Atrial fibrillation is the most frequent arrhythmia in the general population, the most frequently diagnosed, and the most frequent hospitalizations and health expenses.
Let’s review how the heart contracts. In the right atrium, one of the four heart cavities, there is a set of specialized cells that generate electrical impulses periodically (sinus node). These impulses are transmitted to the rest of the heart and cause it to contract. The path followed by these electrical impulses is called cardiac conduction tissue, which allows the heart to contract properly (first the atria and then the ventricles) to push the blood to the rest of the body. The electrical tissue of the heart is formed by:
- The sinus node is located in the right atrium, near the mouth of the superior vena cava. It is the one that generates the electrical impulse and transmits it to the auricles. Therefore, the sinus node is the one that controls the heart rate.
- Atrioventricular node after the momentum spread through the atria and contract these, electrical stimulation reaches the atrioventricular node. This node is located in the muscular wall separating the two ventricles, at the border with the right atrium. After receiving the impulse, it brakes it for a short period of time to avoid contracting the ventricles at the same time as the atria and then transmits it to the ventricles.
- Make His-Purkinje is the continuation of the atrioventricular node and is in the muscle wall between the two ventricles. It transmits the impulse through the septum and leads it to the ventricles to contract synchronously.
Atrial fibrillation occurs when the electrical impulse that causes atrial contraction does not originate in the sinus node, but there are multiple foci that generate it at the same time, causing the atrium to contract completely irregularly. As a result of this, the atria is contracted with very little force and the passage of blood from the atrium to the ventricle is affected.
According to the clinical presentation, different types of atrial fibrillation are distinguished:
- Paroxysmal: hard arrhythmia less than seven days.
- Persistent: arrhythmia lasts longer than seven days and not resolve spontaneously, so sinus rhythm (normal heart rhythm) is not recovered; It is necessary to perform a pharmacological or electrical cardioversion (see below) to recover the normal heart beat.
- Permanent: when cardioversion has failed or has not been attempted, so the patient remains indefinitely in atrial fibrillation.
Among the risk factors for atrial fibrillation are:
- Chronic lung disease.
- Mellitus diabetes.
- Excessive consumption of caffeine or alcohol.
- Established heart disease (heart muscle disease, heart valve disease, history of myocardial infarction, etc.).
- Arterial hypertension.
Atrial fibrillation can manifest itself in many ways: from almost asymptomatic patients to others in whom the symptoms are very marked and do not allow the individual to perform a normal daily activity.
The most frequent symptoms are palpitations, chest pain, shortness of breath (feeling of difficulty breathing), tiredness, dizziness, and syncope (loss of consciousness). Atrial fibrillation may also occur with an embolus (one of its most serious complications), or as an exacerbation of heart failure.
Atrial fibrillation decreases the amount of blood the heart pumps into the circulation. Therefore, the patient’s ability to perform the daily physical activity is lower, so that his quality of life deteriorates.
If atrial fibrillation remains for more than 48 hours, there is an increased risk of blood clots (thrombi) forming in the atrial cavity. If they become detached, they pass into the general circulation (they are called then emboli), and can obstruct the arteries that irrigate various organs producing embolic pictures, such as stroke (stroke or stroke) or a heart attack.
To reach the diagnosis of atrial fibrillation, it is essential to perform an electrocardiogram (ECG), in which typical alterations of the disease are seen.
Sometimes, atrial fibrillation may not be seen on the ECG because it sometimes occurs paroxysmal, that is, it only lasts for a time and disappears spontaneously by returning the heart to normal barking. Therefore, it may be useful to perform an ECG Holter that monitors the heart’s electrical activity for an extended period of time (such as an ECG recorder, which records from 24 hours to several days).
Today there are various treatments for atrial fibrillation. We will explain them below.
Electrical or Drug Cardioversion
It allows recovering the normal sinus rhythm of the heart. It consists of temporarily blocking the heart cells that cause the abnormal impulses to stop stimulating, and regain control of the sinus node cells. It is performed only in patients with atrial fibrillation in whom it is believed that it is plausible to maintain sinus rhythm.
There are two types of cardioversion: electrical and pharmacological. In electrical cardioversion, an electric shock is given to the heart to restart the cells that cause the arrhythmia. In pharmacological cardioversion, this is achieved by certain drugs called antiarrhythmics, such as amiodarone or flecainide, among others.
Medical Treatment: Heart Rate Control and Anticoagulation
It is based on the use of drugs that control the heart rate, and on the patient’s anticoagulation.
When it is assumed that atrial fibrillation is permanent the most important is to control the heart rate to avoid atrial fibrillation attacks with a very fast heart beat, which can trigger heart failure or other complications. Drugs such as beta-blockers, digoxin or calcium antagonists are often used to slow the heart rate.
Treatment with anticoagulant drugs (the most common is Sintrom) is essential to prevent thrombus formation within the atria since one of the most important complications of atrial fibrillation is the stroke (stroke) or other locations.
Catheter Ablation Of Atrial Fibrillation
It consists of trying to cure atrial fibrillation by using catheters that are inserted through the veins into the heart. These catheters produce electric burns in the atrium that seek to destroy the areas of the catheter (in their union with the pulmonary veins) that facilitate the appearance of atrial fibrillation, or at least create a kind of barrier around the pulmonary veins to prevent The anomalous stimuli generated there may spread to the rest of the atria.
Surgical Treatment of Atrial Fibrillation
In the vast majority of cases, surgical ablation of atrial fibrillation is performed when the heart has to be operated for another cause, usually due to mitral valve disease.
The approach to surgery is usual (see the section: During Cardiac Surgery ). An average sternotomy is performed, which is the longitudinal opening of the sternum, the bone that is in the center of the chest. Subsequently, the pericardium (a kind of sac that surrounds the heart) is opened and, in this way, the heart is accessed.
In theory, the ablation of atrial fibrillation in isolation can be performed without extracorporeal circulation. However, since it is normal for the surgery to be performed due to concomitant valve disease, extracorporeal circulation should be used to perform valvular surgery.
Surgical ablation is based on isolating the areas where the abnormal electrical impulses that trigger atrial fibrillation usually occur. To do this, through various instruments “burn” those regions of the heart, creating a kind of labyrinth (Cox Maze ablation) that prevents the spread of atrial fibrillation.
The basic intervention of any procedure is the isolation of the pulmonary veins since this is where atrial fibrillation usually arises. In addition, burns can be performed in other anatomical regions of the heart to decrease the likelihood of recurrence of atrial fibrillation.
Since the prevention of embolism is a fundamental objective of surgery, the left atrial appendage (which is an appendix of the left atrium) should be attached during the procedure, since it is in this appendage that the intracardiac thrombi most frequently form Which can then migrate to other areas of the body and produce an embolism.
The closure of the surgical wound is performed according to the usual technique (see the section: During Cardiac Surgery ).
As for medication, treatment with anticoagulant drugs will be maintained for at least the first 3-6 months. However, they are likely to be maintained for longer or even for life. In addition, at least during the first few weeks, the patient will receive antiarrhythmic drugs, the most frequent amiodarone.