So, how do we manage these various types of tachycardia?
Well, atrial tachycardia is typically less dangerous
because the ventricles are still firing okay probably,
it's just the atria that aren't doing right.
What we'd like to do is slow the rate at which the electrical signals
can get from the atria into the ventricles.
A good drug for that is beta-blockers.
We'll put these children on beta-blockers so that while there may be some atrial tachycardia,
there will not be ventricular tachycardia,
which is going to significantly interfere with maintaining our blood pressure.
We often might use digoxin or flecainide or any of these drugs
to control, again, that risk of ventricular tachycardia.
For reentrant tachycardias, we're going to treat the patient differently
depending on whether they are stable or unstable.
Let me give you an example.
A child comes in who is two years old
and has a heart rate of 220 and it's been like that for a week.
This is an example of a child with a stable reentrant tachycardia.
Let's say this child has WPW or Wolff-Parkinson-White syndrome.
The way we're gonna reverse this is through a dose of adenosine.
Now, remember this. This is high impact right here for your test.
Adenosine is a short-acting drug. It's gone in about six seconds.
The way we're gonna give this drug is we're gonna place a decubital IV
with a stopcock three ways: we're gonna push the adenosine,
quickly flip it, and push a saline flush.
Now we're gonna watch the heart rate.
What you'll see is the child's very fast heart rate is going to flat-line.
This child will have no heartbeat at all for probably six seconds.
And then we hope it will restart appropriately.
Cardiologists are very, very grateful if you can capture this on the EKG
while you do it, because it will help them understand exactly which way
the reentrant tachycardia was going
which may help them with a cure later on down the line.
But if a patient is unstable, if they are sick, if they have hypotension,
it's going to be very hard to take the time to set up all this stuff
and get the stopcock and get the decubital IV.
In this case we're going to do synchronized cardioversion.
Remember, this is different than un-synchronized.
Un-synchronized is how you shock out V-tach or V-fib;
this is synchronized to the heartbeat, so you have to apply the paddles
and then wait for the machine to find the rhythm and it's gonna synchronize it
at the right time during the cycle so it can stop that reentrants.
For V-tach and V-fib, which are life-threatening tachyarrhythmias,
we're gonna treat them again differently depending on whether the patient is stable or unstable.
If the patient is stable with V-tach which is unusual,
they'll be treated with lidocaine or amiodarone.
Some of these patients have a few rapid beats and then pop out of it.
If they have V-tach with pulsus, we're going to do synchronized cardioversion.
And if they have V-fib or pulseless V-tach, that's when we do
regular old defibrillation -- shock, shock, shock, epi, shock,
et cetera down the line like you learn in adults.
So, you can prevent tachyarrhythmias in children but only in a certain population.
There are some children who have a unique problem of a prolonged QT.
You can see on this drawing of an EKG an example of a child with prolonged QT.
The distance between the Q wave and the end of the T wave is too long.
So, when you look at this, you find a QTC and that should generally be less than 450.
In patients with a prolonged QT at baseline, they may have a syndrome that's causing that.
There are two relatively well-known prolonged QT syndromes that are genetic.
One is called Romano-Ward and that's the most common one,
and another one that's less common which is called Jervell Lange-Nielsen.
That one's interesting because it also comes with deafness in the family.
If you have a patient with a prolonged QT syndrome,
we generally will put them on a controlling medication so that they won't then get
a tachyarrhythmia, something like propranolol.
So, in summary let's go over things we want to make sure we remember from this lecture.
Remember the four types of heart block:
First degree, second degree and there's two types, and then third degree heart block.
Remember that the congenital heart block from maternal lupus is severe
it's usually a third degree heart block, these infants are paced for life.
WPW is a common cause of reentrant tachycardia and that's where you see that delta wave.
And lastly, there are some genetic causes I mentioned too of prolonged QT syndrome.
Patients with prolonged QT need to be on lifelong medication
to prevent them from going into V-tach or V-fib.