What coronary artery, please? Right coronary
artery. Now, special inferior wall MIs.
Quickly we are going to run though this, a true posterior
MI. ST elevation in II, III, aVF, right coronary
artery along with inferior leads. Tall R wave
with ST depression in V1, V2. Now, what that
means? I will tell you in a second. A posterior
descending artery from either RCA or left
circumflex. Now that posterior descending
artery become very important to us. Does it
not? In anatomy if you remember, now you refer
to what is known as right dominant and left
dominant. Majority of your patients will
be right dominant right. That is because of
posterior descending artery might be coming
off of that. So what you need to take out of
this for you clinically and any question that
you might get from anatomy is what is that
dictates or determines whether you are right
dominant or left dominant? If it is right
dominant, it is opposed to descending artery.
If it arises from the RCA, obviously patients
are right dominant. If it arises from your
left circumflex, your patient is left dominant.
Majority of your patients will be right
dominant. Keep that in mind. It will help
you. ST depression and early precordial leads
may actually not be reciprocal changes. Now
this is a bit much in terms of information,
but this is a posterior MI. At least, keep
in mind that we have II, III, aVF with an
ST elevation and keep in mind where you just
explained posterior descending artery and
its determination of dominants.
Take a look at right ventricular infarction. How
does this even occur, right ventricular infarction?
Once again we have the RCA and this would
also be leads to II, III and aVF. Now because
we are in the right ventricle, I want you
to think of V4, not so much V5, V6 because
that will take you to lateral. Profound hypotension
with nitroglycerin, beta-blockers and administer
fluids in your patient. Right ventricular infarction.
You are worried about your patient not having
proper output and hypotension, mean to say
that what you are doing, you are causing preload
to be decreased resulting in profound hypertension
because the right ventricle isn't working properly.
Look for those type of clues in which you
know your patient is suffering from RVI.
Now, ultimately it comes down to cardiac enzymes.
On this table, the most important cardiac enzyme
that I have referred to over and over again
is troponin I. Now there is another enzyme
that we will quickly discuss. That would be
CKMB. And this is the table format in which
we are showing you the cardiac enzyme, but I
would like for you to focus on this graph. I'm gonna walk you
through this so that you clearly see why it
is the troponin I is the gold standard of
your cardiac enzymes. Now, to back up for
a second, please. Would you find any cardiac
enzyme to be elevated in angina? No, you do
not. I do not care if it is stable or unstable.
You are not going to find elevated cardiac enzyme.
Keep that in mind. It is that black and white.
It has to be. Now if you go into myocardial
infarction, sure. Now the one that you are
paying attention to, you see the long dash
green line, the troponins. The X-axis here
represents the days and the time. The Y-axis
represents the amount of concentration.
So the dash long lines are troponin elevates
immediately at 24 hours. Look how long
it lasts, a week. So very difficult for you
to miss an MI in a patient if you are measuring
troponin. Hopefully, it is not beyond a week,
with that I don't even want to say, but
anyhow the other important component is the
CKMB. It used to be the gold standard. Now
pretty much the same reason because it is
elevated within 24 hours, but the reason that
troponin trumps it, what kind of troponin by
the way? I. The reason that it trumps it is because
CKMB disappears, how long? Three days, it
has gone. Now if you did find a CKMB to be elevated
beyond three days, then what do you know about
your patient? Had a re-infarct. Now there
is something called LDH isoenzyme flip in
which the normal an LDH type II is then replaced
by LDH type I. Just know that it exists.
But your goal standard would be troponin,
understand the significance of your CKMB
rising above or beyond day three.