Definition and History
Atrial fibrillation has been around for many thousands of years, and currently affects a 2-5 million Americans. This estimate is so broad due to the fact that many cases of AF are minor and go undetected. Many cases are intermittent, or the inconsistency in the patient's cardiac rhythm is not significant enough to cause any issues for the patient. However, the majority of minor cases often develop into something more serious, and deserve serious attention.
Definition
Simply put, atrial fibrillation is an irregularity in the heart's rhythm. The two upper chambers of heart (the atria), beat very rapidly and erratically, while the two lower chambers of the heart (the ventricles) maintain a more consistent, although much more rapid, pace. This is caused by an issue with the sinoatrial node (known typically as the sinus node) in the right atrium. The sinus node is a cluster of specialized cells (sympathetic nervous system and parasympathetic nervous system tissue) that spontaneously generate electrical impulses which travel across the muscles of the heart and cause it to contract. Functioning as the heart's pacemaker, this nervous cluster is critical to the heart's operation. Below is a picture of typical sinus node operation. Note the smooth transmission of the electrical impulses through the atrium (on the left), as well as the repetitive, consistent ECG reading (right).
To completely understand why this is an issue, one must understand how the atria and the ventricles work together. A simplified explanation says that blood is sucked into the atrium, then pumped into the ventricles, which are surrounded by larger muscles which propel the blood through the rest of the body.
In the case of AF, the sinoatrial node sends rapid, sporadic electrical impulses to the muscles of the atria. This causes erratic contractions, and therefore poor blood flow from the atria to the ventricles. Below is a graphic similar to the one above, except this time with the symptoms of AF. Note the three main differences, the first being the chaotic electric impulses throughout the atria. Secondly, node the chaotic behavior of the atria on the ECG (small wavelengths), and the much more rapid, albeit smoother, ventricle contractions (large wavelengths).
Scientists don't completely understand what causes AF, but there are many factors that can affect whether one develops the disorder or not. For a short list of possible causes, visit the Mayo Clinic link here.
History
A-fib has a long but simple history. The disorder has been recognized for thousands of years, with written records dating back some four thousand years. Not much progress was made treating or curing the condition until William Withering, and English physician, discovered the first useful treatment in 1785 when he gave one of his patients suffering from the disorder a leaf of the plant known in England as the "foxglove," the chemicals of which are still used today. However, it took until around the early 1900's for scientists to gain a fuller understanding of AF when the electrocardiograph was invented. Modern physicians continue to gain a better understanding of the disease, its causes, and it's treatments, but still have much to learn.
The next lesson covers symptoms and diagnosis.
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