What is atrial flutter?
Atrial flutter is an abnormal heart rhythm.
In atrial flutter, the atria contract at 300 beats per minute and every other impulse goes down into the ventricles and therefore the ventricles beat at 150 beats per minute. In patients who are taking medications such as beta blockers or calcium blockers the impulses reaching the ventricles may be reduced even more so the heart rate can be even lower than 150/min but basically as doctors, whenever we see a heart rate of about 150 in a patient complaining of heart palpitations, we think of atrial flutter as the likely underlying heart rhythm disturbance.
Why is it important?
1) Because it can reduce quality of life
2) It can reduce length of life
How does it affect quality of life?
Atrial flutter can cause abrupt and unpredictable onset of symptoms – These include: Fast heart palpitations, breathlessness, light-headedness, fatigue and exercise intolerance. Often it is poorly tolerated because there is a stepwise increase in the heart rate and it often stays fixed at 150/min
How does it affect length of life?
As the atria are beating so fast, they are not working effectively and therefore blood which would be pushed out may stagnate and clot and that clot can get dislodged and go to the brain or the rest of the body and block the blood supply to important organs. In the brain this results in a stroke. If the clot is dislodged anywhere else it is called a systemic embolism.
How common is it?
Atrial flutter is significantly less common than Atrial fibrillation. Atrial flutter is also, like atrial fibrillation, more common in the elderly..
The incidence in those under 50 years of age is 5/100000 patient years but this rises to 500/100000 patient years in those who are older than 80 years of age. Atrial Fibrillation in contrast, occurs in 1/1000 patient years in those under 40 years of and 19.2/1000 patient t years in those greater than 65 years of age.
It is twice more commonly seen in men than women. It is very unusual to see it in people with normal hearts. Of 100 people with atrial flutter, only 2 will have completely normal hearts. This is in stark contrast to atrial fibrillation which is seen in many young patients who on echocardiography, have structurally normal hearts. We often see atrial flutter in patients who suffer from intrinsic heart disease such as cardiomyopathy and also in those in whom the heart has been exposed to excessive stress such as in people who have bad lung disease.
Any of the disorders that cause atrial fibrillation can cause atrial flutter. These include thyroid dysfunction (overactive), obesity, obstructive sleep apnoea, sinus node disease, alcohol, lung disease and blood clots in the lungs. It is therefore always very important to look for and treat these underlying conditions in any patient who has been diagnosed with atrial flutter.
Atrial flutter may often seen as a ‘transitioning’ rhythm which can occur in patients with atrial fibrillation particularly when they are transitioning from sinus rhythm to atrial fibrillation or when they are reverting back from AF to sinus rhythm and therefore it can co-exist with atrial fibrillation. It is also seen in patients with atrial fibrillation who are given rhythm control medications. It happens in 15% of such patients especially when they are prescribed medications such as flecanide.
How does it feel?
Atrial flutter often presents with sudden onset of fast regular heart palpitations. Often the heart rate rises to 150 beats per minute. It is not uncommon for the patient to feel tired, dizzy and breathless during the episode of atrial flutter. Often the offset is also sudden.
How is it diagnosed?
Atrial flutter is best diagnosed by ECG which is done during the episode of atrial flutter. It can be impossible to diagnose for certain unless it is ‘caught’ on an ECG when it is happening and therefore if you are having palpitations, the foremost priority should always be to have an ECG as soon as possible so that it is captured before it self terminates.
What tests do you need?
At the very least a blood count, some blood electrolyte levels, thyroid tests and assessment for underlying sleep apnoea or lung disease. I think everyone with atrial flutter should also have an echocardiogram because it is very commonly associated with underlying heart disease.
What is the treatment for atrial flutter?
There are 4 important steps to management of atrial flutter:
1) Control of the heart rate
2) Control of the heart rhythm
3) Maintenance of the heart rhythm
4) Prevention of blood clots to reduce the formation and subsequent embolization of blood clot.
Control of the heart rate:
This is important to do for two reasons:
- The fast heart rate can be very uncomfortable for the patient and is often responsible for the symptoms of breathlessness, fatigue and exercise intolerance
- A very fast heart rate can lead to something called a tachycardia-induced cardiomyopathy which means that the heart can weaken over a period of time. The good news is that with effective heart rate control, the tachycardia-induced cardiomyopathy can be reversed.
The bad news is that rate control in atrial flutter is difficult to achieve. We can use beta blockers, calcium antagonists or even sometimes digoxin but often what we end up doing is converting the patient from atrial flutter to atrial fibrillation and rate control in fibrillation is much easier to achieve. Sometimes Intravenous Amiodarone may be used to control the fast heart rate in flutter. The most effective strategy to control the rate is to control the rhythm by electrical cardioversion (see below).
Control of heart rhythm:
In the acute setting a small electrical shock delivered to the heart under a general anaesthetic is very effective at converting patients from atrial flutter to a normal rhythm. This is called a cardioversion. Unfortunately cardioversion cannot be carried out safely unless the patient has been adequately anticoagulated beforehand. The risk is that if a clot has already formed within the heart, then the electrical shock and subsequent restoration of normal atrial function could dislodge the clot and therefore a period of 4 weeks of anticoagulation prior to the cardioversion is mandatory. In an emergency setting, a transesophageal echo can allow detailed visualisation of the heart chambers and if no clot is seen, then a cardioversion may be performed even without prior anticoagulation. If the patient has been in atrial flutter for less than 48 hours then cardioversion can also be performed without requiring prior anticoagulation. The main problem with cardioversion is that whilst often initially successful, a majority of patients (50-70%) will have a recurrence within a year despite maintenance medications.
Given the high risk of recurrence with cardioversion, most patients end up requiring an ablation. Atrial flutter ablation is often highly effective and reduces recurrence. The success rates are up to 92% for a single procedure and 97% for multiple procedures.
Prevention of blood clots:
In one study 100 people with atrial flutter were listed for an ablation but were not anticoagulated and 6 of them had an embolism attributable to the atrial flutter and therefore atrial flutter does predispose patients to embolism although perhaps the risks are not as great as with atrial fibrillation.
Currently the risk of strokes/systemic embolism is calculated in exactly the same way as in atrial fibrillation using the CHADS2VASC scoring system. As the score increases, the risk of clots increases and therefore patients who are older and who have co-morbidities should be anticoagulated. Anticoagulation has been show to reduce the risk of strokes by at least 60%.
Anticoagulation should continue for life regardless of whether the patient remains in atrial flutter or not. A significant proportion of patients who have had atrial flutter which has been successfully ablated will at some point develop atrial fibrillation and therefore if a patients CHAD2VASC score is high, they should be anticoagulated for life.
Here is the link to a video i have done on the subject: