Ventricular fibrillation is a heart rhythm problem that occurs when the heart beats with rapid, erratic electrical impulses. The heart is unable to effectively pump blood. Ventricular fibrillation is frequently triggered by a heart attack and is an emergency that requires immediate medical attention. A person with ventricular fibrillation will collapse within seconds and soon won't be breathing or have a pulse. Emergency treatment for ventricular fibrillation includes cardiopulmonary resuscitation (CPR) and shocks to the heart with a device called a defibrillator.