Now, we're gonna talk about the second part of cardiac arrest or advanced life support.
So, there are three major cardiac arrest rhythms that we need to be aware of.
Ventricular fibrillation and ventricular tachycardia,
pulseless electrical activity, and asystole,
and we're gonna talk in some detail about each of those three
identifying some of the key similarities and differences between them.
Let's start off with V-Fib and V-Tach.
So, these rhythms both represent disorganized electrical conduction
which originates in the ventricles.
There's a number of different causes for a ventricular fibrillation and tachycardia
but they're most strongly associated with primary heart disease
in particular coronary ischemia, so, myocardial infarctions, etc.
However, you can also see V-Fib and V-Tach in the setting of structural heart disease,
inherited channelopathies, and other clinical situations.
Least commonly, you see V-Fib and V-Tach with systemic metabolic derangements
things like electrolyte disturbances, autoimmunity, toxic ingestions
but that's really quite rare.
The vast majority of these are caused by heart attacks.
So, here's just a review on ventricular fibrillation like we said in the last lecture,
this is one of our two shockable rhythms.
So, this is randomly fluctuating, completely disorganized electrical activity,
no pattern, no QRS complexes, the heart is literally just going,
"blblblblbl" in the chest,
it's not actually beating.
Meaning, that there's no cardiac output whatsoever
associated with this because the heart's not contracting.
This rhythm, if it’s not terminated, is completely incompatible with life.
By contrast, here's V-Tach.
So, we mentioned this in the prior lecture as well
but V-Tach is organized, it's just bizarre.
So, these QRS complexes are big and tall and wide
but they are organized and they are regular.
Now, you wanna think about V-Tach anytime you see tachycardia.
Meaning, a heart rate of greater than a hundred
most commonly greater than 150,
that means your QRS complexes are gonna be coming along
more than every 3 millimeters on your tracing
or more than every 2 millimeters in the case of a heart rate of 150.
In this case again, the QRS is wide,
so, it's got to actually be wider than 3 millimeters to be considered V-Tach,
but usually it's pretty obvious, these are a big, wide, very strange looking complexes.
And patients in V-Tach, can be completely pulseless, apneic, and dead.
They can be completely stable and in some cases, asymptomatic,
or they can be anywhere in between.
So, the important thing with V-Tach
is when we talk about it in the context of cardiac arrest,
we're talking specifically about pulseless V-Tach,
meaning we don't wanna treat V-Tach in a patient with a pulse
especially a stable patient the same way as we would in a pulseless patient.
Clearly, a stable conscious patient is gonna hate if we start CPR on them.
Alright, so single most important intervention for V-Fib and V-Tach,
we eluded to this before but I wanna emphasize again, it is to defibrillate.
Now, the great thing about defibrillation is this is such an important intervention.
We've started putting defibrillators in public places all over the world.
So, you can now find defibrillators in shopping malls, at sports stadiums,
in the back seats of police cars,
all kinds of places around the world where first responders
can access them easily and use them quickly to save lives when needed.
So, we're gonna go through the V-Fib and V-Tach algorithm now in some detail.
So, first and foremost, when you have a cardiac arrest,
you gonna wanna get help right away, and you're gonna wanna initiate CPR,
the highest quality CPR you can possibly manage.
Next priority is to get your hands on a defibrillator as quickly as you can
and to administer a shock for V-Fib or V-Tach.
We don't shock other rhythms but for these rhythms, electricity is key.
Your next maneuver, is gonna be to continue CPR for five cycles or 2 minutes
before you perform another rhythm check.
At that point, if you're still in a shockable rhythm,
you're going to administer yet another shock,
and this is also when you're gonna give a vasopressor drug, like epinephrine.
After that, we're gonna continue CPR for another 5 cycles or 2 minutes
where once again we check the rhythm,
we defibrillate if we're still in a shockable rhythm,
and now we're gonna think about use of antiarrhythmic drugs, in particular amiodarone.