Alternate Names: Dysrhythmias; Abnormal heart rhythms

Causes and Risks:

Arrhythmias are caused by a disruption of the normal electrical conduction system of the heart. Normally, the4 chambers of the heart (2 atria and 2 ventricles) contract in a very specific, coordinated manner.The signal to contract is an electrical impulse that begins in the "sinoatrial node" (also called the SA node), which is the body’s natural pacemaker.

The signal then travelsthrough the 2 atria and stimulates them to contract. The signal passes through another node (the AV node),and finallytravels through the ventricles and stimulates them to contract.

Problems can occur anywhere along the conduction system, causing various arrhythmias. There can be a problem in the heart muscle itself, causing it to respond differently to the signal, or causing the ventricles to contract independently of the normal conduction system.

Arrhythmias include "tachycardias" (the heartbeat is too fast), "bradycardias" (the heartbeat is too slow) and "true" arrhythmias (a disturbed rhythm).

Arrhythmias are classified as lethal if they cause a severe decrease in the pumping function of the heart. When the pumping function is severely decreased for more than a few seconds, blood circulation is essentially stopped, and organ damage (such as brain damage) may occur within a few minutes. Lethal arrhythmias include ventricular fibrillation; ventricular tachycardia that is rapid and sustained, or pulseless; and sustained episodes of other arrhythmias.

Other arrhythmias include atrial fibrillation/flutter, multifocal atrial tachycardia, paroxysmal supraventricular tachycardia, Wolff-Parkinson-White syndrome, sinus tachycardia, sinus bradycardia, bradycardia associated with heart block, sick sinus syndrome, and ectopic heartbeat.

People who have a history of coronary artery disease, heart valve disorders, or other cardiac disorders, and people with imbalances of blood chemistries, are at higher risk for arrhythmias and complications from arrhythmias.

Arrhythmias are also caused by some drugs. These include anti-arrhythmics, beta blockers, caffeine, cocaine, psychotropics, and sympathomimetics.

Prevention: Methods of preventing other heart diseases (e.g., coronary artery disease) may decrease the likelihood of developing an arrhythmia.

Symptoms:

• Changes in the rate, rhythm, or pattern of the pulse
• Sensation of feeling the heart beat (palpitations)
• Chest pain
• Shortness of breath
• Fainting
• Light headedness, dizziness

Note: The person may be without symptoms. The first symptom may be sudden cardiac death (loss of heart beat) associated with lethal arrhythmias.

Additional symptoms that may be associated with this disease:

• Clammy skin
• Weak or absent pulse
• Paleness
• Temporarily absent breathing
• Low blood pressure

Signs and Tests:

Listening to the heart with a stethoscope (auscultation) or feeling the pulse may indicate an arrhythmia. Blood pressure may be low or normal.

Tests that reveal arrhythmias, and differentiate the type of arrhythmia, include:

• ECG
• 24-hour cardiac monitoring
• 24-hour Holter monitoring
• Echocardiogram
• Coronary angiography

Various tests to confirm or rule out suspected causes of the arrhythmia may be appropriate.

Treatment:

Medications may include anti-arrhythmic medications, medications to speed up or slow down the heart rate, and others.

Treatment may include electrical "shock" (defibrillation or cardioversion).

Prognosis:

The outcome is dependent on several factors:

1. The kind of arrythmia -- whether it is simply an atrial arrythmia (originating from the atrium) or a more potentially lethal arrythmia, such as ventricular tachycardia or ventricular fibrillation.
2. The "ejection fraction" of the heart, or the overall pumping ability of the heart.
3. A person’s differing response to the same arrhythmia.

When an arrythmia is serious and not well-tolerated by the person, there may not be enough blood flowfrom the heart to vital organs such as the brain, the kidneys, and to the heart itself.

Complications:

• Angina (the arteries supplying the heart itself are not getting enough blood)
• Heart attack
• Heart failure
• Stroke

Call your health care provider if symptoms indicate an arrhythmia may be present.

Call your health care provider if an arrhythmia has been diagnosed and symptoms worsen or do not improve with treatment.