Understanding Ventricular Fibrillation
Ventricular fibrillation is a chaotic, disorganized electrical activity in the heart's lower chambers that causes them to quiver uselessly instead of pumping blood—it is essentially cardiac arrest and will cause death within minutes without immediate treatment. 1
What Happens During Ventricular Fibrillation
The heart's electrical system goes haywire, firing signals at extremely rapid rates (over 300 beats per minute) in a completely disorganized pattern, with no coordination between different parts of the heart muscle 1
The ventricles (lower pumping chambers) cannot contract effectively—instead of squeezing blood out to the body and lungs, they just quiver or "fibrillate" like a bag of worms 1, 2
Blood circulation stops immediately because the heart cannot pump, meaning no oxygen reaches the brain, heart, or other vital organs 1, 2
On a heart monitor (ECG), ventricular fibrillation appears as rapid, grossly irregular waves with no recognizable pattern—the electrical signals are completely chaotic with marked variability in size, shape, and timing 1
Why Ventricular Fibrillation Happens
The underlying mechanism involves abnormal electrical circuits (reentry pathways) or rapidly firing abnormal electrical foci in damaged or diseased heart muscle. 3, 4
Common triggers include:
Heart attacks (acute myocardial infarction)—the most common cause, where damaged heart tissue creates unstable electrical conditions 2
Severe heart failure with weakened heart muscle 1
Inherited electrical disorders of the heart in otherwise structurally normal hearts 3
Electrolyte imbalances (particularly low potassium or magnesium) 5
Electrical shock or trauma to the chest 2
Immediate Management: The First Minutes Are Critical
Ventricular fibrillation requires immediate electrical defibrillation (shock) to restore normal rhythm—this is the only effective treatment and must be delivered within minutes to prevent death. 1
Step-by-Step Emergency Response:
Recognize cardiac arrest immediately: Patient is unresponsive, not breathing normally, and has no pulse 1
Begin CPR immediately while preparing the defibrillator—chest compressions maintain minimal blood flow to vital organs 1
Deliver electrical shock as soon as possible: The defibrillator delivers a controlled electrical current that "resets" the heart's electrical system 1
Resume CPR immediately after each shock for 2 minutes before checking rhythm again 1
Administer epinephrine (adrenaline) 1 mg IV every 3-5 minutes to improve blood flow and increase chances of successful defibrillation 1
If ventricular fibrillation persists after 3 shocks, give amiodarone 300 mg IV bolus followed by 150 mg if needed—this is the most effective medication for shock-resistant ventricular fibrillation 1, 5, 6
Long-Term Management for Survivors
All survivors of ventricular fibrillation cardiac arrest require an implantable cardioverter-defibrillator (ICD) to prevent recurrence and sudden death. 5
ICD Implantation:
An ICD is a small device implanted under the skin (similar to a pacemaker) that continuously monitors heart rhythm 5
If ventricular fibrillation occurs again, the ICD automatically delivers a shock within seconds to restore normal rhythm 5
This is a Class I recommendation (highest level of evidence) for anyone who has survived cardiac arrest from ventricular fibrillation, assuming they have reasonable life expectancy (>1 year) and acceptable quality of life 5
Additional Protective Medications:
Beta-blockers are mandatory for all patients with history of ventricular fibrillation and underlying heart disease—they reduce the risk of recurrence 5
Amiodarone or sotalol may be added to the ICD for patients with frequent episodes or recurrent shocks 5
ACE inhibitors and optimal heart failure medications are essential if there is underlying heart muscle weakness (reduced ejection fraction ≤40%) 1, 5
Critical Pitfalls to Avoid
Never delay defibrillation to establish IV access or give medications—the shock is the only definitive treatment, and every minute of delay reduces survival by 7-10% 1
Do not confuse ventricular fibrillation with other rapid heart rhythms—if the patient has no pulse, assume ventricular fibrillation and shock immediately 1
Recognize that patients with advanced heart disease may have wide QRS complexes that make it difficult to distinguish ventricular from supraventricular rhythms—when in doubt with an unstable patient, cardiovert regardless 1, 5
After successful resuscitation, do not discharge the patient without ICD evaluation—the recurrence risk without an ICD is extremely high 5
Special Considerations for Patients with Known Heart Disease
Patients with prior heart attacks, heart failure (ejection fraction ≤30-35%), or certain inherited heart conditions require preventive ICD implantation even before experiencing ventricular fibrillation. 5
For heart attack survivors with weak heart muscle (LVEF ≤30-35%) at least 40 days post-heart attack: ICD prevents sudden death as primary prevention 5
For non-ischemic cardiomyopathy with LVEF ≤30-35% and heart failure symptoms: ICD is indicated 5
Optimal medical therapy must be maximized first: ACE inhibitors, beta-blockers, and aldosterone antagonists at target doses 1, 5