Atrial Fibrillation and the Left Atrial Appendage
What Is Atrial Fibrillation?
In a patient with a normal heart rhythm (sinus rhythm), an electrical signal spreads through the top chambers of the heart (the atria), causing them to squeeze and fill the lower chambers (the ventricles), which then pump the blood all over the body. When a patient is diagnosed with atrial fibrillation (AFib), the electrical signals become disorganized and the atria no longer contract effectively. Rather, they quiver at rapid rates, so blood is not pushed to the ventricles as efficiently. With blood sitting stagnantly in the atrium, blood clots are more likely to form. These clots can travel from the heart to the brain, causing a stroke.
Left Atrial Appendage
The most common spot for clots to form is a small wind-sock shaped sac off the left atrium, called the left atrial appendage (LAA). The LAA is thought to be the site of over 90 percent of blood clots associated with AFib. Similar to the appendix in the abdomen, the LAA has no critical function in the heart.
Am I at Risk for Stroke from Atrial Fibrillation?
Your doctor can do a standardized stroke risk assessment called a CHADSVASc score. This score is based on common risk factors such as high blood pressure, age, and diabetes. Your CHADSVASc score can predict your annual risk of stroke without therapy and determine if you require treatment to prevent blood clots from forming.
Treatment Options for Atrial Fibrillation
The traditional way to prevent stroke in patients with Afib is to take strong blood-thinning medicines called anticoagulants. Patients need to take these medications for the rest of their lives. However, this can be challenging for patients: Medications like Warfarin (coumadin) require strict dietary restrictions, the medication dose needs to be changed frequently, and blood testing is required at least monthly. While there are a number of newer anticoagulant medications available that are safer and easier to take, the risk of bleeding while taking these medicines increases as patients age.
Minimally Invasive Procedures
There are minimally invasive procedures that can also reduce the risk of clot formation and stroke. These are called cardiac catheterizations and are performed by inserting a small tube through a vein in the leg to reach the heart.
The goal of radiofrequency ablation is to restore normal heart rhythm, reducing the stroke risk. The ablation is performed by an electrophysiologist, a type of cardiologist that specializes in abnormal heart rhythms. An ablation catheter uses high-frequency electrical energy to scar the specific tissue responsible for the abnormal rhythm. As a result, the tissue can no longer send the electrical signal causing the Afib. This procedure is not effective in all cases and tends to be more successful in younger patients.
Left Atrial Appendage Closure (or Exclusion)
In this procedure, a small plug called a Watchman device is placed into the LAA to seal it off from the rest of the heart. This keeps blood clots from forming in the LAA, reducing the risk of stroke significantly.
The procedure is performed with general anesthesia and takes about one hour. Patients can return home the next day and to full activities within 2–3 days. The Watchman procedure is an excellent alternative to blood thinners in many patients.
Medical trials comparing the Watchman device to ongoing blood-thinner therapy have shown that patients who receive the Watchman have fewer strokes, fewer bleeding complications, and live longer. Since its approval in 2015, there have been over 60,000 Watchman devices implanted in the U.S., with remarkable safety rates reflected in the latest studies.