Welcome to episode 96 of the Audio PANCE and PANRE PA board review podcast.
Today is part five of this fabulous five-part series with Joe Gilboy PA-C, all about cardiac murmurs. In this week’s episode of the Audio PANCE and PANRE podcast, we continue our discussion of cardiac murmurs with a focus on Mitral Valve Prolapse (MPV) and Hypertrophic Obstructive Cardiomyopathy (HOCM).
We’ll cover the ins and outs of these two NCCPA content blueprint murmurs and learn how to identify and differentiate them from other types of murmurs.
If you haven’t already, make sure to listen to our previous podcast episodes where we covered tricuspid stenosis, aortic valve murmurs, mitral valve murmurs, and pulmonic valve murmurs.
Hypertrophic Obstructive Cardiomyopathy (HOCM) is a cardiac abnormality that leads to the muscle in the wall of the heart growing and thickening to the point that it blocks blood flow exiting the heart.
The condition can be mild or severe, and it can lead to a variety of symptoms, including shortness of breath, chest pain, and irregular heartbeat. Complications may include heart failure, an irregular heartbeat, and sudden cardiac death.
HOCM is a hereditary condition, and it is usually diagnosed in adulthood. There is no cure for HOCM, but treatments are available to manage the symptoms and help reduce the risk of complications. With proper care, people with HOCM can live long and healthy lives.
*Hypertrophic cardiomyopathy is covered under the PANCE cardiology content blueprint -> cardiomyopathy -> hypertrophic cardiomyopathy
HOCM is also covered as part of the PAEA EOR pediatric rotation -> cardiovascular topic list -> hypertrophic cardiomyopathy
Mitral Valve Prolapse (MPV) is a condition in which the leaflets of the mitral valve bulge or prolapse back into the left atrium during systole. This may cause blood to flow backward into the left atrium, leading to a heart murmur.
In some cases, MPV may also cause symptoms such as fatigue, dizziness, chest pain, and shortness of breath.
While MPV is usually benign, it can occasionally lead to serious complications such as heart failure or stroke.
Treatment for MPV typically involves lifestyle modification and management of symptoms. In severe cases, surgery may be necessary to repair or replace the mitral valve.
*Miral valve prolapse is covered under the PANCE cardiology content blueprint -> valvular disorders -> mitral valve prolapse
Below is a transcription of this podcast episode edited for clarity.
Welcome back, everybody out there in the podcast world. This is Joe Gilboy, and I work with Stephen Pasquini at Smarty PANCE.
Today is part five of our five-part series covering heart murmurs – one of the most dreaded subjects in PA land.
Today we are going to cover what I call the low-volume lovers.
And who are the murmurs that like low blood volumes? In other words’ low blood volumes make these murmurs sound louder? That is Hypertrophic Obstructive Cardiomyopathy (HOCM) and mitral valve prolapse.
So, what is happening with HOCM? Let us go back and view this from a pathophysiology point of view. So what do you have with HOCM?
I have this young adult, and he is going to start exercising. So what is the left ventricle going to do on a typical day during exercise? You will stress out the left ventricle, which can lead to hypertrophy.
I want everybody to look in the space you are in right now. Maybe you are in a room. Perhaps you are in a car. I want you to look at the volume of this room or car and look at the wall.
Now I want you to imagine that you start working out. You see, the wall will get thicker.
Now, what happens when those walls are thicker, my muscles get thicker. Thus, what is going to happen next? My stroke volume will go up, my cardiac output will increase, and my resting heart rate will decrease. And that is a nice normal day. That is the way it is supposed to work.
This is why aerobic exercise is so good. That’s what your Apple Watch or Fitbit is telling you. They are going, “Hey, we hit the target zone. You’re stressing out your left ventricle.” Your left ventricle will hypertrophy, which is a normal response to exercise.
Your wall will get thicker, but the volume of the room you are sitting in stays the same. Let this marinate for a second. I stress out my left ventricle, and it’s going to hypertrophy. The wall is going to get thicker, with more healthy tissue. My stroke volume will go up, my cardiac output will go up, my resting heart rate will go down, and my exercise tolerance will improve. That’s a nice normal day.
