be increased of vagal tone. Let us now move on
to second degree. Now things
get a little more complicated, but stick with
me here. Under second degree AV block, there
will be two subtypes that you, at least, want
to know. At least want to know two subtypes.
The first one is called Mobitz type 1. Mobitz
type 1 from henceforth if you want to pronounce
1 as when why not? Because this brings us
to Wenckebach. So Wenckebach is specifically
Mobitz type 1. What kind of heart block are
we dealing? Our topic at hand second degree
AV block. What have we completed with
discussion? Our first degree, we are done.
That was every single PR interval was fixed
and prolonged with first degree. Second
degree is different. The EKG here if you take
a look at the PR interval, the first one normal.
The second one a little bit longer. The third
one even longer. Fourth one, oh! my, the PR
interval the P wave is there, I don't find any QRS
complex. That is my problem. So if you take
a look at this EKG, you will find that the
PR intervals are prolonging progressively,
then the QRS complex drops spontaneously abruptly.
What happens subsequently? It comes back to
normal. What does? The PR interval. The PR
interval would be normal on that first strip
rhythm, the second one, the PR interval will
be a little bit longer and by this that's what
I mean to say, you really want to know what
a little box is. What is that little box time?
0,04. What is the big box time? 0,2 seconds.
Do you remember that? So, therefore, if you find
progressive prolongation of PR interval with
a drop in your QRS complex, this to you represents
a second degree Mobitz type 1 a.k.a. Wenckebach.
This is a frequently tested rhythm. You want
to know it? Yes, you do. Beat has dropped.
Don't forget that. Subsequently, things come
back normal and you begins the cycle again.
That completes our discussion of Wenckebach.
Let us move on to Mobitz type 2. Before we
do so, though, I want you to take a look at
the bottom strip here. On the bottom strip, you
will notice that the PR interval is progressively
getting long and then in certain rhythms here,
you will find that the QRS complex is not
even present and then once again you begin
that cycle of progressive prolongation of
your PR interval. Spend a minute or two. Take
a look at the bottom strip, understand what
I said in terms of definition. This is still
Wenckebach but what may happen? Because on
your license exam or in attending, in which you
moved into a cardiology rotation
will hand you a 12 lead ECG and what is your
reaction? Smile, take it and look like you
know what are you doing, because you do. Once
you panic, game over. Okay. So don't panic
please. Take a deep breath whatever it is.
Every single patient, every single question,
every single piece of paper that you get is
kind of like how an ER does triage, okay. If you
prioritize and maintain composure, once you
panic everything in front of you is going
to die, including your patient. Maintain composure
at all times. It is amazing what you are capable
of doing. Believe in yourself. This is Wenckebach.
You got this, move on. Progressive prolongation,
your QRS-drop takes place.
Talk about second degree AV block and talk
about type 2. This is interesting. Here the
bottom line is, P wave without subsequent QRS
complex and no change of your PR interval. You see that?
So here we will have a heart block, a second-degree
type, Mobitz type 2. That PR interval is going
to be within normal range. Once again what
is your normal range? 0,12 to 0,2 seconds. Here
it will be within normal range, but the QRS
complex certainly dropped. There is no cycle
per se. That is the biggest difference between
Wenckebach, Mobitz type 1, Mobitz type 2. Both
of these come under what please? Second degree
AV block. Let us move on. Here you will notice
the PR interval, the bottom strip is the most
important one. It is the normal PR intervals
then every once in a while, the QRS complex
is not present, but there is no cycling here of
progressive prolongation. Once again you might
be given a 12 lead ECG. You go with the basics,
you look for that P wave, you look for an upright
QRS complex after your P wave, you take a
look at the PR interval. Take a look at the
ST segment. Take a look at the T wave and
make sure that you know the basics here. Take
a look at the rhythm. How did you figure out
the rhythm? The number of lines between the
R waves. What was your phone number? My phone
number is 300, 150, 100, 75, 60, 50. What does that
mean? Each one of those numbers that I have
mentioned would be the number of lines that
are separating the R wave. Call me. I will
be available to you, anytime. Move on.
Now we are going to third-degree AV block.