Valvular heart disease, the causes of this can be congenital in congenital heart disease.
Actually, most commonly is going to be bicuspid aortic valve.
Roughly, one percent of the population will have a bicuspid aortic valve
which leads to increased incidence and propensity
to develop calcific aortic degeneration with stenosis.
That's the most common congenital lesion.
But there are a variety of acquired lesions. Most impact the mitral valve.
In fact, most valvular disease, if you had to take a guess on the boards
which valve is going to be affected,
mitral valve is going to be the dominant player in most valvular disease. Why is that?
Well, it's actually in part because it's the only native valve that has just two leaflets.
All of the other valves have three.
And so, have a different flow configuration
and are much less prone to potential inflammatory degenerative changes.
The other thing about the mitral valve is it sits between a very low pressure left atrium
and a very high pressure left ventricle.
And so, the mitral valve has abnormal - not abnormal,
but very significant force differentials, and it's only got two leaflets.
So, the majority of diseases affecting valves will affect the mitral valve first.
Second behind them is going to be the aortic valve, third is going to be the tricuspid valve,
and the pulmonic valve is very rarely affected.
So, when the mitral valve has acquired disease,
the most common acquired disease is regurgitation.
Stenosis, when it does occur, 85% of the time, mitral valve stenosis is rheumatic,
and we'll talk about how rheumatic heart disease occurs.
The mitral valve diseases, whether it's regurgitation or rheumatic can be acute or chronic.
And so, there is a tempo of effects on the mitral valve,
and clearly, there's a tempo of compensation by the myocardium.
The aortic valve, which I said is second in the most common valvular diseases
is most commonly stenosis especially in bicuspid valves.
So, the aortic valve can develop regurgitation, insufficiency,
but more commonly, it's going to become fibrotic and calcified, and therefore stenotic.
Insufficiency is usually due to dilation of the root.
So, it's not necessarily even the valve itself.
Remember that the annulus, I talked about the annulus of the atrioventricular valves,
well, the annulus of the semilunar valves, the aortic and pulmonic valve,
are also very important in maintaining valve integrity.
And if you have dilation on that root because of connective tissue disorders
or dilation of the aorta for any particular reason,
then you will have the annulus pull apart and the leaflets won't be able to close appropriately.
And again, aortic valve disease that's acquired can be acute or chronic.
And again, depending on the tempo, you may be able to adapt for long periods of time.
Acute fulminant endocarditis that causes valve destruction of the aortic valve may be lethal.
Slow motion insufficiency of the aortic valve, say, due to a progressive annular dilation
can be actually reasonably well-tolerated. So, tempo has an effect.
Let's look at some of the ideologies of common valvular diseases.
So, for mitral stenosis, as I've already said, 85% of mitral stenosis
is due to a rheumatic heart disease causing valvular fibrosis, valvular scarring.
So, that post-inflammatory scarring is demonstrated here in the circle on the left.
You can see that the valve leaflets are quite thickened and fibrotic, and they will become stiff.
So, you can have a degree of stenosis.
You can also have the valves, because they become so stiff, become insufficient.
And it affects not just the valve, but also potentially the chordae tendineae.
Aortic stenosis, being the most common lesion of the aortic valve,
is now seen in the circle, is most commonly due to age-related accumulation of calcification.
We'll talk a little bit more about that etiology,
but it's something that we're all going to be very prone to over the course of our lifetimes.
And if you take care of patients in the geriatric population, 70, 80, and 90,
they have a very high incidence of some degree of aortic stenosis
due to the senile calcific degeneration.
The calcification will actually be accelerated
as we'll talk about in congenitally deformed valves
or bicuspid aortic valve is the most common thing.
So, we can see it, that same age-related change,
in patients who are 40, 50, and 60 years of age.
Aortic stenosis can also occur due to post-inflammatory scarring.
So, I said the mitral valve is most prone to post-inflammatory or rheumatic scarring,
aortic valves are second in line and will often be affected in roughly 20 to 30% of cases.
Mitral regurgitation, on the other hand, is usually due to abnormalities of the leaflets,
mitral valve prolapse, defective extracellular matrix synthesis
such as in Marfan syndrome, or due to endocarditis.
So, those are the common causes of mitral regurgitation.
You can also have abnormalities of the chordae and the papillary muscles.
So, rupture or scarring of the papillary muscle due to ischemic heart disease
or rupture of the chordae tendineae due to collagen vascular synthetic disorder
such as Marfan will also cause mitral regurgitation.
Left ventricular or annular changes as well, as we talked about previously,
can be causes of mitral insufficiency.
So, a dilated left ventricle or calcification of the mitral ring,
which will change the geometry of the mitral apparatus.
Aortic regurgitation is due to abnormalities primarily of the cusps.
That can be post-inflammatory scarring or endocarditis,
but it can also be due to things that affect the aortic root and the aortic annulus.
So, you can have degenerative aortic dilation which will cause expansion
and widening dilation of the aortic annulus,
and that will cause the valve leaflets to not be able to close appropriately.
You can have Syphilitic aortitis which will cause, obviously, inflammatory destruction
of the ascending aortic because that's where most tertiary syphilis involving the aorta occurs.
You can have various inflammatory aortitis.
Lesions, such as giant cell aortitis or IgG-4 associated aortitis.
And then, connective tissue disorders where we have diminished synthetic capacity
such as Marfan syndrome will also dilate the aortic root and will cause valvular insufficiency.