00:00
Well, since the development of atherosclerosis
in the aortic valve is associated with worsening
valve function and eventually, severe aortic
stenosis, it was early on suggested, let’s
put these patients on Statin drugs. You’ll
remember from the pharmacology lecture, Statins
actually retard the development of atherosclerosis.
00:23
So, there had been a number of studies where
statins were tried in a double blind randomized
fashion. A very excellent study in the New
England Journal, a few years ago, was in Norway
and unfortunately, it didn’t work. There
was no improvement in the group that got Statins
versus the group that got placebo. Most people
seem to think that the reason for this is
that the Statins were started too late. The
process was already far advanced in the aortic
valve before the Statins were given.
There are now some other trials underway,
trying to give Statins much earlier in the
course, in an attempt to be preventive or
prophylactic, if you will, in terms of development
of aortic stenosis, but we don’t have the
results of that yet.
In any case, many of these patients will have
elevated lipids that require Statin therapy
anyway and the decision is made not based
on the presence of the bicuspid valve or atherosclerotic…
early atherosclerotic aortic valve, but much
more on the likelihood of developing coronary
artery disease.
01:31
A question that often arises is, does the
patient with aortic sclerosis, which is extremely
common, eventually develop into aortic stenosis?
In fact, studies have shown that aortic sclerosis
is the beginning of the atherosclerotic process
in the aortic valve. You might consider it
very, very mild aortic stenosis. And just
as atherosclerosis in the coronary arteries
and elsewhere in the body can develop and
get worse with time, the same thing can happen
with the atherosclerosis in the aortic valve.
So, when you identify a patient with aortic
sclerosis, you have identified a patient
with atherosclerosis, probably not only in
the aortic valve, but also in the coronary
arteries. It correlates with all the risk
factors that lead to atherosclerosis. I use
it in my clinical practice. When a patient
comes in and tells me they're having chest
discomfort with exertion and I hear an aortic
sclerosis murmur, I’m quite convinced that
I’m dealing with atherosclerosis in the
coronary arteries because I’m already hearing
atherosclerosis in the aortic valve.
02:37
So, it’s important to listen carefully to
these patients with the stethoscope to see
if you can identify an aortic sclerosis murmur.
Aortic sclerosis murmurs are very common in
the elderly. And guess what? Atherosclerosis
is very common in the elderly. So, the two
of them go together. And in fact, there have
been a number of studies that have actually
looked at this. This is what I’m demonstrating
to you. Here, is a study from Seattle, Washington
in which 5,000 elderly patients were followed.
You can see quite a large percentage had aortic
sclerosis and a much smaller percentage actually
had gone on to significant clinical aortic
stenosis.
So, the atherosclerotic aortic valve initially
is just producing a very limited little murmur,
an atherosclerosis murmur. And then with time,
that murmur becomes more prolonged and loud
as the patient develops various phases of
aortic stenosis.
Well, let’s talk for a moment about the
risk factors. As you might imagine, since
atherosclerotic aortic stenosis is related
to the development of atherosclerosis, it
is no surprise that it’s related to the
presence of risk factors. So, patients who
are smokers, patients who have hyperlipidemia,
patients who are diabetic and hypertensive
are going to be much more likely to develop
aortic sclerosis that proceeds to aortic stenosis
than individuals who are lacking in those
risk factors.
So, when you develop a preventive cardiology
program and treat these risk factors, you
are not only decreasing the likelihood that
the patient will develop coronary artery disease,
but very likely, you are also decreasing the
risk that they will develop atherosclerotic
aortic stenosis.
04:33
Many years ago, when we had a patient with
severe aortic stenosis that was due to atherosclerotic
calcific disease, about 50% of the patients
turned out to have associated coronary disease.
04:44
No surprise since atherosclerosis is a diffused
disease affecting, in this case the aortic
valve, and of course, in about half the patients,
it affected the coronary arteries.
04:56
Today, actually 70 to 80% of patients with
calcific atherosclerotic aortic valve disease
have significant coronary disease. What’s
the reason? The patients are a lot older today
than they were some years ago when they presented
with… when they presented with atherosclerotic
calcific aortic stenosis. So, they’ve had
much more time to develop coronary artery
disease. They're older, they're sicker and
they have more co-morbid condition in particular,
a greater incidence of significant narrowings
in the coronary arteries from atherosclerosis.
05:28
Well, let’s talk about the three symptoms.
I mentioned them earlier, the three warning
symptoms that say, “This patient really
needs to be considered for urgent operative
intervention.” The three symptoms are angina,
heart failure and syncope.
