Left atrial appendage occlusion is a treatment strategy to prevent blood clot formation

Thrombosis

Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...

 in atrial fibrillation

Atrial fibrillation

Atrial fibrillation is the most common cardiac arrhythmia . It is a common cause of irregular heart beat, identified clinically by taking a pulse. Chaotic electrical activity in the two upper chambers of the heart result in the muscle fibrillating , instead of achieving coordinated contraction...

 (AF). In this heart rhythm disorder, blood clots form in the left atrial appendage (LAA) in 90% of cases.
During cardiac catheterization

Cardiac catheterization

Cardiac catheterization is the insertion of a catheter into a chamber or vessel of the heart. This is done for both investigational and interventional purposes...

, an expandable nitinol frame can be introduced into the appendage.

LAA occlusion can be used as an alternative for patients who cannot use oral anticoagulants such as warfarin

Warfarin

Warfarin is an anticoagulant. It is most likely to be the drug popularly referred to as a "blood thinner," yet this is a misnomer, since it does not affect the thickness or viscosity of blood...

, although it has been studied and approval is sought as an alternative in patients who are eligible for oral anticoagulants. Some patients can not take anticoagulants because of a recent or previous bleeding, non-compliance or pregnancy (17% in one study).
A sizeable portion of patients (21% in the above mentioned study) eligible for anticoagulants are not offered them, or are not taking them. This goes especially for the elderly, although studies have indicated that they can also benefit from anticoagulants.

Devices and alternatives

On April 23, 2009 an U.S. Food and Drug Administration Advisory panel voted 7 to 5 in favor of approval of the WATCHMAN device (by Atritech Inc., Plymouth

Plymouth

Plymouth is a city and unitary authority area on the coast of Devon, England, about south-west of London. It is built between the mouths of the rivers Plym to the east and Tamar to the west, where they join Plymouth Sound...

, Minnesota

Minnesota

Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...

) for use in patients with non-valvular AF in centers with heart surgery backup. The panel also advised creation of a registry and a certification program for physicians who implant the device. This decision was based on the results of the PROTECT-AF trial (presented at the 2009 American College of Cardiology

American College of Cardiology

The American College of Cardiology is a nonprofit medical association established in 1949 to advocate for quality cardiovascular care through education, research promotion, development and application of standards and guidelines, and to influence health care policy...

 Scientific Sessions), which showed less hemorrhagic stroke with the device compared to treatment with warfarin; stroke

Stroke

A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...

 and all-cause mortality outcomes were non-inferior.

Another device termed PLAATO (percutaneous left atrial appendage transcatheter occlusion) was the first LAA occlusion device,
although it is no longer being developed by its manufacturer (Appriva Medical , Inc. from Sunnyvale, CA).
In 210 patients receiving the PLAATO device, there was an estimated 61% reduction in the calculated stroke risk.

Both LAA occlusion systems are introduced into the right atrium

Right atrium

The right atrium is one of four chambers in the hearts of mammals and archosaurs...

 and are then passed into the left atrium

Left atrium

The left atrium is one of the four chambers in the human heart. It receives oxygenated blood from the pulmonary veins, and pumps it into the left ventricle, via the mitral valve.-Foramen ovale:...

 through a patent foramen ovale or through a puncture hole. These small iatrogenic atrial septal defects usually disappeared within six months. Although these are catheter-based techniques, they are generally performed under general anaesthesia

General anaesthesia

General anaesthesia is a state of unconsciousness and loss of protective reflexes resulting from the administration of one or more general anaesthetic agents...

.

The Amplatzer device, used to close atrial septal defects, has also been used to occlude the left atrial appendage in one small series. This can be performed without general anaesthesia and without echocardiographic

Echocardiography

An echocardiogram, often referred to in the medical community as a cardiac ECHO or simply an ECHO, is a sonogram of the heart . Also known as a cardiac ultrasound, it uses standard ultrasound techniques to image two-dimensional slices of the heart...

 guidance.
Transcatheter patch obliteration of the LAA has also been reported.

The LAA can also be surgically removed simultaneous with other cardiac procedures such as the maze procedure or during mitral valve

Mitral valve

The mitral valve is a dual-flap valve in the heart that lies between the left atrium and the left ventricle...

 surgery.
Finally, the left atrial appendage has been closed in a limited number of patients using a chest keyhole surgery

Thoracoscopy

Thoracoscopy is a medical procedure involving internal examination, biopsy, and/or resection of disease or masses within the pleural cavity and thoracic cavity...

 approach.

Adverse events and limitations

The main adverse event

Adverse event

An adverse event is any adverse change in health or side effect that occurs in a person who participates in a clinical trial while the patient is receiving the treatment or within a previously specified period of time after the treatment has been completed.AEs in patients participating in...

s related to this procedure are pericardial effusion

Pericardial effusion

Pericardial effusion is an abnormal accumulation of fluid in the pericardial cavity. Because of the limited amount of space in the pericardial cavity, fluid accumulation will lead to an increased intrapericardial pressure and this can negatively affect heart function...

, incomplete LAA closure, dislodgement of the device, blood clot formation on the device requiring prolonged oral anticoagulation, and the general risks of catheter-based techniques (such as air embolism

Air embolism

An air embolism, or more generally gas embolism, is a pathological condition caused by gas bubbles in a vascular system. The most common context is a human body, in which case it refers to gas bubbles in the bloodstream...

).
The left atrium anatomy can also preclude use of the device in some patients.

Following implantation, a transesophageal echocardiography has to be performed to judge completeness of closure and the presence of blood clots. Patients need to use low dose aspirin

Aspirin

Aspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...

 indefinitely, and prolonged clopidogrel

Clopidogrel

Clopidogrel is an oral, thienopyridine class antiplatelet agent used to inhibit blood clots in coronary artery disease, peripheral vascular disease, and cerebrovascular disease. It is marketed by Bristol-Myers Squibb and Sanofi-Aventis under the trade name Plavix. The drug works by irreversibly...

 can be prescribed as well; oral anticoagulants are needed following implantation of the WATCHMAN device to allow blood vessel lining to form around the device (endothelialization).

Theoretical concerns surround the role of the LAA in thirst

Thirst

Thirst is the craving for fluids, resulting in the basic instinct of animals to drink. It is an essential mechanism involved in fluid balance. It arises from a lack of fluids and/or an increase in the concentration of certain osmolites, such as salt...

 regulation and water retention because it is an important source of atrial natriuretic factor.
Preserving the right atrial appendage might attenuate this effect.