Physiology Question on Q & R Waves

[AnthonyM83]

It sounds like you are trying to make more of the situation than is actually there.

That I certainly am...sigh, it's always been a recurring theme and I often end up missing the big picture, b/c I get stuck on something like this.

So, my question comes down to this:

If the R wave is always representing depolarization of the ventricles (rather than septum) in normal physiology AND depolarization toward a lead creates a wave with a positive amplitude, then why does the lead V1 which is is on the RIGHT side of the heart (thus impulse travelling AWAY from it) have a positive amplitude?

[AZCEP]

Let's see if I can clear this up. In V1, the normal healthy DEFLECTION of the QRS complex will be predominantly negative (pointing down). If there is some type of disease process at work that will alter the direction of the electricity, then you can get a positively deflected QRS in this lead. Right ventricular hypertrophy, COPD, or a RBBB will cause this pattern to show.

If you measure the amount of electricity (amplitude), which is what the ECG measures on the vertical, you can end up with a positive number. Typically, and more accurately, it would be measured as a negative

[fiznat]

If the R wave is always representing depolarization of the ventricles...

Thats where you're getting messed up. It isnt the R wave itself that illustrates ventricular depolarization, it is the entire QRS complex.

P wave: atrial depolarization

QRS complex: ventricular depolarization (and a hidden atrial repolarization)

T wave: ventricular repolarization

Worth 1000 words. Normal 12 lead ECG:

[AnthonyM83]

Ohhhkay.

I was thinking the V1s normally had short R waves and that the following dip was an S wave.

I'm looking up "normal sinus" ekgs online and looking at Fiznat's picture, though, and V1 seems to regularly have a little spike after the P and right before the dip. What's that from?

Also, the text said "The left side of the septum depolarises first, and the impulse then spreads toward the right. Lead V1 lies immediate to the right of the septum and thus registers an initial small positive deflection (R wave) as the depolarisation travels ward the lead. " So, I just assumed that little spike was the small positive deflection they were talking about. But you guys are saying that's not what I'm seeing when I look at the V1 examples...

[AZCEP]

Ohhhkay.

I was thinking the V1s normally had short R waves and that the following dip was an S wave.

I'm looking up "normal sinus" ekgs online and looking at Fiznat's picture, though, and V1 seems to regularly have a little spike after the P and right before the dip. What's that from?

The small positive deflection you see is the Q wave. Remember this is normal in V1 because the wave of depolarization is moving towards the lead as the septum is stimulated.

Also, the text said "The left side of the septum depolarises first, and the impulse then spreads toward the right. Lead V1 lies immediate to the right of the septum and thus registers an initial small positive deflection (R wave) as the depolarisation travels ward the lead. " So, I just assumed that little spike was the small positive deflection they were talking about. But you guys are saying that's not what I'm seeing when I look at the V1 examples...

[AnthonyM83]

So, it's okay to have predominantly negative R waves in 'normal' rhythms...without violating the definition that an R wave is a the first positive deflection after the Q... everything seems so contradictory. But okay, if that dip in V1 after the spike is an R wave, then it now makes sense how the R waves in V1 and V6 are measuring the same thing.

[AZCEP]

Just the definitions of the different waves get bunged up. Many students have the same problem, particularly when they learn interpretation by only looking at lead II.

The QRS complex is the same. There may not be a Q, or an R, or an S-wave specifically, but we still call them "QRS". Once this is settled for you, things will become easier.

[AnthonyM83]

Well thank you AZCEP and the rest for your help!

Sorry it took so much back and forth...message boards can be a difficult medium!

[AZCEP]

As long as you now understand what you need, the information will always be here to be referenced.

I'm glad to help when I can.

[fiznat]

The small positive deflection you see is the Q wave.

V1 initially shows a positive Q-wave then a predominantly negative R wave, with the S-wave moving back to the baseline.

Woah woah wait a minute! Now I am willing to admit that - as a new medic - I may be wrong here, but my understanding is that:

Q wave- first DOWNWARD wave of the QRS complex

R wave - UPWARD wave following the Q and before the S

S wave - DOWNWARD wave following the R

That is, a Q is always a negative deflection, an R is always a positive deflection, and a S is always a negative deflection.

To be sure, I confirmed this with my handy-dandy Dr. Dubin book and it is so. A quote from the book:

An upward wave is always called an R wave. Distinguishing between the downward Q and the downward S waves really depends on whether the downward wave occurs before or after the R wave. The Q occurs before the R wave, and the S wave follows the R. Just remember your alphabet.

Sometimes (like in V1) the R wave isnt very visible. That doesnt make the large downward deflection an R. Sometimes there arent any R waves visible at all, and the first major deflection in the "QRS" complex is negative.

Consider this EKG:

This EKG has a number of things going on (LAD/LVH, LAH, huge PR), but check out the QRSs in v2 for example. No R wave. We wouldnt call this (downward) wave an R wave simply because it is large-- it is a QS wave. ...Named that way because it is indistinguishable as a Q or S as the definition of those two are dependent on a visible R wave. The R is always up, the Q and S are always down, regardless of which lead youre looking at.

V1 seems to regularly have a little spike after the P and right before the dip. What's that from?

By definition, it is the R wave. Its small because of the angle you are looking from, but it is still the R.