So with arrythmias, well we said there was two major categories.
One was one in which it was conduction system
diseases and then the vascular component.
Now what we will first discuss would be the
conduction system disease category first, and
our first topic under this would be bradyarrhythmia.
So what is brady? I told you earlier that
if you find your beats per minute, which is
normally 60 to 100 to be less than 60 and trust
me you will know if your patient has decreased
heart rate. Fifty is the actual technical
definition of bradycardia. Bradycardia and
what does that mean to you? It means that
R wave, when you compare one R wave to another
are further apart and earlier told you about
"what sounds like a telephone number" which
is your "300, 150, 100". So what exactly does
that mean? Well when we look at that EKG,
if there is one line separating an Rwave
from each other, that is 300 beats per minute.
What if there's two lines separating an Rwave?
150. Three lines, 100. You group those together
300, 150, 100. Just like a phone number, divide
that into whatever numbers so that you can
remember this easily. The other three numbers
were 75, 60 and 50. So 50 brings you to six lines
separating an R wave from one another, and that
is 50 beats per minute. Welcome to bradycardia.
And sinus means what to you? Sinoatrial wave
representing the existence of a P wave.
Is that clear? It can be seen in competitive
athletes. It is perfectly normal and that
you can expect. So if you take a look at the
R waves that the upper deflection here and
you find a number of lines in between them
or you are in the realm of bradycardia. Now
with a competitive athlete, just one more
thing that I wish to bring to your attention.
Apart from having a normal sinus bradycardia,
you can also have a patient who is an athlete,
that has a well trained and very efficient
left ventricle. What are you referring to?
I am referring to the fact that with your very
efficient left ventricle that could be enlarged,
by your proper cardiac output, you might hear
what heart sound? Granted, S1 and S2. You have
to right if the person is alive. But it is
the S3 that I am really having you pay attention
to. The S3 would be found in that patient and
we have discussed that earlier. If symptomatic
in older patients, well syncope is what you
are worried about. So now let us go into our
clinical manifestations. So could it be normal?
Sure, competitive athletes, marathon runners
well-conditioned individuals right. But you
can also have symptomatic. If you have an
older patient that has sinus bradycardia, that
means perhaps this patient might not have
enough cardiac output. There is not enough
cardiac output, then the patient may be suffering
from syncope. That is not very good. It is
not a good feeling and treated with what?
A permanent pacemaker, right. Now heart
block is where we go next. So with sinus
bradycardia, I gave you two differentials
there. A competitive athlete and an older patient
in which unfortunately there is a sinus brady
and may require pacemaker, okay. But if it
is a heart block, what does that mean to you?
It is not that a conduction or an impulse is not
traveling through at all. Are you with me?
So the impulse will be traveling through,
but it might be retarded. It might be delayed.
At some point in time, when the heart block
gets bad enough and it doesn't travel through
it at all, guess what degree we are in now?
A third-degree AV block, okay. Now the same
concept was also used for LBBB and RBBB, where
there is the bundle-branch block. You call
that block, but the impulse is still traveling
through, at a very slow rate.
Let's talk about heart block. First degree,
second degree, third degree. Under second
degree, we will then get into Mobitz type
1 and Mobitz types 2 at least. Know that before
you walk into any medical environment.
Third degree, that is a complete heart block,
okay. Obviously, I will have to talk about
physio here and some of the fundamentals that
we have already laid down for EKG. So what
interval would you name this if I was to describe
to you the impulse that's originated in an SA
node making us way down to the AV node? What
interval would you define that as being?
PR interval, good. You tell me what the time is
normal? 0.12 seconds to 0.2 seconds. Do you remember
that? Good. So now you start having issues
with a delayed impulse, what can you expect
that PR interval to do? Good. Increase to be
great than 0.2 that is what you are paying
attention to, so far, so good. Now is that
in every single case? No and you will see why.
You will see conditions in which you won’t
always find a PR interval, but still would
be defined as being a type of heart block.
You see what I am referring to. Now the second
part of this so that it makes sense to you
is say that you did have a third degree AV
block okay. And if you did have a third degree
AV block may be because of myocardial infarction
there is no impulse that is being dictated
by your SA node. Remember, the SA node is the
conductor of the heart. It is the Zubin Mehta
of your conduction of your symphony. And so
therefore if the SA node loses control, how?
With the third degree AV block, then who is
controlling your ventricles? An ectopic foci.
What does that mean? Every single part of
the heart is its own pacemaker right. But you have to
have a ring leader. That is an SA node
and if that SA node loses the control of the
conduction system of the heart, trust me the
heart itself has an inherent ability of creating an
ectopic foci, alright? Now that ectopic foci
may still cause contraction of left ventricle
or create electrical activity, but it does not look
normal. You tell me, what is the ventricular
depolarization represented as on your EKG?
QRS complex. Are you picturing that? Now say
that if it is an ectopic foci, the QRS complex
looks bizarre. There is going to be no correlation
between the P wave and the QRS complex. So
these are things that you are want to lay
down before even move forward with any of
these so that when we get to the topic at
hand, we will be able to go through efficiently.
Okay. First degree AV block, what does that mean?