Ventricular fibrillation: arrhythmia
Many factors can trigger the onset of atrial fibrillation. A person may have a normal heart rhythm, a second later may have ventricular fibrillation.
Ventricular fibrillation is a potentially fatal, uncoordinated series of very rapid, ineffective contractions of the ventricles (lower chambers of the heart) caused by many chaotic electrical impulses.
The most dangerous state of arrhythmia is ventricular fibrillation. If it does not end within 1 to 3 minutes, it will almost certainly lead to death. Ventricular fibrillation is caused by a pulsating rhythm in the ventricular mass, causing total ventricular depolarization, followed by another beat, then continued, and finally retrograded itself to continuously re-depolarize the ventricular mass nonstop. When this happens, many parts of the ventricles contract at the same time, while others are resting.
Therefore, never combine ventricular contractions at the same time, ventricular contractions at the same time create the pumping rhythm of the heart. Despite the massive migration of excitatory impulses to the ventricles, the ventricular chambers do not dilate, contract, pump, or pump insignificant amounts. Therefore, after the tremor begins, loss of consciousness occurs within 4 to 5 seconds because of ischemia to the brain and irreversible tissue death occurs throughout the body within minutes.
Many factors can trigger the onset of atrial fibrillation. A person may have a normal heart rhythm, a second later may have ventricular fibrillation. It can be (1) sudden cardiac shock or (2) myocardial ischemia, control ischemia, or both.
Figure. Ventricular fibrillation (lead DII).
Cardiac arrest is diagnosed when a person suddenly collapses, turns deathly pale, stops breathing, and has no detectable pulse, heartbeat, or blood pressure. Ventricular fibrillation is diagnosed as the cause of cardiac arrest by Electrocardiography (ECG).
Ventricular fibrillation must be treated as an extreme emergency. Cardiopulmonary resuscitation (CPR) must be started as soon as possible. It must be followed by defibrillation (an electrical shock delivered to the chest), as soon as the defibrillator is available. Drugs used to treat abnormal heart rhythms (see table Some Drugs Used to Treat Arrhythmias ) may then be given to help maintain the normal heart rhythm.
When ventricular fibrillation occurs within a few hours of a heart attack in people who are not in shock and who do not have heart failure, prompt cardioversion restores normal rhythm in 95% of people, and the prognosis is good. Shock and heart failure suggest severe damage to the ventricles. If the ventricles are severely damaged, even prompt cardioversion has only a 30% success rate, and 70% of people who are resuscitated die without regaining normal function.
People who are successfully resuscitated from ventricular fibrillation and survive are at high risk of another episode. If ventricular fibrillation is caused by a reversible disorder, that disorder is treated. Otherwise, most people have an implantable cardioverter-defibrillator (ICD) surgically implanted to correct the problem if it recurs. ICDs continually monitor the rate and rhythm of the heart, automatically detect ventricular fibrillation, and deliver a shock to convert the arrhythmia back to a normal rhythm. Such people are often also given drugs to prevent recurrences.