Does left atrial appendage closure prevent strokes?

Photo of a couple talking to a doctor (Alex Raths / iStock / Thinkstock)

Atrial fibrillation increases the risk of a stroke caused by blood clots that develop in the left atrium (left upper heart chamber). Implants that block part of the heart known as the left atrial appendage are sometimes used to try to prevent strokes. But studies on this treatment approach leave many questions unanswered.

In atrial fibrillation, the upper heart chambers (the atria) don’t pump out all of the blood, and they contract (squeeze) too slowly. This means that blood clots are more likely to form. If a blood clot is carried to the brain in the bloodstream, it may lead to a stroke.

Many studies have shown that oral anticoagulants (anti-clotting medication) can greatly reduce the risk of a stroke. They are recommended by medical societies as a routine treatment for the prevention of strokes, and most people with atrial fibrillation take them.

But because they increase the risk of bleeding, anticoagulants aren’t suitable for some people – for instance, those who have had a brain hemorrhage (bleeding in the brain) in the past. Anti-clotting medication is particularly dangerous if the potential causes of bleeding can’t be influenced. In such situations, closing off the left atrial appendage with an implant may be considered as a treatment option, in order to reduce the risk of a stroke.

Implants to block the left atrial appendage

It is estimated that about 90% of the blood clots that cause strokes develop in a part of the heart known as the left atrial appendage. This is a pouch-like bulge in the left atrium (left upper heart chamber). As an alternative to treatment with anticoagulant medication, implants have been developed to close off the left atrial appendage and try to stop blood clots entering the bloodstream from there.

Two such implants that are used in Germany are called the Watchman implant and the Amplatzer septal occluder device. The Watchman implant looks like a parachute made out of wire mesh with a polyester cover. The Amplatzer septal occluder has a similar structure but a different shape.

The devices are implanted using a cardiac catheter. In order to find out which size of implant is needed, the size of the left atrial appendage is determined beforehand using ultrasound and sometimes special X-ray examinations. The catheter is then inserted into a vein in the groin and pushed along until it reaches the right atrium. The left atrium is reached by puncturing the wall between the two atria with the catheter. Once the catheter is in the correct position, the implant is pushed out and placed in the left atrial appendage.

The atrial appendage can also be surgically closed or removed. But this is only considered in people who have to have heart surgery, such as bypass surgery, anyway.

Once the left atrial appendage closure has been carried out, the success of the procedure has to be assessed – for instance using a special kind of ultrasound scan. Only then can the patient stop taking anticoagulants.

What are the advantages and disadvantages of implants?

Implants are used to close off the atrial appendage, with the aim of allowing people to stop continuously taking anticoagulants. But anticoagulants still need to be taken in the first few weeks after the procedure.

One disadvantage of implants is that – unlike medication – they don’t offer protection from blood clots that develop elsewhere in the heart or bloodstream.

And the catheter procedure carries risks too. The sac enclosing the heart may fill up with fluid after the procedure. In severe cases, this can become life-threatening because the heart can then no longer pump properly. The treatment for this condition usually involves puncturing the sac and removing the fluid through a hollow needle (cannula). Further possible complications of the procedure include bleeding that may require a blood transfusion, as well as damage to the heart muscle.

After the implant has been placed in the left atrial appendage, blood clots may form on the surface of the wire mesh. These, too, might block a blood vessel and cause complications such as a stroke. For this reason, long-term treatment with antiplatelet medication is recommended afterwards. Like anticoagulants, antiplatelets reduce the clotting ability of the blood, but their effect is much weaker. The antiplatelet acetylsalicylic acid (the drug in e.g. Aspirin) is generally used for this purpose.

Research results

An independent group of researchers from the University of Portland in the U.S. analyzed studies on left atrial appendage closure. They wanted to find the answers to several questions:

  • How effective are procedures to close off the atrial appendage compared to treatment with medication?
  • What complications are they associated with, and how common are complications?
  • Is the procedure particularly effective or particularly risky in certain groups of people?

