Ventricular fibrillation is an abnormally irregular heart rhythm caused by rapid, ineffective, uncoordinated contraction of the ventricles which produce no peripheral pulse.
Patients of ventricular fibrillation usually present with sudden loss of consciousness . Signs and symptoms of ventricular fibrillation include chest pain, rapid heartbeat, dizziness, nausea, shortness of breath and collapse. If untreated, the person usually has a seizure and then becomes limp and unresponsive. The patient suddenly collapses, turns deathly pale, stops breathing, and has no detectable pulse, heartbeat, or blood pressure. The patient develops irreversible brain damage after 5 minutes because of lack of oxygen to the brain. This leads to sudden cardiac arrest and death of the patient.
Ventricular fibrillation is always diagnosed in an emergency setting.
Ventricular fibrillation is treated by delivering a quick electric shock through the chest, within a few minutes of attack, using a device called an external defibrillator. Although a moderate alternating-current voltage applied directly to the ventricles almost invariably throws the ventricles into fibrillation, a strong high-voltage alternating electrical current passed through the ventricles for a fraction of second can stop fibrillation by throwing all the ventricular muscle into refractoriness simultaneously. This is accomplished by passing intense current through large electrodes placed on two sides of the heart. The current penetrates most of the fibers of the ventricles at the same time, thus stimulating essentially all parts of the ventricles simultaneously and causing them to become refractory. All action potentials stop, and the heart remains quiescent for 3 to 5 seconds, after which it begins to beat again, usually with the sinus node or some other part of the heart becoming the pacemaker. When electrodes are applied directly to the two sides of the heart, fibrillation can usually be stopped using 110 volts of 60-cycle alternating current applied for 0.1 second or 1000 volts of direct current applied for a few thousandth of a second. When applied through two electrodes on the chest wall, the usual procedure is to charge a large electrical capacitor up to several thousand volts and then to cause the capacitor to discharge for a few thousandth of a second through the electrodes and through the heart.
Unless ventricular fibrillation is defibrillated within a minute from its onset, the heart is usually too weak to be revived because of the lack of nutrition from coronary blood flow. A technique for pumping the heart without opening the chest consists of intermittent thrusts of pressure on the chest wall along with artificial respiration. This technique in combination with the use of a defibrillation is called cardiopulmonary resuscitation.
The prognosis of ventricular fibrillation involves consideration of the underlying cause of cardiac arrest and presence of co-morbidities such as metastatic cancer and dementia  . The chances of survival after an acute attack of ventricular fibrillation depend on cardiopulmonary resuscitation rapid availability, advanced life support and transport to a hospital. The probability of success generally declines at a rate of 2-10% per minute. An estimated 20% of patients with cardiac arrest survive to hospital discharge. After return of heart function, there is a moderately higher risk of death due to recurrent ventricular fibrillation when compared to myocardial infarction patients   . With immediate angioplasty and stent placement, the prognosis is good.
The most common cause of ventricular fibrillation is myocardial infarction, particularly due to inadequate blood flow to the heart muscle because of coronary artery disease . The patients with a previous episode of ventricular fibrillation or a previous heart attack are more prone to develop this condition. Moreover, increased risk for the development of ventricular fibrillation is also found in conditions such as congenital heart disease, cardiomyopathy, myocarditis, heart surgery, hypoxic ischemia, narrowed coronary arteries, damage to the heart muscles by electrocution, use of illegal drugs (such as cocaine and methamphetamine), commotio cordis in athletes and electrolyte abnormalities involving potassium and magnesium .
A number of people with ventricular fibrillation have no history of heart disease. However, they often have risk factors of cardiovascular disease, such as smoking, high blood pressure, obesity, dyslipidemia, sedentary lifestyle and diabetes.
Sudden cardiac arrest is the leading cause of death in the developed world. The World Health Organization estimates a significant mortality with approximately 70,000 to 90,000 sudden cardiac deaths each year in the United Kingdom with survival rates of only 2%. Up to 30% survivors of cardiac arrest may experience recurrent ventricular fibrillation in the first year after the heart complication . According to one study, 31% of deaths are sudden in people aged between 20 to 29 years and a greater proportion have been common in blacks than in whites. The incidence of ventricular fibrillation is usually higher in men than in women. If prompt treatment is not given, death usually occurs within minutes.
Ventricular fibrillation is a life-threatening cardiac arrhythmia which results from cardiac impulses that have gone berserk within the ventricular muscle mass, stimulating one portion of the ventricular muscle, then another portion, then another, and eventually feeding back onto itself to re-excite the same ventricular muscle over and over again without never stopping. When this happens, many small portions of the ventricular muscle will be contracting at the same time, while as many other portions will be relaxing. Thus, there is never a coordinated contraction of all the ventricular mass at once, which is required for a normal pumping cycle of the heart. Despite massive movement of stimulatory signals throughout the ventricles, the ventricular chambers neither enlarge nor contract but remain in an indeterminate stage of partial contractions, pumping either no blood or negative amounts of it. Therefore, after fibrillation begins, unconsciousness occurs within 4 to 5 seconds due to lack of blood flow to the brain, and irretrievable death of tissues begins to occur throughout the body within a few minutes.
Ventricular fibrillation is based upon the phenomenon of re-entry that leads to “circus movements”.
It is a condition that causes the cardiac impulse to continue to travel around in a circle resulting in the”re-entry” of the impulse into muscle that has already been excited. A long conductive pathway and decreased rate of conduction frequency results in repetitive electrical stimulation. Thus, in many cardiac disturbances, re-entry can cause abnormal patterns of cardiac contraction that ignore the pace-setting effects of the sinus node.
People who are successfully resuscitated from ventricular fibrillation and survive are at high risk of another episode. In order to reduce the risk of future ventricular fibrillation, the treatment options include the following.
Ventricular fibrillation is an abnormally irregular heart rhythm caused by rapid, ineffective, uncoordinated contraction of the ventricles; producing no peripheral pulse. It is a life-threatening medical emergency which, if not stopped within 1 to 3 minutes, is almost invariably fatal . The lower chambers of the heart quiver and it fails to pump any blood to the vital organs, causing cardiac arrest. The patient can sustain irreversible brain damage and possibly become brain-dead due to effects of cerebral hypoxia. Ventricular fibrillation is very common during electric shock and during ischemia of conductive system. It also occurs in conditions like coronary artery disease, chloroform anesthesia, heart muscle disease and trauma to heart. Emergency treatment includes cardiopulmonary resuscitation and shocks delivered to the heart with a defibrillator.
Ventricular fibrillation is a severely abnormal heart rhythm. It is a life-threatening emergency and causes death within few minutes. Emergency treatment requires immediate resuscitation and defibrillation. Drug therapy and defibrillators can correct abnormal rhythms in high-risk patients.