Cardioembolic Stroke in AFib: Defining the Subtype and Its Mechanism

Welcome back to another AJMC Insights series. In "Cardioembolic Stroke in AFib: Defining the Subtype and Its Mechanism," Dr. Barnes joins us to open the series on cardioembolic stroke in atrial fibrillation.

Dr. Barnes begins by introducing himself as a cardiologist and vascular medicine specialist at the University of Michigan. He then defines cardioembolic stroke for the audience. It is one of five recognized stroke subtypes. In this subtype, the clot is thought to originate in the heart. The clot then travels to the brain and blocks blood flow to one side of the brain or the other.

Dr. Barnes lists the remaining subtypes for context. They are large artery atherosclerotic stroke, small artery or lacunar stroke, and undetermined stroke, in which clinicians cannot identify why the event occurred. He stresses that cardioembolic strokes are the ones that start in the heart. They are often related to atrial fibrillation.

He explains why this subtype matters clinically. Cardioembolic stroke accounts for between a quarter and a third of all strokes, so it is a large subtype. It is not the majority, but it is also one of the most severe and most significant stroke types.

Dr. Barnes describes two main sources of cardiac clots. One is the left ventricle, a small subset that usually appears in people who recently had a heart attack or have severe heart failure. The other, and overwhelmingly the larger, is atrial fibrillation, which he says accounts for about four in five cardioembolic strokes.

He then walks through the mechanism. In atrial fibrillation, the upper chambers of the heart, the atria, do not squeeze in a coordinated fashion. They quiver instead. Blood tends to pool and swirl in one part of the heart called the left atrial appendage. Clots tend to form there. If a clot breaks free, it leaves the heart and travels to the brain, and that event causes the stroke.

The next episode in this series, "Cardioembolic Stroke Severity: Disability, Mortality, and Recurrence Risk in AFib," features Dr. Barnes presenting the data on disability, mortality, and recurrence.