Introduction
Atrial Fibrillation can be referred to as the abnormal beat or rhythm of the atrium (the upper chambers of the heart). It is one of the most common types of arrhythmias. An arrhythmia is simply an abnormal beat or impulse that originates outside the SA-node. The SA or sinoatrial node is known as the hearts real pacemaker. It is where impulses are the quickest at 60-80 beats per minute. It is located in the upper right quadrant of the heart, in the right atrium. Abnormal electrical signals that cause atrial fibrillation often originate in the left pulmonary veins rather than the sinoatrial node causing irregularities in the pattern of the heart depolarizing.
Atrial Fibrillation is classified by a disordered rate of the natural rhythm of the heart, generally as quick as 40 to 180 beats per minute. This causes the heart to inadequately depolarize. It is common for the condition to fluctuate between Atrial Flutter and atrial fibrillation. Atrial Flutter is different primarily because the rhythms are quick with an active atrial rate of 180 to 350 beats per minute however it is a rapid but regular rhythm which differs to the anarchic rhythm of atrial fibrillation. It is common for people who develop atrial flutter for it to transcend to fibrillation.
The chances of this condition increases with age and with reference to recent research it is present in 10% of a population over the ages of 80 years and is significantly uncommon in people aged 30 years or less.
In atrial fibrillation, because of the irregularity of the beats the upper chambers of the heart are unable to completely empty into the ventricles (the lower chambers of the heart). This poses a risk of blood pooling or clot formation and has been known to be the cause of stroke in some patients.
This condition is not usually a life threatening arrhythmia but can have a serious effect on cardiac output. Cardiac output is the volume of blood ejected from the ventricle per minute and can be equated using this formula CO= (stroke volume x heart rate). An adequate atrial contraction is important to left ventricular filling particularly during exercise, when the bodies demand for blood and oxygen is greater. The decrease in cardiac output signifies the loss of an effective atrial pump because of the rapid, irregular ventricular contraction which can lead to abnormally low blood pressure, termed hypotension and pulmonary congestion. These disorganized contractions also increases the chances of thrombus (clot) formation promoting the chances of stroke.