Paroxysmal atrial fibrillation is often undetected because characteristics such as short duration, episodic, and frequently asymptomatic nature make it challenging to diagnose at the bedside, leading to suboptimal secondary prevention. It is not uncommon for paroxysmal atrial fibrillation to be undetected in a single electrocardiogram (ECG) on admission. Conventional 24-hour Holter monitoring is often used to detect paroxysmal atrial fibrillation. However, systematic review suggests Holter monitoring will identify atrial fibrillation in only an additional 4.6% of patients, no better than detection rates observed in groups lacking routine monitoring. On the other hand, for ischemic stroke patients with sinus rhythm at baseline but paroxysmal atrial fibrillation still suspected, no recommendation beyond repeated 12-lead ECGs is made in the United Kingdom guideline. Serial 12-lead ECG has been used to detect possible paroxysmal atrial fibrillation among acute ischemic stroke patients and found 15 new cases of atrial fibrillation in 133 acute ischemic stroke patients (11.3%) without atrial fibrillation at baseline. The optimal investigation strategy, including modality, duration of investigation, and patient subgroup remains undefined, not only for efficacy in the detection of atrial fibrillation, but also cost-effectiveness in healthcare systems. The objective of this project is to conduct a pragmatic multicenter randomized controlled trial for the comparison of serial 12-lead ECG once daily for 5 days and 24-hour Holter to detect paroxysmal atrial fibrillation in acute ischemic stroke patients without atrial fibrillation identified by baseline ECG or history.

Investigators plan to enroll 900 participants from six hospitals in Taiwan. Patients will be eligible for enrollment if they are admitted due to acute ischemic stroke within 2 days, with 65 years of age or older, do not have known atrial fibrillation on history or baseline ECG at admission. Investigators will randomly assigned participants in a 1:1 ratio to undergo daily 12-lead ECG once daily for 5 days (intervention group) or 24-hour Holter monitoring (control group).

Inclusion Criteria:

1. Cerebral ischemia defined as stroke (sudden focal neurologic deficit lasting >24 h consistent with the territory of a major cerebral artery and categorized as ischemic) and/or a corresponding lesion on brain imaging
2. Stroke symptoms within 2 days
3. Age ≥65 years

Exclusion Criteria:

1. History of atrial fibrillation or documented atrial fibrillation prior to randomization
2. Indication for oral anticoagulation at randomization
3. Absolute contraindication for oral anticoagulation at randomization
4. Intracerebral hemorrhage in medical history
5. Implanted pacemaker device or cardioverter/defibrillator
6. End stage renal disease