The American frontier comprises the geography, history, folklore, and cultural expression of life in the forward wave of American westward expansion that began with English colonial settlements in the early 17th century and ended with the admission of the last mainland territories as states in 1912.
Atrial Flutter Causes. Atrial flutter may be caused by abnormalities or diseases of the heart, by a disease elsewhere in the body that affects the heart, or by consumption of substances that change the way electrical impulses are transmitted through the heart. In some people, no underlying cause is ever found.
Atrial flutter (AFL) is a common abnormal heart rhythm, similar to atrial fibrillation, the most common abnormal heart rhythm. Both conditions are types of supraventricular (above the ventricles) tachycardia (rapid heart beat).