Decreasing Stroke Risk When Ablation for Atrial Fibrillation Isn’t Possible

August 2, 2010 8:05 AM CT

By Christine Welniak

Dr. Mubashir Mumtaz, Chief of Cardiovascular and Thoracic Surgery at Pinnacle Health in Harrisburg, PA, sees a new way to reduce stroke risk for his atrial fibrillation patients who can’t have afib surgery. Just last week, Dr. Mumtaz implanted the AtriClip Left Atrial Appendage Exclusion device in a patient who had an operation to replace her mitral valve. Performing afib ablation wasn’t an option, but by using the AtriClip, Dr. Mumtaz likely reduced her stroke risk.

People with AF have a five-fold greater risk of having a stroke compared to those who don’t have atrial fibrillation according to the Framingham Heart Study. Doctors believe the higher risk is because AF causes blood to pool in the left atrial appendage, sometimes referred to as the LAA, which is a small pouch attached to the left atrium. When blood is caught in the left atrial appendage, clots can form because the inside surface of the appendage is rough and irregular, unlike the rest of the left atrium. If clots detach, they can travel through the blood stream and cause a stroke. Thus, preventing blood from flowing into the left atrial appendage, which is known as “occluding” the LAA, could lower an afib patient’s stroke risk.

The AtriClip, which is the first left atrial appendage occlusion device to be approved in the US and is used in open heart surgeries, is an important advancement for atrial fibrillation patients. The device is applied on the outside of the left atrial appendage. By pinching the opening of the appendage, the AtriClip prevents blood from entering the appendage where it could get caught on the rough surface.

Most of the other LAA occlusion devices that are in clinical trials are placed inside the appendage. When a device is placed inside the appendage, blood cells need to form around it in order to create a smooth surface. This may place a person at higher risk of stroke during the four to six weeks after the procedure when the appendage is not fully occluded. Devices, such as the AtriClip, that go outside of the left atrial appendage, do not have this risk.

This may be particularly important for patients who can’t have an ablation for atrial fibrillation (either catheter or surgery). Factors that could prevent a patient from having an ablation include an enlarged left atrium, age, and general health. These patients are subject to the high stroke risk that’s associated with AF.

According to Dr. Mumtaz, the AtriClip is simple to implant and the procedure takes less than two minutes. He commented, “The ease of placing this device to occlude the atrial appendage may add to reduced risk of strokes in the long run.”

To Occlude or Not to Occlude

The left atrial appendage is thought to be a remnant from embryonic development of the left atrium, meaning that it isn’t essential for the heart to work. However, the appendage plays a role in cardiac function, albeit a minor one, accounting for 10–20% of cardiac output in a normal heart. In addition, the left atrial appendage produces a hormone (atrial natriuretic peptide) that helps regulate the balance of water, sodium, and potassium in the heart. So should the left atrial appendage be left alone in order to preserve these functions? 

Not for patients with afib, says Dr. Mumtaz, who describes the left atrial appendage as providing “an extra kick” to cardiac output for individuals with normal hearts. AF patients, however, tend to have abnormal appendages (enlarged, thickened, and/or weakened muscle), so it’s thought that the left atrial appendage has less of a role in cardiac output. For AF patients, Dr. Mumtaz believes the benefit of occluding the left atrial appendage, which lowers stroke risk, far outweighs any downside that could come from a somewhat reduced cardiac output. He notes that other areas in the heart also produce atrial natriuretic peptide, so even if the left atrial appendage is occluded, at least some of the hormone will continue to be produced.

Can Warfarin Be Stopped?

Theoretically, afib patients who have had the left atrial appendage removed or occluded should not have to take anticoagulant medication, such as warfarin (Coumadin). However, proving this hypothesis depends on large clinical trials being performed.

A patient’s risk factors for stroke influence a doctor’s decision to prescribe warfarin. Several methods to assess risk are in use. The most commonly used scoring system is called CHADS2, which is an acronym of the major risk factors for stroke (congestive heart failure, hypertension, age, diabetes, and previous stroke or mini-stroke).

Afib patients who can’t have an ablation may have to remain on warfarin even if their left atrial appendage is occluded. However, Dr. Mumtaz believes that occluding the appendage is still beneficial since warfarin doesn’t completely eliminate stroke risk—there’s still a 33% chance of having a stroke related to afib while taking the anticoagulant.

Dr. Mumtaz commented, “I am very optimistic that further trials will show the true efficacy of the AtriClip. Stroke is devastating. I’m glad we now have a way to lower risk easily and quickly. Since AtriClip decreases the risk of clot formation in patients with atrial fibrillation, their stroke risk should also be reduced. This is important for any patient with AF since the risk is not completely resolved with warfarin alone. However, further trials on the AtriClip are needed to validate it.”

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Christine Welniak writes about atrial fibrillation and other heart diseases and conditions for patients, medical professionals, and investors.