- So what does this bad cholesterol do? Well as I talked about, the cholesterol can form plaque
between the layers of the artery walls and then this plaque can result in inflammation. And the
plaque does two things. One is it actually limits the blood flow getting to the organs that are
being supplied by that blood vessel, and the second is that if it breaks open it can cause clots and
completely limit blood flow. So let's talk about this in a little more detail. So here are your
coronary arteries, which are the blood vessels that feed blood to your heart. Now if you think about
your heart it's a muscle that pumps all day every day, and so it needs oxygen constantly. So it needs
these blood vessels that are feeding it to be open. What happens when you have high cholesterol is the
LDL that's circulating around in your bloodstream goes and deposits itself in the wall of the blood
vessels. This results in an inflammatory process where inflammatory cells called macrophages come
to the site where the cholesterol is deposited and actually engulf the cholesterol to become
even more activated in a form called foam cells. And what these foam cells do is they cause lots
and lots of inflammation which causes the plaque to get bigger and bigger. And so then these are
the two mechanisms then by which then the plaque can cause a problem. One is that it can limit the
blood flow because it gets bigger and bigger. And these are the types of people that you hear that
have angina when they walk up a flight of stairs, because when they exercise their heart and their
heart needs more oxygen, that plaque is limiting the amount of blood flow that can get to their
heart. The second is that the inflammatory process can actually thin out this cap that sits on top
of the plaque and cause the cholesterol to spill over into the blood stream. And when that happens
the body's reaction is to form a clot. So what this clot does is it completely limits blood
flow. So if you think about what happens in your heart which needs oxygen all the time, if you have
an occlusive thrombus or a clot that's completely limiting blood flow, that piece of the heart muscle
is deprived of oxygen and starts to get damaged and dies off. And that's what a heart attack is. It
should be no surprise that the same process can occur in the blood vessels that feed blood to our brain. And
shown here the carotid artery and the vertebral artery two of the blood vessels that take blood to
our brain. And in the same way that they do damage in the heart these plaques can cause problems in
the brain, and if you have a complete blockage of blood flow to the brain you have a stroke. And then
again no surprise that the same thing can happen in our legs and that's called peripheral arterial
disease. And people can get cramping and pain in their legs when they walk up a flight of stairs or
sometimes if the plaque ruptures they can actually get necrosis or ischemia of a leg causing them to
potentially lose that leg. So I I see many thin people in this room and at this point you may be
saying - well all of this is great but it doesn't really apply to me because I'm thin and I don't
need my cholesterol checked. And I would say that that is the exact opposite of the truth. The new
ACCAHA guidelines recommend cholesterol screening for everyone, starting in young adulthood. In fact
the new pediatric guidelines are even recommending cholesterol screening for adolescents because of
the rising obesity epidemic in the United States. So even though it's true that overweight or obese
people are more likely to have high cholesterol, even thin people can be at risk. And that goes back
to the two mechanisms that I talked about in the beginning. One is what you eat so you could be very
very thin and eat very healthy, but the other is your body's endogenous ability to make cholesterol.
And a large part of that is determined by your genetics. So, I consider myself a thin person but
I'm of South Asian ancestry, and most South Asians tend to have high cholesterol. And indeed my
cholesterol is off the charts. So you can be very very thin and still have high cholesterol. So you
should discuss with your doctor how frequently you should have your own cholesterol checked and
this will be a factor of your age, your family history, your risk factors, your body mass index,
a number of other things, but you need to come up with an individualized plan with your doctor.