#KYJ - Why are ECG waves called PQRST and not ABCDE

#KYJ -Why are ECG waves called PQRST and not ABCDE?

In short, the first ecg was ABCD.

So to answer the question we need to go back to the late 1800s. Electricity was a new thing and we were still understanding ways to measure it.

The first ECGs waves were measured by a Lippmann capillary electrometer device that measured current in liquid mercury rising and falling in a fine glass tube.   There were actually only 4 waves and rightly called ABCD.

But the mercury was heavy and subject to friction in the glass tubes where it fluctuated with current, so Einthoven in 1895, devised the precursor of today’s ECG.

He used a more sensitive technology called a String Galvanometer, that demonstrated a more mathematically correct 5 distinct waves.  Naturally these were different to the Mercury Glass system and the ABCD needed to be replaced.

So why PQRST?

These go back historically to Descartes.  Where a set of variables were grouped XYZ if there was 3 ; ABCD if there was 4, or PQRST if there were 5.

Einthoven therefore named his 5 ecg waves of the normal sinus rhythm, PQRST.

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Bruising v Eccymosis

#KYJ- Bruising vs Ecchymosis

Bruises change colour, but why?

So I’m in Mt Isa today teaching a plaster/trauma slab workshop,

(Yes your facility can book one- but more on that later), and one of the discussion points is eccymosis and bruising associated with trauma.

Eccymosis is the external bruising that results from skin vessels rupturing and bleeding into the layers of the skin.   Eccymosis can be called a bruise, but not all bruises are eccymosis.

If you rolled your ankle- inversion injury results in stressors places on the ligaments that hold your ankle together.  The Fibula, the Tibia, the Talus. 

Should a ligament rupture (tear) occur- this is called a sprain (as opposed to ‘strain’ which is muscle or tendon).... anyhooo....

The commonest site of these ankle sprains is the ligament binding the Talus to the fibula head( the nobbly bit on the outside of your ankle (called the lateral malleolus).  There is three ligaments there, but it’s the one in front (Anterior  Talofibular (ATFL) ) that cops 70% of injuries.

That ligament and structures surrounding will bleed when torn.

Initially this will cause swelling into soft tissues around the ankle, but in the surface of the skin, redness may not be immediate.  In 24 hours the classic bruising emerges from deep tissues, and is seen as ankle discolouration.   Now over the next week or so, this bruise fades from Deep Purple (purpura) to greenish yellow/brown and fades with time.  This is bruising.

Eccymosis is bruising from external trauma, like a blunt impact.... see the difference?

Significant- probs no- but can imply an injury mechanism like indirect internal trauma (bruise) and direct surface injury (eccymosis).

The colour of the bruising can indicate time since injury occurring.   Be wary of a child presenting with an orthopedic injury reported to have happened this morning, when the bruise is coloured like a 2 day old injury.   Delayed presentation is a red flag for SCA&N .... but that’s a whole other post.