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Ventricular Fibrillation

Ventricular Fibrillation

One of the most dangerous and life-threatening forms of arrhythmia is ventricular fibrillation (VF). VF occurs when organized electrical activity originating in the ventricles causes heart muscles to quiver instead of depolarizing regularly. This causes a termination of cardiac output and cessation of blood flow to the rest of the body). 

VF is the most common mechanism of sudden cardiac arrest and can also quickly develop into asystole (flatline), and death, it requires immediate treatment. The treatment process will focus on terminating the VF and restoring movement of blood toward vital organs and a return of spontaneous circulation (ROSC).


As with VT, dynamic ECG monitoring is required to determine the cardiac rhythm of the patient. VF can be quickly identified by the ECG and assessment of the patient.

ECG Pattern and Key Features

Because VF is characterized by a lack of proper rhythm, the patient will have no detectable pulse. Likewise, the ECG readings will not have a P-wave or a QRS complex. Instead, the reading will show smaller, irregular waves that indicate a quivering of the myocardium and lack of ejection.

Physical Symptoms

Aside from the lack of pulse, the patient experiencing VF will exhibit physical symptoms such as immediate loss of consciousness and complete physical collapse. The patient will also have no blood pressure.


While the cause of Ventricular Fibrillation is not always known, there are a number of possible factors that put patients at risk.

Prior Conditions

VF can very quickly develop from  unstable VT, and treatment methods can be similar for these critical conditions. VF is often caused by lack of blood or oxygen to the heart muscle. However, other factors such as heart disease, cardiomyopathy, poor blood flow, electrolyte abnormalities, and scarring of heart tissue from prior heart attacks can also increase the likelihood of the patient developing VF.

Reversible Causes

While some factors that induce VF are irreversible conditions, other causes are reversible. After the patient reaches a non-shockable rhythm, you will want to treat for hypoxia, hypovolemia, hyper- or hypokalemia, hypothermia, hydrogen ion acidosis, cardiac tamponade, drug use and other toxins, pulmonary thrombosis, and coronary thrombosis.


When a patient experiences VF, (sudden cardiac arrest), blood supply to the brain and heart stop, and death can happen quickly. That said, treatment for VF focuses on two main stages. 

The first stage of treatment focuses on rapid termination of the VF which often provides an immediate  restoration of blood flow to vital organs. Once the patient exhibits return of spontaneous circulation (ROSC), the second stage is about preventing another incident. 

Before taking any additional steps, defibrillate immediately and administer oxygen with manual ventilation. If a defibrillator is not present, begin quality CPR. As soon as the defibrillator arrives, access the ECG using quick-look paddles, adhesive chest patches. The ACLS algorithm will then direct you through pathways and dosages for subsequent CPR, defibrillation, and medication.

CPR and IV Infusion

Any witnessed incident of VF should be immediately treated with defibrillation, if not available,  high-quality CPR. 

For adults, this means performing 2-inch chest compressions at a pace of 100-120 per minute. For children and infants, this means compression depths at ⅓ of the anteroposterior dimension of the chest. 

Immediate defibrillation is the first priority. If not immediately available, CPR can increase blood flow to vital organs such as the brain and heart, it cannot restore the patient’s regular rhythm. Because of this, defibrillation is the first step in an ideal environment. CPR will then be part of subsequent steps to get the patient out of cardiac arrest.

When possible, you will also want to establish IV access. If not possible or practical due to obstructions or other issues with vascular access, many drugs can be delivered via an endotracheal tube (transbronchial route) or as a last choice, intra-osseous (I/O) access can be considered.


Use of dynamic ECG monitoring to assess the specific rhythm of the patient throughout treatment is mandatory. Both unstable VT and VF are considered shockable rhythms. This means that if the patient exhibits either of these patterns which caused the arrest, immediate electrical countershock is required.  

Specific shock dosages will depend on the type of unit you are using. For monophasic devices, start with a dose of 360 joules. For biphasic devices, use 120-200 joules. When in doubt, be sure to follow the specific recommendations listed for your defibrillator. 

If the initial shock fails, you will need to perform CPR, administer an IV/ET/IO drug if indicated. If the rhythm is still shockable, additional defibrillation and subsequent rounds of CPR will be required until a non-shockable rhythm is achieved. For specific steps, be sure to consult the ACLS algorithm for VF and unstable VT.


Once the patient reaches a non-shockable rhythm,medications are advisable to prevent recurring VF. The AHA advises the use of epinephrine, amiodarone,and lidocaine in the doses detailed below. Consult the ACLS algorithm for when to administer each. 

Post-Treatment Prevention

After the VF is converted and the patient reaches a stable condition, a few options may be advisable for those who are at risk.

ICD Implantation

In many cases, a cardiologist-electrophysiologist may recommend an ICD (Implantable Cardioverter-Defibrillator). This battery-powered, implanted device can detect VF and other arrhythmias and administer initial shocks that are critical to survival. Some modern versions can also include pacemaker capability.

While ICDs are recommended for patients with pre-existing heart conditions that put them at risk for VF, they are not used when the cause of VF is found to be reversible.

Catheter Ablation

While it is uncommon, catheter ablation can also help prevent future episodes of VF in some patients. This method uses a small amount of energy to destroy specific areas of the heart that are found to trigger chaotic electrical impulses. This is typically a low-risk procedure that is also used when other medications are ineffective or unusable.

Final Thoughts

Ventricular fibrillation is a critical condition that requires immediate medical attention, as it can quickly end up in asystole and death. To increase the patient’s chance of survival, take action quickly and administer a shock as soon as possible. Coupled with CPR and medications, the steps listed in the ACLS algorithm can help restore the patient to a stable condition and proper rhythm.

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