Defibrillation

Let’s talk about what happens when you defibrillate a heart.

In plain language, the idea is to stop someone’s heart from beating for a moment. The hope is that it starts back up again, but without the issues it was having. These issues are normally based on an irregular rhythm, which means blood can’t pump in everywhere as quickly as it needs to.

In turn, that means that oxygen can’t get to your brain (and other areas of your body). You need that oxygen for energy, and you need energy even to think. If the blood stops going to your brain, it can be lights out for good.

Defibrillation—the word—breaks down into Latin and Greek roots (shocker, right?!?). The Latin prefix de- is common in English today, and we use it to mean undoing or removing something. Fibrillation comes from the Latin word “fibra” (fiber), so adding the Greek suffix -ation at the end indicates that the fibers are in the middle of some kind of action.

The fibers in question here are muscle fibers in your heart.

When they aren’t twitching in unison, they’re fibrillating, and your heart is beating chaotically. Defibrillating, therefore, undoes this chaotic beating (hopefully). But how and why should shocking the heart and stopping it work in the first place? Is this just one of those cases of tough love?

To understand this, we need to understand how a heart operates under healthy conditions. When blood pumps through your body, your central organ doesn’t just arbitrarily keep a beat because it just heard something it liked on the radio. Instead, there are carefully coordinated pulses of energy in command of your blood.

This all starts with spontaneous sync, the same sort of phenomenon you see when you put metronomes or pendulum clocks in the same room and start them ticking. Eventually, they’ll all sync up and beat in unison.

Muscle cells in your heart are subject to this same phenomenon, only instead of a little nudge from the pendulum that’s nudging each of those devices ever closer to sync with every tick, it’s an electrical signal. There’s a specific part of your heart called the SA node (sinoatrial node if you’re nasty) that acts like the body’s metronome, setting the beat for the rest of the cells to follow.

Sodium ions slowly creep into the cells of the SA node. Each of these ions carries a faint electrical charge, so nothing much happens whenever one of them enters. However, as soon as you hit a critical mass, there is a sudden reversal of polarity that causes the muscles to contract all at once, and that’s what causes your heart to beat.

Stopping the heart with an electrical signal, then, just might be the thing to do if you want everything to work in unison once again.

Do you know anyone who has been through defibrillation? Have you yourself done this? Tell me how it was, and whether I did a good job today!