Teachable moment in classrooms:

  1. heart chapter – description of blood flow through the chambers of the  heart 
  2. blood chapter – mechanism of blood clotting
  3. hemodynamics chapter – connection of atria to systemic veins and systemic arteries

The news item:  Recently the following report appeared online:

Durham VA Performs Second Watchman Procedure in North Carolina, First in VISN 6 | VA Durham health care | Veterans Affairs

On August 21, 2023, the Durham VA Health Care System achieved a significant medical milestone as it became the second hospital in North Carolina and the first facility in VA’s Mid-Atlantic Health Care Network to perform the Watchman FLX Left Atrial Appendage Closure Device procedure.

The article describes the first implantation of the Watchman FLX Pro device for left atrial appendage closure, and that the device is used to reduce the incidence of stroke in patients with atrial fibrillation who can not tolerate long-term use of blood thinners. The article also describes atrial fibrillation as a form of arrhythmia.

So, Why Do I Care??  There are over 10 million Americans with atrial fibrillation, and all of them have an increased risk of stroke. Because strokes can have debilitating consequences, it is important to prevent atrial fibrillation or stop the process of blood clot formation. While pacemakers and blood thinners serve to prevent atrial fibrillation in most people, in patients who cannot tolerate long-term blood thinner treatment other treatment alternatives must be used.

Plain English, Please!!!  First, let’s talk about the connection between stroke and the atria of the heart. A stroke is a consequence of a blood clot blocking blood flow through an artery in the brain. During atrial fibrillation the muscle of the atria shivers, and the ejection of blood from the atria slows down. Think about when your teeth chatter in the cold. Your jaw muscles shiver and cannot create force. Similarly, the atria cannot create force to push out blood. Blood clots form with ease in such very slowly flowing blood. The critical location for the formation of blood clots can be pinpointed to the appendage of the left atrium. From there normal blood flow takes the blood clots from the left atrium to the arteries of the brain.

Second, let’s talk about the atrial appendage. While the atrium is a chamber shaped like a wide-open cave, the appendage is shaped like a pocket of a pita bread. The opening of the pocket is connected to the cave, and, so, the blood flow into the atrium inflates the pocket. Because the pocket remains thin even when it is filled with blood, blood flow is especially slow coming out of the pocket. That makes the left atrial appendage a critical site for clot formation during atrial fibrillation.

Third, let’s talk about the implantation process. It is intuitive to think that if we could plug the left atrial appendage then we would prevent clot formation. The device that fills up and closes off the left atrial appendage is moved into the left atrium using a catheter. The catheter is introduced into a vein in the groin area. Now, if we follow the coursing of the catheter tip from the femoral vein, we will pass through the external and then the common iliac veins, and then into the inferior vena cava. From the inferior vena cava the catheter enters the right atrium. How are we going to move the catheter tip to the left atrium? In an unusual design, the catheter must be pushed across the wall that separates the right from the left atrium. In other words, the catheter makes a small hole in the atrial septum. Once in the left atrium, the catheter tip is guided into the opening of pita bread-like appendage, and made to unfold, expand to a biscuit shape, and fill the appendage. With that accomplished the appendage has no blood flow into it, so clots can no longer form. Once the catheter is withdrawn a new endocardial layer forms on the exposed surface of the implant, and the hole in the atrial septum heals.

Go back

Your message has been sent