A left atrial appendage occluder device is a new technology, considered for patients with atrial fibrillation (AF) at risk of stroke who are not suited to conventional stroke prevention, namely anticoagulation (blood thinning). In AF the upper chambers of the heart beat irregularly which can lead to blood clots forming. These blood clots can dislodge into the circulation and travel to the brain causing a stroke. These clots most often form in the left atrial appendage (LAA) of the heart.  Patients with AF at risk of stroke are frequently treated with blood thinning medication such as warfarin or dabigatran to reduce stroke risk. A LAA occluder device is designed to permanently close the LAA and may be considered as an alternative method of stroke prevention in patients with AF who are unsuitable for standard blood thinning medications.