This was provided by our electrophysiologist at the Hennepin Heart Center.
The patient was having symptomatic atrial fibrillation and was to be cardioverted by a Zoll machine:
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Notice there is a Paced Rhythm. The small white arrows show each time the machine detects a QRS. This is also the location on the QRS complex where it is programmed to cardiovert.
Notice that it is recognizing the T-wave as a QRS.
This has two effects:
1) It measures the heart rate at 110, instead of 55 (the actual heart rate)
2) It will cardiovert on the T-wave, which is highly likely to result in ventricular fibrillation.
Learning Point:
Always look for these arrows to be certain you will not cardiovert at the wrong part of the cycle!!
If the algorithm is sensing wrong, change the lead that is being sensed.
