Torsades de Pointes

Question 1

Answer 1

Rate = 300bpm (300/ square box between R-R which is 1 in this case)

Rhythm
R-R: regular
P wave: none
P–>QRS: AV dissociation
QRS: Wide QRS complex

Tachycardia + regular + Wide complex tachycardia–> ventricular tachycardia until proven otherwise
The QRS complexes all look different –> polymorphic ventricular tachycardia (increased QT interval: normal in male is <440ms, in female <460ms)) –> Torsade de pointes)

Torsade de pointes is related to prolonged QTi –> prior to starting TdP must calculate QTi
Use Bazzettes formula
QTi in this case is more than 2 big square (>400ms)
Rate prior to TdP: (300 divide by large squares between R-R around 3) = 90bpm = 1.5 beats/sec
1 sec/ 1.5 bps = 1/3 seconds

Question 2

What are the causes of Torsade de Pointes?

Answer 2

• HypoK
• HypoMg
• Drugs (amiodarone, procainamide, antipsychotics (risperidone, ziprasidone)
• Long QT channelopathies (genetics)

Question 3

Treatment for TdP?

Answer 3

IV MgSO4