Arrhythmias

Sinus node disease
The sinoatrial node, located in the atrium, contains cells that send electrical signals to the other parts of the heart.
There are different types of sinoatrial conduction disorders, ranging from a simple slowing to complete interruption.
They may be acute or chronic, permanent or paroxysmal.

There are various causes:

• Myocardial infarction, particularly when it affects the lower part of the heart.
• Medication overdoses.
• Most often, fibrotic degeneration of the sinus node, occurring mainly in older people. In this case, it may be associated with episodes of paroxysmal atrial fibrillation or flutter. This results in partial interruption of sinoatrial conduction, leading to bradycardia (a slow heart rate).

Symptoms may range from presyncope to syncope.
Treatment consists of inserting a pacemaker with two leads, one in the atrium and the other in the right ventricle.

Atrioventricular blocks
This is impaired atrioventricular conduction, ranging from slowing to complete interruption.
It indicates lesions affecting the conduction tissue located in the atrioventricular node.

There are several causes:

• Myocardial infarction.
• Acute inflammatory and/or idiopathic atrioventricular block.
• Medication overdoses.

However, the most common cause is fibrotic degeneration of the atrioventricular conduction tissue. Its origin is undetermined. It occurs in older people.
The clinical manifestations may be asymptomatic, meaning that the person feels nothing, but they mainly involve a slow heart rate (bradycardia), characterised by fatigue and even recurrent syncope.

There are several classifications:

• First-degree atrioventricular block (which does not require a pacemaker).
• Second-degree atrioventricular block, which is divided into Mobitz I and II.
• Third-degree atrioventricular block.
• Treatment consists of inserting a pacemaker with two leads, one in the atrium and the other in the right ventricle.

Fibrillation
Atrial fibrillation is a heart condition characterised by random contractions of the atria (the small chambers of the heart), causing the overall heart rhythm to become irregular. It is the most common heart rhythm disorder in the population and can cause very serious complications, such as cerebral embolisms. These are small blood clots that block arteries in the brain and are one of the causes of cerebrovascular accidents.

This condition, which is more common in people over 60, may have several causes:

• Heart disease (mitral valve disease, myocardial infarction, etc.).
• A non-cardiac condition (excess thyroid hormones, a lung infection, pulmonary embolism, alcohol consumption, etc.).
• Sometimes no cause is found; this is then referred to as idiopathic atrial fibrillation. The doctor may suspect the diagnosis during the clinical examination, mainly finding that the pulse is fast and irregular. However, atrial fibrillation is not always permanent, which makes diagnosis more difficult. Doctors then refer to it as paroxysmal atrial fibrillation.

Cardiac arrhythmias are treated at the Arrhythmology Clinic. 

An electrocardiogram can reveal the irregular, chaotic and rapid activity of the atrium. When the electrocardiogram is normal but the doctor strongly suspects the presence of atrial fibrillation, the cardiologist will perform a 24-hour electrocardiogram recording (an examination known as a 24-hour Holter monitor). Various treatments are available to treat this condition or prevent its complications.

Overall, many medicines, known as antiarrhythmics, can treat the vast majority of patients. If the response to medication is inadequate—that is, if the patient continues to experience symptoms that are difficult to tolerate (troublesome palpitations, discomfort, fainting, etc.)—or if the patient cannot tolerate the medicines prescribed by their cardiologist, a more radical method is available. This involves “burning” the areas of the heart responsible for the arrhythmia in order to restore a regular heart rhythm. This burning is performed by applying an energy source (usually radiofrequency) directly to the inner wall of the atria.

This beating-heart technique, generally used in some specialised cardiology centres, involves ablating or isolating the pulmonary veins (which are responsible for the arrhythmia) by introducing several probes, or catheters, into the heart under fluoroscopic guidance. The advantage of this procedure is that it can be performed under local anaesthesia, through a puncture (= the first step in advancing a catheter) in the groin and, if necessary, in the neck.

Unfortunately, this technique can be laborious and lengthy, and it sometimes needs to be repeated a few days later.
The final outcome cannot be predicted with certainty, but the current expectation in the best centres is a 50–60% cure rate for symptomatic atrial fibrillation (also called paroxysmal atrial fibrillation). It should nevertheless be noted that these results will probably improve with the emergence of new technological developments.
Since June 2003, we have developed a surgical approach designed to increase the chances of success of the pulmonary vein isolation procedure while maintaining its minimally invasive nature. It involves encircling the areas potentially responsible for atrial fibrillation (the pulmonary veins) from outside the heart, using a surgical robot.
This tool is particularly useful: not only does it facilitate the surgical procedure (the robot’s wrists have a much greater range of movement than the surgeon’s hands), but it also makes it possible to operate on the heart without actually opening the sternum or thorax, except for three small incisions of less than 1 cm between the ribs.