Inclusion Criteria:  I. Patients admitted to the UOC of Neurology and Metropolitan Stroke Network diagnosed with IS or TIA. The diagnosis will be confirmed through standardized clinical practice which may include one or more of the following diagnostic tests:  imaging tests such as computed tomography (CT), magnetic resonance imaging (MRI), computed tomographic angiography (ANGIOTC), magnetic resonance angiography (MRA), blood flow tests such as cerebral angiography or cerebral arteriography. II. Patients with IS or TIA within 7 days of the clinical episode. III. Obtaining informed consent (signed and dated). IV. Adult patients (over 18 years of age).  Exclusion Criteria:  I. Patients with PM o ICD. II. Patients diagnosed with hemorrhagic stroke. III. Patients who have undergone cardiac surgery in the 30 days prior to enrollment.  IV. More than 7 days between the IS or TIA episode and patient enrollment. V. Patient diagnosed with AF based on a resting ECG performed at the time of enrollment.  VI. Patient with a previous diagnosis of permanent AF or persistent AF. VII. Patient previously enrolled in this clinical study. VIII. Pregnancy.