Now, what happens if you don't get
that conduction past the AV node?
Remember, Purkinje fibers can beat on their own.
They beat very slow, though, right?
30 to 40 beats per minute.
That’s a slow, slow beat.
But if you don't get enough information,
they will take over and beat anyway.
And these generate ectopic foci,
a place in the ventricle,
I didn't get enough information,
I don't know when I should beat,
I'm just going to beat anyway,
you can't stop,
because, you know, why not?
That's what happens.
They take over their heart rate
and they will beat on their own
if they don't get enough signal.
So, unless you get SA node,
AV node signals down the ventricular myocytes
and the Purkinje fibers will take over beating.
This causes havoc.
It makes the QRS complex very wide
and creates a process called a
premature ventricular complex.
And these PVCs are seen very
often in electrocardiogram.
And the reason why they happen is because
the Purkinje fibers did not get signal
from the SA node or the AV node.
You might ask, at this point,
well, why don't they beat on their own anyway?
I mean, because, you know,
they have that intrinsic rhythm,
30 to 40 beats.
The reason why they normally
don't take over beating
is because every time an
action potential comes through,
it resets the clock.
So, if you have something like a sinoatrial node
that beats 60 to 100 times per minute,
it's going to reset the clock of
the AV node and Purkinje fibers
every time it happens.
So, you'd have to have a block in the system
for those other pacemaker cells to take over.