January 23, 2018

Ventricular Fibrillation (VF)

Adult ACLS Cardiac Arrest Algorithm for Ventricular Fibrillation

Ventricular Fibrillation Defined

Ventricular Fibrillation or VF (sometimes V-fib) is a condition where there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart. The result is these muscles quivering rather than contracting in rhythm. Ventricular Fibrillation is the most common arrhythmia in cardiac arrest patients. The only method by which to confirm this arrhythmia is by electrocardiography. The treatment of such an arrhythmia is included in the ACLS pulseless arrest Algorithm. Ventricular Fibrillation is a shockable rhythms and is treated in a similarly to Ventricular Tachycardia (VT). The pulseless arrest algorithm has been established as the best practice in treating ventricular fibrillation.

Defibrillation and the Shock

Biphasic defibrillator

The majority of defibrillators available today are biphasic. The Biphasic defibrillator passes electricity from one paddle through the patient to the other paddle and then back to the other direction completing one cycle in approximately 10 milliseconds. The Biphasic shock requires less energy to restore normal heart rhythm and reduces skin damage as well as damage to heart cells.

Monophasic defibrillator

The monophasic defibrillator works by simply passing electricity from one paddle through the patient into the other paddle. This method requires much more energy approximately 360 joules, instead of the 120-200 joules required by Biphasic.


A vasopressor is a medication that produces vasoconstriction. Vasoconstriction helps increase blood flow to the brain and the heart as it increased blood pressure. This is helpful during CPR as increased flow to the heart and brain is essential when the heart itself is not pumping correctly. Epinephrine is the primary vasopressor used because of its vasoconstrictive effects, though vasopressin may also be used and has shown to be nearly as effective as epinephrine.

View the Adult Cardiac Arrest Algorithm