Antiarrhythmic Drug used to prevent or correct a heart rhythm disturbance such as atrial fibrillation.

Anticoagulant Drug used to delay blood clotting or prevent clots from becoming larger. Warfarin (Coumadin^®) is an oral anticoagulant (pill). Heparin is injected into a vein (IV tube).

Antiplatelet Drug used to prevent platelets (blood cells) from binding together to form blood clots. Aspirin and clopidogrel (Plavix) are antiplatelets.

Atria Upper right and left chambers of the heart.

Atrial fibrillation Heart rhythm disturbance characterized by the rapid, irregular beating of the left and right atria.

Catheter Flexible tube inserted into a body cavity or blood vessel for diagnosis or treatment.

Catheterization laboratory (cath lab) Examination room in a hospital or clinic equipped to support catheterization procedures such as WATCHMAN LAA closure.

Coumadin^® Brand name for the anticoagulant, warfarin, manufactured by Bristol-Myers Squibb.

Echocardiography (echo) Medical imaging technique that uses ultrasound energy and the acoustic (sound) properties of heart tissue to produce real-time images in multiple planes. See also transesophageal echo (TEE) and transthoracic echo (TTE).

Embolus Blood clot (thrombus) that breaks loose from the site of formation and circulates through the bloodstream until it plugs a small blood vessel and obstructs blood flow (oxygen delivery).

Fluoroscopy (fluoro) Medical imaging method that uses x-rays to acquire real-time images of motion. Fluoro is used in procedures that require immediate feedback, for example, catheter placement.

International normalized ratio (INR) Mathematical standard used to evaluate the time it takes for blood to clot and determine the effective warfarin dose in patients at risk for stroke.

Ischemia Pain caused by insufficient blood flow (oxygen delivery) to an organ. See also transient ischemic attack (TIA).

Left atrial appendage (LAA) Small pouch-like structure that arises from the left wall of the left atrium. The LAA is lined with muscle ridges that tend to collect blood in the presence of abnormal blood flow. In patients with atrial fibrillation (AF), blood clot formation in the LAA is common.

Magnetic resonance imaging (MRI) Medical imaging method that uses radio waves and a stable magnetic field to obtain images.

Stroke Rapid loss of brain function due to insufficient blood flow (oxygen delivery) to brain tissue, usually associated with complete obstruction of a blood vessel. The result may be weakness, speech defects, paralysis, or death.

Thromboembolic stroke Disruption of the blood supply to the brain caused by an embolus. Also called cerebrovascular accident (CVA).

Thrombus Blood clot that forms in a blood vessel or heart chamber. See also embolus.

Transesophageal echo (TEE) Echo imaging method in which an ultrasound probe is positioned in the esophagus to acquire heart images without interference from the ribs, chest wall, and lungs.

Transient ischemic attack (TIA) Temporary episode of insufficient blood flow to the brain, usually associated with partial obstruction of a blood vessel. Transient (temporary) symptoms include numbness or tingling, blurred vision, or impaired speech. Also called mini-stroke.