Cardiology Made Clearwith Dr. Freeman
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AFIB · THE SIMPLE EXPLANATION

AFib, made clear.

Start with three things: your heart rhythm, stroke prevention, and how ablation works.

01 · YOUR HEART RHYTHM

What is AFib?

An electrical problem in the upper chambers of the heart.

Normal heart conduction showing the SA node, AV node, bundle branches, and pathways into the ventricles.
First, a normal heartbeat: The signal starts in the SA node, spreads through the atria, pauses briefly at the AV node, then travels through the heart’s electrical pathways to the ventricles. The upper chambers squeeze first; the lower chambers follow in a coordinated heartbeat.
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What changes in AFib?

Heart cutaway showing disorganized electrical signals in both upper chambers during AFib. The left atrial appendage is visible.

The top chambers (atria) are caught in an electrical storm called fibrillation. Instead of pumping blood forward normally, they quiver.

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Left atrial close-up showing gold AFib trigger cells near the pulmonary vein openings.

AFib can start when trigger cells in the pulmonary veins send out rapid electrical signals. These veins connect to the left atrium.

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You may feel palpitations, tiredness, or shortness of breath—or have no symptoms.

02 · STROKE PREVENTION

Why does AFib increase stroke risk?

Blood thinners lower the chance of clot formation.

A clot forms in the left atrial appendage, travels to the brain, and blocks a brain artery.
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When the atria do not squeeze normally, blood may pool in a small pouch called the left atrial appendage.

A clot can form, travel to the brain, and cause a stroke.

Blood thinners reduce this risk, but do not eliminate it.

03 · TREATING THE RHYTHM

How does AFib ablation work?

Pulmonary vein isolation (PVI) blocks electrical triggers.

A catheter passes through the right atrium and atrial septum into the left atrium, with its circular tip around a pulmonary vein opening.
The catheter is inserted through a femoral vein in the groin and advanced up to the heart. It then reaches the left atrium to treat the area around the pulmonary veins.
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Close-up labeling the trigger cells and the ablation catheter around a pulmonary vein opening.Open full-size image →

Ablation creates an electrical barrier around the pulmonary veins.

Triggers inside the veins can no longer reach the atrium if isolation remains intact.

Ablation treats the heart rhythm. Blood thinners may still be needed afterward.

Ready to learn more?

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