Don, vfib, which stands for ventricular fibrillation, is usually fatal if not converted within 4 minutes. When a patient goes into ventricular fibrillation, the heart's ventricles no longer contract in a sinus rhythm, but instead the ventricles go into a non-rhythmic contractions that looks like a bag of worms. At this stage, blood ceases to flow and within 4 minutes the lack of oxygen to the brain causes your untimely demise.
With Afib, or atrial fibrillation, only the atrial chambers go into fibrillation, while the ventricular chambers continue to function normally. Yes, this too is very dangerous, but usually is not immediately fatal. Though, if left untreated, atrial fibrillation can often lead to ventricular fibrillation, therefore it must be corrected ASAP.
Sometimes, medications will bring about the conversion, but most of the time, an electrical shock must be applied (defibrillation) either directly to the heart, or to the chest. This electrical shock causes the heart to go into complete standstill. If everything goes well, the heart will resume a normal, sinus rhythm and the patient is then regulated with medications. If the afib returns, a pacemaker is the best option to control the problem. The pacemaker usually has a built-in defibrillator, which is triggered by any onset of afib detected by it's internal monitor. When it fires off, the patients usually say it felt like they were kicked in the chest by a mule.
All the best,
Gary