Ventricular Fibrillation

Ventricular fibrillation is a lethal heart rhythm disorder that requires an immediate therapy. During ventricular fibrillation, the walls of heart ventricles begin to oscillate at high speed totally disrupting their blood pumping abilities.


Note: Ventricular fibrillation has a similar name as the atrial fibrillation, but that is a completely different rhythm disorder. Atrial fibrillation causes similar oscillation of heart atria but their dysfunction is not hemodynamically as important as in case of heart ventricles.


The causes of ventricular fibrillation are related to disorders in conduction system transmitting the electric signals throughout the hear myocardium. Electric signals are conducted from heart atria to ventricles and ensure coordinated contractions of the heart compartments.


The causative factors damaging this electric system of the heart may be various heart diseases including chronic ischemic heart disease, heart attack, cardiomyopathies (especially hypertrophic cardiomyopathy) and internal environment disturbances (ion imbalance such as severe hypokalemia, hyperkalemia, etc). However, in many cases, the ventricular fibrillation occurs in a seemingly completely healthy individual, often a sportsman.


As the heart looses the ability to pump blood into the blood stream including brain, the first and only symptom is a sudden loss of consciousness followed by brain damage and death within few minutes. However, this time period can be affected by some other factors, especially the body temperature. Decreased body temperature lowers the brain intake of oxygen and makes the brain more resistant to ischemia, thus lengthening the above-mentioned interval.


The affected person is unconscious, does not breathe and has no palpable pulse. The diagnosis is confirmed by ECG (usually made by a portable defibrillator used during the CPR) that shows classic disorganized wide waves completely different from the normal ECG record.

First Aid

We have to think about ventricular fibrillation in every case of sudden signs of cardiac arrest in an adult. Within 30 seconds from the onset of symptoms (unconsciousness), we can execute the precordial thump, which is a strong punch to the chest targeting the bottom area of the sternum. Such strike can occasionally “reset” the heart rate back to normal and restart normal rhythm. However, many physicians evaluate the precordial thump as controversial and therefore it can not be fully recommended.


The most essential is to call an emergency as soon as possible as the patient with suspected ventricular fibrillation needs professional medical assistance. After calling the paramedics or other emergency services (depending on current country), it is important to start the classic CPR.


The method of choice is the electric defibrillation. We use special portable defibrillators. We attach their electrodes to the patient's chest, the machine monitors the patient's rhythm and when we see the fibrillation pattern, we administer a strong electric discharge via the electrodes to the patient's chest to restore the normal rhythm. Imagine it as a reset button on your computer. The better the previous CPR was, the better is the myocardium oxygenated and the better is the outcome of the defibrillation. In patients who undergone successful CPR is often performed the so-called therapeutic hypothermia to minimize the brain ischemic damage.


Note: In developed countries there are deployed automatic defibrillators in public areas. These defibrillators are devices that can be used by practically anyone. It is sufficient to only attach two electrodes to the chest of an unconscious person and activate the machine. The device automatically checks the heart rate and either charges itself and orders the rescuer to press a button to carry the electric discharge, or advise the rescuers in further CPR.


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources