Tv and movies show them as a magical heart restart machine, bringing people back from the dead. But I’ve heard medical professionals say that’s not true, but they never elaborate. I’ve seen portable ones everywhere, so they must be needed fairly regularly.
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Heart defibrillators are used to treat life-threatening cardiac arrhythmias, such as ventricular fibrillation and ventricular tachycardia, which can lead to sudden cardiac arrest. They deliver an electric shock to the heart to restore a normal rhythm. Automated External Defibrillators (AEDs) are commonly used by bystanders or medical professionals when a person’s heart rhythm becomes irregular or stops, and immediate intervention is necessary to increase the chances of survival.
They are the medical equivalent of [this classic scene.](https://www.youtube.com/watch?v=d1Cpc8Vw-2A)
Sometimes, for various reasons, the heart freaks out and beats frantically like a newborn horse trying to run. This means a chamber might be squeezing before it has enough blood in it, or not squeezing at all, meaning blood is flowing erratically, if at all. This is just really bad and will usually kill you.
A heart defibrillator basically *slaps* the heart with a bolt of electricity and then the heart reboots like a computer, hopefully back to normal.
The implication is that the heart is *still beating* in the first place, just beating wrong. If the heart is fully stopped the electricity isn’t to magically make it start beating again. There are other techniques that can help with that, such as CPR, but the AED is for making the heart beat normally, not restart it.
In simple terms the heart is made up of several muscles. These have to contract in a specific order to pump blood properly. One muscle compresses while the other relaxes and vice versa. This requires the muscles to be in rhythm with each other. If they get out of rhythm for whatever reason the heart does not work. This is when the defibrillator might be used. You shock the heart to stop it and hope that when it starts up again by itself it will be in rhythm again.
They are not needed very often though. But when they are needed it is very time critical, the heart is not pumping blood. This is most commonly due to a heart attack. Even waiting for an ambulance takes too long. Cheats compressions may help but are not as good as fixing the problem with the heart at once. The portable defibrillators you see are an easy way to provide this first aid as soon as the heart attack takes place.
They’re used when the heart goes into fibrillation, which causes cardiac arrest – the heart is twitching uncontrollably out of rhythm. You’ve still got a heart-beat, but it’s completely ineffective and your brain will run out of oxygen real fast. The defibrillator shocks it back into normal rhythm.
They are NOT used when someone has a heart attack, and their heart is flat-lining, contrary to what you’ll see on TV.
The purpose of a heart defibrillator is to stop a heart. Doing so, the heart’s natural pacemaker can take over and make the heart beat in a regular way.
Also, there’s a time limit. If a AED is used in the first 3 minutes of whatever is going on, there’s a 70% chance of survival. At 10 minutes, it’s 10% with likely irreversible brain trauma from lack of oxygen being pumped to the brain.
The survival rate drops by about 7–10% for every minute it takes to get a AED to that person.
Note: this is why you see them everywhere, as well.
the heart normally beats in what’s called a sinus rhythm. this is the usual thump-thump you’ll hear if you listen to a normal heart. sometimes the heart freaks out and beats in an erratic rhythm… the defibrillator literally shocks the heart in the hopes that it will start to beat normally again. if the heart is not beating, shocking does nothing.
if you recall (or have seen in movies) old TVs, usually, they work fine, but sometimes the picture goes wavy, or staticy, or starts doing weird things, and someone goes up and give the tv a solid WHACK on the side and now the picture is back to normal… that’s basically what’s going on. whacking a TV that isn’t turned on won’t magically make the picture appear…it has to be at least on.
Cardiac ICU nurse here :
I thik you mean ICD (implanted cardioverter=defibrillator)
They are put in in people who have quite weak hearts (heart function less than 35% [normal is 60%] ) who are at risk of a lethal abnormal heart rhythm so that if the rhythm occurs people dont die or atleast suffer as much. The heart has to be remain weak despite doctors trying to improve it with medcines /surgery/ procedures / etc.
They are put in as an after thought for people who have had their heart stop due to a wierd heart rhythm (not a heart attack) after coming to hospital with evidence of it occurring ( this is called secondary prevention).
They are put in people who have genetic heart shape problems and are at higher risk for lethal heart rhythm abnormalities. ARVD, channel-ion pathologies.congential heart defects etc.
They only work of the person has hearth rhythm that can be reset by shocking. The heart.uscle still has to be able to move. The heart is moving in a very dangerous way that doesnt push blood out the heart. So even though the heart is beating there is no or barely any blood coming out the heart.
We say we can bring people back from the dead with them because if the heart is in these abnormal rhythms… death is very likely to occur in the next 5minutes and the person should be unconscious.
The portable ones are every because THE single most important predicator to surviving a lethal heart attack or event like this is how quickly a person can get shocked.
Basically, CPR is used to restart the heart if it stops, but the beats might be erratic, the defib will restart the heart if its already beating, hopefully back in a good rhythm
Several reasons!
Some background, the heart’s job is to basically contract in specific places at specific times to squeeze blood through your arteries to get oxygen to all your organs and cells. To coordinate this specific type of movement, ie a heartbeat, an electrical signal originates in one part of the heart and travels to other parts of the heart via a specific pathway, allowing everything to contract precisely when it’s supposed to.
Sometimes for whatever reason that electrical pathway can get messed up and instead of a single coordinated signal, you get multiple electrical impulses firing off when they’re not supposed to, which in turn causes parts of the heart to contract when they’re not supposed to, which leads to blood not getting squeezed forward to your organs (including your brain, which is why people in this situation will often feel lightheaded/pass out).
In the cases of two specific abnormal rhythms – called ventricular fibrillation and pulseless ventricular tachycardia – delivering a big electrical shock basically “resets” the heart – essentially, all the ions needed to create an electrical current are temporarily depleted all at once, giving a window for the natural automatic electrical signaling intrinsic to the heart to jump in and get everything coordinated again.
This means that defibrillators don’t work like in the movies for several reasons:
They won’t work if you have zero electrical activity going on (asystole or pulseless electrical activity).
They won’t work if you don’t have one of the specific two rhythms above, eg you have an atrial tachycardia instead of ventricular, you have a pulse, you are in sinus rhythm, etc.
Most importantly, movies usually show a person getting shocked and recovering immediately without any issues, but in real life many people who end up in situations where they need a defibrillator are very, very sick already – they have significant cardiac disease already or are having a massive heart attack, their electrolytes are all wacky, something else was wrong with their heart’s electrical system already, etc. And that’s not even going into the potential consequences of your brain being deprived of oxygen for a long time. Movies never seem to show the many months of rehab a patient might have to undergo after getting defibrillated, or the family gathered at the bedside being told that their loved one’s brain has suffered massive injury and they are unlikely to ever make a significant recovery.
So I guess TL;DR: you can only defibrillate in very specific circumstances, and defibrillation does not equal 100% recovery to baseline?
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