Ventricular fibrillation (V-Fib) is a chaotic and life-threatening arrhythmia characterized by rapid, disorganized electrical activity in the ventricles. It leads to an immediate loss of cardiac output and is the most common cause of sudden cardiac arrest.
What is Ventricular Fibrillation?
V-Fib occurs when the electrical impulses in the ventricles fire erratically from multiple foci, preventing coordinated contraction. As a result:
- The ventricles quiver instead of pumping blood
- No cardiac output is generated
- No oxygen reaches vital organs
- Immediate cardiac arrest follows
EKG Features of V-Fib
The electrocardiogram (EKG) provides the hallmark diagnosis:
- Rate: Unknown (too chaotic to measure)
- Rhythm: Chaotic and irregular
- P waves: Not visible
- PR interval: Absent
- QRS complex: Not visible (disorganized waveforms)
Key Point: Unlike ventricular tachycardia, where wide QRS complexes are visible, V-Fib shows completely irregular, wavy lines with no identifiable complexes.
.jpg "Ventricular Fibrillation (V-Fib) – Causes, Symptoms, EKG Features & Treatment")
Causes of Ventricular Fibrillation
V-Fib often develops in the setting of underlying cardiac or systemic issues:
1. Cardiac Causes
- Myocardial infarction (heart attack)
- Severe heart failure
- Structural heart disease
2. Medication-Induced
- Digoxin toxicity
- Pro-arrhythmic effects of antiarrhythmics
3. Electrolyte Imbalances
- Hypokalemia
- Hyperkalemia
- Hypomagnesemia
4. Arrhythmia-Related
- Untreated ventricular tachycardia (VT can deteriorate into V-Fib)
Clinical Manifestations
Because V-Fib causes immediate cardiac arrest, patients rapidly develop life-threatening signs:
- Loss of consciousness within seconds
- No pulse or blood pressure
- Respiratory arrest (breathing stops)
- No cardiac output → no oxygen delivery to organs
- Death within minutes without intervention
Red Flag: If a patient suddenly collapses, is pulseless, and the monitor shows chaotic waves, assume V-Fib and act immediately.
Emergency Treatment of V-Fib
Management of ventricular fibrillation follows the Advanced Cardiac Life Support (ACLS) protocol.
1. Immediate CPR
- Begin chest compressions immediately.
- Provide high-quality compressions (100–120 per minute, depth of 2 inches in adults).
2. Defibrillation
- Defibrillation is the treatment of choice.
- Deliver unsynchronized shock to depolarize all myocardial cells, giving the SA node a chance to re-establish rhythm.
- Follow shock with immediate resumption of CPR.
Memory Tip: “Defib the V-Fib.”
3. Oxygen Therapy
- Provide supplemental oxygen during resuscitation.
4. Medications
- Epinephrine every 3–5 minutes during resuscitation
- Amiodarone or Lidocaine as antiarrhythmic therapy
- Magnesium sulfate in cases of torsades de pointes
5. Advanced Airway Management
- Intubation may be required if bag-mask ventilation is insufficient.
Cardioversion vs Defibrillation
These two terms are often confused, but they are very different:
| Feature | Cardioversion | Defibrillation |
|---|---|---|
| Shock type | Synchronized with QRS | Asynchronous |
| Energy level | Lower | Higher |
| Used in | Stable arrhythmias (e.g., atrial fibrillation) | Pulseless VT, V-Fib |
| With CPR | Not used with CPR | Always combined with CPR |
| Goal | Restore normal rhythm in stable patients | Restart effective cardiac rhythm in cardiac arrest |
Key Rule:
- Cardioversion → Stable patients
- Defibrillation → Unstable patients or cardiac arrest
Complications of V-Fib
If not treated immediately, V-Fib leads to:
- Brain injury due to lack of oxygen (hypoxic encephalopathy)
- Multi-organ failure
- Sudden death
Even with successful resuscitation, patients may suffer long-term neurological damage if oxygen delivery to the brain was interrupted for too long.
Long-Term Prevention After V-Fib
Patients who survive V-Fib are at high risk of recurrence. Preventive measures include:
- Treating underlying cause (e.g., revascularization for myocardial infarction, correcting electrolytes)
- Implantable Cardioverter-Defibrillator (ICD) – monitors rhythm and delivers shocks automatically
- Medications: Beta-blockers, antiarrhythmics (Amiodarone, Sotalol)
- Lifestyle changes: Avoid stimulants, treat hypertension, diabetes, and other cardiac risk factors
Comparative Overview: VT vs V-Fib
| Feature | Ventricular Tachycardia (VT) | Ventricular Fibrillation (V-Fib) |
|---|---|---|
| Rate | 100–250 bpm | Unknown, chaotic |
| Rhythm | Regular | Irregular, chaotic |
| QRS Complex | Wide, “tombstone” shaped | Absent, wavy baseline |
| Pulse | May be present | Always absent |
| Treatment | Cardioversion (if stable), Defibrillation (if pulseless) | Immediate Defibrillation + CPR |
| Outcome | Dangerous, but can be stable initially | Fatal within minutes without treatment |
Frequently Asked Questions (FAQ)
Q1. What is the survival rate of ventricular fibrillation?
Survival depends on how quickly defibrillation is performed. With immediate defibrillation, survival can reach 50–70%. Without it, survival drops below 10%.
Q2. Why is defibrillation needed for V-Fib?
Because there is no organized electrical activity. Defibrillation resets the heart’s electrical system, giving the SA node a chance to restart normal rhythm.
Q3. Can V-Fib occur without prior heart disease?
Yes, although it is more common in people with coronary artery disease or structural heart conditions. Electrolyte imbalances or drug toxicity can also trigger V-Fib in otherwise healthy individuals.
Q4. What is the difference between V-Fib and asystole?
V-Fib shows chaotic electrical activity on the EKG, while asystole shows a flat line. Importantly, defibrillation is effective in V-Fib but not in asystole.
Q5. Can CPR alone treat V-Fib?
No. CPR maintains some circulation temporarily, but defibrillation is essential to restore an effective cardiac rhythm.
