00:01
Welcome back to Vascular Medicine - The Advanced
Venues.
00:05
We are going to discuss today venous diseases.
We’ve been talking a lot about arterial
diseases up to this point. Now we’re going
to look at the second component of the cardiovascular
system: the venous diseases.
00:18
We’re going to start with a definition of
the various kinds of venous diseases. It turns
out that, just as in the arterial disease,
thrombosis – or the development of a blood
clot –can develop in patients in the veins
just as they can in the artery. And just as
in the artery, pieces of the blood clot can
break off and go elsewhere in the circulation
and cause mischief. The same thing can happen
in the venous system.
00:48
In the venous system, when a blood clot forms
and breaks off it goes to the lung and is
known as pulmonary embolism.
00:58
What often leads to clot in the veins is an
inflammatory process called deep venous thrombosis
or DVT. And that inflammation in the wall
of the vein – and we’ll talk about the
reasons why that can happen – results in
a blood clot forming. The blood clot can get
bigger and bigger and bigger, pieces can embolize
and result in pulmonary embolism. If enough
blood clot gets into the lung, you can have
enough obstruction of blood flow through the
lung that the patient may develop shock – the
subject of the last lecture.
01:37
So, often this disease is called venous thromboembolism
because there’s clots in the leg and there’s
clots embolising to the lung. And that’s
often abbreviated as VTE.
01:50
Remember what a thrombus is. A thrombus is
a solid mass of platelets and / or fibrin
that has formed locally in a vessel. It’s
a blood clot. And it forms when the clotting
mechanism is activated.
02:07
Thrombosis is actually obstruction of a blood
vessel by a thrombus. And, of course, when
that happens in the arterial system, nourishing
blood fails to get to a blood vessel. In the
venous system, that doesn’t happen because
we have so many reserve veins. Blood usually
goes around the area where there’s a thrombus
or thrombosis. However, when pieces break
off and embolize to the lung, that causes
real trouble.
02:35
The most common form of embolism, much more
common than arterial embolism, is venous thromboembolism.
02:43
And the commonest form of venous thromboembolism
results from deep venous thrombosis.
02:48
And there’s a whole variety of illnesses
that increase people’s risk for developing
thrombosis in the veins. For example, long
periods of bed rest; or long periods of travel
in an aeroplane where you’re seated with
your legs down; or cancer increases the clotting
ability of the blood and can result in that;
pregnancy. A whole variety of conditions can
lead to either increased clotting tendency
or injury to the vein. For example, a fracture,
a trauma can injure the vein and lead to deep
venous thrombosis. And, again, a piece of
the clot breaks off, goes up to the lung and
that can cause lots of trouble.
03:32
Occasionally, for example in some forms of
trauma, you can have fat or air that embolizes
or even little bits of an atherosclerotic
plaque that can embolize. But in fact the
vast majority of embolism on the venous side
is blood clot. And it’s a blood clot that
results from deep venous thrombosis.
03:55
When the embolus lodges downstream, it often
lodges in the narrowest area. And so in the
lung the thrombus will travel until it finds
a small enough blood vessel that it gets stuck
and then, of course, it causes obstruction
of blood flow through that area of the lung.