Let’s talk about another very simple and
commonly performed test: the electrocardiogram.
This is really a heart test but it gives us
important information about the heart that
is relevant to the peripheral vascular system.
This is an enlarged version of one complex
from the electrocardiogram. In blue, you see
the P wave. That is the depolarisation – the
electrical activity running through the atrium.
Then in grey the QRS. That is the ventricular
depolarisation – or electrical activity
– running through the ventricle. And then
in brown the T wave. That is the ventricle
resetting itself for the next beat.
The electrocardiogram shows the flow of electrical
depolarisation current as it passes through
the heart. It’s one of the first tests done.
It’s a simple test that’s often done in
the doctor’s office. It’s the cheapest
test. It’s the most easily obtained cardiovascular
test. And it has reasonable accuracy for a
variety of heart conditions. For example,
arrhythmias – electrical short circuits
- or myocardial infarction – heart attack.
But there are many non-specific and non-diagnostic
patterns so you need to interpret it in light
of the patient’s history, the patient’s
physical exam and any other pieces of information
you might have about the patient.
Here are two examples. The one at the top
is normal. This slide shows a normal electrocardiogram
with a normal triphasic up and down and up
again wave form for the ventricular depolarisation
as I showed you previously. The small hump
in the front is atrial depolarisation and
the large hump after the triphasic depolarisation
is the ventricle resetting itself.
Let’s look at one very simple example of
an arrhythmia – of an abnormality. This
is atrial fibrillation in which the little
P wave has gone and, instead, you can see
lots of bouncing-around activity because the
atrium is fibrillating – that is it’s
in a chaotic electrical and mechanical state.
And you can see that the rhythm is very, very
irregular. So this is one thing that’s very
easily identified. And, as we’ll see in
later lectures, sometimes this entity can
result in a blood clot forming in the heart
that can get out and cause a stroke or other