In order to answer these research questions, the researchers did a systematic search for suitable studies, and assessed the quality of the studies and how reliable the results were.

They found two suitable studies on the Watchman implant. In both studies, the implant was compared with medication-based treatment. There were only three small studies on the Amplatzer septal occluder. The results of these studies weren't reliable enough to be able to draw any conclusions about how effective they are.

A total of around 1,100 people who had atrial fibrillation took part in the two studies on the Watchman implant. About 70% of them were men. Their average age was 73, and they had a moderate risk of stroke. People who aren't able to take anticoagulants weren't allowed to take part.

The studies compared two treatment approaches with each other:

  • Watchman implant: The participants in this group had a Watchman device implanted. They carried on taking anticoagulants for a few weeks after the procedure, until a thin layer of tissue had grown over the surface of the implant and the atrial appendage had been closed off. Up until six months after the procedure, the participants took two different antiplatelet drugs (clopidogrel and acetylsalicylic acid – the drug in medications like Aspirin). After that, they took acetylsalicylic acid continuously.
  • Treatment with medication: The other group of participants took oral anticoagulants known as vitamin K antagonists.

After about two years, the researchers compared how many people had passed away, had a stroke or – for example – had a heart attack or thrombosis. They also looked at how often the implantation procedure was successful, and how often the treatments led to side effects or complications.

Research results not very reliable

The Watchman device was successfully implanted in 90 out of 100 participants. In the other 10 out of 100, it usually wasn’t possible to put the device in the correct position, or in a stable enough position, so it had to be removed again.

There were no clear differences between the two treatment groups: The frequency of strokes and other conditions caused by blocked blood vessels was similar in both groups. So was the frequency of deaths. However, strokes caused by blood clots were somewhat more common in the Watchman group. The Watchman implant might possibly reduce the risk of bleeding in the brain, though, because people no longer need to take anticoagulants.

Generally speaking, the results of the studies were very unreliable because the studies were quite small and didn’t last very long. Studies that compare medications for atrial fibrillation usually have several thousand people in them. According to the FDA (U.S. regulatory authority), it isn’t currently possible to draw any clear conclusions about the long-term effectiveness of the Watchman implant.

How common are complications?

On average, 8 out of 100 participants who had a Watchman implant experienced complications (medical problems caused by the treatment). These were mainly bleeding that required treatment, and fluid around the heart that had to be treated – either surgically or using a cannula to drain the fluid. 1 out of 100 people had a stroke during the procedure to implant the device.

The risk of complications depends on a lot of factors, such as the patient’s general health and how skilled the surgeon is. Because of this, the research results can only give a rough estimate of how likely complications are. They may be more likely in the “real world” (rather than in studies) because the surgeons who operated in the studies generally had a lot of experience with this specific type of surgery.

Treatment with anticoagulants can have side effects too. The most common ones include bleeding in the brain (brain hemorrhage) and bleeding in the stomach or bowel. Bleeding in the brain is very rare, but particularly serious. Only one of the studies compared how often the treatments led to side effects and complications. In that study, the Watchman implant led to slightly more side effects and complications than the medication did.

Unanswered questions

Closing off the left atrial appendage, for instance with the Watchman implant, is mainly considered as a treatment for people who can’t take anticoagulants – for instance because they have a very high risk of bleeding. But this group of people weren’t allowed to take part in the studies.

Also, the people who received a Watchman implant took anticoagulants for a while. So it isn’t possible to know for sure what would happen if people who can’t use anticoagulants received a Watchman implant.

What do medical societies recommend?

Cardiology societies in Europe regularly issue recommendations on the treatment of atrial fibrillation. Because the study results aren’t very reliable, they do not yet consider left atrial appendage closure to be an alternative to treatment with anticoagulants.

Treatment with a Watchman implant or similar product is therefore only recommended in people who have a high risk of stroke and who can’t take anticoagulants because they have a high risk of bleeding too. The societies also advise people to carefully consider the risk of complications associated with implants, as well as the fact that most people who have atrial fibrillation can take anticoagulants.