In most popular medical dramas, when a patient has a cardiac arrest and "flatlines" the doctors many times use a defibrillator to "shock the heart back into rhythm'. I know that actually, the proper protocol is CPR and epinephrine (if possible), and that you should shock rhythms such as ventricular fibrillation. But why doesn't shocking the heart in asystole help?

If anyone could please explain, that'd be great.


In layman's terms: an Asystole is not affected by the electric shocks of a defibrillator. A defibrillator is used when the heart goes in fibrillations because it actually CAUSES an asystole. The idea is that you basically reset the heart to a blank state so you can start normal CPR procedure to help the heart go back to a normal rythm. That's why you see them applying CPR between shocks.



http://en.wikipedia.org/wiki/Defibrillation#In_popular_culture (citation needed)


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    $\begingroup$ Would you please provide a reference or two to support your answer? $\endgroup$ – Michael S Taylor Sep 11 '14 at 13:27
  • $\begingroup$ @MikeTaylor I added a few references. While I cannot find an obvious reference for the "causes asystole" bit, I think that the calsprogram link might have it in a linked page. $\endgroup$ – Nzall Sep 11 '14 at 14:16
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    $\begingroup$ @GeorgeDaccache Please note: I have ZERO medical experience or knowledge about defibrillators. All this info was found in 5 minutes of googling. I really suggest you try doing this research yourself next time. It'll be faster that way. $\endgroup$ – Nzall Sep 11 '14 at 20:34
  • $\begingroup$ CPR doesn't put the heart back in normal rhythm. That's an electrical phenomenon initiated by pacemaker cells in the SA node (which I agree can be allowed to function normally by means of defibrillating VT/VF but not asystole). CPR merely provides a semblance of circulation mechanically while the heart is not doing so intrinsically due to whatever arrhythmia. $\endgroup$ – Susan Sep 12 '14 at 22:20

The heart has nerve cells which are supposed to fire synchronously. This is what allows the heart to pump effectively. Fibrillation is when nerve cells (or the cardiac cells themselves, which have some "pacemaker" activity) are firing asynchronously, which means blood isn't getting pumped.

The shock causes all of the units to fire at once (which isn't exactly asystole), in the hopes that when electrical activity resumes (after giving a shock, we wait and look at the monitor to see if there is a regular heart beat, we do not start CPR unless there is not), it will do so in an orderly, synchronous manner.

In asystole (flat line), there is no longer any effective electrical activity of the heart. There is basically no disorganized electrical activity to try to reset with a shock.

That is why it makes no sense to shock someone in asystole. On television, people in flatline are shocked into a stable sinus rhythm. That just doesn't happen in real life. Neither does a deep breath and fluttering open of eyelids, as often shown on television when someone arrests and resuscitation is successful.

Asystole @ Medscape.com
Treatment of Asystole @ Medscape.com


Defibrillators are used to correct certain cardiac arrhythmias (heart is beating out of rhythm) like fibrillation - hence the name defibrillator.

It basically shocks the heart to make it stop beating completely, and hoping that when it starts beating again the arrhythmia will be corrected. It is kind of like "turning it off and turning it on again" to solve a computer problem.

When you're asystole, shocking it will do nothing because the problem lies elsewhere. It would be like trying to reset a computer when you have no power.

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    $\begingroup$ @VanceLAlbaugh - The request for references if fine. If you think the answer is too simplified, write your own. The answer - though it's an analogy - is basically correct. In fact, the more I think about it, the more I would like to see your answer. $\endgroup$ – anongoodnurse Dec 8 '15 at 18:13

When the heart is in "ASYSTOLE" mode and you visualize a straight horizontal line on the screen it means there is no electrical signal passing through the ventricle which is the discharging chamber contracting to pump blood from the left side to systemic circulation. "SYSTOLE" means contracting. "ASYSTOLE" means not contracting. There is no activity in the ventricle to fix so no point shocking the heart when there is no power on that is in "ASYSTOLIC" mode but when you visualize an so abnormal rythm such as seen in VF or in V-Fib then you shock the heart to jumpstart it back to a normal rythm.

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    $\begingroup$ Hi Welcome to Bio.SE! We ask that answers provide sources to back up their claims. Anecdotal info or info "based on experience" alone is great, but without further sources (preferably reputable sources) they belong as a comment. Please see here for a guide to writing good answers in this community. Thanks! $\endgroup$ – theforestecologist Mar 13 '17 at 17:14

if electric bulb is blinkking ,u can reset it as power is on .but if power off then useless to reset the bulb.so in asystole electrical activities are off ,no utility of resetting the electrical activities of heart as no electrical activities are present in heart.

  • $\begingroup$ Welcome to Biology.SE! It isn't clear that this adds anything to the existing answers. In addition, answers are much more likely to receive a favorable response if you include supporting references (primary literature is best). Without that support, your answer is indistinguishable from opinion. ——— Please take the tour and then consult the help pages for additional advice on How to Answer effectively on this site and then edit your answer accordingly. Thanks! 😊 $\endgroup$ – tyersome Dec 23 '19 at 20:14

I found this in a "Science Daily" article: Defibrillation is a medical technique used to counter the onset of ventricular fibrillation, (VF) a common cause of cardiac arrest, and pulseless ventricular tachycardia, which sometimes precedes ventricular fibrillation but can be just as dangerous on its own.

Defibrillation is a technique used in emergency medicine to terminate ventricular fibrillation or pulseless ventricular tachycardia.

It uses an electrical shock to reset the electrical state of the heart so that it may beat to a rhythm controlled by its own natural pacemaker cells.

It is not effective for asystole (complete cessation of cardiac activity, more commonly known as "flatline") and pulseless electrical activity (PEA).

The purpose of defibrillation of ventricular arrhythmias is to apply a controlled electrical shock to the heart, which leads to depolarization of the entire electrical conduction system of the heart.

When the heart repolarizes, the normal electrical conduction may assert itself, in which case the ventricular arrhythmia is terminated.

However, if not enough energy is used for defibrillation, the heart may not be completely depolarized, in which case the ventricular tachycardia or fibrillation may not be terminated.

Also, if the heart itself is not getting enough oxygen or if there is an instability of the electrolytes in the cardiac cells, the ventricular arrhythmia may recur.

Note: The above text is excerpted from the Wikipedia article "Defibrillation", which has been released under the GNU Free Documentation License.


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