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The R wave
The R wave represents early ventricular depolarization.
Electrographically, it is defined as the first positive deflection after the P wave.
Observe our good friend the ECG depicting a normal sinus rhythm
As discussed in the previous chapter, the anterior leads should have no Q waves.
The next concept to wrap your head around, is the notion of "R wave progression"
Note how in a "normal sinus rhythm" ECG, the R wave progressively gets larger as it goes along from V1->V4/5, before getting smaller again.
Referencing an image i've made earlier, the reason for this is to do with the relative position of the "view" of the lead, vs the waveform.
As V3/V4 is more "head on" compared to the lateral leads, these leads therefore "see" this as a more +ve signal.
Thus, the "R wave progression" references this fact - as the "views" of the lead vs the waveform become more "head on" they in turn become larger.
and then shrink again when they go over the other side, to V5/V6, be less head on, and thus being less head on - become smaller.
We use this as our baseline, and deviations from this can imply pathology.
Observe:
V1-V2 look more at the Right side of the heart.
Larger R wave? Larger R ventricle.
V5-V6 look at the Left side of the heart.
Larger R wave here? Larger L ventricle.
Simples.
(no image will be inserted here, as again i don't wish to be struck off for copyright infringement.)
This therefore brings us to the following:
If you've been paying attention you will notice the large anterior Q waves, and why these are bad.
Hopefully you will now also notice there are no R waves.
This is still coined under the umbrella term "Poor R wave progression" as opposed to the technically correct "no R wave progression" or "There are no R waves" or "this is a medical problem."
All equally valid, but generally only one of these is utilised overall.
For those who enjoy pathology, R wave sheningans are summarised under the mneumonic "LATE"
LAFB/LBBB
Anterior MI
Tension
Emphysema/ECG placement
For the sake of everyone's sanity and this pre-course's brevity, I will likely explain the above under a linked pathology section.
But for now, that'll suffice.
Onto the next stop:
The Intrisicoid deflection
This is the technical term for "time to reach the peak of the R wave from baseline".
I haven't really seen or heard anyone use this term outside of textbooks and fancy (read: utterly unintelligible to anyone beside themselves) papers.
The term "R wave peak time" is sometimes used in the context of describing certain branch blocks.
(The reader will be relieved to hear we are not going into that concept at this point in time.)
The best analogy I can think of to describe this concept is with the following:
If you have three lanes of traffic, and no BMW drivers causing abject misery, then ideal circumstances can exist whereby there are no delays.
In the alternative, if instead real world problems kick in like road works and diversions then some lanes might be closed.
This will then cause the existing traffic to need to be squeezed into whatever remains.
This causes delays.
Therefore, the presence of an increase R wave peak time suggests there is a delay.
Observe:
The astute reader will realise that the R wave peak time in the above ECG is merely one small square. Which is normal.
Nevertheless, the author will state that the ECG shows a pattern in keeping with a LAFB.
To explain this paradox, the author proposes the following as to why most sources nowadays emphasize axis/vector interpretation, and drop the "R wave peak time" concept.
I feel that, in nutshell, medics up and down the country feel that to do the following to diagnose a condition is, quite frankly, stupid.
Whilst strictly speaking, cardiologists may be correct*** in demanding an R wave peak time for some definitions, just like their intrinsicoid deflections the majority view is that nobody really cares besides them, leading to the following scenario:
Click for the next part!
***(The author accepts no liability if the reader attempts to argue this fact with a cardiologist, and for some reason finds themselves condemned to TTO duty on the long stay geriatric ward.)
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