Question 15.5

College answer

Syllabus topic/section:

2.1.4 Cardiovascular Intensive Care /Interpretation of the electrocardiogram: L1

Discussion:  

Overall answered well. Candidates are encouraged to practice interpreting ECGs of common or potentially life-threatening conditions where ECGs are key to diagnosis.

Discussion

This ECG demonstrates polymorphic VT, and presumably  candidates who called this torsades de pointes would have been marked wrong, as the QT following the shock looks to be of a reasonably normal duration, and you need a long QT to turn polymorphic VT into torsades. 

The arrow pointing to the shock suggests that probably the shock should have been noted in the answer, and it is the most obvious thing on the ECG after the VT. 

The ECG that follows is more subtle, showing pacing spikes before every P and QRS, suggesting that there is a dual chamber pacemaker. Was it an AICD that fired? Who can know. There is no difference between the ECG appearance of exterior and interior shocks. However, as the rhythm strip appears to be printed on the same paper, one might surmise that these were all recorded together, which suggests that this was an AICD discharge: because it does not seem plausible that the V1-V6 electrodes would have been left on the chest, under the defibrillator pads, as the patient was given 200 joules.