Hi, I have HOCM by genetics, no fault of my own. I was just born with this genetically. I will stress out my left ventricle, except instead of hypertrophying out, with HOCM, I am going to hypertrophy in.
Okay, please stop and think about what I am saying. Now. See the room you are sitting in, that wall. It is coming in. Not out, but in. Look at the volume. You have in your room now. What have you done? You have decreased the volume (the size) of your room.
Now, since I have less volume, what is the last thing you want to take away from me? Volume? So what drug is contraindicated in HOCM? Diuretics!
The last thing I want to do is have these walls hit with low volume and a high pulse. That’s when bad things can happen. This is the VTACH and the VFIB that you see these young athletes with HOCM die from.
So, these walls get thick and come in and make my room smaller. So, the last thing I want to do is take volume away, and the last thing I want to do is give them a diuretic.
What is a lifestyle thing I can tell my patients with HCOM to do? Drink more water! This will increase the volume, and the walls to be pushed apart. Does everybody see that?
Okay, my patient with HCOM is sitting at the edge of the bed at rest. He is not exercising, and he does not have an elevated pulse and low volume – that’s that nightmare scenario we were talking about where a patient with HOCM is exercising, and they have low volume. They are sweating, and their pulse is high. Now the walls hit, and this is when the bad things happen.
So, I have this patient sitting at the edge of the bed in an exam room at rest. Remember, HOCM is not a valvular issue. No valve is not functioning correctly here. These are walls that are enlarged (hypertrophied).
Now I want to hear the walls hit each other while my patient with HOCM is at rest. That’s all I want. I want the walls to hit. What is in the way between those two walls? Blood!
If I want the walls to hit, I have to get the blood out. I can do this with my low-volume maneuvers. What are my low-volume maneuvers? Standing and Valsalva.
When I have HOCM, if I perform standing and Valsalva (the low volume maneuvers), I can get the blood out of the way so walls can get closer and hit. So, what makes the murmur of HOCM sound louder? Standing and Valsalva.
How do I push the walls of the ventricle apart? I can add more blood. How do I add more blood? If I squat! That is right; squatting is a party. If I go in there and squat and all this blood comes running back home, what will I do with the walls of the left ventricle? I am going to push them apart.
So, this is the opposite of all those murmurs I learned about! This is why I call HOCM and MVP the low volume lovers – because they like low volume.
Let us take it one step further. Let’s do that one maneuver everybody hates out there in the podcast world: Handgrip.
Okay, think about it. Stop memorizing. Let’s make sense of this.
So, we perform handgrip. What am I doing? I am sitting on the aortic valve. You sat on the aortic valve and added more pressure to the valve by doing this. You have added more afterload.
What is the left ventricle going to do? Well, since I have more afterload, I need more preload. So, my ventricles are going to have to fill up more. With the increased volume, the walls will move apart from each other.
So, you are telling me that when I squat and put all that blood into the left ventricle, it will push the walls apart? Furthermore, when I do handgrip, it will also cause those walls to move apart because I must increase my preload and increase the volume. Exactly!
So, when I perform handgrip and have HOCM, the murmur goes away.
This is everything you need to know about HOCM: It is not a valvular issue. To make HOCM louder, you want the volume out so the walls can hit. What are the low-volume maneuvers? Standing and Valsalva. How do you put volume (aka blood) in the room? Standing and handgrip? Exactly. That is precisely how this works.
The next murmur that likes low volume is the murmur of mitral valve prolapse. In comparison to HOCM, this one takes a bit more thought.
To demonstrate mitral valve prolapse put your two hands together like you are making the letter A.
Okay, see how your fingertips are touching each other. This is how the mitral valve usually closes.
Now point your thumbs in the middle and view your thumbs as the chordae tendineae. They are pulling your fingers down. That is how it works on an average day.
To demonstrate mitral valve prolapse, take your right hand and place it where your metacarpals are – again, kind of like the letter A.
Do you see how your fingers are over the top of the other ones? They do not match up perfectly. This is what we sometimes call a redundant valve. In other words, there is extra tissue, and things are not lining up.
