So let's just talk about right and left atrial enlargement by themselves just to review.
We've talked about this before. Here's the normal P wave, right?
It's 3 boxes in duration or less, not wider than that. It's upright in leads 1 and 2
and doesn't have a big negative deflection for example in V1. In V1,
you'll see in a moment the big negative deflection that suggest left atrial enlargement.
So here we see a very nice example. Spiky, tall, and broad P wave in lead 2.
Right atrial enlargement. In this case, it's 2.5 mm in height and in V1, it's upright.
It's not inverted as here in left atrial enlargement, look at the secondary component of the P wave.
You notice how inverted and deep it is?
That's left atrial enlargement.
And you could see at the length of the P wave is also prolonged more than three little boxes
so it's more than a 120 ms and there's the downward deflection
of greater than 40 ms and 1 mm wide big deep inverted secondary component of V1 suggest left atrial enlargement.
Here we see another form of left atrial enlargement.
This is often seen with mitral stenosis.
You'll notice the big broad P wave and the double hump on it spelling the letter M.
So, it says mitral valve disease--mitral stenosis--and over in V1,
again, you see a prolonged deep inverted secondary component.
Both of these suggesting left atrial enlargement.
Tall P waves higher than 2 little boxes, notice in aVL in green, this suggests right atrial enlargement.