- Hi, I'm Sanjiv.
We're in the Willis Annexe laser lab.
This is PJ.
PJ, do you want to give an introduction of yourself
and what you do here?
- Yeah, sure.
Well, my name's PJ and I'm one of Tracey's post docs
and I'm currently working on this rig over here
which is called the myocardial bridging rig.
- Cool, myocardial bridging, that's, what's that?
- So, myocardial bridging is an inborn condition,
so it's something you're born with
and it's actually quite common as well
it occurs in about 19% of people,
from what a recent study has shown.
And it's basically a condition
wherein the coronary arteries,
which supply blood to the heart, pass through
the heart muscle itself, as opposed to lying
on top of the surface of the heart
which is what would normally be the case.
So, what can result is that every time the heart contracts
it causes the artery to be compressed.
- Yeah.
- Because the artery's surrounded on all sides
by the heart muscle.
- Okay. - Okay.
- So, is that the main motivation,
to save the contraction is doing to the artery, or?
- Yeah, exactly.
So we wanna perform a series of flow visualization
studies using this rig to try and get an understanding
of what's happening to the flow,
because the condition has been linked
with a series of diseases, such as
deprived blood flow to the heart muscle
and also irregular heartbeats as well.
- Right.
- At its worst, in the worst case it's been linked with
sudden cardiac death, as well.
- Okay yeah, intense, yeah.
- So, that's the main motivation.
The other motivation is because it's really difficult
to visualize this stuff in an actual person.
So, the only real option we have to properly see
what happens due to the contraction of the heart muscle
on the arteries is to perform it
in the lab using this in vitro rig.
- Okay, okay.
So yeah, you'd have to on this in vitro rig
which is a very complex system.
Do you want to show us different components and explain?
- Yeah, sure.
So, I may have mentioned earlier that we're interested
in looking at the pressure and flow data within the artery.
- Yes, you did.
- So, one of the things we're using to measure the pressure
is this, it's a pressure wire which was modified by Joseph,
who's one of Jason's PhD students.
And what we can do is we can feed this pressure wire
anywhere though the artery and the artery's
right over there, by the way.
- Yeah.
- And we can measure the pressure both anywhere
upstream and downstream of where the heart muscle
causes the artery to contract.
- I guess, because you see disturbances on both sides,
not only at the-- - Yeah, exactly.
- Okay.
So that's the pressure side, as well.
What's this big arm that you've got?
I guess that's, assuming is what the heart is,
but do you wanna?
- Yeah, so this is designed by Josh,
one of Tracey's previous PhD students
and basically it moves up and down.
I can show you how it works, actually.
- Cool, yeah that'll be--
- So.
- [Sanjiv] Yeah, okay.
- [PJ] So, as you can see it's moving up and down
and causing the artery to compress at the moment.
So this is just replicating what the heart does
to the arteries.
- Okay, that's really cool, yeah.
Sorry, going back the pressure data, it's
pressure where, that's from the clinic?
I've heard of that in the clinic, as well.
- Ah yeah, so this pressure wire was actually taken directly
from the clinical pressure wire.
- Yeah.
- And modified using Joseph's software
so we can use it in the lab.
- Oh, okay, cool.
So you've got software controlling the pressure wire
and, I guess, the rig as well.
- Mm-hmm.
- Okay and you've got the artery sitting in a bath by visor.
- The bath was there so that we can fill the tank up
with glycerol water-- - Yeah.
- Which is used to closely match the refractive index
with the artery that we see clearly here.
- Yeah.
- So this artery's made out of silicone
which is made by mixing these two components over here.
So this is polydimethylsiloxane or PDMS.
So by combining the base with the curing agent
we can get arteries of varying stiffnesses.
- Okay.
- So this one's quite flexible and that was designed
to simulate a healthy artery.
- Okay.
- However, if we want to simulate a more diseased artery
and make it stiffer we just have to add
a bit more curing agent.
- Right, okay.
- So the bath was created so that we can cause
these arteries to disappear, essentially.
