Common Causes of Sudden Cardiac Arrest

Cardiac arrest is a medical term that some may find difficult to understand. On the surface, it's very easy: "Cardiac" means "heart" and "arrest" means "to stop." Any time you see the term "arrest" paired up with a body system, it refers to that system ceasing its function. For example, respiratory arrest means the same thing as "not breathing."

Since cardiac arrest is the same as clinical death, looking for causes of cardiac arrest is a little bit like looking for causes of why the car broke down—it's a really large list.

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Sudden Stops

To keep things manageable, we're going to focus on sudden cardiac arrest. Below are the most common causes of sudden cardiac arrest. Each cause includes at least one example.

Regardless of the cause of sudden cardiac arrest, CPR is the first treatment and remains the gold standard. Whether you are a little league coach or a brain surgeon, CPR is performed the same way.

Cardiac Arrhythmia

By far, the most common cause of cardiac arrest—especially sudden cardiac arrest—is an arrhythmia. A cardiac arrhythmia is a problem in the heart's electrical communication system, the system responsible for making the heart beat regularly at the right rate. Of all the causes of cardiac arrest, this is the one most likely to actually cause the heart to stop.

Asystole is the medical term for the cardiac arrhythmia most people know best—the flat line on an electrocardiogram (it even had its own movie). Ventricular fibrillation is the arrhythmia most often responsible for sudden cardiac arrest and is one of the most treatable if quickly corrected.

Bleeding and Shock

Shock is a complicated medical condition with several causes. A simplified version is basically to say shock is really low blood pressure. If the blood pressure gets too low, there won't be a pulse or enough blood flowing to the brain to keep the victim alive.

Electrolyte Imbalances

Electrolytes are important for body chemistry to function correctly. Calcium, sodium, and potassium are the most important electrolytes.

Calcium and potassium have to be in balance—sitting on either side of cell membranes, ready to switch places—in order to cause muscles to contract or nerves to transmit impulses. Once calcium and potassium swap places and cause things to happen, sodium puts them back in their place for the next time.

If there aren't enough of one or two or all of these electrolytes, then the heart muscle cells can't move, which means the heart won't pump. Heat illness patients (heat exhaustion or heat stroke), kidney failure patients, and people on certain types of medications are prone to electrolyte imbalances.

Cardiac Arrest in Kids

Kids don't suffer sudden cardiac arrest as often as adults, and when they do, it is usually due to a structural problem with the heart, such as hypertrophic cardiomyopathy. Very rarely, cardiac arrest caused by ventricular fibrillation induced by a fairly soft strike to the chest occurs in children; this is called commotio cordis. In most cases, it comes from a baseball hitting the chest.

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