Ventricular fibrillation, known commonly as v-fib, is caused by multiple ectopic electrical impulses that depolarize the myocardium in a chaotic fashion. This results in a quivering or fibrillating heart that does not produce a pulse or adequate cardiac output.

Ventricular Fibrillation ECG

ECG Interpretation:


  • Is the rhythm regular or irregular?
    • It is irregular


  • What is the rate?
    • Between 200-250 bpm
  • Is the rate normal, fast, or slow?
    • Extremely fast

P Wave

  • Are they present?
    • There are none. Fibrillatory waves only.  
    • No other P wave questions are relevant.

PR Interval

  • There is no P wave, so there isn’t a PR interval

QRS Complex

  • Is the QRS interval less than 0.12 seconds?
    • No. Fibrillatory waves only.
    • No other QRS questions apply.

Cardiac Interpretation

Ventricular fibrillation is a non-perfusing and lethal dysrhythmia. It is most commonly seen within the first few minutes of cardiac arrest. Because of this, high-quality CPR and immediate defibrillation are vital to increasing the chance for successful resuscitation.