Atrial fibrillation is the most common type of arrhythmia, or heart rhythm disorder. Atrial fibrillation happens when an irregular electrical activity in the heart affects the atria—the upper chambers of the heart.

When the atria are working properly, electrical activity in the heart causes the atria to contract in regular and ordered beats that pump blood into the lower chambers of the heart—the ventricles. Each heartbeat represents the contraction of the ventricles. However, when the electrical activity becomes chaotic and fast, the atria no longer behave properly.

Instead of steadily pumping, the atria twitch, quiver or contract. The blood they once pumped into the ventricles remains in the upper chambers, increasing the risk of clot formation, or merely empties into the lower chambers without force. That can cause shortness of breath, weakness and heart palpitations.

Stroke also becomes five times more likely: Atrial fibrillation accounts for about 15% of strokes in the United States.

Unfortunately, age increases the risk of atrial fibrillation. More than 2.3 million Americans are affected by the condition—most are age 65 and older. 

Other forms of heart disease, high blood pressure, chronic conditions like sleep apnea, and thyroid problems also raise the risk. Alcohol consumption and stress can also contribute.

Women with atrial fibrillation are more likely to have a stroke than men. Adopting a healthy lifestyle that includes regular exercise and stress reduction can help, as can prompt treatment of those health issues that contribute to risk.

Patients with metabolic syndrome, diabetes, or obesity may have a higher risk of atrial fibrillation.

Symptoms of atrial fibrillation can include:

• Shortness of breath
• Weakness
• Fatigue
• Heart palpitations
• Irregular heartbeat
• Light-headedness or dizziness
• Loss of consciouness
• Chest or abdominal pain

Some patients with atrial fibrillation actually feel no symptoms – making it more difficult to diagnose the disease to prevent consequences such as stroke and heart failure.

Some people with atrial fibrillation may be prescribed blood thinners to reduce the risk of blood clots. Others may be treated with medications that work against arrhythmia, such as sodium channel blockers and potassium channel blockers.

A procedure called ablation eliminates the heart tissue believed responsible for the disruptive activity. That can be done with heat or cold. Recently, Stanford became one of the first hospitals to offer new ablation treatment called Focal Impulse and Rotor Modulation (FIRM).

With FIRM, ablation is guided by a new electrical activity mapping software that pinpoints in the heart the exact electrical sources that drive atrial fibrillation. These sources, called rotors because of their circular shape and spinning motion, are small electrical sources that cause the disorganized activity that produces atrial fibrillation.

In humans, the existence of these rotors had been suspected but only recently confirmed. One of Stanford’s leading experts in atrial fibrillation, Sanjiv Narayan, MD, PhD, discovered these rotors through research and helped develop the mapping software.

In 2013, the FDA approved the mapping catheter used in FIRM ablation. In a study first presented in 2011, the multicenter CONFIRM clinical trial of 107 patients showed that two years after treatment, 86% of those treated with FIRM ablation had not had a recurrence of atrial fibrillation, compared to 44.9% of those who received traditional therapy.

FIRM ablation can be completed in less time than traditional ablation, and is being used at Stanford for routine clinical care and as part of several clinical trials with or without conventional ablation (pulmonary vein isolation).