LEFT ATRIAL APPENDAGE CLOSURE
First of all, when talking about left atrial appendage (LAA) closure, you need to know about a few anatomical bases.
WHAT IS THE LEFT ATRIAL APPENDAGE?
Here is a brief reminder of the anatomy of the heart
The heart is an organ that includes 4 chambers:
- the atria (right and left)
- the ventricles (right and left).
The atria are used to fill-up the ventricles. This is done thanks to two valves:
- The tricuspid valve on the right
- The mitral valve on the left.
The ventricles enable the release of blood to irrigate the surrounding organs.
- On the right, non-oxygenated blood (blue) is sent to the pulmonary circulation via the pulmonary artery.
- On the left, the oxygenated blood (red) is sent to the so-called systemic circulation via the aorta.
Note that the atria are somewhat spherical cavities (like a soccer ball) while ventricles are rather somewhat cylindrical (like a rugby ball cut in 2 widthwise).
Description of the atrial appendage.
It is an anatomical structure that is connected to the atria which is a kind dead end looking like an ear-shaped bag in the muscle of the atria. In the same way that there are two atria there are two atrial appendages.
WHAT IS THE ATRIAL APPENDAGE FOR?
In physiology, the role of the atrial appendage, if any, remains unclear. It is an embryonic remnant totally useless to the functioning of the heart and patients whose auricle is is occluded (during surgery for example) can have a completely normal life. On the other hand, the auricle can play a crucial role in certain pathologies such as atrial fibrillation. Indeed, the anarchic rhythm of the atria which is typical of atrial fibrillation leads to a slowing down of the blood circulation in that area, and it can induce the formation of clots, most often in the left atrial appendage. If the clot migrates, it can result in a stroke or, in rarer cases, peripheral embolism. However, the risk depends on a great number of parameters which will have to be assessed by the cardiologist in consultation.
WHY AND WHEN SHOULD THE LEFT ATRIAL APPENDAGE BE OCCLUDED?
Closing or occluding the left atrial appendage means preventing the formation of a clot in a patient with atrial fibrillation. But it is not a first-line therapy. Indeed, patients suffering from atrial fibrillation are often prescribed an antithrombotic treatment. These blood-thinning drugs are easy to use (generally in the form of a tablet) and perfectly effective in preventing clots from forming in the heart, in particular in the left atrial appendage. However, it significantly increases the risk of bleeding. Thus, although often well tolerated, antithrombotic drugs may sometimes induce severe haemorrhages, which may be a contra-indication to their use. That is why it is necessary to close the left atrial appendage in these patients.
HOW IS THE LAA OCCLUDED?
There are 2 methods of proceeding:
The first one is surgical. It is usually performed during open heart surgery. The surgeon makes a few stitches at the base of the atrial appendage which can then be occluded. However, this technique is extremely invasive. It is used in patients with arrhythmia, only when cardiac surgery has already been scheduled (valve replacement or bypass surgery, for example).
The second method uses the percutaneous route. In this case, the term percutaneous closure of the left atrium is used. The operators are generally interventional cardiologists. The procedure does not require any opening: everything is done by the vascular route. A small puncture in the femoral vein is used to introduce a prosthesis which is then released into the left auricle through a sheath. The closure of the left auricle by the prosthesis in place will then prevent a clot from forming there. Nevertheless, the procedure requires a transseptal puncture and precise guidance, radioscopic as well as electrocardiographic, to reach the left atrium via the right atrium. This is why it is most often performed under general anesthesia. The intervention lasts about thirty minutes and requires a minimum of 2 nights in hospital.