Definition

Cardiac disease characterized by irregularity the pace of contraction of the Atria with irregularity full rhythm of the heart ventricles. This heart rhythm disorder is characterized by the disappearance of normal sinus rhythm (normal heart rhythm) replaced by rapid contractions (occurring about 400 to 600 times per minute). These atrial contractions are ineffective and cause contractions irregular and generally of the ventricles.

Causes

• Heart disease represent the majority of cases of occurrence of atrial fibrillation. This type of condition is most often associated with a breach of the valves (valvular disease), essentially the mitral valve (the valve between the left atrium and left ventricle). Coronary artery disease (coronary disease), a communication between the Atria, abnormal elevation of blood pressure, impairment of the muscular wall of the heart itself and inflammation of the membranes of recovery and protection of the heart (pericarditis) represent another possible association resulting in the occurrence of atrial fibrillation.
• About 10 to 30% of patients with cardiac pump failure have atrial fibrillation. This figure rises as heart failure worsens.
• There is atrial fibrillation of genetic nature due to a (transformation) mutation of the gene KCNQ1 (locus 11p15.5). Genetic modification is the potassium channel and excitability of myocyte (muscle cells). The potassium channel is an ion channel allowing potassium (in the form of K + ion) out of the cell. There are many varieties of potassium channels which the operation is complex. Their opening and closing are directly dependent on many factors (ion calcium, acetylcholine, adenosine triphosphate, ligands).
• In atrial fibrillation of genetic nature, include a mutation occurring on chromosome number 10 (10 q 22-24) that was highlighted in some forms of family atrial fibrillation.
• Certain conditions, and particularly pneumonia
• An endocrine dysregulation (hormonal disturbance), and more precisely on the thyroid gland (hyperthyroidism: excessive secretion of thyroid hormone)
• Wolff-Parkinson-White syndrome
• Bradycardia-tachycardia syndrome
• Injuries as surgical intervention on the chest or a direct trauma of thorax

Symptoms

• Sometimes, the patient feels no symptoms
• Palpitations
• Pain located behind the sternum (chest)
• Failure of operation of coronary (anginal pain)
• Loss of knowledge
• Faintness
• Syncope
• Fatigue
• Shortness of breath (Dyspnea) during an effort, likely failure of cardiac pump function
• Acceleration of heart rate (tachycardia), and most often tachyarrhythmia (acceleration of heart rate with irregularity of beats)
• Sometimes, the atrial fibrillation is revealed by the occurrence of an embolism (migration of a blood clot in the general circulation): this phenomenon is linked to the absence or insufficiency of effective contraction of the Atria, which causes the shutdown or slowdown of the blood.

Consultation doctor

• Review of the pulse (at the level of the radius) to highlight an irregularity of it.
• Difference between cardiac pulsation seen on the edge of the heart and the number of pulses that we feel: this phenomenon is known as pulse deficit.
• Taking blood pressure shows a variability and difficulty to determine with precision the figures from systole to diastole (figures maxima and minima).

Medical examination

• The ECG shows a completely irregular ventricular rhythm. There is the presence of a complete arrhythmia and a tachyarrhythmia (acceleration of heart rate with irregularity of beats) generally.
• Sometimes, the electrocardiographic path carried out over a short period is insufficient for wear with certainty the diagnosis of atrial fibrillation. This is the reason for which is called the 24-hour Holter.
• Other paraclinical examinations, and more specifically echocardiography, to highlight the exaggerated dimensions of the two atria.
• Ultrasound shows sometimes (more precisely to transoesophageal ultrasound) the presence of blood clot within the atria.

Evolution of the disease

The prognosis of atrial fibrillation depends on its cause. Generally, when there is a heart disease, evolution is pejorative (the occurrence of death is twice higher than in the general population).

Complications of the disease

• The major complication of atrial fibrillation is the occurrence of thrombi (blood clots) within the heart Atria. These thrombi are likely to migrate in the general circulation and cause brain embolism. They are much more common that the subject is old.
• The occurrence of a rheumatic disease, elevation of blood pressure, of a failure of the cardiac pump or a recent stroke increases the risk of thrombus.

Treatment

Outside of the drugs used in cardiology, medical teams are sometimes appeal to the cardioversion, i.e. the external shock, or the type pacemaker pacemaker.Some cardiac teams try to slow down the frequency of the ventricles using certain medicines (Digitalis toxicity, beta blocker, anticalcique).

Prevention

The use of oral anticoagulants (tablets) and antiplatelet agents (as aspirin in other) sometimes prevent thromboembolic complications (occurring blood clots in the bloodstream).