The present study is an investigator-initiated, single-center, retrospective study based on data from the London Ontario Stroke Registry (LOSR), aiming to compare the characteristics and outcomes of ECG-detected and Device-Detected atrial fibrillation in patients with ischemic stroke and transient ischemic attack.

Patients with ischemic stroke and transient ischemic attack (TIA) without known atrial fibrillation (AF) are investigated with Prolonged Cardiac Monitoring (PCM) to detect AF. It is unclear if AF detected on 12-lead ECG after stroke occurrence bears the same risk of stroke as Device-detected AF. The investigators hypothesize, that Device-detected AF has a lower risk of ischemic stroke recurrence. The investigators will conduct a retrospective analysis of prospectively collected data from consecutive patients enrolled in the London Ontario Stroke Registry, (Ontario, Canada). The primary outcome will be a recurrent ischemic stroke at the end of the available follow-up window. The investigators will include ischemic stroke and TIA patients with ECG-detected AF and those with Device-detected AF on at least 7 days of Holter monitoring.

Inclusion Criteria:

• Age ≥18 years
• Patient with a diagnosis of ischemic stroke or TIA.
• ECG-diagnosed AF or PCM-detected AF post ischemic stroke or TIA

Exclusion Criteria:

• Individuals younger than18 years-old
• Patients without IS or TIA diagnosis

Patients with an acute ischemic stroke or TIA in the London Ontario Stroke Registry without known AF, who are newly diagnosed with AF on a 12-lead ECG or a ≥7-day external cardiac monitor.

Individual patients data will be made available upon reasonable request, conditional to approval from Western University Ethics Review Board