PQRST: but why?

ECG tracings. I am forever trying to discombobulate them.
Arrhythmia’s? No problems. It doesn’t take long to figure them out. The important ones, at least.

But when it comes to peering deeper into the structure and physiology and interplay of those cryptic PQRST waves splayed out across their 12-leads, it all gets a little onerous for the small gaggle of functioning neurons I possess.
Can I have some cake instead?

Ever wondered why they are labelled , from the P to the T?
Well, read on…..

The P wave:

In 1887, with the aid of a rather intimidating instrument known as Lippman’s, Capillary Electrometer, the first ECG was performed by Augustus Waller.
It detected 2 deflections to its baseline that were produced from ventricular activity. Accordingly, they were labeled as V1 and V2.
Around the same time, Willem Einthoven, also using the Lippman’s Electrometer, found these waves….but he labeled them A and B.
Later (when the Electrometer 2 was released from beta), Waller detected a deflection arising from the atria, and labeled it ….A.
Einthoven, not to be outdone, also detected the electrical activity from the atria. But he could not use Wallers ‘A’ because he had already used it for the ventricles. Bugger.

Now Einthoven was a bit of a fan of Descartes…you know, the guy who invented analytical geometry and who often used the letters P and Q to label the points on his own curves. So Einthoven decided that it he could really stamp a little credible ownership on this new wave by naming it ‘P’.
After all, wasn’t it Descartes who said: Cogpeeto ergo sum (I ‘P’ therefore I am)?.

Waller was not impressed.

This is all news to me. I always thought the ‘P’ wave was named after the trajectory my urine stream makes when standing at the urinal and aiming high.
I have of course attempted to confirm this by experimenting with generating QRS urine streams……but with disastrous results.

QRST waves:

An even more powerful Electrometer was developed and a further 2 electrical deflections were detected by Einthoven. As he published diagrams explaining the differences between the older ECG tracing and this newer version his lettering was beginning to get a little confusing.

As he had now decided to label the atrial wave ‘P’, it made grammatical sense to just relabel the consecutive waves QRST.
Einthoven was now out-publishing Waller and he had far more friends on Facebook. So his nomenclature became accepted as the norm.

But wait there are more:

As if it isn’t enough to get your head around the PQRST waves, more were discovered.

• U Wave: Occurs after the T wave.
• Delta wave: seen in WPW syndrome, and named due to its similarity in appearance to the Greek letter.
• Osborn Wave: Seen in hypothermia, and named after one of the doctors who first described it.
• Epsilon Wave: Seen in patients who experience ventricular arrhythmias or posterior infarction and named because it comes after delta in the Greek alphabet. It is seen on the opposite side of the QRS complex to the delta wave.

So there you go, a little history of the development of ECG waves.
And a little side-note to file away in case you ever find yourself needing to stand next to me at the urinal.

Reference: All this information has been lifted from a far more thorough examination of the provenance of ECG labelling: Naming of the Waves in the ECG, With a Brief Account of Their Genesis