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Polymorphic Ventricular Tachycardia

Polymorphic ventricular tachycardia

Basic Classification

• Ventricular tachycardia (VT) consists of at least 3 consecutive ventricular beats
• If fewer beats are present, it is classified as ventricular extrasystoles
• VT almost always occurs in a structurally damaged heart
  
  
• VT by Duration
• Non-sustained VT: at least 3 ventricular QRS complexes lasting < 30s
• Sustained VT: lasts > 30s
  
  
• VT by Hemodynamics
• Hemodynamically stable: the patient is hemodynamically stable
• Usually associated with VT with a frequency of < 160/min.
• Hemodynamically unstable: the patient is hemodynamically unstable
• Usually associated with VT with a frequency of > 160/min.
• Not precisely defined, the patient's blood pressure, pulse, and respiratory rate...

Monomorphic Ventricular Tachycardia

• Frequency: 170/min.
• Identical and Wide QRS Complexes (> 0.12s)
• A re-entry impulse always exits in the same direction
• Therefore, all QRS complexes are identical
• P Waves are not visible
  • They are hidden within the wide QRS complexes
  • And the atria are activated retrogradely

Multifocal Polymorphic VT

• There are at least 3 ectopic foci in the ventricles
• Ventricular vector from each focus has a different direction
  
  • Therefore, the QRS complexes are polymorphic
• Occurs during myocardial infarction with ischemia
• May progress to ventricular fibrillation

Unifocal Polymorphic VT

• There is 1 ectopic focus in the ventricles
• Vector from the focus changes direction
• Therefore, the QRS complexes are polymorphic
• Most commonly occurs in Torsades de Pointes (TdP)
• TdP occurs in the case of a prolonged QT interval
• Mechanism is triggered activity
• TdP is the most common polymorphic VT

ECG and Polymorphic Ventricular Tachycardia

• Can have characteristic features of ventricular tachycardia
• Frequency 100-300/min.
• Wide QRS complexes (>0.12s)
• Width and amplitude vary (QRS complexes exhibit waviness)
  
  
• Can progress to ventricular fibrillation
• The key difference is that in ventricular fibrillation, the heart no longer functions as a pump

Polymorphic VT and Ventricular Fibrillation

• Polymorphic VT and ventricular fibrillation have a similar appearance on ECG
• Both have wide QRS complexes that change in width and amplitude
• ECG does not have precise criteria to differentiate between polymorphic VT and ventricular fibrillation
• The basic difference is that in ventricular fibrillation, the heart no longer functions as a pump
• Patient is hemodynamically unstable

Ventricular Fibrillation

• In the ventricles, there are multiple foci
• The mechanism is most commonly micro re-entry
• Frequency is 300-450/min.
• Width and amplitude of QRS complexes change
• QRS complexes are low, and their amplitude is not precisely defined
• The heart does not function as a pump
• At such a high frequency, diastole is ineffective
• This is the basic difference from polymorphic VT
• Signs of ventricular tachycardia are not present
• QRS complexes decrease in amplitude and approximately 2 minutes later asystole occurs

Polymorphic Ventricular Tachycardia (Torsades de Pointes)

• Frequency 290/min.
• Wide QRS complexes that change in amplitude and width
• Again, the patient has severe hypokalemia (1.7 mmol/l)
• Inverted T waves
• U wave
• Prolonged QT interval
• Ventricular extrasystole occurred on the T wave (R on T phenomenon)
• On the ECG is Torsades de Pointes
• Which is polymorphic VT that occurs with a prolonged QT interval
• In this case, there was spontaneous termination (resolution) of Torsades de Pointes after approximately 5 seconds

Polymorphic Ventricular Tachycardia (Torsades de Pointes) and Ventricular Fibrillation

• Prolonged QT interval (480ms)
• Ventricular bigeminy
• Initially, a ventricular extrasystole follows each sinus beat
• R-on-T phenomenon
• Ventricular extrasystole occurred during the T wave (in the vulnerable phase)
• Subsequently Torsades de Pointes (TdP) develops
• Frequency: 300/min.
• Wide QRS complexes that change in amplitude and width
• Approximately 5 seconds later, ventricular fibrillation occurs
• QRS amplitude decreased
• Frequency increased to approximately 310/min.
• The heart stopped functioning as a pump (the patient was unconscious)
• The patient requires urgent treatment - defibrillation