Question 15.1

College answer

a) 
Torsade de pointes/ VT triggered by a R on T phenomenon 
 
b) 
Congenital Long QT syndromes 
Acquired long QT 
     Drugs 
     Hypokalemia, hypomagnesemia 
     MI, Takotsubo cardiomyopathy 
     SAH 
     Female gender 
     Bradycardia 
 
c) 
Assess ABC, ALS algorithm, unsynchronized defibrillation. Magnesium. Prevent recurrence by pacing or isoprenaline to increase the heart rate to a level that prevents further torsade. 
 

Discussion

The official college ECG image is of course not available, and in most such cases the reader needs to acknowledge the possibility that the author has substituted something completely different to the official college paper. Fortunately, this time examiners made the mistake of leaving a faint "e-cardiogram.com" watermark on their paper, which makes it possible for track down their source to this page, where a detailed exploration of "tachycardie ventriculaire polymorphe" takes place. This file (torsades-de-pointes-web-free.jpg) has been reproduced multiple times, and appears to be something of a classic.

a) What is your diagnosis?   To be perfectly precise, that would have to be "Polymorphic VT". If the complexes clearly demonstrated a rotation around an isoelectric point "Torsades des Pointes" would also be reasonable, especially given the file name, and the fact that the one visible normal-looking QRS complex appears to have a relatively long-looking QT interval. The fact that the VT begins during the T-wave suggests that the R-on-T phenomenon is responsible. For 10% of the total SAQ marks, no more detail would be expected. Given that the patient has lost consciousness, "cardiac arrest" is another potentially valid way to describe the situation.

b) is also a 10% question. "What risk factors could precipitate this arrhythmia?" Generally speaking, non-Torsades VT is associated with organic and structural heart disease, whereas Torsades tends to be related to molecular and channel related problems.

• Acute coronary ischaemia
• Long QT (congenital or acquired)
• Brugada syndrome
• Catecholaminergic polymorphic VT
• Arrhythmogenic right ventricular dysplasia (ARVD)
• Cardiomyopathy of any cause
• Hypokalemia
• Hypomagnesemia

c) How will you manage the patient? 

Thomas and Behr (2015) have published a good article which describes the management strategies for Torsades, which is also helpful for people trying to answer part (b) of Question 30.1 from the second paper of 2017. In short:

• Preventative strategies
  • Stop the QT-prolonging drugs
  • Keep the serum K⁺ around 4.7 - 5.2 mmol/L
• Immediate treatment
  • IV magnesium sulfate
  • Isoprenaline (to increase heart rate to 100-110)
  • Overdrive pacing
  • Lignocaine
• Experimental treatments and last resort measures
  • Clonidine
  • Ranolazine