Atrial Flutter vs Atrial Fibrillation: What Are the Main Differences?

Atrial flutter and atrial fibrillation are both arrhythmias which affect the electrical signals that control your heartbeat. There’s a big overlap in how they are treated, and they unhelpfully share the same initials. If you or someone close to you has been diagnosed with one of these conditions, it's natural to wonder how they compare to each other. This guide sets out the differences between atrial flutter and atrial fibrillation so you can better understand these conditions. 

What Are Atrial Flutter and Atrial Fibrillation?

Both atrial flutter and atrial fibrillation originate in the atria, the two upper chambers of the heart. Usually, the atria and ventricles, the lower chambers, contract in a coordinated sequence, controlled by the electrical signals which follow a predictable path. In atrial flutter and atrial fibrillation, the electrical signalling breaks down, causing the atria to beat abnormally fast. Both are recognised types of arrhythmia by the British Heart Foundation, and both can occur alongside other heart conditions or on their own.

The key differences between Atrial Flutter and Atrial Fibrillation

Atrial flutter: This happens when an electrical signal moves in a tight, repeating loop, usually around the right atrium. Because the signal follows the same path each time, the resulting rhythm is fast but regular, like a racetrack; the signal keeps circling.

Atrial fibrillation: This occurs when electrical signals become disorganised and chaotic rather than following a single path. The atria no longer contract properly. Instead, they quiver, producing a rhythm that's fast and irregular.

Feature	Atrial Flutter	Atrial Fibrillation
Electrical pattern	Organised, single circuit	Chaotic, disorganised
Rhythm	Regular	Irregular
Typical atrial rate	Up to around 300 bpm	Variable, often 100 to 175 bpm at the ventricles
ECG appearance	Sawtooth pattern	Irregular baseline, no clear P waves
Relative prevalence	Less common	More common

It's also worth noting that these conditions aren’t always separate. Atrial flutter can convert into atrial fibrillation, and the reverse can happen too. Some people are diagnosed with both conditions at different points.

Symptoms of Atrial Flutter vs Atrial Fibrillation

Many of the symptoms of atrial fibrillation and atrial flutter overlap, which is one of the main reasons the two conditions get confused.

Both atrial flutter and atrial fibrillation share the following symptoms:

• Palpitations, or a noticeable fluttering or pounding in the chest

• Breathlessness, particularly on exertion

• Fatigue or reduced exercise tolerance

• Light-headedness or dizziness

• Chest discomfort, in some cases

The main practical difference is in how the palpitations feel. With atrial flutter, the fast heartbeat tends to feel regular, even though it's rapid; with atrial fibrillation, it usually feels more erratic with no consistent pattern to the beats. Some people with either condition have no noticeable symptoms at all, particularly if their heart rate stays below 100 beats per minute.

Why symptoms of atrial flutter vs atrial fibrillation alone aren’t enough to tell them apart

As symptom overlap is significant, it isn't possible to always reliably distinguish atrial flutter from atrial fibrillation based on how they feel. Two people with different conditions can describe almost identical sensations. Confirming which one is present, or whether both are, depends on recording the heart's electrical activity directly.

How are atrial flutter and atrial fibrillation diagnosed?

An electrocardiogram (ECG)  is the standard test for diagnosing both conditions, and it's what allows a specialist to tell them apart with confidence. On an ECG, atrial flutter typically produces a distinctive sawtooth pattern reflecting the regular looping electrical circuit. Atrial fibrillation, by contrast, shows an irregular baseline with no clearly defined P waves, reflecting the erratic, chaotic signal pattern.

Where symptoms are intermittent, a single ECG taken during a symptom-free period may not capture anything unusual. In these cases, a longer period of monitoring, such as a 24-hour or 48-hour Holter monitor or an extended patch monitor, is often used to catch the arrhythmia as it occurs. Many patients now buy devices capable of recording an ECG, such as the Apple Watch, Omron Complete blood pressure machine with ECG or AliveCor handheld Kardia ECG. Learn more about the diagnoses and management of atrial flutter and atrial fibrillation.

