The heart is a muscle that works tirelessly to pump blood throughout our entire body. It consists of four chambers – two atria and two ventricles – and is controlled by a complex electrical system. Like a conductor leading an orchestra, this system sends electrical signals that trigger the rhythmic contraction of the atria and ventricles. These electrical signals originate in the atria. The atria also fill the ventricles, which then pump blood to all the organs. In healthy people, this rhythm is regular, with a resting heart rate typically ranging from 60 to 100 beats per minute.
A heart rhythm disorder or cardiac arrhythmia is when the heart does not beat at a normal, regular rate.
Atrial fibrillation is a heart rhythm disorder that originates in the atria. It is the most common arrhythmia in the world.
In atrial fibrillation, the electrical activity in the atria becomes completely disorganized and can reach up to 600 beats per minute. At this rate, the atria do not contract effectively, making it difficult for the ventricles to fill, which hinders blood flow.
There are several forms of atrial fibrillation:
- Paroxysmal: this involves episodes of atrial fibrillation that come and go spontaneously. They usually last between a few hours to a few days.
- Persistent: These fibrillation episodes last longer than 7 days and do not stop on their own (medical intervention is needed to restore the heart’s normal rhythm).
- Permanent: atrial fibrillation is continuous and cannot be treated.
Atrial flutter (often called “typical flutter”) is another form of cardiac arrhythmia that originates in the atria. It is similar to atrial fibrillation, but its electrical pattern is more organized. The heart rhythm is usually fast (around 150 beats per minute) but is more regular.
In atrial fibrillation and atrial flutter, reduced contraction of the atria can cause blood to stagnate in the atria and blood clots to form. These clots can then be pumped into the circulatory system with the blood, potentially blocking the arteries that supply blood to the organs.
When blood clots block a cerebral artery, it results in a stroke (cerebrovascular accident – CVA). Clots can also obstruct renal arteries (renal infarction) and leg arteries (ischemia of the lower limbs), among other potential complications.
The rapid, irregular contraction of the heart in atrial fibrillation, which disrupts the rhythm and can prevent efficient blood filling of the ventricles, can also lead to heart failure or worsen pre-existing heart disease.
The diagnosis and management of atrial fibrillation is a public health concern, as atrial fibrillation is responsible for complications that can be serious for patients and costly for healthcare systems. These include an increased risk of stroke and dementia, a higher risk of heart failure, increased cardiovascular mortality and more frequent hospitalizations.
Symtoms
Sometimes, atrial fibrillation does not present any noticeable symptoms. Some patients are therefore unaware that they have an arrhythmia. However, certain symptoms, such as palpitations, are much easier to identify. Other symptoms may be present but are less specific, such as fatigue and shortness of breath, reduced exercise tolerance, dizziness, loss of balance or even consciousness, chest pain and anxiety.
Unfortunately, in many cases, atrial fibrillation is first detected when a complication occurs, such as stroke or heart failure.
Diagnosis
An electrocardiogram (ECG or EKG) is used to diagnose atrial fibrillation by providing an electrical recording of the patient’s heart rhythm.
There are now several methods for performing an ECG:
- A standard ECG can be performed during an appointment with your primary care physician, cardiologist or in the emergency room.
- A Holter ECG : this is a device that continuously records the heart’s rhythm over a 24 to 72-hour period.
- Smart devices:
- Most smart watches and some smartphones (using the camera flash on your finger) can detect an irregular and rapid heart rhythm suggestive of atrial fibrillation, but they do not provide an ECG trace that can confirm the diagnosis with certainty. They then advise the user to schedule an appointment with a physician.
- Some smart watches and other “AliveCor” devices allow you to directly record an ECG trace which you can then share with your physician.
- A long-term implantable heart monitor: this small device is implanted under the skin to record the heart rhythm and detect any arrhythmias. It can last up to 3 years.
One of the key issues with atrial fibrillation is early detection to enable treatment and prevent possible complications. This is, of course, easier when patients experience symptoms that prompt them to see their physician. Diagnosis is sometimes challenging in the case of brief, acute episodes, since they must be recorded when they occur. Wearable smart devices now facilitate this process.
5-10 %
The percentage of people aged 70 and over affected by ventricular fibrillation. In those under 60, it affects only 1% of the population. In France, this disorder affects 250,000 people.
Treatment
One of the first steps in managing fibrillation is to estimate the risk of complications, such as a stroke. This risk is different for each patient.
If the risk is high, a long-term anticoagulant treatment will be prescribed to thin the blood and prevent this type of complication.
It is also important to manage any risk factors and predisposing conditions for atrial fibrillation — being overweight, high blood pressure, diabetes, smoking, alcohol consumption, sleep apnea — and to reintroduce an appropriate physical activity.
Finally, there are several strategies for treating arrhythmia:
- Antiarrhythmic medication: this type of medication reduces the duration and frequency of episodes. They are often effective during the first signs of atrial fibrillation but become less effective over time. In any case, they are always less effective than the current ablation techniques. They may also cause some side effects.
- External electric shock: this medical procedure, performed under very brief general anesthesia, “resets” the heart to restore a normal rhythm. However, it does not treat the underlying cause of the fibrillation, which may return at any time.
- Atrial fibrillation ablation techniques: one or more catheters are inserted into the atria of the heart to treat the areas responsible for arrhythmias. This “ablation” technique was developed by the teams supervised by Michel Haïssaguerre, MD, PhD, at Bordeaux University Hospital (CHU) and at the Liryc Institute. Various techniques are now used: heat ablation (radiofrequency), cold ablation (cryoablation) and the use of pulsed electric fields (electroporation).
Reviewed and approved by Romain Tixier, MD, Cardiologist at Bordeaux University Hospital (CHU)
