Arrhythmia

An arrhythmia is a disorder of the heart rate or heart rhythm. This includes beating too fast (tachycardia), beating too slow (bradycardia), or beating irregularly.

Although most arrthymias are harmless, some can be serious and even life threatening. Arrthymias may cause the heart to not be able to pump enough blood to the rest of the body. If this occurs, there could be damage to the heart, brain, and other organs.

The heart is normally able to pump blood out to the body without working too hard. It has an electrical system that ensures that it squeezes regularly. The impulse signaling the heart to squeeze starts in the sinoatrial node, a group of cells also known as the sinus node or SA node located in the upper right chamber. This impulse acts as a natural pacemaker.

The electrical impulse normally:

• leaves the SA node and goes through the two upper chambers of the heart (atria). The atria then contracts, and blood is pumped into the two lower chambers of the heart (ventricles).
• Then it goes through a different group of cells known as the antrioventricular node  (AV node). The AV node is between the ventricles and the atria. The signal slows and the ventricles finish filling with blood.
• Lastly, it travels along a divided pathway, the left bundle branch and right bundle branch. The signal then goes from each pathway to the ventricles, and they pump blood to the rest of the body, including the lungs.

The electrical impulse uses different nerve messages to tell the heart to beat slower or faster. Problems occurring anywhere along this electrical system cause various arrhythmias.

Examples Include:

• Atrial fibrillation or flutter
• Atrioventricular nodal reentry tachycardia (AVNRT)
• Heart block or atrioventricular block
• Paroxysmal supraventricular tachycardia
• Sick sinus syndrome
• Wolff-Parkinson-White syndrome
• Ventricular fibrillation

Alternative names for arrhythmia include:

• Dysrhythmia
• Abnormal heart rhythms
• Bradycardia
• Tachycardia

The risk of getting an arrhythmia varies depending on:

• Blood chemistry imbalances, such as abnormal potassium levels
• Cardiomyopathy a weakening of the heart muscle or a change in the heart muscle
• Heart failure
• Overactive thyroid gland
• Heart attack
• High blood pressure
• Coronary heart disease
• Rheumatic heart disease

Some substances or drugs may also cause arrhythmias:

• Amphetamines
• Smoking
• Caffeine
• Cocaine
• Beta blockers
• Psychotropics
• Sympathomimetics
• Anti-arrhythmic medications prescribed to treat one type of arrhythmia can sometimes cause another type of arrhythmia

Congenital heart defects can also cause some arrhythmias. "Congenital," means that the defect is present at birth. An example is Wolff-Parkinson-White syndrome.

The cause of an arrhythmia can also be unknown.

See your doctor if you notice a fluttering, racing, or skipping heartbeat, especially with dizziness or fatigue. Call 911 for fainting, chest pain, or severe shortness of breath with an irregular heartbeat.