Causes and Risk Factors: Atrial Flutter vs Atrial Fibrillation

Atrial flutter and atrial fibrillation share many of the same underlying risk factors, including high blood pressure, structural heart disease, previous heart surgery and increasing age. Thyroid problems, alcohol intake and untreated sleep apnoea are also linked to both conditions.  As the risk factors overlap so closely, having one condition increases the likelihood of developing or being diagnosed later.

Treatment approaches: Atrial flutter vs atrial fibrillation

Both conditions are treated with a combination of medication and, where appropriate, procedural intervention, but the approaches diverge in some important ways.

Rate and rhythm control 

Medication is used for both conditions to manage heart rate or maintain a normal rhythm.

Catheter ablation

Catheter ablation is often more straightforwardly curative for typical atrial flutter since the abnormal signal follows a single well-defined circuit that can be precisely targeted and interrupted. Ablation for atrial fibrillation is more complex because the chaotic signal patterns do not follow one fixed path, so the procedure typically involves isolating the areas of the atria most often responsible for triggering it with a pulmonary vein isolation ablation.

Anti-coagulation 

Reducing stroke risk is a consideration for both conditions based on individual risk factors rather than which arrhythmia is present. We use a risk scale to work this out called CHA2DS2Vasc. The exact reason patients suffer stroke due to arrhythmia is not well understood, and it appears strokes can happen even when there have been no recent disturbances of rhythm. There may instead be a general increase in atrial wall stickiness and blood coagulation, which also promotes arrhythmia. If your risk of stroke was high enough to consider anticoagulation before a successful ablation, you may well continue to need it while in a normal rhythm afterwards to prevent stroke. Ablation is not a means to come off anticoagulation.

Outlook: Living with Atrial Flutter or Atrial Fibrillation

Both conditions are manageable with the right diagnosis and an appropriate treatment plan. Many people with either arrhythmia go on to live full, active lives once their condition is properly identified and treated. The value of understanding the difference can be fully understood under the guidance of a specialist with whom you can ask questions and understand treatment plans and management.

Getting an accurate diagnosis of atrial flutter vs atrial fibrillation

As atrial flutter and atrial fibrillation can look and feel so similar, in some circumstances even developing into the other, an accurate diagnosis depends on proper ECG assessment rather than symptoms alone, If you have been diagnosed with either condition and you’re wanting more guidance or you’re experiencing palpitations and want clarity on what’s causing them, as a specialist heart rhythm assessment I can confirm exactly what’s happening and guide the next steps for treatment.

Book a consultation with me, Dr Chris Skene, an electrophysiologist specialising in the diagnosis and treatment of heart rhythm disorders, to get a clear picture of your condition and the options available to you.

Atrial Flutter vs atrial fibrillation Frequently asked Questions

Can you have both atrial flutter and atrial fibrillation at the same time?

It's common for the two conditions to coexist or for one to convert into the other. A person may have episodes of atrial flutter that shift into atrial fibrillation, or the reverse. This is one of the main reasons an ECG is needed to confirm exactly which rhythm is present at any given time, rather than relying on a single past diagnosis.

Can atrial flutter turn into atrial fibrillation?

This happens fairly often. The two arrhythmias share overlapping risk factors and can affect the same areas of the heart, so a person diagnosed with flutter may later be found to have fibrillation, or experience both at different points.

Can you feel completely normal with atrial flutter or atrial fibrillation?

Some people have no noticeable symptoms at all, particularly if their heart rate stays below 100 beats per minute during episodes. This is one of the reasons both conditions are sometimes picked up incidentally, during a routine check-up or an ECG done for an unrelated reason, rather than because of symptoms.

Can lifestyle changes improve atrial flutter or atrial fibrillation?

Managing underlying risk factors, such as high blood pressure, excessive alcohol intake, and untreated sleep apnoea, can help reduce the frequency or severity of episodes in both conditions. Lifestyle changes support treatment rather than replace it, and any changes should be discussed with your specialist alongside your existing management plan.

Does an ECG always catch atrial flutter or atrial fibrillation?

Not always, particularly if symptoms are intermittent. A standard ECG only records the heart's activity at that exact moment, so if the arrhythmia isn't present during the test, it may not show up. Longer-term monitoring, such as a Holter monitor worn for 24 to 48 hours, is often used to catch episodes that come and go.