So that--
- Why would you want that to happen?
- That's so that we can shine a laser through the tank and--
- Okay.
- So that we can pass some fluorescent particles
through the artery itself.
- Okay.
- And by doing so we can visualize exactly what's happening
to those particles as they're going through the artery,
which is only possible because everything's transparent.
- Right, okay.
And you don't see, there's no contortion
or there's no obstruction?
- Exactly, so the laser just goes straight up
through the artery instead of being distorted.
- Okay, but this definitely is bigger than a normal artery.
I guess you need to scale it up to see more resolution,
but what does that come with?
Like, what does that come with?
You probably need to change the conditions, is that--
- Yeah, that's right.
So, in order to exactly replicate what would happen
in a life-sized artery, which is about
three and a half millimeters in diameter.
- Oh, okay.
- So this one's scaled up four times
so that it's 15 mils in diameter.
- Right.
- And in order to exactly match what's happening
to the fluid dynamics we would have to
make adjustments to the timescale of the,
we have to adjust the period over which the pulses
are generated by our pump.
- Yeah.
- And we also have to adjust the density and viscosity
of the fluid, as well.
- Okay, with Ramsey's number and Reynolds number.
- Yep, that's right.
- Just was getting, yes.
- By matching base two non-dimensional numbers
we can achieve the same flow characteristics.
- Cool.
You mentioned a path so it's not just steady flow?
You're varying the flow as well, is that right?
- That's courtesy of this big pump over here.
- Okay.
- Which is designed by Vince, one of our machinists.
- Right.
- So it's a piston pump and it's capable
of generating physiological flows.
- Okay and it varies the pressure, I guess, as well.
- Yes, that's right.
I can show you what that looks like, now.
- Yeah. - If you want.
- Cool.
- So I'll just set it to okay.
(machine clicks)
- Right, okay .
Let's push it out.
- As you can see, it's causing the pressure to change.
- Yeah, yeah, no.
That's pretty cool, yeah.
So there's another component that has been controlled
electrically, I guess.
So, was this problem given to you from the clinic
or was it the engineers that tried to fix a problem?
- We're actually performing this problem,
we're learning about this problem
in conjunction with Concord Hospital.
- Yeah.
- Who have done extensive research
into myocardial bridging, as well.
- Okay.
- And they've actually supplied us with pressure data
from patients who have this condition.
- Okay.
- And, so they've obtained this data from patients
with mild and severe bridges.
- Right.
- From which we can use to validate our experimental model.
- Okay, okay.
So yeah, actual physiological data for validation.
- Mm-hmm.
- This is a very complex system.
Do you wanna outline some challenges you've faced with this?
- The main challenge which I'm currently trying to overcome
is to try and make sure that all of these components
can work together so that everything's synchronized,
'cause what would happen in the ideal case
is that the pump would be synchronized with the
myocardial bridging rig.
- Yeah.
- As well as the laser so that
we can get the pulses occurring at exactly the right time.
- Okay.
- During the, whilst the bridging takes place.
- Right, okay, yeah.
So like, three components that you need to control,
I guess, with one trigger, I guess, yeah.
- Mm-hmm.
- Oh, that's intense.
Where do you see this research developing into
and forward from here?
- Well, in the short term we'll be using
this experimental model to validate
one of Jessie's computational models.
Jessie's one of Tracey's PhD students.
So she's looking at myocardial bridging
but from a computational point of view.
- Okay.
- But the problem is that we don't really have
any clinical, well, it's not really possible
to obtain the flow data in any decent resolution
in the clinic.
So, that's what we'll be using this rig for
in the short term, to try and validate
Jessie's model and from that she can hopefully create
more complex bridging models with physiological arteries.
- Mm-hmm. - As well.
Right, so yeah.
Very interesting, yeah.
A prevalent condition that you're trying to match up
to the physiological condition to as much as possible
with this complex setup.
Thanks a lot for showing us all these components.
- Yeah, no worries, thanks.