• Ventricular Fibrillation
• Causes of Ventricular Fibrillation
• Mechanism of Ventricular Fibrillation
• Onset of Ventricular Fibrillation
• ECG and Ventricular Fibrillation
• Polymorphic VT and Ventricular Fibrillation
• Defibrillator
• Electrical Cardioversion
• Defibrillation

Ventricular Fibrillation

• Ventricular fibrillation is an electrical chaos of ventricular impulses
• The ventricles (QRS complexes) “quiver” at a rate of 300-450/min.
• The ventricles contract in a disorganized manner and the heart does not function as a pump
• This is the fundamental difference from polymorphic ventricular tachycardia
• During ventricular fibrillation:
• Syncope within 10 seconds (loss of consciousness)
• Irreversible brain damage in 3-5 minutes
• Often progresses to asystole within 2 minutes
• It is the most common cause of sudden cardiac death
• Requires urgent treatment - electrical defibrillation
• Almost always occurs in structurally or electrically damaged ventricles
• Most commonly during myocardial infarction
• Idiopathic ventricular fibrillation
• Is very rare
• Occurs from an unknown cause without structural damage

Mechanism of Ventricular Fibrillation

• The mechanism of ventricular fibrillation is not clear, but the most likely are 2 mechanisms:

Multiple Micro Re-entries

• In the ventricles, there are numerous micro re-entries
• which generate impulses independently of each other
• The ventricles quiver at a frequency of 300 - 450/min.

Mother Rotor Re-entry Circuit

• In the ventricles, there is a mother macro re-entry
• from which additional micro re-entries arise
• Micro re-entries generate impulses independently of each other
• The ventricles quiver at a frequency of 300 - 450/min.

ECG and Ventricular Fibrillation

• Often starts with the R-on-T phenomenon
• Frequency: 300 - 450/min.
• Wide QRS complexes (>0.12s)
• Width and amplitude vary (QRS complexes are undulating)
• Cannot identify
• P wave
• T wave
• ST segment
• Amplitude of QRS complexes gradually decreases (Heart runs out of energy - ATP)
• About 2 minutes before transitioning to asystole
• Based on the height of QRS complexes, we recognize 2 types of fibrillation
• Coarse Ventricular Fibrillation
• Fine Ventricular Fibrillation

Fine Ventricular Fibrillation

• Frequency approximately 350/min.
• Irregular QRS complexes with low amplitude
• No exact ECG boundary for amplitude
• Between coarse and fine ventricular fibrillation
• However, this fibrillation has lower QRS amplitude

Polymorphic VT and Ventricular Fibrillation

• Polymorphic ventricular tachycardia and ventricular fibrillation both have a similar appearance on ECG
• Both show wide QRS complexes on ECG, which change in width and amplitude
• There are no precise ECG criteria to distinguish between polymorphic VT and ventricular fibrillation
• The key difference is that in ventricular fibrillation, the heart no longer functions as a pump
• The patient is circulatory unstable

Polymorphic Ventricular Tachycardia

• There are at least 3 ectopic foci in the ventricles (most commonly)
• Width and amplitude of QRS complexes change
• Signs of ventricular tachycardia may be present
• The mechanism is most often triggered activity (Torsades de Pointes)
• Frequency is 100-300/min. (on this ECG, 280/min.)
• The heart still functions as a pump
• At a frequency > 160/min, it gradually stops functioning as a pump

Defibrillator

• A defibrillator is a device that delivers an electrical shock
• The shock passes through the heart via electrodes placed on the chest
• It records the EKG and can time the shock
• It is used for cardioversion
• Cardioversion is changing an arrhythmia to sinus rhythm
• Based on shock timing, there are 2 treatment principles
• Electrical cardioversion (synchronized cardioversion)
• Defibrillation (unsynchronized cardioversion)

Defibrillation

• It is non-synchronized cardioversion
• The shock occurs independently of the cardiac cycle
  • Regardless of the R wave and T wave
  • The electrical shock occurs immediately upon pressing the buttons
• Used for emergency treatment
  • hemodynamically significant arrhythmias, most commonly:
    • Ventricular fibrillation
    • Ventricular flutter
    • Torsades de Pointes
      
      
• Coarse (tonic) ventricular fibrillation
  • (Tonic ventricular fibrillation)
  • QRS complexes are relatively high (The heart has "enough" energy - ATP)
  • Defibrillation is still effective
    
    
• Fine (atonal) ventricular fibrillation
  • (Atonic ventricular fibrillation)
  • QRS amplitude decreases (The heart has "little" energy - ATP)
  • Asystole begins to form asystole
  • Defibrillation at this stage is often ineffective

Ventricular Fibrillation

• On this ECG, you can clearly see how the ECG device records the ECG curve
• First, the leads (I, II, III) are recorded simultaneously
• Then the leads (aVR, aVL, aVF) simultaneously
• Then the leads (V1, V2, V3) simultaneously
• Finally, the leads (V4, V5, V6) simultaneously
• Continuous II lead (Rhythm strip) records the ECG after the V6 leads
• It is not a rule, but this device records the continuous II lead at the end
• The dynamics of this 12-lead ECG are as follows:
• Phenomenon R on T -> Torsades de Pointes -> Ventricular Fibrillation
• Ventricular fibrillation is best seen on the continuous II lead (rhythm strip)
• The patient with the onset of ventricular fibrillation lost consciousness
• The patient needs to be urgently defibrillated

Ventricular Fibrillation and Accelerated Ventricular Rhythm

• The patient received ventricular fibrillation in the ambulance
• Over 10 minutes, continuous ECG (only 1 lead) was recorded
• The patient was defibrillated 5 times (NON-synchronized shock)
• After each defibrillation, an accelerated ventricular rhythm appeared
  • which again progressed to ventricular fibrillation
• In the 2nd recording after the shock, we see blended and captured contractions