Heart Arrhythmias Overview

Heart arrhythmias (dysrhythmias) are a disorder of the heart's electrical activity, which alters the speed and rhythm of the heartbeat. There are several types of arrhythmias, including:

• Tachycardia
  Tachycardia is a faster-than-normal heartbeat. Tachycardia is often a normal response to exercise or stress. In some cases, however, tachycardia may prevent the heart from pumping an adequate supply of blood to the rest of the body.
• Bradycardia
  Bradycardia is a slower-than-normal heartbeat. Although bradycardia may be normal in physically active people, the condition is sometimes due to a problem with the heart's electrical system.
• Atrial fibrillation
  Atrial fibrillation is the most common type of heart arrhythmia. It causes the heart's atria (upper chambers) to quiver quickly, preventing them from completely pumping out the blood. Blood may pool and clot inside the atria. If a blood clot breaks off and reaches the brain, it can cause a stroke (a blockage of blood flow to the brain).
• Ventricular fibrillation
  Ventricular fibrillation causes the heart's ventricles (lower chambers) to quiver instead of pumping blood out of the heart. The condition can be fatal if not treated immediately.

How the heart works

The heart is a muscle that pumps blood throughout the body. The heart, blood vessels, and blood make up the body's cardiovascular system, which helps:

• Bring oxygen and nutrients to the body.
• Remove carbon dioxide and waste products from the body.

The right side of the heart pumps oxygen-poor blood to the lungs, where the blood picks up oxygen. The blood is then returned to the left side of the heart, which pumps the oxygen-rich blood to the body. Each side of the heart has two chambers. The upper chambers are called atria (singular: atrium). The lower chambers are called ventricles. Valves control the flow of blood between the atria and the ventricles.

A heartbeat is a single pulsation of the heart. First the atria contract, then the ventricles contract, and then the entire heart relaxes. The heart's electrical system controls the speed of a person's heartbeat.

About heart disease

Heart disease is a general term for any disorder of the heart and its ability to circulate blood throughout the body. The common types of heart disease include heart arrhythmias, angina, coronary artery disease, heart attack, and heart failure.

Most types of heart disease are usually caused by atherosclerosis, which is a build up of fatty deposits (plaques) on the inner walls of the blood vessels. If left untreated, the blood vessels narrow and may become blocked, which interferes with the supply of blood throughout the body. Heart disease may also be caused by an infectious disease (such as rheumatic fever due to strep throat) or a congenital heart disease (such as heart obstruction defects present at birth)

According to the Centers for Disease Control and Prevention (CDC):

• Heart disease is the leading cause of death in the United States and is a major cause of disability.
• Almost 700,000 people die of heart disease in the U.S. each year. This is 29% of all deaths.
• Approximately half of the heart disease deaths were women.
• The age–adjusted death rates for heart disease were 30% higher among African Americans than among whites.