fibrillations

Fibrillation refers to rapid, uncoordinated contractions of muscle fibers. In clinical practice the term most often describes disorganized electrical activity in the heart, where it prevents effective pumping. Fibrillation can involve the atria (atrial fibrillation) or the ventricles (ventricular fibrillation). It can also describe spontaneous muscle fiber activity detected by electromyography (EMG) as fibrillation potentials.

Atrial fibrillation is characterized by an irregularly irregular rhythm and lack of organized atrial contraction, increasing stroke risk due to emboli from the left atrium. Ventricular fibrillation is a chaotic, unsynchronized rhythm that eliminates effective ventricular output and is a life-threatening emergency.

Causes include ischemia, electrolyte disturbances (notably potassium and magnesium imbalances), structural heart disease, drug toxicity, and postoperative states. The mechanism involves multiple reentrant circuits and unstable atrial or ventricular electrical activity; in VF, the ventricles cannot sustain a pulse.

Diagnosis is by electrocardiography, with VF showing no identifiable QRS complexes and AF showing continuous irregular activity and absence of organized atrial activity. Treatment depends on type: ventricular fibrillation requires immediate defibrillation and ACLS; atrial fibrillation is managed with rate or rhythm control and anticoagulation, plus treatment of underlying causes.

In EMG, fibrillation potentials are spontaneous, brief discharges arising from denervated or irritable muscle fibers, indicating nerve or muscle pathology. They are distinct from macro-level cardiac fibrillation and are used to evaluate neuromuscular disorders.