Introduction To Atrial Fibrillation

Atrial Fibrillation is the most common irregular heart rhythm and is characterized by irregular, disorganized electrical signals that cause the upper two chambers of the heart -the atria to contract very fast and irregularly.

The Physiology:
In order to understand atrial fibrillation it is important to explain the normal physiology of the heart’s electrical system. Each heart beat occurs due to the spread of the electrical signals that originate in the sino-atrial node located in the upper part of the right atrium, from where it travels to the right and the left atria and then to the atrio-ventricular node. After a slight delay the signals then pass to the ventricles.

In atrial fibrillation the signals do not generate in the sino-atrial node , instead they arise from another part of the atria and they do not travel normally. Theses abnormal signals spread through out the atria in a rapid disorganised way causing the atria to fibrillate meaning to contract fast and irregularly. Because of this faulty spread of the signals the atria and ventricles do not contract in a coordinated way , creating a fast , irregular heart rhythm.

The heart rate may reach up to 100 to 175 beats per minute in contrast to a normal heart rate of 60 to 100 beats per minute, and the ventricles cannot pump the blood to the body in a normal pattern.

Causes And Risk factors For Atrial Fibrillation:Damage to the heart’s electrical system causes atrial fibrillation. There are several conditions that may lead to atrial fibrillation like:

• High blood pressure.
• Coronary artery disease.
• Mitral stenosis.
• Heart failure.
• Rheumatic heart disease.
• Congenital heart defects.
• Mitral regurgitation.
• Mitral valve prolapse.
• Pericarditis.
• Hyperthyroidism.
• Excessive alcohol consumption.
• Pulmonary embolism.
• Advancing age

Clinical Signs and Symptoms:
The symptoms of atrial fibrillation differs from patient to patient with a large number of people having no symptoms at all. The most common symptom is palpitations that is a feeling of heart beating rapidly making a person anxious. Some patients may get light headed or faint. Sometimes there may be chest discomfort or breathing difficulty.

ECG Findings: On ECG the characteristic findings of an atrial fibrillation are the absence of a P wave, disorganized electrical activity and irregular R-R interval. QRS complexes are narrow. Sometimes if atrial fibrillation is paroxysmal it can be missed during a ECG.

Management:
Treatment depends on the presence of an existing heart disease and how often and how severe the symptoms occur. The goal of treatment includes preventing blood clots and thus reducing the risk of stroke and restoring a normal heart rhythm so as the blood can be properly pumped to the body.

1. Medicines To Control The Rhythm (anti arrhythmic drugs): Theses drugs help return the heart to normal sinus rhythm. They are of several types some of them include:

• Procainamide.
• Amiodarone.
• Sotalol.
• Flecainide etc.

2. Medicines To Control The Rate: Sometimes medications are needed to slow the heart rate during atrial fibrillation. They include:

• Beta blockers like metoprolol.
• Calcium channel blockers like verapamil.
• Digoxin etc.

3. Medicines To Prevent Clot Formation: These drugs reduce the risk of blood clots and stroke. They include:

• Warfarin.
• Haparin.
• Aspirin etc.