This was an unusual case with an unfortunate outcome.
Let's look at the heart rhythm again.
The rhythm is slow and irregular with strange looking complexes. At first glance it's difficult to distinguish QRS complexes from T-waves. It looks like a pre-morbid rhythm.
However, on closer inspection we can see that the QRS complex is present but near isoelectric. The QRS duration is > 200 ms which is extremely abnormal. Whenever you see a QRS complex > 200 ms you should suspect hyperkalemia!
In addition, when the S and T-waves merge together and the ST-segment becomes non-distinct you've moved into what is sometimes referred to as the "sine wave" ECG. This is an ominous finding.
Unfortunately, at the time this ECG was recorded (several years ago) our paramedics weren't trained to recognize hyperkalemia. It's one of the many ways the paramedic profession has evolved throughout the course of my career.
However, they knew the heart rhythm was "bad" and they wanted to see something a little bit less scary on the monitor so they elected to perform transcutaneous pacing (TCP).
Did they achieve capture? Let's take a look.
They did not achieve capture, although I can understand whey they thought they had intermittent capture.
A shows the morphology of the underlying rhythm. B shows a (presumed to be) transcutaneously paced QRS complex. It is classic for false capture. C shows a "phantom" QRS complex (caused by pacing artifact) that coincidentally falls directly on top of the (unsensed) native QRS complex. This makes it appear as though capture has been achieved. D shows a "phantom" QRS complex falling in the absolute refractory period of the underlying rhythm (proving beyond any shadow of a doubt that these QRS complexes are the result of pacing artifact).So what ended up happening?
The patient survived to arrival at the emergency department. However, during transfer of care the emergency physician asked that the TCP be turned off so that he could examine the underlying rhythm.
Moments later the patient was shocked x2 by his ICD and the resultant heart rhythm was asystole.
He was not successfully resuscitated.
It was later that they found out the potassium level was > 9 mEq/L (I don't remember the exact value).
I don't know why this patient's ICD shocked him. I was not present when the device was interrogated. But I suspect that it may have been confused by the TCP.
If I am ever faced with a situation in the future where I feel that TCP is indicated and the patient has an ICD I will be contacting Online Medical Control and asking permission to disable tachy therapy with a ring magnet.
Obviously there are a lot of lessons to be learned from this case.
Transcutaneous pacing (TCP) – The problem of false capture
Transcutaneous pacing (TCP) with a Lifepak 12
Using capnography to confirm capture with transcutaneous pacing (TCP)
Transcutaneous pacing (TCP) for asystole