Ventricular fibrillation

Alternative names

VF

Definition

Ventricular fibrillation (VF) is a severely abnormal heart rhythm (arrhythmia) that, unless treated immediately, causes death. VF is responsible for 75% to 85% of sudden deaths in persons with heart problems.

To pump blood out to the body, all areas of the heart normally squeeze (contract) in an organized, synchronic manner. The heart's upper chambers (the atria) contract first, and then the heart's bottom two chambers (ventricles) contract. During VF, however, the ventricles contract independently of the atria, and some areas of the ventricles contract while others are relaxing, in a disorganized manner.

Causes, incidence, and risk factors

The most common cause of VF is a heart attack, but VF can occur whenever the heart muscle is affected by a poor supply of oxygen or by specific heart disorders.

Conditions that can lead to VF include:

• acute or previous heart attack
  
• ischemia (lack of oxygen to the heart muscle because of narrowed coronary arteries or shock)
  
• congenital heart disease
  
• heart surgery
  
• diseases of the heart muscle, such as cardiomyopathies
  
• electrocution accidents or accidents involving direct trauma to the heart
  

Ventricular fibrillation is the main cause of sudden cardiac death, which in turn affects nearly 300,000 people each year in the U.S.

While most people suffering from VF have no previous history of heart disease, many have risk factors for cardiovascular disease, such as smoking, hypertension, and diabetes.

Symptoms

The person having VF suddenly collapses or falls unconscious, because the brain and muscles have stopped receiving blood from the heart. Within one hour before the collapse (or sudden death from VF), some people complain of symptoms such as chest pain, palpitation, shortness of breath, dizziness, or nausea.

Signs and tests

The person will be unresponsive. The carotid pulse in the neck and femoral pulse in the groin may be hard or impossible to detect. When listening to the heart with a stethoscope, the heartbeats cannot be heard or they may have varying intensity and be very irregular.

If the person having VF was already in the hospital, or if paramedics have connected the person to a cardiac monitor, the monitor will show a disorganized arrhythmia (VF). The VF in turn can evolve into a flat line or cardiac arrest.