When the left atrium contracts on a normal day, the mitral valve comes down, and everything works as expected. However, we will run into trouble with MVP when the left ventricular pressure is highest. And when is the left ventricular pressure at its highest? Oh, that is right, I memorized that during PA school. It is highest during mid systole. That’s why we get a mid-systolic click – because the valve cannot hold the pressure below it during mid-systole.
That is because the connection is not very good. It is loose. So, the valve pops open during mid-systole, and we call that a mid-systolic click.
How can I crank that pressure up in the left ventricle? Oh, I could exercise. Exactly! This is why we often hear about people with mitral valve prolapse having palpitations with exercise.
Okay. I want the murmur of MVP to sound louder. Think about this. Let us go back to where my hands were in the example above. Remember how my fingers were coming together to form the letter A? Except when I have mitral valve prolapse, my right hand is touching my metacarpals, and I have these extra fingers on top of each other, creating a redundant valve.
So, I want this valve to collapse in on itself. I want it to fall in on itself.
What is down in the left ventricle? Blood. Now we need to get the blood out of there so the valve can fall down on itself. We will need to call in our low-volume maneuvers to do this.
What are our low-volume maneuvers? Standing and Valsalva! Standing and Valsalva are low volume maneuvers and will make the murmur associated with mitral valve prolapse sound louder.
Now, if I put blood back in the ventricle, can that redundant valve fall down on itself? No, it cannot. So, squatting is a high-volume maneuver that puts blood back into the left ventricle, and it is not going to make the murmur of MVP sound louder because the valve is not going to fall in on itself. However, if I take the blood away, there is nothing down there in the left ventricle, and the valve will fall back down. So mitral valve prolapse is also a murmur that gets louder with low volume maneuvers.
There is just one more thing we need to cover. The ultimate apex question. Are you ready? Handgrip! With handgrip and HOCM, I could see how by increasing the volume of blood in the heart, the ventricle walls would get pushed apart, and the murmur goes away. Now we will cover handgrip and mitral valve prolapse.
Okay, handgrip, so what did I say? I am sitting on the aorta. Okay. So, what is the left ventricle going to do? I just increased my afterload. This means I also increased my preload.
So what did you do? You just put more blood in your left ventricle! Now you need to push that blood out, and you are pushing out more blood. The mitral valve is prolapsed and does not have a good connection. Is it going to be able to hold? No. So, will I hear the murmur of mitral valve prolapse if I do handgrip? Yes, the murmur of MVP will increase with handgrip.
How do I differentiate the low-volume lovers (MVP and HOCM)? By having the patient perform handgrip. With HOCM, when handgrip is applied, you push the walls of the ventricles apart. With mitral valve prolapse and handgrip, you increase left ventricular pressure, and what happens to the mid systolic click? Oh, it is still there, and if ff anything is louder. Because what did I do? I increased the pressure in my left ventricle.
Come back to this podcast and replay it again when you have a moment. This will make so much sense if you follow my physics, especially the laminar flow physics part.
Remember that HOCM and MVP are low volume lovers – meaning they like low volume – that is when the murmurs sound louder. They are the opposite of mitral stenosis, mitral regurgitation, aortic stenosis, and aortic regurgitation. Those usual players like more blood against the diseased valve.
Remember, in HOCM; it is not a valve issue; it is a wall issue. Mitral valve prolapse is a valve issue, but remember that the valve does not connect very well. It is still there. It works well, but the connection does not hold tight.
Next week we are going to start doing murmur questions.
We have covered aortic stenosis and aortic regurgitation, we went over mitral stenosis and mitral regurgitation, we covered pulmonic stenosis and pulmonic regurgitation, we have learned about tricuspid stenosis and tricuspid regurgitation, and in this episode, we covered what I call exceptions to the rule – which is HOCM, and mitral valve prolapse.
What is next? Test questions – where I will present these murmurs to you in a very ambiguous way, and you will have to figure out which murmur it is.
Take care of yourselves, and stay safe. I will see you soon.
Take care, Joe.
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