Ventricular fibrillation
Ventricular fibrillation (VF) is a rapid, chaotic ventricular arrhythmia that immediately brings to a halt all meaningful ventricular contractions. Blood therefore immediately stops flowing, and loss of consciousness occurs within seconds. Unless cardiopulmonary resuscitation measures are initiated within a few minutes of the onset of VF, sudden death will occur.Figure 5 - Ventricular fibrillation. The multiple purple lines represent the chaotic electrical activity seen in VF.
As a general rule, neither VT nor VF occur in patients without underlying cardiac disease. For people who have underlying cardiac disease, in general, the worse the left ventricular function, the higher the risk of developing life-threatening ventricular tachycardias.
There are exceptions to this general rule. One such exception is long QT syndrome, a condition in which a specific type of ventricular tachycardia occurs that is associated with certain ECG abnormalities (a prolonged QT interval). Patients with long QT syndrome usually have no identifiable underlying cardiac disease, but appear to be born with the propensity to develop a particular variety of ventricular tachycardia under certain circumstances. (These circumstances can include exercise, or the administration of certain drugs). These patients most often present with episodes of syncope (fainting) due to episodes of ventricular tachycardia. (Click here for a discussion of long QT syndrome.)
While in some cases life-threatening VT or VF can be controlled with antiarrhythmic drugs, by far the most effective means to prevent sudden death is to insert the implantable defibrillator.
