The Primary Objective of the study is to establish the One-year recurrence rates of atrial fibrillation (AF) following new-onset atrial fibrillation during intensive care unit (ICU) admission.

The Secondary Objective is a composite of death from cardiovascular causes, stroke (either ischemic or hemorrhagic), or hospitalization with worsening of heart failure or recurrent AF.

The prevalence and recurrence rates of AF will be divided into sub-groups based on primary ICU admission diagnosis.

All-cause mortality.

Patients will be screened for atrial fibrillation during hospitalization in the intensive care unit and will be followed until discharge. Once discharged home or to a rehabilitation center, they will be invited to a routine follow-up clinic at RMC cardiology institute 4-6 weeks after hospital discharge. During the clinic visit, patients will be recruited to the study follow-up plan.

The follow-up plan will consist of 3 clinical visits at 4-6 weeks, 6-months and 1 -year after discharge.

The follow-up program will include a comprehensive screening for symptomatic and asymptomatic atrial fibrillation events as following:

Patients will be provided with a home cellular-digital 12-lead ECG transmitter. They will be instructed to conduct routine weekly transmission in order to record asymptomatic events as well as to transmit at any time they suspect an event/feel symptoms (palpitations). Home routine testing will be initiated and guided by a telephone call from a medical monitoring center. A blinded, independent, on-call medical professional team will analyze the received ECG.

A 48-hour Holter ECG will be performed at 6 months and 12 months after ICU discharge

Clinical visits will include 12 leads ECG, physical examination, vital signs, symptoms evaluation for suspected AF events, questioning for hospital admissions, or any other documented AF event. Patients will be asked to perform echocardiography as part of their clinical evaluation. For both the study and control group, documented AF events will be managed according to physician discretion based on clinical practice and guidelines.

Long-term follow-up- 3 years- data regarding recurrent events of AF, hospitalization due to thromboembolic events, and mortality will be evaluated by telephone call or by matching patient identification numbers with the Israeli National Population Register.

Inclusion Criteria:

• Admitted to ICU over 24 hours
• Diagnosed with new-onset atrial fibrillation
• The patient survived the index hospitalization and was discharged home/ to a rehabilitation center.

Exclusion Criteria:

• Previously documented atrial fibrillation

Patients diagnosed with new-onset atrial-fibriltion using 30-second telemetry recording or a 12 lead ECG indicating AF during general ICU hospitalization.