Division of Cardiology

Can the shape of the left atrial appendage affect stroke risk?

A recent study presented by Dr. Luigi Di Biase has identified a strong link between the structure of the upper left portion of the heart and the occurrence of stroke and/or transient ischemic attack (TIA, or mini-stroke) in patients with atrial fibrillation.

Luigi Di Biase, MD, PhD, FACC, FHRS
The left atrial appendage (LAA), a small muscular pouch connected to the left atrium of the heart, squeezes rhythmically and ejects blood into the left atrium with each heart muscle contraction. The LAA is one of the major sources of clot formation contributing to stroke and TIA in patients with atrial fibrillation (AF). During AF, as the heart beats erratically due to irregular contraction of its upper two heart chambers and the LAA compresses inconsistently, blood may stagnate inside the pouch, forming clots that release into the blood stream and travel to the brain, causing a stroke.

In patients with atrial fibrillation, stroke risk is managed with oral anticoagulants (blood thinners such as warfarin or the newer oral anticoagulants such as pradaxa, rivaroxaban and apixaban) or occlusion devices (WATCHMAN, LARIAT, AtriClip, and many others), which divert the blood flow by closing off the LAA to prevent pooling and clot formation.

The CHADS2 score and more recently the CHADSvasc score represent the most utilized classifications to identify patients at higher risk for stroke and the decision on oral anticoagulation. "Identification of patients at higher risk for stroke is key. Although these scores have an important predictive value, we still have patients with low scores who experience stroke," said Dr. Di Biase, MD, PhD, FACC, FHRS, Associate Professor of Medicine (Cardiology) at Albert Einstein College of Medicine/Montefiore Medical Center and Senior Researcher at Texas Cardiac Arrhythmia Institute at St. David’s Medical Center, Austin, Texas, USA.

Dr. Di Biase’s study, the first of its kind to link different LAA structures with the risk of prior stroke/TIA, examined the left atrial appendages of 932 U.S. and Italian patients with drug-resistant atrial fibrillation who were planning to undergo catheter ablation. Using computed tomography (CT) and magnetic resonance imaging (MRI), Dr. Di Biase and colleagues identified four different categories of LAA morphologies: "Chicken Wing", "Cactus", "Windsock", and "Cauliflower".

The Chicken Wing LAA, found in nearly 50% of the patient population, had a prominent bend in the middle part of the dominant lobe, folding back onto itself.*

The Cauliflower LAA had no dominant lobe, limited length, and complex internal characteristics including variations in its shape (oval vs. round) and number of lobes.*

The Cactus LAA had a dominant central lobe with small secondary lobes extending from each side.*

The WindSock LAA had one dominant lobe, with variations of secondary and even third-level lobes arising from it.*

*Images were modified from Di Biase et al J Am Coll Cardiol. 2012 Aug 7;60(6):531-8. 

Dr. Di Biase and colleagues analyzed patients’ LAA morphologies alongside information about their history of stroke/TIA (collected from chart reviews) and CHADS2 score (congestive heart failure, hypertension, age under 75, diabetes mellitus, and prior stroke or TIA). "We found that patients with the Chicken Wing LAA morphology have a statistically significant lower risk of previous stroke/TIA when compared with all the remaining LAA morphology described," said Dr. Di Biase, who was among world-renowned atrial fibrillation experts presenting their work at the Boston Atrial Fibrillation Symposium in Orlando, Florida earlier this month.

Patients who had Chicken Wing morphology were found to be four times less likely to have had a prior stroke/TIA than patients with Cactus morphology, five times less likely than those with Windsock morphology, and eight times less likely than those with Cauliflower morphology. The Chicken Wing morphology was concluded to be protective.

"If confirmed by further studies, these results could have a relevant impact on the oral anticoagulation management and occlusion device management of patients with an intermediate risk for stroke, because we will be able to identify patients with low stroke risk who might benefit from oral anticoagulation," said Dr. Di Biase.

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