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Course: Health and medicine > Unit 3
Lesson 9: Cardiomyopathy- What is cardiomyopathy?
- Cardiomyopathy signs and symptoms
- Dilated cardiomyopathy: Pathophysiology and diagnosis
- Hypertrophic cardiomyopathy: Pathophysiology and diagnosis
- Restrictive cardiomyopathy: Pathophysiology and diagnosis
- Cardiomyopathy treatment
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Hypertrophic cardiomyopathy: Pathophysiology and diagnosis
Created by Matthew McPheeters.
Want to join the conversation?
- When listening to the chest , you hear lub systole dub diastole then the murmur or squish or do you hear the squish before the dub(4 votes)
- The S1 heart sound ("lub") occurs before systole, then the S2 heart sound ("dub" ) occurs before diastole, which looks something like this.
--"Lub"--(systole)--"Dub"--(diastole)--"Lub"--(systole)--"Dub"--(diastole)
A systolic murmur (as in hypertrophic cardiomyopathy) will therefore occur after "lub" and before "dub." Whereas a diastolic murmur will occur after "dub" and before "lub."(3 votes)
- How decreased afterload exacerbate the outflow obstruction?(2 votes)
- The decreased afterload of hypertrophic cardiomyopathy is caused by the drop in the volume the ventricles can hold since their muscle cells have been enlarged. Since there's less volume available for the blood in the atria to flow into the ventricles, when the heart is beating quickly (during exercise, for example) there is less time for the ventricles to fill, and thus there is a significant drop in the afterload.(3 votes)
- Can aortic valve stenosis cause hypertrofic cardiomyopathy? Because of the increased working load of the left ventricle.(2 votes)
- Yes this can be a factor because with aortic valve stenosis (stiff) the LV may not be filling with enough blood thus the LV is having to work harder.(2 votes)
- Can you have hypertrophic cardiomyopathy in your atria?(2 votes)
- No. You cant cardiomyopathy is a disease of the hearts muscles. The muscles of heart are located mainly in ventricles.(2 votes)
- what is small bowel obstruction(2 votes)
- An obstruction of the small bowel, also known as the small intestine. When it's obstructed chyme cannot progress through the digestive system and becomes trapped.(1 vote)
- 11:01do we see signs of hypertrophy on an ECG?(2 votes)
Video transcript
Let's talk about the
pathogen assist in diagnosis of hypertrophic cardiomyopathy. Now, before we dive into
the specifics, let's just briefly review normal cardiac physiology, so I'm going to just draw
in a simplified diagram of the heart. Now, as we go through the cardiac cycle, I want to emphasize the two major phases that are known as diastole and systole, and I'm going to describe what's going on in these phases by what's
occurring in the ventricles, and by the ventricles, I
mean these lower chambers down here, and regarding
the ventricles, we'll talk about what's happening with the muscles, and what's happening
with blood, and so during diastole, muscles are
relaxing, which causes dilation of the chamber,
so you can think of D for diastole, and this causes
blood to fill the chamber. During systole, the
muscles are contracting, and this causes the
blood to be ejected from the chambers. So as we're looking at this diagram, I want you to think about
this heart as if it's sitting inside someone
that you're looking at, so over here, on the
left side of the diagram, if it was sitting inside
of someone, that would be their right heart, and
over here on the right side of the diagram,
that is their left heart, so let's start over here
in the right atrium, so I'm just going to fill
this with some blood here, and this blood is coming from the body, and then over here, in the left atrium, and I'll also fill this
with blood, and this blood is now pink because it's
been freshly oxygenated as it's coming from the lungs. Alright, so the first
stage of this cardiac cycle is diastole, so as these
muscles of the ventricle dilate, it draws blood
from the atrium into the ventricles, and this causes
filling of the ventricles, and you can see now that
the atria has emptied all their blood, and the
ventricles are now filled, so that's diastole, and
now we're going to switch to systole, so you can
see that during systole, the muscles are contracting,
of the ventricles are contracting, causing the
chambers to get smaller, and blood is starting
to be ejected out of the ventricles, and what you
can also note is that during this phase, I'll go back
one step here, during this phase, the atria are
also filling with blood. Now, as the muscles of
the ventricles finish contracting, and systole
ends, we return to diastole, where these muscles relax,
