Now, overall, these were things becoming important.
The important points of what you want to know about
ECG are the following. What is the rate that
you are looking for? How do you find the rate?
You are going to take a look at the space
or the span between the R waves. Think about
the R wave, first major positive deflection
and what is my phone number? 300-150-100,
75-60-50 keep saying it over and over again, practice
them here, practice with me so that you get
those firmly etched in your head. For every
line, that is seperating the R wave, you are
going from 300 beats per minute all the way
down to six lines seperating R wave resulting
in brady and 50 beats per minute. That is
your rate. Is it regular or irregular? Mean
to say, let me give you prime example. An atrial
fibrillation was it irregular or regular type
of rhythm that you saw on that lead? Atrial
fibrillation, you had a P wave, which was
fibrillating and wavy and it was irregular.
The QRS complex showed up randomly. Whereas
an atrial flutter, I will show you at a 2:1
type of ratio. That type of pattern was two
P waves to every QRS complex and that was
irregular rhythm. You see that now. Crystal
clear. Now, what about the QRS complex. Is
it narrowed or is it perhaps widened? So far
what we have seen is a widening of a QRS complex.
Prime example, WPW. Wolf-Parkinson-White.
What caused that widening of that QRS complex?
QRS complex, the delta wave. What happened
to PR interval in WPW? It got shortened. Are
you able to do with that quickly? Yes, you
are. You will get it.
Clinical picture. What about your patient
hemodynamically? Is your patient hemodynamically
stable? If they are, just maybe you have enough
time and you have the luxury of using medical
cardioversion. In other words drugs. Or if
your patient is hemodynamically unstable, what
does that mean to you? There is syncope. There
is dizziness, decreased cardic output. There
is dyspnea. Things are backing up into the
lungs. Hemodynamically unstable. Hypotension
and now are you thinking about what kind of
issue or what kind of cardioversion? Electrical.
Blood pressure, consciousness, distress that
to you should indicate in the setting of an
arrhythmia as to whether or not your patient
is hemodynamically stable or unstable. Know
this forever more not only you are going
to save the lives of your patients, but really
you are going to build confidence in yourself
to make sure you can approach any scenario
and you can walk away knowing that you have
done a good job.
Now, what else do you want to know? Clinically
unstable, shock is which you
are worried about. The heart is failing.
Cardiogenic shock. How is the patient going
to feel with this type of shock where the
heart is not pumping properly? You tell me.
Decreased cardiac output so therefore what
happens to blood pressure? Decreased. Tell
me about your baroreceptor reflex. Decreased
firing, increased sympathetic activity. With
that increased sympathetic activty, how is
the skin going to feel? Cold and clammy and
there is going to be diaphoresis. Are we clear?
Why? Because increased sympathetic activity.
Shock, hemodynamically unstable.
Narrow complex, regular tachy and clinically
stable. What about this patient?
Let me give you big one physiologically, right
here. Carotid massage. A carotid massage has
a particular component in the carotid in this
components called the sinus and this sinus
houses what exactly? The carotid sinus houses
baroreceptors. Chemoreceptors are in your
bodies, aren't they? So, here, let us focus
on the carotid sinus that contains baroreceptors
and your patient has regular tachy, narrow
complex of your QRS complex. Clinically stable
there is no major hypotension. Distress not
so much and the syncope and dizziness not
there. We are okay. Shock, no. Obviously
not. Stable. You want to slow
down the heart rate. Are you seeing it now?
You massage the carotids. Let me give you
worst case scenario. What if you are doing a thyroid
exam on your patient that has a goiter, and
you come from the back and you press upon
the carotids, both at the same time, you might
have just killed your patient. The cardiac,
the heart you have a cardiac arrest. Why?
You massage a carotid. You have stimulated
the baroreceptors. When do you have your baroreceptors
being stimulated? Increased or decreased blood
pressure? You tell me. Take your time. You
got this. Increased blood pressure. Increased
amounts of blood passing through the carotid.
That is more sensitive, isn't it? When you
have increased blood pressure and you are
stretching your blood vessel, you are stimulating
the baroreceptor, outcomes to parasympethetic.
You by performing carotid massage are mimicking
high blood pressure, increased blood flow.
So hemodynamically stable, be careful when
you do carotid massage, you would expect the
heart weight to decrease. Valsalva, what does
that mean? The same thing in which we talked
about the early with valsalva when we did phase
II and such and doing a maneuver
where I decreased preload. Valsalva could
also result in maneuvering in vagal response.
Adenosine IV unless which one please? WPW.
We are also going to avoid WPW one more time.
You tell me about dig, dig is the big one. Technically
calcium-channel blockers as well. May terminate
your reentry tachycardias. You pay attention
to RT right now. That is good enough. Reentry
tachycardia. We will make flutter waves more
clear. Adenosine because you are slowing down
conduction. May not terminate atrial tachy,
but will slow AV conduction so that abnormal
P waves focus is what you are paying attention
to. Is that clear? So you are really slowing
down the AV conduction, but may not necessarily
terminate the atrial tachy. We will transiently
slow atrial fibrillation and as we move on
to clinical medicine and those of you that
are already cardiologists, those of you that
have done your cardiology rotation, you know
exactly what I am referring to. Many times
you use adenosine to do what? Diagnose your
patient, right? You use adenosine to see as to
whether or not by giving it, have you slowed
down the heart rate just a little bit? And
if you have done so, well maybe you have diagnosed
your patient with an SVT of some type. Keep that
in mind. Transiently, will slow down atrial fibrillation.