00:01
So, moving on to the first of these diseases,
pulmonary emboli. These are blood clots occluding
the pulmonary arterial circulation- they are
very common, 1 per 1000 per year and, where
they come from is, generally speaking, the
distal deep leg veins. So, somebody has a
deep vein thrombosis with a clot in one of
their leg veins, then that clot can break
off, move up the vein, venous circulation,
reach the right side of the heart and then
gets fired into the lung, whereas the pulmonary
arteries could get smaller, it will eventually
lodge and cause damage distal to where it's
lodged. You can also get clots moving it from
the arm veins and the right atrium itself, but
those are usually associated with indwelling
lines. So the patient who has had a long-term
catheter in for intravenous antibiotics or
has cystic fibrosis for example or perhaps
they got a pacing wire or something similar,
which allows a clot to form in a place where
normally they do not form.
01:05
There are some rare causes of pulmonary emboli,
where the material that is embolized to the
lung may not actually be clots, and these
amniotic fluid embolism which occurs during
delivery of a baby, fat embolism which occurs
in patients who have had long bone fractures
after a motorcycle accident for example, tumor
embolism that occasionally occurs where a
tumor may actually cause lumps of cancer to
fall off into the circulation and fly around
to the lungs, and the same thing can happen with
infected clots, which it most often occurs
in patients who've had intravenous drug abuse,
when they have right side endocarditis, and
small bits of infected material can fall off
the infected valve and go into the lungs to
cause clots and abscesses there. And sickle-cell
disease is often associated with pulmonary
emboli or disease that's similar to
pulmonary emboli.
01:58
Deep vein thrombosis and pulmonary emboli
have the same risk factors, because deep vein
thrombi are the source for pulmonary emboli
most of the time. And these risk factors can
be divided into three different categories-
one is increased coagulation of the blood
and the commonest cause of that would be pregnancy,
the oral contraceptive pill or other hormonal
therapy and malignancy but also occurs when
patients have congestive cardiac failure,
if they have an increased platelet count due
to problems with myeloproliferative disorders
of their marrow, in patients with chronic
inflammation, and also in smoking.
02:31
Endothelial wall damage will make a clot more
likely to occur and this is most obvious in
patients who've had pelvic surgery of some
description, either gynecological or orthopedic
surgery, in which case they have a very high
risk of developing a DVT and then potentially
a PE after that. And then if the blood flow is
reduced because of immobility, surgery, pregnancy,
etc. that also make a clot more likely to
form. And so, from this you can identify the
patients who are most at risk of DVT's and
therefore of PEs, and those are patients with
malignancy, recent surgery especially pelvic
or orthopedic, those who are pregnant, those
who've been immobile, due to a long flight
or a long car journey etc.
03:16
Emboli to the lungs will vary in their clinical
presentation depending on the size of the
embolus. And we can divide these into three
main categories. In the acute presentation
this might be a medium-sized clot, and this
will fly off into the pulmonary circulation,
but not lodged at the beginning of the pulmonary
artery but deeper down in one the medium pulmonary
arteries and causing infarction of tissue distal
to that. And these patients present with a
short history largely of cough, breathlessness,
hemoptysis.
03:50
A large clot, large enough to block a pulmonary
artery will have a very sudden history, and
the main problem these patients will present
with is the cardiovascular disturbance from
blocking the pulmonary artery. The whole of
the body's circulation goes through the pulmonary
arteries and therefore if you make a significant
obstruction to that, then that's going to
have very marked effects on your blood pressure
and your cardiovascular function.
04:15
The last presentation is much more chronic,
and those are multiple small clots and these
patients have a long history which may be
developing over weeks or months, and this
is due to small emboli clogging off individually
a small artery but, which in itself probably
has little effect, but when you have multiple
emboli clogging off multiple arteries then
that eventually will lead to breathlessness,
problems with gas exchange, and the patient
will present with breathlessness and potentially
the consequence of pulmonary hypertension
developing due to loss of the arterial circulation
due to multiple small clots.
04:54
So the acute presentation, any age, either sex
equally, there is usually an obvious pre-existing
risk factor, recent surgery, have just been
back from Australia, is on the oral contraceptive
pill for example. The type of presentation,
well the very large clots, that may be cardiac
arrest, the patient may just drop dead, essentially.
A sudden onset clot not quite enough to stop
the heart or cause hypotension, cardiovascular
shock, significant respiratory distress.
05:25
The smaller clots, the medium-sized ones, they
will cause infarction of the lung and that
causes pleuritic inflammation and therefore
pleurisy, and pleuritic chest pain, hemoptysis
and breathlessness. Those are the classical
presentations of somebody with acute PEs.
05:41
With acute PE, the general signs will show
that there has been some form of physiological
disturbance, there'll be tachycardia, then
maybe a 3rd heart sound, raised JVP showing
that there's some sort of right heart strain,
and of course there might be evidence of the
pre-existing DVT, although in many patients
that is not clinically apparent. And then
there are the respiratory symptoms and signs,
they have a raised respiratory rate, there
may be a pleural rub over the affected area
where the infarction has occurred, and there
might be signs of a small effusion which is
often associated with that pleural inflammation.