so let's see that here, and notice that as they
relax, before we start getting filling of the ventricles,
not all of the blood from the ventricle was ejected. There's a certain, small
amount of residual blood that is left in these ventricles
after systole, and the amount of blood that was
ejected, so this kind of empty space here, over
the amount of blood, the total blood that was
in the chamber, is known as the ejection fraction,
and a normal ejection fraction is between 50 and
75 percent, and this is important because the
ejection fraction can be used as a measure of
systolic function of how well the heart is able to contract. So once again, we go back into diastole where the muscles dilate
and cause filling of the ventricles, and the cycle
just repeats itself. So now that we reviewed
normal cardiac physiology, let's talk about the pathogenesis of hypertrophic cardiomyopathy. Do you remember that
cardiomyopathy is a disease of the heart muscle by
the name, pathy meaning disease, cardio meaning
heart, and myo meaning muscle, so disease of the heart muscle, so the first step in the
pathogenesis of hypertrophic cardiomyopathy is that
you have a problem with the heart muscle, and in hypertrophic cardiomyopathy, this problem
is a genetic abnormality of the muscle cell proteins,
and what happens is that some of these proteins,
these abnormalities in the proteins, don't
allow the muscle to contract properly, and so since the
heart muscle isn't able to contract as forcefully,
it compensates for this decreased contraction
ability by hypertrophying, and what hypertrophy
means is, the cells get bigger, so let's see this
over here on the diagram. What I'm going to do
is just make the normal muscles here kind of
orange, just to demonstrate that they're diseased, and
since this diseased muscle isn't able to contract
properly, the muscle cells get bigger, they hypertrophy over time. This is just a compensation for not being able to contract properly,
so that kind of looks like this, and something
that's very specific to hypertrophic cardiomyopathy is that this hypertrophy of the septum,
or this wall between the two ventricles, is
asymmetrically enlarged. It's a lot bigger than the
hypertrophy of the outer walls, so let's just draw
that in, and this hypertrophy of the muscle walls results
in two major problems, and the first problem is
that now, since these walls are bigger, the chambers
have become smaller. You can see that the
space in the ventricles is smaller, and this smaller
space results in a decreased ability of the heart to fill
properly, and if the heart isn't getting enough
blood into the chambers, it can't pump enough blood
out, so this actually, even though, so this actually
results in a decreased outflow, and since it's
a problem with filling, which over here we
mentioned filling is during diastole, this is known as
diastolic heart failure, and this, in a sense,
is somewhat similar to restrictive cardiomyopathy,
but there's another problem in hypertrophic
cardiomyopathy that makes it a very dangerous
disease, and this problem is known as an intermittent
outflow obstruction. What does this mean? Well, let's go back over
to the diagram here to understand this a little bit better. So, you can see that the septum here is hypertrophied, and this
hypertrophy causes a narrowing of this outflow
track from the left ventricle, so blood is
normally coming in, and then going out through the
aorta, but when this space is narrowed, you kind
of get a blockage here, and it's intermittent
because it's dependent on how hard the heart muscle is working, and certain parts of
the cardiac cycle, so, for instance, if an
individual with hypertrophic cardiomyopathy is working
really hard, and their heart rate is really fast,
the diastolic period, that filling period, is
shorter due to the increased heart rate, and since it's
shorter, you have even less filling into the
ventricle, and so this space is even smaller than normal, and so you get intermittent blockage, versus when an individual with
hypertrophic cardiomyopathy has a normal heart rate,
he or she would be able to fill properly, and blood
would be able to get out, since that space is a little
bit expanded, so that's why you have this intermittent outflow obstruction, and it's
the combination of these two problems that result
in the signs and symptoms of hypertrophic
cardiomyopathy, so now we're talking about the signs and symptoms of cardiomyopathy, let's
discuss how hypertrophic cardiomyopathy is diagnosed. So the first step of all
diagnosis is to talk about the history and physical,
which I'm just going to abbreviate H and P,
and what's important about hypertrophic cardiomyopathy is that an individual may
