00:01
So let's talk a little bit more
about syncope,
and how we approach syncope?
First of all,
let's start with a definition.
00:07
Syncope is sudden onset of loss
of consciousness, that's syncope;
or near loss of consciousness,
which is presyncope.
00:16
The etiology.
00:17
There are really three things
that cause this.
00:20
A heart problem can cause
cardiogenic syncope,
reduced blood flow
out of the heart.
00:26
A blood vessel problem,
one of the major blood vessels
like the aorta or carotid arteries
can cause this problem
cardiovascular or
vascular related syncope.
00:36
And then the last is an issue
with vascular tone,
which we call
neurally mediated syncope.
00:41
The blood vessels are critical for
pumping blood back to the heart.
00:45
And when there's less blood
pumping back to the heart,
patients can pass out.
00:50
So, we'll walk through each of
these three causes of syncope.
00:53
Cardiogenic syncope,
syncope from a problem
with the blood vessels
and then an issue
with vascular tone
or neurally mediated syncope.
01:02
At the end of the day,
the final common pathway
is reduced blood flow
to the brain.
01:08
And whether it be from a
heart source or cardiogenic source,
or a problem with the blood vessels
or a vascular tone,
what's going on is reduced
blood flow to the brain
or reduced
cerebral perfusion pressure.
01:22
When blood flow is
reduced to the brain,
it's also reduced to the
reticular activating system
and the bilateral
cerebral hemispheres.
01:28
And that's what keeps us awake,
and thinking, and not passing out.
01:33
The reticular activating system
in the brainstem
lights up the
bilateral hemispheres,
and reduction in perfusion
to any of those areas
will present with
presyncope or syncope.
01:45
So let's walk through each of those
three causes of syncope.
01:49
And let's start with the heart
or cardiogenic syncope.
01:55
The final output,
the final common pathway,
what's going on in patients
is cerebral hypoperfusion
and with cardiogenic syncope,
the problem comes from the heart.
02:06
What a patient say?
Patients will either describe
presyncope, near fainting episodes,
syncope,
frank fainting episodes.
02:16
What are the causes?
The cause in cardiogenic syncope
is reduction in blood flow
out of the heart.
02:22
That may be from a
bradyarrhythmia.
02:24
The heart may be slowing down
and there may be less blood,
pumping out of the heart.
02:29
Patients could be suffering
from heart block.
02:31
A blockage of the conduction of
the electricity through the heart,
and then reduced output
cardiac ejection fraction.
02:39
There could be a QTc abnormality,
and many of those things
will be discovered on an EKG.
02:45
So when we evaluate patients,
we evaluate cardiac conduction
problems and ejection fraction.
02:51
We do that with
an electrocardiogram.
02:54
Sometimes with prolonged
ECG or EKG recording
with a holter monitor
or other measures
to prolong monitor
the heart.
03:03
And transthoracic echocardiography.
03:06
With cardiogenic syncope,
the problem is reduced blood flow
out of the heart
because of reduction in the speed
of the pumping of the heart
or the amount of blood
that is pumped out.
03:15
And so we evaluate those things with
EKG prolonged monitoring and TTE.
03:23
What about for problems that arise
from the major blood vessels?
The aorta and carotid arteries.
03:28
Syncope arising from
the major blood vessels.
03:33
Well, again, the final result
is cerebral hypoperfusion.
03:36
Any problem that reduces blood flow
up to the brain
will present with syncope.
03:42
The patients in this case
also describe
either presyncope or syncope,
just like with cardiogenic syncope.
03:49
But the causes are different.
03:51
Here we look for aortic stenosis
or blockage of blood flow
out of the heart.
03:56
Proximal aortic lesions
like coarctation of the aorta
which can be associated with
a number of
connective tissue diseases
or neurofibromatosis.
04:05
And bilateral carotid disease.
04:07
Unilateral carotid stenosis is
insufficient to generate syncope.
04:12
There's plenty of blood flow going
through the opposite carotid,
but bilateral carotid stenosis can
present with presyncope or syncope.
04:20
That's very uncommon,
but is something to be aware of.
04:24
So how do we evaluate
these patients?
Well, we look
at each of these areas.
04:28
Carotid artery ultrasound
is important
for evaluating carotid stenosis
and again, we're looking for
bilateral carotid disease.
04:35
We do vertebrobasilar imaging
either with ultrasound
or a CTA, angiography of the
head and neck, or even chest
to evaluate the proximal aorta,
and the carotid
and vertebral arteries.
04:48
And then,
transthoracic echocardiography
is typically the first line test
for evaluating aortic stenosis.
04:54
So again, problems with
blockage of blood flow
through the major blood vessels
the aorta, or the
vertebral arteries,
or carotid arteries
can present with syncope.
05:05
We see those descriptions
from patients
and we'll evaluate that
on exam and diagnostic testing.
05:13
And then the last category are
problems with vascular tone.
05:16
And this is coined
neurally mediated syncope.
05:19
This is the most
complex category of conditions
that cause syncope.
05:23
And so we'll spend
the most time talking about
neurally mediated syncope.