How many times have you seen it? You are watching a dramatic scene that takes place in a hospital’s operating room or emergency room. The slow, steady beep of the EKG abruptly changes to a long, ominous monotone. A nurse calls out, “He’s flatlining!”
Just in the nick of time, a doctor arrives on the scene. He calls for the paddles to be charged and yells, “Clear!” The patient’s body convulses as a powerful burst of electricity rips through his body. You know that it’s going to take more than one zap of the paddles, but you’re also reasonably confident that the doctor’s efforts will pay off. Sooner or later, the persistent drone from the heart monitor gives way to a tentative beep. It is followed by more. Everyone lets out a big sigh of relief, grateful that yet another patient has been brought back from the dead by the electrical paddles.
This happens so often on television that you may not have considered how often it occurs in real life. The answer, surprisingly, is not at all.
To understand why reality is so much at odds with Hollywood, we need to understand a few basic things about the heart. The key thing that keeps it pumping away is the Sinoatrial node (SA node). It is a collection of naturally-developed pacemaker cells. They generate an electrical differential in the charge between the inside and outside of the cells. They send regular “shocks” through the cardiac muscle of the heart, causing the heart to contract and release.
The SA node works its magic with electrolytes. Essential nutrients such as calcium, potassium, and sodium have electrical charges. The body makes ingenious use of electrolytes charges. Potassium is typically found inside cells before contraction. Calcium and sodium are on the outside of the cell. Your blood pressure forces the calcium inside your cells, generating electrical potential in the process. Once the potential gets high enough, your body opens calcium channels to regulate the voltage. Once these channels are opened, sodium and calcium rush inside the cell, triggering a precisely-measured electrical charge. The fancy name for this charge is “depolarization.” The less fancy name is a “shock” or “heartbeat.”
When your heart stops beating, the medical term is “asystole.” This simply means the heart is no longer contracting. It would make sense, therefore, that the solution to this would be to give it a jumpstart with a good dose of external electricity, right?
The problem with this attempt — aside from being pointless — is that it misunderstands the role of electrolytes in the heartbeat process. In normal heart contraction, the SA node shocks the atria chambers of the heart. That shock then goes to the Atrioventricular node (AV node), where it assists the bottom part of the heart in receiving blood from the top. From the AV node, the charge passes down to the bundle of His (it has the same name in females, by the way) before going down the two pathways called the right and left bundle branches. From there, the charge goes to the rest of the ventricles through Purkinje fibers. All of this takes no longer than a heartbeat — precisely because that is what causes a heartbeat. This elaborate process is what shows up on an EKG screen.
A cardiac arrest occurs when the heart abruptly stops. The most common thing that goes wrong is when the SA node fails to trigger a beat, cells throughout the heart attempt to compensate by marching to the beat of a different drummer. In reality, these individual cells try to create their own beat. The result is that the heart gets shocked from multiple places at the same time. It is as if the heart is having an epileptic seizure. This phenomenon is known as ventricular fibrillation.
This qualifies as cardiac arrest, but it does not result in “flatlining.” Since there are electrical impulses taking place in the heart, those impulses show up on an EKG. They show the signs of a heart in extreme distress, but they are there nonetheless.
In a situation such as ventricular fibrillation, shocking the heart has some value. Since the different areas of the heart are not cooperating with each other, a strong electrical charge might fix the problem. When the heart is zapped, all of the electrolytes are forced out of all of the cells simultaneously. Once this happens, hopefully, the proper electrolytes will re-enter the cells the way they are supposed to, thus triggering the resumption of a healthy heartbeat.
What is happening when the patient flatlines? In that situation, the heart has gone into asystole. There is no electrical activity in the heart that the EKG is able to detect. That’s what triggers the long, flat line on the monitor and the ominous monotone alarm. Chemically, this means that there are no electrolytes in the cells.
Since there are no electrolytes in the cells and the purpose of shocking the heart is to force electrolytes out of the cells, shocking an asystole heart doesn’t accomplish anything helpful. Unless, of course, your objective is to cook the person’s heart. If that’s the case, then crank up the voltage. In terms of restoring a life-giving beat, the shocking truth is that shocking will do nothing.
The best way to restart a heart that has stopped is with CPR and an assist with an electrical charge. This assumes, of course, that the heart is in ventricular fibrillation. If someone collapses in front of you, it’s unlikely that you will know whether he or she is in asystole or something that is treatable. That being the case, you should perform CPR and make use of a defibrillator, if one is available.
The next time you see doctors on television valiantly work to restore a flatlined patient to life, rest assured that the only flatline that will be affected is the show’s ratings.
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Categories: Biology, Debunked Legends, Health, Human body, Science
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