged monitoring yields higher percentages of detected AF (12.0%). Devices used in these trials suffer from drawbacks. The investigators' hypothesis is that a new, smartphone compatible device, producing a single lead ECG (single lead ECG device), can be used for prolonged ECG monitoring in cryptogenic stroke patients. Objective: The main objective of this study is to compare the incidence of detected AF in cryptogenic stroke patients by a single lead ECG device with the incidence of detected AF by a 7-Day Holter ECG. Study design: A multicenter randomized trial. Study population: Cryptogenic stroke patients admitted to a hospital participating in the study. The calculated sample size is 200 (100 per arm). Intervention: After inclusion, patients will be randomized to either a single lead ECG device or a 7-Day Holter Monitor. Main study parameters/endpoints: The main endpoint will be the percentage of detected atrial fibrillation in both the single lead ECG device group and the 7-Day Holter group after one year. Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Both devices are battery powered and electrically safe. Patients face a 2-3% risk that AF is detected false-positively; this might lead to incorrect oral anticoagulation (OAC) prescription. However, a potential benefit of the investigators' study is that if AF is detected and treated with OAC, this significantly reduces the chance of recurrent stroke.

Rationale: A standard work-up of stroke patients to identify a cause of stroke consists of Computed Tomography (CT), CT angiography of head and neck arteries, transthoracic echocardiography, 12-lead 10-seconds electrocardiogram (ECG), blood tests and 24-hour ECG monitoring. A stroke is called "cryptogenic" if no cause can be determined after standard work-up. Current detection of atrial fibrillation (AF) after stroke is 2.0%. Recent studies revealed that prolonged monitoring yields higher percentages of detected AF (12.0%). Devices used in these trials suffer from drawbacks. The investigators' hypothesis is that a new, smartphone compatible device, producing a single lead ECG (single lead ECG device), can be used for prolonged ECG monitoring in cryptogenic stroke patients. Objective: The main objective of this study is to compare the incidence of detected AF in cryptogenic stroke patients by a single lead ECG device with the incidence of detected AF by a 7-Day Holter ECG. Study design: A multicenter randomized trial. Study population: Cryptogenic stroke patients admitted to a hospital participating in the study. The calculated sample size is 200 (100 per arm). Intervention: After inclusion, patients will be randomized to either a single lead ECG device or a 7-Day Holter Monitor. Main study parameters/endpoints: The main endpoint will be the percentage of detected atrial fibrillation in both the single lead ECG device group and the 7-Day Holter group after one year. Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Both devices are battery powered and electrically safe. Patients face a 2-3% risk that AF is detected false-positively; this might lead to incorrect oral anticoagulation (OAC) prescription. However, a potential benefit of the investigators' study is that if AF is detected and treated with OAC, this significantly reduces the chance of recurrent stroke.

Inclusion Criteria: - Patients must have had an episode of symptomatic Transient ischemic attack (TIA) or episode of ischemic stroke. - Ischemic stroke is defined as an episode of transient or neurological dysfunction caused by focal brain or retinal ischemia with recent infarction on imaging - A TIA is defined as transient episode of neurologic dysfunction typically lasting less than one hour caused by focal brain or retinal ischemia without recent infarction on imaging. Exclusion Criteria: - Known etiology of TIA or ischemic stroke - TIA or stroke caused by spinal ischemia - TIA only presenting with non-localising symptoms - Uncertainty about the diagnosis of TIA because of unclear clinical symptoms - Myocardial infarction <6 months before stroke - Coronary Artery Bypass Grafting <6 months before stroke - Severe valvular heart disease - Documented history of atrial fibrillation or atrial flutter - Permanent indication for oral anticoagulation at enrolment - Patient has permanent OAC contraindication - Patient is included in another randomized trial - Left ventricular aneurysm on echocardiography - Thrombus on echocardiographyRenal dysfunction (creatinine clearance <30 mL/min/1.73m2) - Patient has life expectancy of <1 year - Patient is not willing to sign the informed consent form - Patient is <18 years of age - Patient is considered an incapacitated adult - Patient is not in possession of a smartphone with Android Operating System (OS) or iOS.

Inclusion Criteria: - Patients must have had an episode of symptomatic Transient ischemic attack (TIA) or episode of ischemic stroke. - Ischemic stroke is defined as an episode of transient or neurological dysfunction caused by focal brain or retinal ischemia with recent infarction on imaging - A TIA is defined as transient episode of neurologic dysfunction typically lasting less than one hour caused by focal brain or retinal ischemia without recent infarction on imaging. Exclusion Criteria: - Known etiology of TIA or ischemic stroke - TIA or stroke caused by spinal ischemia - TIA only presenting with non-localising symptoms - Uncertainty about the diagnosis of TIA because of unclear clinical symptoms - Myocardial infarction <6 months before stroke - Coronary Artery Bypass Grafting <6 months before stroke - Severe valvular heart disease - Documented history of atrial fibrillation or atrial flutter - Permanent indication for oral anticoagulation at enrolment - Patient has permanent OAC contraindication - Patient is included in another randomized trial - Left ventricular aneurysm on echocardiography - Thrombus on echocardiographyRenal dysfunction (creatinine clearance <30 mL/min/1.73m2) - Patient has life expectancy of <1 year - Patient is not willing to sign the informed consent form - Patient is <18 years of age - Patient is considered an incapacitated adult - Patient is not in possession of a smartphone with Android Operating System (OS) or iOS.

The overall status was updated to "Recruiting" at Medisch Centrum Haaglanden.

The overall status was updated to "Recruiting" at Bronovo ziekenhuis.

The overall status was updated to "Recruiting" at Leiden University Medical Center.