What Is Atrial Fibrillation (AFib)? Causes, Symptoms, and Treatment
A clear explanation of atrial fibrillation, why the heart suddenly beats irregularly, and how doctors diagnose and treat AFib
When the Heart Suddenly Starts Racing
David is sitting upright in the emergency department bed, looking a little pale and flushed. His smartwatch keeps buzzing with alerts. His heart rate is hovering around 160.
He says it started suddenly earlier in the day. No chest pain. Just a pounding, chaotic heartbeat and a sense that something is not right. When we connect him to the cardiac monitor, the rhythm tells the story immediately. His heart is not just fast. It is irregular.
This pattern often points toward a very specific diagnosis.
What Atrial Fibrillation Actually Is
Atrial fibrillation is an abnormal heart rhythm. In a healthy heart, electrical signals travel through a carefully organized pathway. These signals trigger each heartbeat in a steady pattern that allows the heart chambers to contract in a coordinated way.
In atrial fibrillation, that electrical system becomes chaotic. Instead of a steady rhythm, the electrical signals fire randomly and rapidly across the upper chambers of the heart.
Doctors often describe the rhythm as “irregularly irregular.” There is no predictable pattern between beats.
Why the Heart Starts Beating This Way
AFib often appears when the heart’s electrical system becomes unstable.
Alcohol use is a common trigger. In emergency medicine, we sometimes see AFib appear after heavy drinking, a pattern sometimes called holiday heart syndrome. Severe dehydration, vomiting, or diarrhea can also disrupt electrolytes like potassium or magnesium, which the heart relies on for electrical stability.
Other medical problems can trigger AFib as well. Heart attacks, thyroid disease, infections, stimulant drugs, and chronic heart disease can all disturb the heart’s electrical system and lead to this rhythm. Pasted text
Why Doctors Take AFib Seriously
AFib is not dangerous only because of the fast heart rate.
When the heart beats chaotically, the upper chambers stop squeezing blood effectively. Instead of moving forward with each beat, blood can swirl and stagnate inside the heart.
Over time, this stagnant blood can form clots. If one of those clots travels through the bloodstream and reaches the brain, it can cause a stroke. That is why doctors focus not only on controlling the heart rate, but also on reducing the risk of clot formation.
How Doctors Restore a Safer Rhythm
Treatment depends on how long the arrhythmia has been present and how stable the patient is.
If AFib started recently, doctors may try to restore the normal rhythm through cardioversion. This can be done with medications or with a brief electrical shock that resets the heart’s electrical system.
If the timing of the rhythm is unclear or it may have been present for more than two days, doctors often focus first on slowing the heart rate and starting blood thinning medications to prevent clots. Later, imaging tests like heart ultrasound can help guide further treatment decisions.
THE BOTTOM LINE
• Atrial fibrillation is a chaotic heart rhythm where the heart beats irregularly and often rapidly
• AFib can be triggered by alcohol, electrolyte imbalance, infections, heart disease, or thyroid problems
• The biggest long term risk of AFib is stroke, which is why doctors often treat it with both heart rate control and blood thinners
By Dr. Karim Ali, Emergency Physician