Aortic valve disease – causes, symptoms, diagnosis, treatment, pathology


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much more. Try it free today! The aortic valve is typically made up of three
leaflets – the left, right, and posterior leaflet and it opens during systole to allow
blood to be ejected to the body. During diastole, it closes, to allow the heart
to fill with blood and get ready for another systole. If the aortic valve doesn’t open all the
way, it gets harder to pump out to the body, and this is called aortic stenosis. If it doesn’t close all the way, then blood
leaks back into the left ventricle, called aortic valve regurgitation or aortic insufficiency. Usually, the aortic valve opens to about 3-4
cm2, but with stenosis it can become less than 1 cm2. This is usually caused by mechanical stress
over time, which damages endothelial cells around the valves, causing fibrosis and calcification,
which hardens the valve and makes it more difficult to open completely. This type usually shows up in late adulthood,
with patients over 60 years old. Similarly, patient that have a bicuspid valve,
with two leaflets, as opposed to a tricuspid with three, are more at risk of fibrosis and
calcification since the mechanical stress that’s usually distributed between three
leaflets is now being split by two leaflets, and therefore they see more stress per leaflet. Another important cause of aortic stenosis
is chronic rheumatic fever, which can cause repeated inflammation and repair, leading
to fibrosis. In this case, the leaflets can actually fuse
together, called commissural fusion, which can be an important distinction from the type
caused by mechanical stress over time. When the valve fuses together or hardens,
it doesn’t open as easily, right? And so as the left ventricle contracts, it
creates this high pressure that eventually pushes on the valve until it finally snaps
open, causing a characteristic “ejection click”. Since the blood has to flow through a narrow
opening, there’s turbulence which creates noise or a murmur, which gets initially gets
louder as more blood flows past the opening and then quieter as the amount of blood flowing
subsides because less remains in the ventricle. This is called a crescendo-decrescendo murmur. Since now it’s harder to open and push blood
past this hardened valve, the left ventricle has to generate higher pressures each time
it contracts to get the same amount of blood through. To accomplish this, the left ventricle can
thicken its muscles, called concentric left ventricular hypertrophy. This happens because new sarcomeres are added
in parallel to the existing ones. Even though you have this bulked up ventricle,
the heart still might struggle to get enough blood through the narrowed opening and the
body, and ultimately to the vital organs, and that means that the person’s at risk
of developing heart failure, and various symptoms related to whichever organ’s involved. For example, if there’s a reduction in blood
flow to the brain, it could lead to syncope, and a reduction in blood flow through coronary
arteries to the heart’s own myocardium could cause chest pain and angina. Patients might not initially experience symptoms
at rest, only during exercise, because exercise requires more blood, right? And this heart isn’t able to increase blood
flow through the small opening. A final complication is called microangiopathic
hemolytic anemia, which is essentially damage to red blood cells as they’re forced through
the smaller valve, splitting them into smaller fragments called schistocytes, leading to
hemoglobinuria, which is hemoglobin in the urine. Treatment is usually replacement of the valve,
which often doesn’t happen until after the onset of symptoms. Alright so that was aortic stenosis, what
about aortic regurgitation? Well normally, right after the ventricle pumps
blood out through the aortic valve, the valve shuts and remains shut until the ventricle
fills again. With aortic regurgitation, or sometimes called
aortic insufficiency, blood flows back from the aorta into the left ventricle during diastole,
or during ventricular filling. About half of cases are caused by aortic root
dilation. Which is where the root dilates, or gets bigger,
and in doing so pulls apart the leaflets, making it harder for the valves to fit snugly
together and close all the way and letting some blood flow backward. The vast majority, about 80% of aortic root
dilations are idiopathic, which means that the cause is unknown. The remaining 20% of causes are things like
aortic dissection, aneurysms, and syphilis, all of which can ultimately lead to a widened
the aortic root. Besides root dilation, regurgitation may happen
due to valvular damage, from something like infective endocarditis, a bacterial infection
of the inner lining of the heart, or again from chronic rheumatic fever. In this situation, the chronic inflammation
leads to fibrosis, but instead of fusing the valve leaflets together, it makes it so that
they don’t form a nice seal and instead let blood leak through. Patients with aortic regurgitation will have
an early decrescendo diastolic murmur, caused by the blood flowing back through the valve. Since blood’s leaking back from the aorta
into the left ventricle, the left ventricular blood volume increases which increases the
stroke volume or the amount that the left ventricle pumps out during contraction, or
systole. More blood pumped out of the heart per squeeze,
requires more pressure, so systolic blood pressure increases. During diastole, though, there’s less blood
volume in the aorta since some has leaked back into the ventricle, which means that
diastolic blood pressure decreases. A higher systolic pressure and lower diastolic
pressure means an increase in pulse pressure, which is just systolic pressure minus diastolic
pressure. A large pulse pressure, meaning a large difference
between systolic and diastolic pressure, is referred to as a hyperdynamic circulation. Patients with a hyperdynamic circulation have
bounding pulses, or water-hammer pulses because the blood (which is mostly composed of water)
slams like a hammer against the walls of the arteries with each heartbeat. These bounding pulses can be dramatic enough
that they cause head bobbing that’s in tune with the heartbeat, as well as causing the
capillary beds in the fingernails to pulsate, sometimes called Quincke’s sign. Over time, the increase in blood volume in
the left ventricle causes the chamber to grow larger, called eccentric ventricular hypertrophy. In this situation, new sarcomeres are added
in series to existing ones. Just like aortic stenosis, treatment for aortic
regurgitation is replacement of the valve after symptoms and left ventricular dysfunction
develops. All right, as a quick recap…. Aortic stenosis happens if the aortic valve
doesn’t open all the way, and aortic valve regurgitation happens if the valve doesn’t
close all the way. Both can cause murmurs and hypertrophy of
the left ventricle. Stenosis can also lead to heart failure and
microangiopathic hemolytic anemia, while regurgitation can also cause hyperdynamic circulation. Treatment for both is replacement of the valve
after symptoms have developed.