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Torsades de Pointes

Polymorphic ventricular tachycardia associated with a long QT, Twisting of the points

Torsades de Pointes

Prolonged QT Interval

• QT_C = 0.58s (QT_C > 440ms)

• First described in 1966 by the French physician François Dessertenne
• It is the most common polymorphic VT
• Heart rate is 160-250/min.
• It is a polymorphic VT that occurs with a prolonged QT interval
• TdP has a characteristic onset
• It is triggered by a ventricular premature beat (R-on-T phenomenon)
• The mechanism is triggered activity
• At the onset, a typical short-long-short RR interval occurs
• During TdP, QRS complexes change amplitude, "twisting" around their axis
• Because the direction of the main vector changes
• TdP is translated as "twisting of the spikes" ("dancing spikes")
• The QRS complex cycle repeats approximately every 5-20 beats
• It is a "short-lived" nonsustained ventricular tachycardia
• Because it spontaneously resolves within 30 seconds
• Rarely, it does not resolve spontaneously and may progress to ventricular fibrillation

Torsades de Pointes vs. Polymorphic VT

Polymorphic Ventricular Tachycardia

• According to the provided ECG, we cannot determine whether it is TdP or polymorphic VT
• The onset of tachycardia is not visible
• It is unknown whether the patient has a prolonged QT interval
• Polymorphic VT and Torsades de Pointes present the same appearance on the ECG during tachycardia (as shown in the ECG)
• Torsades de Pointes is a polymorphic VT that occurs with a prolonged QT interval
• Distinguishing between polymorphic VT and Torsades de Pointes is important for treatment
• Torsades de Pointes should not be treated with antiarrhythmics that prolong the QT interval

Transmural Dispersion of Repolarization

• Action Potential has a different duration
• Even during conduction through the myocardial wall
  
  
• Transmural Dispersion of Repolarization
• It is the difference in the duration of repolarization within the ventricular wall, in:
• The endocardium
• The mid-myocardium (M-cells)
• The epicardium

Prolonged QT Interval

Prolonged QT Interval and Transmural Dispersion of Repolarization

• Transmural Dispersion of Repolarization (TDR)
• Mainly refers to the difference between repolarization of the epicardium and the mid-myocardium (M-cells)
• If a patient has a prolonged QT interval
• The repolarization of the mid-myocardium (M-cells) is mainly prolonged
• Prolongation of the epicardial repolarization is not significant
• Therefore, transmural dispersion of repolarization is also prolonged
• There is a greater distance between the repolarization of the epicardium and the mid-myocardium (M-cells)
• The likelihood increases that a ventricular extrasystole will "strike" during the vulnerable period
• Because the vulnerable period is prolonged

Re-entry and Torsades de Pointes

• Prolonged Transmural Dispersion of Repolarization
• Creates a substrate for re-entry
• Changes in the refractory period of the myocardial wall layers
• The impulse can start to circulate in the myocardial wall
• Ventricular Extrasystole (R-on-T phenomenon)
• Triggers the circulation of the impulse through the myocardial wall layers
  
  
• The mechanism of maintaining TdP is re-entry in the myocardial wall

Torsades de Pointes

• SLS sequence (short-long-short interval "short-long-short interval")
• Short interval
• The sinus beat is followed by a ventricular extrasystole (with a short coupling interval)
• Long interval
• After the ventricular extrasystole, a compensatory pause occurs followed by a sinus beat
• Short interval
• Following the compensatory pause, another ventricular extrasystole occurs (with a short coupling interval)
• Phenomenon R on T
• This is the onset of Torsades de Pointes
• Torsades de Pointes
• Wide QRS complexes that change in amplitude and width

Pause-dependent Torsades de Pointes

Pause-dependent Torsades de Pointes

• (Pause-dependent SLS Torsades de Pointes)
• Most common variant
• Has a SLS sequence (short-long-short interval)
• Sinus beat (1)
• Ventricular extrasystole (2)
• Sinus beat (3)
• Ventricular extrasystole (4)
• Before TdP there is a pause in the RR interval (2 - 3)
• Patient has a prolonged QT interval (during sinus rhythm)

Sinus Rhythm and Ventricular Couplets

• The patient is young and has no structural heart damage
• The patient came to the hospital for recurrent syncopes (loss of consciousness)
• Sinus Rhythm
• QT Interval is not prolonged (400ms)
• Ventricular Couplet (2 extrasystoles in a row)
• Coupling Interval is shortened < 300ms
• The patient was given a 24-hour ECG Holter monitor

Torsades de Pointes (SLS Sequence)

• The patient had a prolonged QT interval
• At the beginning, we see a typical SLS sequence (short-long-short RR interval)
• Followed by the R-on-T phenomenon and Torsades de Pointes

Torsades de Pointes (SLS Sequence)

• The patient had a prolonged QT interval
• Continuous Lead II:
  • After the end of TdP, an SLS sequence follows (short-long-short RR interval)
  • After the SLS sequence, Torsades de Pointes reappears
  • "Dancing QRS complexes"
• TdP is often nonsustained ventricular tachycardia
• Spontaneously ends within 30 seconds
• The patient had paroxysms of TdP
• Recurring episodes of TdP that spontaneously ended within 30 seconds