As much as 20-30% of all strokes are attributed to atrial fibrillation (AF), making the detection of AF highly important, as AF-related strokes are largely preventable with optimal treatment. Therefore, most guidelines recommend screening patients for AF after a stroke, although the optimal timing and choice of monitoring device for screening remain undefined. Our aim is to investigate whether AF screening as early as possible after stroke symptom onset provides a higher detection rate compared to screening after discharge. Additionally, we aim to determine if a 3-lead ECG device provides a higher detection rate compared to a 1-lead patch recorder.

Atrial fibrillation (AF) is one of the most common cardiac arrhythmias, affecting over 2% of all adults in the general population, with prevalence increasing with age and cardiovascular risk factors. AF is responsible for at least 20% of all stroke cases, and stroke may often be the first manifestation of AF. Compared to strokes of other etiologies, AF-related strokes are associated with larger infarctions, worse outcomes, and higher mortality. Detecting previously undiagnosed AF in stroke patients is crucial for optimal secondary prevention through oral anticoagulation therapy.

As a result, guidelines emphasize the importance of AF screening in stroke patients to prevent recurrent strokes. Since AF can be asymptomatic and occur only intermittently, diagnosis may be easily missed or delayed. Studies have shown that prolonged screening increases detection rates. According to current knowledge, international AF and stroke guidelines recommend prolonged cardiac monitoring of at least 24 hours to detect subclinical AF if no other cause of stroke is identified.

However, while guidance exists on screening duration, none of the guidelines provide specific recommendations regarding the choice of device or the timing of screening. The sensitivity of AF detection likely depends on the screening strategy, timing, device, and algorithm used, but this area has been only minimally studied. Evidence suggests that the highest yield for AF detection may be early after stroke symptom onset. Nevertheless, significant knowledge gaps remain, and current screening strategies are not fully satisfactory.

Efforts to improve AF detection are warranted. This project aims to explore:

i. Whether prolonged AF screening initiated upon hospital admission after acute stroke results in a higher detection rate compared to prolonged ambulatory screening after discharge ii. Whether a 3-lead continuous ECG device has a higher detection rate compared to a 1-lead continuous patch recorder iii. A comparison of continuous vs. intermittent ECG AF screening for detection

The design involves a prospective observational trial of an unselected cohort of patients admitted with acute stroke to Bærum Hospital. Eligible participants include all patients above 18 years old without known AF or those with previously diagnosed paroxysmal AF exhibiting sinus rhythm upon admission. Upon admission to the Stroke Unit, patients will as soon as possible undergo a 48-hour in-hospital continuous heart monitoring, followed by a second 48-hour continuous heart monitoring upon discharge (ambulatory).

In addition, an intermittent AF screening with hand held thumb ECG, will be performed 3 times a day for 30 seconds, and for 3 consecutive days during the hospital stay in a sample of the participants, and compared to detection rate with continues heart monitoring.

Inclusion Criteria:

• 18 years or older
• Ischemic stroke
• Without known AF or those with previously diagnosed paroxysmal AF exhibiting sinus rhythm upon admission

Exclusion Criteria:

• AF at hosptial admission
• Unable or unwilling to provide informed consent
• A life expectancy of less than one year

The design involves a prospective observational trial of an unselected cohort of patients admitted with acute stroke to Bærum Hospital.