The aim of the study is to compare intermedium-term clinical outcomes, including thromboembolic events and bleeding complications between patients with non-valvular atrial fibrillation treated with either oral anticoagulation or who had undergone LAA-closure (left atrial closure).

A questionnaire is sent to the patients and if there is some information missing or unclear, the investigators will contact the patient or the treating physicians to get the missing/unclear information.

The study population consists of 500 patients with non-valvular atrial fibrillation (AF) who underwent LAAC between the years 2009 and 2014 in two centers (the Bern University hospital und Zurich University hospital) and a similar group of 500 patients with non-valvular AF treated with oral anticoagulation (OAC).

In order to compare the two groups and reducing the bias due to confounding variables, a propensity score matching will be performed.

Study hypothesis is that left atrial appendage closure is non-inferior in terms of efficacy and safety in comparison to lifelong oral anticoagulation in patients with non-valvular atrial fibrillation.

Non-valvular atrial fibrillation is the most common arrhythmia with an estimated prevalence of 1-2% in the general population, increasing with age. Patients with AF are at increased risk of thromboembolism, in particular ischemic stroke.

LAAC seems at the actual knowledge to be a valid alternative to OAC. The objective of this study is to compare intermedium-term clinical outcomes, including thromboembolic events and bleeding complications between patients receiving Amplatzer devices vs. propensity score matched patients treated with OAC.

A questionnaire is sent to the patients asking about thrombo-embolic events, stroke, death, any bleeding but also on their current medication, comorbidities (i.e. arterial hypertension, diabetes mellitus, renal impairment and liver disease), any hospitalizations and their quality of life. If there is some information missing or unclear, the investigators will contact the patient or the treating physicians to get the missing information.

The study is an investigator-initiated, retrospective analysis of prospectively collected data. The study population consists of 500 patients with non-valvular AF who underwent LAAC between the years 2009 and 2014 in two centers (the Bern University hospital und Zurich University hospital) and a propensity score matched patients group of 500 patients with non-valvular AF treated with OAC.

Covariates for matching will be age, gender, renal function, coronary artery disease and its status of revascularization, left-ventricular function, HAS-BLED and CHA2DS2-VASc-Score.

Study hypothesis is that left atrial appendage closure is non-inferior in terms of efficacy and safety in comparison to lifelong oral anticoagulation in patients with non-valvular atrial fibrillation.

Inclusion Criteria:

• Age >/= 18 years
• Written informed consent to participate in the study
• Paroxysmal, persistent, or permanent non-valvular atrial fibrillation.
• Group A ("OAC"): Having been hospitalized between 2009 and 2014 in the Bern university hospital and discharged with either OAC or NOAC.
• Group B (LAA-closure): Underwent LAAC between 2009 and 2014 at the University hospitals Bern or Zurich

Exclusion Criteria:

• No full data on matching criteria (which are described below under "study design")
• Only for group A: Not matched patients having been dropped out after the propensity score matching

• Group A ("OAC"): Patients having been hospitalized between 2009 and 2014 in the Bern university hospital and discharged with either OAC or NOAC.
• Group B (LAA-closure): Patients who underwent LAAC between 2009 and 2014 at the University hospitals Bern or Zurich