Fibrillation

Fibrillation is the rapid, irregular, and unsynchronized contraction of muscle fibers. An important occurrence is with regards to the heart.

Cardiology

There are two major classes of cardiac fibrillation: atrial fibrillation and ventricular fibrillation.

• Atrial fibrillation can be a chronic condition, usually treated with anticoagulation and sometimes with conversion to normal sinus rhythm. This originates in the Atrium and an electrical impulse is "quivering" (fibrillation). An electrical pulse is given off, but is not the optimal way of sending an electrical pulse.

• Ventricular fibrillation is rapidly fatal if not reversed by defibrillation. No electrical impulse is given off in this form of dysrhythmia.

Fibrillation may sometimes be used after heart surgery to stop the heart from beating while any minor leaks are stitched up.

Musculoskeletal

Fibrillation also occurs with individual skeletal muscle fibers. This happens when muscle fibers lose contact with their innervating axon producing a spontaneous action potential, "fibrillation potential" that results in the muscle fiber's contraction. These contractions are not visible under the skin and are detectable through needle electromyography (EMG) and ultrasound. Fibrillations do not occur in healthy individuals. They are a major symptom in acute and severe peripheral nerve disorders, in myopathies in which muscle fibers are split or inflammed, and lower motor neuron lesions.

They contrast with fasciculations that are visible spontaneous contractions involving small groups of muscle fibers. Also, fasciculation does not necessarily denote pathology, as does fibrillation, although it can be seen in lower motor neuron lesions as well.

References

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