Arrhythmias

Causes and Risks:
Arrhythmias are caused by a disruption of the normal functioning of the electrical conduction system of the heart. Normally, the chambers of the heart (atria and ventricles) contract in a coordinated manner. The signal to contract is an electrical impulse that begins in the sinoatrial node (sinus node, SA node). It is conducted through the atria and stimulates them to contract. The impulse passes through the atrioventricular node (AV node), then travels through the ventricles and stimulates them to contract. Problems can occur anywhere along the conduction system, causing various arrhythmias. Problems can also occur in the heart muscle itself, causing it to respond differently to the signal to contract, also causing arrhythmias, or causing the ventricles to contract independently of the normal conduction system.

Arrhythmias include tachycardias (heartbeat too fast), bradycardias (heartbeat too slow) and "true" arrhythmias (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, also ventricular tachycardia that is rapid and sustained, or pulseless, and may include sustained episodes of other arrhythmias.

Some 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 antiarrhythmics, Beta blockers, caffeine , cocaine , psychotropics, and sympathomimetics.

Prevention:
Interventions that are aimed at prevention of other heart diseases (e.g. coronary artery disease ) may decrease the likelihood of development of an arrhythmia .

Symptoms:

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:



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:

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

Treatment:
Medications may include antiarrhythmic medications, medications to speed up or slow down the heart rate , and others.
Treatment may include electrical "shock" (defibrillation or cardioversion).

Prognosis:
Prognosis (probable outcome) is variable depending on the arrhythmia and the individual response to the arrhythmia. The arrhythmia may be well tolerated. It may cause symptoms from reduced pumping action of the heart (cardiac output), causing lack of blood flow to the brain, heart, and body. Arrhythmias may be dangerous, causing other disorders. Some arrhythmias can be lethal, especially ventricular tachycardia and ventricular fibrillation.

Complications:



Call Your Healthcare Provider:
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.


This is a cross-sectional view of the interior of the heart. The valves, chambers, and associated vessels are labeled.



This is an illustration of the exterior of the heart. The arteries are colored blue and represent blood that is flowing into the heart. The veins are red and indicate blood flow out from the heart. The chambers are also labeled.



This picture shows an ECG (electrocardiogram, EKG) of a person with an abnormal rhythm (arrhythmia) called an atrioventricular (AV) block. P waves show that the top of the heart received electrical activity. P waves are usually followed by the tall (QRS) waves. QRS waves reflect the electrical activity that causes the heart to contract. When a P wave is present and not followed by QRS wave (and heart contraction), there is an atrioventricular block, and a very slow pulse (bradycardia). (Courtesy of the Centers for Disease Control.)