Atrial Fibrillation and the Left Atrial Appendage
The human heart has four chambers: the right and left atrium (the upper chambers) and the right and left ventricle (the lower chambers). When a patient is diagnosed with atrial fibrillation (or AFib), it means that the two atria are "quivering", or contracting irregularly at extremely rapid rates, instead of pumping in a synchronized fashion.
Each atrium also has a small outpouching called the left atrial appendage (LAA), which becomes relevant when patients are in AFib. Instead of contracting regularly, the atria of patients in AFiv are relatively stagnant, with blood often pooling in the atrial appendage. This can lead to the formation of clots at this site. If a piece of this clot were to break off, or embolize, and travel to the brain, a stroke will result. In fact, in patients with atrial fibrillation who suffer a stroke or mini-stroke, the overwhelming majority are caused by a clot from the left atrial appendage embolizing to the brain.
Treatment Options for Atrial Fibrillation
In order to minimize the stroke risk, most patients with AFib are required to take blood thinners, usually warfarin (Coumadin), for the rest of their lives to prevent blood clot formation in the LAA. This treatment is very effective for many patients. However, these are difficult medications to take. Warfarin/Coumadin requires strict dietary restrictions, the dose of the medication needs to be changed frequently, and blood testing is required at least monthly. Newer medications such as Pradaxa, Eliquis, and Xarelto have fewer dietary restrictions, and do not require blood testing, but are extremely expensive. All of these drugs carry a significant risk of bleeding complications, especially as patients grow older.
Recently, the Food and Drug Administration (FDA) approved a new technology called the WATCHMAN device for closure of the LAA. The purpose of this device is to eliminate the LAA as a potential source of clot and stroke. The closure of the LAA is a catheter-based procedure in which the WATCHMAN device is inserted into the LAA through a small tube (catheter) advanced to the heart from the femoral vein in the leg. Once the catheter is placed in the LAA, the device expands as it comes out the end of the catheter. The procedure, called a left atrial appendage closure (or exclusion), is typically performed under general anesthesia and takes approximately one hour. Patients normally remain in the hospital for approximately 24 hours following the procedure.
A large clinical trial (PROTECT AF Trial) has demonstrated that compared to patients who remain on warfarin, the patients who had the WATCHMAN device placed and who come off the warfarin have a 35% reduction in mortality (they live longer), a 40% reduction in stroke, and an 85% reduction in bleeding strokes.
The device is now approved by Medicare and many other insurers, and is available to any patient who wishes to come off the blood thinners, or who is at high risk of stroke because they cannot take the blood thinners. Other similar devices will soon begin comparative clinical trials in the United States, to assess the outcomes compared to the WATCHMAN device.