English subtitles for clip: File:Aortic valve disease video.webm

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The aortic valve is typically made up of three leaflets - the left, right, and posterior

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leaflet and it opens during systole to allow blood to be ejected to the body.

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During diastole, it closes, to allow the heart to fill with blood and get ready for another

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systole.

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If the aortic valve doesn’t open all the way, it gets harder to pump out to the body,

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and this is called aortic stenosis.

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If it doesn’t close all the way, then blood leaks back into the left ventricle, called

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aortic valve regurgitation or aortic insufficiency.

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Usually, the aortic valve opens to about 3-4 cm2, but with stenosis it can become less

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than 1 cm2.

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This is usually caused by mechanical stress over time, which damages endothelial cells

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around the valves, causing fibrosis and calcification, which hardens the valve and makes it more

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difficult to open completely.s This type usually shows up in late adulthood, with patients

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over 60 years old.

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Similarly, patient that have a bicuspid valve, with two leaflets, as opposed to a tricuspid

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with three, are more at risk of fibrosis and calcification since the mechanical stress

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that’s usually distributed between three leaflets is now being split by two leaflets,

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and therefore they see more stress per leaflet.

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Another important cause of aortic stenosis is chronic rheumatic fever, which can cause

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repeated inflammation and repair, leading to fibrosis.

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In this case, the leaflets can actually fuse together, called commissural fusion, which

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can be an important distinction from the type caused by mechanical stress over time.

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When the valve fuses together or hardens, it doesn’t open as easily, right?

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And so as the left ventricle contracts, it creates this high pressure that eventually

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pushes on the valve until it finally snaps open, causing a characteristic “ejection

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click”.

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Since the blood has to flow through a narrow opening, there’s turbulence which creates

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noise or a murmur, which gets initially gets louder as more blood flows past the opening

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and then quieter as the amount of blood flowing subsides because less remains in the ventricle.

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This is called a crescendo-decrescendo murmur.

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Since now it’s harder to open and push blood past this hardened valve, the left ventricle

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has to generate higher pressures each time it contracts to get the same amount of blood

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through.

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To accomplish this, the left ventricle can thicken its muscles, called concentric left

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ventricular hypertrophy.

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This happens because new sarcomeres are added in parallel to the existing ones.

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Even though you have this bulked up ventricle, the heart still might struggle to get enough

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blood through the narrowed opening and the body, and ultimately to vital organs, and

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that means that the person’s at risk of developing heart failure, and various symptoms

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related to whatever organ’s involved.

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For example, if there’s a reduction in blood flow to the brain, it could lead to syncope,

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and a reduction in blood flow through coronary arteries to the heart’s own myocardium could

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cause chest pain and angina.

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Patients might not initially experience symptoms at rest, only during exercise, because exercise

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requires more blood, right?

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And the the heart isn’t able to increase blood flow through the small opening.

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A final complication is called microangiopathic hemolytic anemia, which is essentially damage

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to red blood cells as they’re forced through the smaller valve, splitting them into smaller

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fragments called schistocytes, leading to hemoglobinuria, which is hemoglobin in the

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urine.

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Treatment is usually replacement of the valve, which often doesn’t happen until after the

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onset of symptoms.

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Alright so that was aortic stenosis, what about aortic regurgitation?

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Well normally, right after the ventricle pumps blood out through the aortic valve, the valve

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shuts and remains shut while the ventricle fills again.

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With aortic regurgitation, or sometimes called aortic insufficiency, blood flows back from

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the aorta into the left ventricle during diastole, or during ventricular filling.

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About half of cases are caused by aortic root dilation.

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Which is where the root dilates, or gets bigger, and in doing so pulls apart the leaflets,

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making it harder for the valves to fit snugly together and close all the way and letting

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some blood flow backward.

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The vast majority, about 80% of aortic root dilations are idiopathic, which means that

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the cause is unknown.

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The remaining 20% of causes are things like aortic dissection, aneurysms, and syphilis,

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all of which can widen the aortic root.

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Besides root dilation, regurgitation may happen due to valvular damage, from something like

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infective endocarditis, a bacterial infection of the inner lining of the heart, or again

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from chronic rheumatic fever.

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In this situation, the chronic inflammation leads to fibrosis, but instead of fusing the

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valve leaflets together, it makes it so that they don’t form a nice seal and instead

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let blood leak through.

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Patients with aortic regurgitation will have an early decrescendo diastolic murmur, caused

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by the blood flowing back through the valve.

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Since blood’s leaking back from the aorta into the left ventricle, the left ventricular

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blood volume increases which increases the stroke volume or the amount that the left

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ventricle pumps out during contraction, or systole.

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More blood pumped out of the heart per squeeze, requires more pressure, so systolic blood

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pressure increases.

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During diastole, though, there’s less blood volume in the aorta since some has leaked

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back into the ventricle, which means that diastolic blood pressure decreases.

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A higher systolic pressure and lower diastolic pressure means an increase in pulse pressure,

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which is just systolic pressure minus diastolic pressure.

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A large pulse pressure, meaning a large difference between systolic and diastolic pressure, is

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referred to as a hyperdynamic circulation.

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Patients with hyperdynamic circulation have bounding pulses, or water-hammer pulses because

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the blood (which is mostly composed of water) slams like a hammer against the walls of the

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arteries with each heartbeat.

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These bounding pulses can be dramatic enough that they cause head bobbing that’s in tune

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with the heartbeat, as well as causing the capillary beds in the fingernails to pulsate,

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sometimes called Quincke’s sign.

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Over time, the increase in blood volume in the left ventricle causes the chamber to grow

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larger, called eccentric ventricular hypertrophy.

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In this situation, new sarcomeres are added in series to existing ones.

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Just like aortic stenosis, treatment for aortic regurgitation is replacement of the valve

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after symptoms and left ventricular dysfunction develops.