actually be asymptomatic. They may have no signs,
but if he or she does have signs of hypertrophic
cardiomyopathy, some of the things that might
be seen are things like dysmia, fainting, which
is known as syncopy, or occasionally, the presenting symptom of hypertrophic cardiomyopathy,
unfortunately, is sudden death, and since hypertrophic cardiomyopathy is frequently asymptomatic and can have a very
serious presenting symptom, it's a condition that is
important to be screened for, and screening for
hypertrophic cardiomyopathy is performed in all young
children, and it's done by listening to the
heart with a stethoscope, and a child with hypertrophic
cardiomyopathy has a very characteristic heart
murmur that's known as a systolic ejection
murmur that increases with valsalva, so what does this mean? Well, let's go through it. Systolic ejection murmur. Well, that probably
means it's a murmur that happens during systole that's caused by the ejection of blood. Remember that the heart,
that systole occurs when the heart is contracting
and blood is flowing out of the ventricles, and since
you have this obstruction from the septum, you get
a turbulent blood flow going out of the left
ventricle, and that turbulent blood flow can be heard
with a stethoscope, and this is known as a
systolic ejection murmur, but how about this heart that increases with valsalva? Well, a valsalva is a
maneuver that an individual can perform in which he or she bears down, like they're about to
have a bowel movement, and this is important,
because what happens when a valsalva is performed,
less blood returns to the heart, and this causes
this chamber to become smaller, and as I mentioned
earlier when we were talking about that intermittent
outflow obstruction, when that chamber is
smaller, that degree of obstruction increases,
so a valsalva worsens the obstruction, increasing
the turbulent blood flow, causing the murmur to
become louder, so any time a child has a systolic
ejection murmur that increases with valsalva, that child
needs to be worked up for potential hypertrophic cardiomyopathy because it can have some
very serious outcomes, such as sudden death. Well, the next step is to
perform some routine tests, and normally when we think
of routine tests, one of the things we think about
is labs, but there's not really any specific labs to hypertrophic cardiomyopathy, so I'm
going to kind of just skip that part of routine tests,
and the next one is a chest x-ray, which I'm
going to abbreviate CXR, and actually, in
hypertrophic cardiomyopathy, a chest x-ray is most
likely going to be normal, and the same is going to be true of an electrocardiogram, or an
ECG, so really, even though these tests may be performed,
anyone who has this positive screening test
is going to go straight to their special tests,
and the most important special test for
hypertrophic cardiomyopathy is an echocardiogram,
which is an ultrasound of the heart, and what the
echocardiogram is going to show is an increased
septum to left ventricular wall thickness ratio,
so what that means is, the ratio of the width
of the septum compared to the left ventricular
wall out here, is going to be increased, and specifically
this ratio is going to be greater than one point three to one. Once the echocardiogram
is positive, the last step is confirmatory tests,
and the first type of confirmatory tests are
genetic tests, so I mentioned that hypertrophic
cardiomyopathy is caused by genetic abnormalities of
the muscle cell proteins, and these abnormalities
can be detected in blood tests, and the other type
of confirmatory tests is a cardiac muscle biopsy,
and this isn't necessary to diagnose hypertrophic cardiomyopathy, but it does have a very
characteristic finding, known as myofibral disarray,
and so this is something that's seen under the
microscope, so if you can imagine that muscle cells
are kind of normally lined up linearly, like this. Well, in hypertrophic cardiomyopathy, these muscle fibers are in disarray. They're kind of lined up
in all sorts of different directions, and that
disarray of the muscle fibers is what causes the
original decreased ability of the muscle to contract,
so if you can remember that hypertrophic
cardiomyopathy is a disease of the heart muscle
that's caused by a genetic abnormality of the muscle
cell proteins resulting in a myofibral disarray
that causes a decreased contraction ability and
subsequent heart muscle hypertrophy, causing
these characteristic signs and symptoms, and that it
is screened by listening to the heart with a
stethoscope, and that most important tests in diagnosing hypertrophic cardiomyopathy is an
echocardiogram, which will show an increased septum
to left ventricular wall thickness ratio.