Dawn's picture

These two strips are from one patient who was electrically cardioverted twice in a few minutes.  The original reason for the cardioversion was Torsades de Pointes, a type of polymorphic ventricular tachycardia associated with a long QT interval.  For more information about TDP, go to this LINK.  It is a bit difficult to comment on the patient's post-cardioversion rhythm, because so little of it is shown.  It appears to be sinus, with a wide QRS.  The QT interval appears slightly prolonged at .44 sec, but it is not known what the QT interval is corrected to a rate of 60/min.  TDP is often seen with QT intervals greater than 600 ms (.6 seconds).  Also THESE STRIPS ARE NOT SIMULTANEOUS, they were taken two minutes apart.  In the first one, the P waves and T waves look so much alike, they could all be P waves.  They do not "march out".  It is necessary to get a long strip, preferably in multiple leads, and a 12-Lead ECG, to properly evaluate the rhythm post-cardioversion. 

Rate this content: 
Average: 4 (2 votes)


ekgpress@mac.com's picture

     The ECG posted by Dawn is a "picture-perfect" example of Torsades - in that there is true "twisting of the points" about the baseline. In each tracing - note slinky-like alternating of negative and positive deflections. Alas, we now require QT prolongation for qualify as "Torsades" vs PMVT (PolyMorphic Ventricular Tachycardia).

  • The clinical reality, however - is that it is often impossible to determine IF the preexisting QT interval is normal or prolonged ... (For REVIEW of this Concept Please see my ECG Guru Comment #605 ). 
  • That said - I believe the preexisting QT is prolonged in this example. Looking at the TOP rhythm strip - the QRS complex for the 3 beats of sinus rhythm seen after conversion of Torsades is clearly wide (~ 0.12 second). Using the complex for which I can best see onset and offset of the QT (the 2nd sinus beat) - I measure the QT = 0.46. Given that the sinus rate is faster than 60/minute - the QT we measure (0.46 sec) needs to be corrected for rate - which when done results in an estimated QTc = 0.50 second. Anything over 0.45 second for the QTc is long - and anything approaching 0.50 second is clearly long enough to be potentially problematic (For REVIEW of my suggested Quick Estimate method for QTc estimation - CLICK HERE).
  • Given how "classic" morphology is in these 2 rhythm strips for Torsades - my tendency (my opinion) is to be "lenient" in requirement of QT prolongation - which is why despite QRS widening, I'd gladly accept an estimated QTc = 0.50 sec as "long".
  • As I discussed in my ECG Guru Comment #605 - initial treatment recommendations (IV Mg++/cardioversion if and as needed) are similar for both Torsades and PMVT - but the response to treatment tends to be different - and secondary treatments may also differ if the rhythm proves refractory.
  • IF you need to get the patient out of the rhythm - cardiovert! This was done (twice) in this case. BUT realize (as is evident in this case) - that the rhythm may recur unless you are able to identify and "fix" the underlying cause of the arrhythmia.

Ken Grauer, MD  www.kg-ekgpress.com   [email protected] 

All our content is FREE & COPYRIGHT FREE for non-commercial use

Please be courteous and leave any watermark or author attribution on content you reproduce.