Atrial Fibrillation

Atrial fibrillation is a relatively common abnormal heart rhythm where the atria beat quickly, irregularly, and unevenly.

Atrial fibrillation always has some degree of atrial-ventricular (AV) block with a 2:1 pattern meaning the rate of the ventricles is usually 150 beats per minute while the atria beat at 300 beats per minute. In other words, every other atrial beat reaches the ventricle. AF is an atrial rate of greater than 300 bpm with an irregular transmission of electrical impulses through to the ventricles, causing a fast, irregular heart beat. this differs from atrial flutter, which causes a fast, regular heart rhythm.

This arrhythmia impairs blood flow out of the heart (cardiac output) and promotes clot (thrombus) formation.

Animation of Atrial Fibrillation

Blood remains in the chamber that leads to clot formation.

In atrial fibrillation, chaotic electrical signals travel across the heart in an abnormal way. Abnormal electrical pathways produce irregular heartbeats and rhythms known as arrhythmias.

Arrhythmias occur when other areas of the heart, other than the SA node, begin sending out their own impulses and take over the pacemaker function of the SA node. The sites that take over could be from any area of the atria, AV node, or ventricles.

The rapid fibrillation of the atria does not allow the complete filling of the ventricles, that pumps blood out to the entire body. Symptoms of atrial fibrillation such as lightheadedness or dizziness may be felt.

Also, some amount of blood remains in the chamber that leads to clot formation.

Atrial fibrillation can be due to abnormalities or diseases of the heart, or by diseases elsewhere in the body affecting the heart. Atrial fibrillation may occur after open heart surgery or substance abuse.

Heart abnormalities and diseases include:

Coronary artery disease (decreased blood supply to the heart) or atherosclerosis
High blood pressure
Heart attack
Cardiomyopathy and congestive heart failure
Rheumatic fever and pericarditis (inflammation of the heart)
Abnormalities of the heart valves, especially mitral stenosis and mitral regurgitation
Hypertrophy (enlarged heart)
Sick sinus syndrome

Diseases elsewhere in the body affecting the heart:

Hyperthyroidism
Pulmonary embolism (blood clot in lung)
Chronic obstructive pulmonary disease (COPD) and emphysema
Sleep apnea

Substance abuse:

Consuming large amounts of alcohol (binge drinking)
Cocaine, amphetamines, diet pills, caffeine, or cold medicines
Tobacco
Carbon monoxide intoxication

Surgery

First week following open heart surgery

Medications

Theophylline

Congenital heart defects (heart defect from birth)

Some patients may be unaware of their heart beating abnormally. Although characteristic symptoms include:

Palpitations (pounding sensation in the chest)
Chest pain
Shortness of breath
Anxiety

Weakness
Dizziness, light-headedness
Fainting
Confusion
Fatigue
Intolerance to exercise
Nausea
Nervousness
Swelling of the legs or abdomen

Chest X-ray- a simple test performed in our office showing the size and shape of the heart.

3. Tests

Certain tests can be performed to determine the cause and severity of your condition including:

Blood tests- to check potassium and thyroid hormone levels
Electrocardiogram- this is a very useful and simple test that records the electrical activity of the heart and reveals atrial fibrillation. Also shows signs of heart attack, conduction abnormalities, hypertrophy, and electrolyte imbalances.

Chest X-ray- a simple test performed in our office showing the size and shape of the heart. Also reveals the presence of fluid in the lungs.
Echocardiogram (ECHO) – a noninvasive test performed in our office to determine the size and function of the heart’s chambers and the structure and function of the heart valves.
24-Hour Holter monitor- records the electrical events of the heart during your normal daily activities. This is useful in detecting evidence of arrhythmias.
Event monitor- If symptoms of arrhythmia are infrequent and do not occur within 24 hours, an event recorder may be ordered for you for up to 30 days.
Stress test- determines how well the heart works during exercise.

Cardioversion– Cardioversion is a medical procedure that restores a normal heart rhythm in people with certain types of abnormal heartbeats (arrhythmias). atrial fibrillation is sensitive to a low electrical energy direct-current (DC) or medical cardioversion (using an antiarrhythmic drug). DC cardioversion converts atrial fibrillation into a normal sinus rhythm with a high success rate. Cardioversion may need to be delayed until starting treatment with an anticoagulant. This medication is usually given for 3-4 weeks, allowing preexisting clots to resolve. A transesophageal echocardiogram (TEE) is an alternative way of delaying cardioversion, if no blood clots are present, cardioversion may be started. A mild sedative is first given, pads are applied over the chest, and then the heart will be shocked into the correct rhythm.

Catheter radiofrequency ablation- is a hospital procedure done to destroy areas on the heart that are causing irregular heart rhythms. A thin flexible tube is inserted into a blood vessel to access the heart. Heat is applied to the tip of the catheter to permanently destroy small areas of abnormal heart tissue. The damaged tissue is no longer capable of generating electrical impulses. A pacemaker may be placed after this procedure.

Pacemaker or Implantable Cardiac Defibrillator (ICD) – a small implantable device used to regulate the heart rate and rhythm. Therefore, the heart contracts in a regular way. An ICD shocks the heart out of the dangerous rhythm.

Animation of Catheter radiofrequency ablation