A sick elderly patient with nonspecific symptoms

 Written by Pendell Meyers

An elderly woman summoned EMS for generalized weakness and multiple vague complaints. She was confused and ill appearing.

Here is her EMS ECG:

What do you think?

Without other ECGs (below), the rhythm differential could include junctional/ventricular escape, or ventricular paced rhythm (with small or filtered-out pacing spikes), or other rhythms. 

Most importantly, the QRS duration is greater than 200 msec. The computerized QRSd is 218 msec. 

When over 200 msec, even during ventricular pacing, there is only a small list of possibilities: 

1) preexisting severe cardiomyopathy (with preexisting QRSd greater than 200)

2) acute hyperkalemia, and/or acute sodium channel blockade. 

No common bundle branch block pattern or paced rhythm should be able to cause a QRS duration greater than 200 msec. We should assume hyperK and/or sodium channel blockade until proven otherwise, and indeed the T waves have a peaked hyperkalemic morphology in many leads.

Here is her ECG on arrival at the ED:

Now we can see pacer spikes, with the same QRS morphology as the first ECG, meaning the first ECG was also paced.

An old ECG was available in the EMR from one month ago:

Also ventricular paced rhythm. Computer QRS duration 186 msec. Similar QRS morphology to the current ECGs, other than the absence of acutely superimposed hyperkalemic findings.

So, at baseline 1 month ago, she has a paced rhythm with QRS duration 186 msec (on the wider end of the bell curve for baseline paced rhythms). Today, something (likely hyperkalemia) has caused additional QRS widening.

Potassium returned at 7.4 mEq/L. 

The QRS duration improved with hyperkalemia treatment (ECG unavailable).

She was diagnosed with rhabdomyolysis and acute renal failure. Final outcome is not available.

Key point for learners:

When the QRS duration exceeds 200 msec, and is not known to be so at baseline, you should assume severe hyperkalemia and/or sodium channel blockade toxicity until proven otherwise.

Other related cases:

A patient with cardiac arrest, ROSC, and right bundle branch block (RBBB).

An elderly patient with syncope, dyspnea, and weakness, but no Chest Pain, and mild hyperkalemia

Is This a Simple Paced Rhythm?

NO.

the K is 6.8 and it results in a paced sine wave

Is This a Simple Right Bundle Branch Block?

Here is a case of RBBB with a K of 7.9 and QRS duration of 194 ms.

Is this just right bundle branch block?

This ECG was texted to me with the text:

"There is a history of RBBB but we do not have an image to compare this with.  I interpret as RBBB with atrial fib.  Anything else?"

Hyperkalemia in the setting of Left Bundle Branch Block

A dialysis patient presented with vomiting.  He has  known baseline left bundle branch block.  Here is his initial ECG:

There is left bundle branch block, with a QRS duration of 220 ms according to the computer analysis.

Weakness and Dyspnea with a Sine Wave. It's not what you think!  (not hyperK!)