05:45
First, let’s talk about angina. In fact,
the patients can have angina even with normal
coronaries because the thickened ventricle
is doing so much increased work because it’s
trying to push the blood thorough the stenotic
aortic valve that it demands a great deal
of oxygen and nutrients, sometimes more than
it can get at a time when the person is exerting
themselves and heart rate goes up and blood
pressure goes up. So, consequently, angina
can occur with coronary disease or without,
but it’s a signal that the patient is coming
into an accelerated phase of aortic stenosis
and needs to be intervened, needs to have
a new valve.
The second symptom is heart failure that is
the patient notices unusual shortness of breath
with moderate exertion or even some shortness
of breath at night or wakes up at night short
of breath. That’s even a more severe warning
symptom than angina and the patient again,
urgently needs to have an aortic valve replacement.
06:46
Finally, there is the patient who faints.
That is the most severe symptom and in that
setting, we push patients very very quickly
to surgical intervention.
06:58
Okay, what are the various surgical interventions
that you can have? Well, first of all, most
patients, particularly if they're young and
reasonably healthy and can withstand surgery,
most patients will go on to… to receive
a valve. They can either receive a tissue
valve, made either from the pericardium of
a cow, bovine pericardium or actually, an
aortic valve from a pig; they are specially
raised and harvested for their aortic valve.
07:28
The advantage of the tissue valve is that
you don’t need to take warfarin. Remember
the anti-coagulant, the anti-thrombotic that
we talked about in the Clinical Pharmacology
lecture? Patients with a prosthetic valve,
plastic and steel, need to be on that drug.
07:43
Patients who receive tissue valves, usually
do not need to be on that drug and therefore,
don’t have the risk of hemorrhage that the
patients who are on warfarin have.
07:52
Secondly, there’s a procedure called
Ross procedure in which the pulmonic valve
is... in a patient, is transplanted into the
aortic area and a prosthetic valve is put
into the pulmonic area. This operation requires
great surgical skill and is only done by a
few people.
And of course, finally, one can actually,
these days, replace the aortic valve with
a catheter procedure. This is only done usually
in very elderly, frail, infirm individuals
who we think will not survive the operation
of a surgical aortic valve replacement.
The surgical aortic valve replacement results
in a valve that’s a little bigger than the
catheter one and consequently, the results
are slightly better. Although they are remarkably
good in a very elderly and frail population
when we do the catheter valve procedure.
After aortic valve replacement, even in very
elderly patients, here you see all individuals
who underwent valve replacement. These were
surgical valve replacements over age 80 and
you can see that even at 10 years, there’s
about a 50% survival and many of these patients
do not die of heart failure or of their valve
disease, they die of other things.
Any elderly population is going to die from
multiple other things, cancer and heart…
disease, heart failure from atherosclerosis
and so forth, many other things. But in fact,
a substantial portion of these people are
still alive even many years after their aortic
valve replacement.
09:27
Just very briefly to talk about the diagnostic
procedures that we do, once as I’ve shown
you a few moments ago, you hear the murmurs
that suggest aortic stenosis, you get an electrocardiogram.
09:38
What this electrocardiogram demonstrates is
a lot of high voltage. You can see the upstrokes
here are very, very large and that is a suggestion
that the left ventricle has become hypertrophied,
that is thickened in response to the increased
work load that it has to face with the stenotic
aortic valve.
The chest x-ray can be surprisingly normal,
but as you can see in the drawing on the right
hand side, there’s a little hint of a dilated
ascending aorta which is dilated because of
the high speed jet coming across the stenotic
aortic valve.
This is an echocardiogram, two-dimensional
echocardiogram. You can see between the LV -
the left ventricle and the AO - the aorta,
that there’s a very calcified aortic valve.
If we saw this as a movie, you would see that
the valve is moving very poorly and hardly
opening at all. And we can actually estimate
the severity of the aortic stenosis from the
two-dimensional echo.
10:38
So, in conclusion then with aortic stenosis,
valvular heart disease these days is much
more either the result of a bicuspid valve
or atherosclerosis that is not what we had
many years ago when we had a lot of rheumatic
fever. Patients who were developing chronic
rheumatic heart disease, that there are a
number of other complications that it can
occur in these patients because of other diseases
because the atherosclerotic folks are often
very elderly and have a lot of other problems,
lung, possibly and kidney disease. The calcific
atherosclerotic aortic stenosis when patients
develop symptoms, it requires that one consider
valve replacement, particularly if they develop
one of the symptoms - angina, heart failure
or syncope.