Good explanation. I would only add that assuming the watchman device has been optimally sized to occlude ( close off / block ) the LAA , the safety and efficacy of Watchman is well established at this point for folks with atrial fib. Lots of skiers sidelined by blood thinners needed to prevent AF complications can eventually get back on snow… and shift their skiing related medical concerns from cardiology/ neurology back to orthopedics!The Watchman is not a filter but rather a "plug". People with atrial fibrillation(uncoordinated contraction of the upper chambers of the heart) can develop blood clots, predominately in the left atrial appendage, a small sack area of the left atrium. This happens because the atria do not contract properly and therefore do not empty well and the blood sits in the left atrial appendage and clots. The danger is this clot can escape and travel to the left ventricle where it is pushed into the aorta. The aorta takes blood from the heart to the rest of the body. The fear is that the clot will go to the brain, causing a stroke, but it can also create havoc by lodging in a blood vessel to the bowel or leg.
The Watchman is placed into the opening of the left atrial appendage and closes it off over time so that blood cannot pool there or clots escape. It will eventually seal it off with tissue ingrowth. One will need to stay on blood thinners for a couple of months while this ingrowth happens and then on platelet inhibitors forever.