Definition of Atrial fibrillation/flutter:

Atrial fibrillation/flutter is a heart rhythm disorder (arrhythmia). It usually involves a rapid heart rate, in which the upper heart chambers (atria) are stimulated to contract in a very disorganized and abnormal manner.

Causes, incidence, and risk factors:

Arrhythmias are caused by a disruption of the normal electrical conduction system of the heart.

Normally, the four chambers of the heart (two atria and two ventricles) contract in a very specific, coordinated way. The electrial impulse that signals your heart to contract in a synchronized way begins in the sinoatrial node (SA node). This node is your heart's natural pacemaker.

The signal leaves the SA node and travels through the two upper chambers (atria). Then the signal passes through another node (the AV node), and finally, through the lower chambers (ventricles). This path enables the chambers to contract in a coordinated fashion.

In atrial fibrillation, the atria are stimulated to contract very quickly and differently from the normal pattern. The impulses are sent to the ventricles in an irregular pattern. Some impulses fail to be transmitted. This makes the ventricles beat abnormally, leading to an irregular (and usually fast) pulse.

In atrial flutter, the ventricles may beat very fast, but in a regular pattern.

If the atrial fibrillation/flutter is part of a condition called sick sinus syndrome, the sinus node may not work properly. The heart rate may alternate between slow and fast. As a result, there may not be enough blood to meet the needs of the body.

Atrial fibrillation can affect both men and women. It becomes more common with increasing age.

Causes of atrial fibrillation include:

• Alcohol use (especially binge drinking)
• Congestive heart failure
• Coronary artery disease (especially after a heart attack or coronary artery bypass surgery)
• High blood pressure (hypertension)
• Hypertrophic cardiomyopathy
• Medications
• Overactive thyroid gland (hyperthyroidism)
• Pericarditis
• Valvular heart disease (especially mitral stenosis and mitral regurgitation)