00:01
To make a diagnosis, well if you can show
that there is new, right ventricular strain,
then that would suggest there has been a large
PE, and to do that an echocardiogram is very
helpful. It's a bedside test, it's very quick
and it can show the very significant right
ventricular strain that you get with very
large PEs in a very short period of time.
00:23
In addition, you may have the raised brain
natriuretic peptide levels suggestive of cardiac
problems, and there might be a raised troponin
T and the ECG can show signs of right ventricular
strain, inverted T waves V1 through to V3
and then there's the specific ECG findings
you often get in, what can get in pulmonary
emboli of a S wave in lead 1, a Q wave in
lead 3, with T-wave inversion in lead 3 which
is the classical ECG abnormalities you see
in somebody presenting with acute PE which
is present in a minority of patients unfortunately.
00:58
CT scan is now the main way for identifying
PEs, and this is a specific type of CT scan
called CT pulmonary angiography, where you
inject contrast into the vein and that will
flow to the heart, and then be sent down the
pulmonary arteries and that allows you to
see the clots as filling defects in the pulmonary
arteries as shown by this example here; the
arrows are pointing to central pulmonary arteries,
and you can see they are partly grey which
represents the clot and the white is the contrast
which is finding it difficult, but just going
around the outside of that clot. And this
is a standard test now for identifying the
presence of pulmonary emboli. In the past, and
for some patients we still
use a radioisotope scan called ventilation perfusion
scan, where you're looking for mismatched
defects in perfusion, that means that the
patient is ventilating that part of the lung,
so the radioisotope which is inhaled is seen
in that area, but the perfusion of that part
of the lung, the radioisotope that reaches
that part through the pulmonary artery is
reduced, so it's a mismatched defect that occurs
in a VQ scan. That's less commonly used nowadays
because of the greater rapidity and ease of
getting CT scans.
02:21
The chest X ray itself actually is very nonspecific,
it sometimes shows reduced vascular markings
but is a very poor test to identify somebody who
may have a pulmonary clot. Occasionally we
need invasive pulmonary angiography, but
that's only rarely needed.
02:37
You can also, using the radiology, see evidence
of the lung damage that's been caused by the
clot and this is the infarcts that I was talking
about earlier, where the tissue distal to
where the clot is occurred has been damaged
and has infarcted and causes a focal area of
consolidation which classically would be a
wedge-shaped pattern based on the pleura.
02:58
And this is CT scan here, and you can see the
clot in the proximal part of the artery and
then distal to that is the patch of grey, which represents
the damaged tissue of the lung due to infarction.
03:10
If you suspect somebody has a PE, another way
of making the diagnosis or at least making
the decision about whether they require treatment
for the pulmonary embolus is to look for a
deep vein thrombosis, and this is very easy
using a noninvasive ultrasound Doppler test
of the leg. And if you identify somebody that
has a DVT, the treatment of that is the same
as it is for a PE, so that's adequate in many
circumstances to give you the information
that you need to start patients on treatment.
In addition, we do blood tests occasionally
to look for evidence of coagulopathy, for
example the blood D dimer level is usually
raised when patients have pulmonary emboli
or DVTs, however it's a nonspecific blood
test, and is often raised for many inflammatory
conditions and therefore, isn't terribly helpful
in identifying a patient who may have a PE versus
a pneumonia or other differential diagnosis.
03:58
If somebody has recurrent pulmonary emboli or
DVTs or a family history of pulmonary emboli,
then we often do blood tests to look for inherited
disorders of coagulation such as protein CNS
deficiencies, which may make them more likely
to have PEs, and these patients often need
a lifelong anticoagulation to prevent further
PEs occurring.