So if a heart stops you can massage, pump or shock it back to life, and surgeons even stop a heart on purpose before firing it back up, so why can’t they do that 100 percent of the time? What is it that makes a heart stop and never come back? If the brain is working then surely the heart should always come back?
In: Biology
# So many wrong answers, some clarifications:
1. **Heart massage will NOT restart a heart ever!** All its does is keep enough blood flowing so your brain survives until hopefully someone comes around and fixes the actual issue. Thats why the first step of CPR is to call for an ambulance. If you dont do that all the pumping is useless to begin with. (You will actually fail your CPR-class if you dont specificly state that you call for help before you start pumping)
2. **A stopped heart (flatline) is NOT a shockable rythm.** The sole puropse of a defibrillator IS to stop the heart! It can happen that the heart gets scrambled up in its rythm and starts to just twitching around and not pumping anything effectivly. In THIS case you use the defibrillator to stop the heart completely so it can start back up properly on its own.
**And this is your answer:** It doesn’t work 100% of the time, because a defibrillator only fixes certain issues and also requires the heart to start back up on its own. If it can’t, your body will die soon, since heart massage can only keep your body alive for so long.
>so why can’t they do that 100 percent of the time?
So this is really answered by your second question.
>What is it that makes a heart stop and never come back?
Lots of different things. Very very different things that range from a sudden electric shock, to an imbalance of salt in your blood, to physical pressure on it, to tissue death.
>If the brain is working then surely the heart should always come back?
Unfortunately no. The heart is surprisingly independent from the brain but even if it wasn’t some things just break the heart. If the muscle tissue dies electrical impulses from your nervous system can’t make the muscle move, it’s dead.
Another very important thing to understand is that a “stopped” heart isn’t always literally stopped. People will often say a heart is stopped because you have no pulse but believe it or not your heard can be going when you have no pulse. I hope you can understand why there might be a mixup with that term in such situations.
In that case your heart might be quivering, trying to beat so fast it doesn’t have time to fully squeeze shut (and thus pump blood anywhere) that is generally known as fibrillation. In that case you get the classic movie situation you might be thinking of where you shock it and the person is suddenly fine. This is closer to pressing reset on the electrical activity.
But this all goes back to your more important question of “what is it that makes the heart stop”. The cause needs to be resolved or the shocks at best only temporarily fix it or at worse do nothing (or make the situation worse).
If you have an imbalance of salts that your body uses to conduct nerve impulses shocking the heart back to “normal” isn’t going to help because the original cause hasn’t been addressed.
In the case of a myocardial infarction (heart attack) your heart stopping will be caused by damage/death of the heart tissue itself. If doctors fix the issue quick enough they can prevent death or limit how much of the heart dies, if they catch it too late shocking dead tissue won’t make that tissue work.
If the heart is stopped because there is physical pressure on it (blood filling the sack around your heart is one cause here) the heart is physically prevented from beating and re-starting it doesn’t address that cause.
And ALL of these issues require timely resolutions because your heart muscle itself never rests and is *very* sensitive to not having blood flow. Why restarting works sometimes and not other times is often a question of time, time until too much damage has been done.
TLDR: different reasons for heart stopping must be fixed in different ways, and all those issues are on a strict clock before permanent damage to the heart muscle kills the cells… because we can’t revive those cells yet.
Warning: the following text is not suitable for actual 5 year olds. I’m discussing life/death/CPR on the emotional level of an adult.
If a heart stops, it’s done and there is (currently) no way to get it restarted and the patient will die within minutes. In some cases a heart transplant might save them, but there is no way to live with the original heart.
However, what we often *call* a stopped heart, like in a heart attack, is not literally a stopped heart. The heart is still beating, but in a messed up rhythm, so not enough blood is pumped around. Like a factory worker that’s dancing instead of moving packages from left to right. Shocking the heart can work to change the rhythm back to a normal rhythm.
Massaging/pumping as in CPR does nothing to help or change the heart’s rhythm. What you’re doing is basically emptying the heart (when you push down), and refilling it (when you let go). That way you make the blood circulate through the body, artificially. The person doing CPR is doing the pumping, not the heart. This helps moving oxygen to the rest of the body, most importantly the brain, so there’s less damage by lack of oxygen after the heart gets shocked back into a normal rhythm.
Lmk if you need an ELI4 version of this!
To add on, the heart is also an organ made of cells that require oxygen. Using electrical stimulation with a defibrillator can help if the normal electrical rhythm of the heart is disrupted, but if the cells themselves die (for example, excessive plaque buildup or formation of scar tissue) it’s not going to help.
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