Coronary artery disease is the most common single cause for the malfunctioning of the SA node. A condition in which the heart rate suddenly increases to 200 to 300 beats per minute, although a normal conduction between atria and ventricles is maintained. The condition characteristically occurs in young persons with no evidence of organic heart disease , but may also occur in older persons with atherosclerosis of the coronary and other arteries. This condition may occur in any organic heart disease , but particularly in atherosclerosis , heart attack , valvular heart disease and inflammation of the atrium . An arrhythmia which results from the continuous and chaotic re-entry of electrical impulses within the muscle of the atrium .
Fibrillation is much more common than flutter , and occurs in the same diseases.
In young people, the condition is most commonly the result of valvular heart disease. In older persons, atherosclerosis of the arteries of the heart is the major cause. A regular rhythm of the ventricles at a rate of between 100 and 200 beats per minute. The condition may occasionally occur in young people without other evidence of heart disease, but it occurs most commonly in those with atherosclerotic heart disease and in overdosages of the heart drug digitalis . An irregular and chaotic arrhythmia of the ventricles , with a rapid rate and disorganized spread of impulses through the muscle of the ventricles.