Not A Heart Attack!

Life support paramedic Simon Andrew explains exercise-induced cardiac arrest, why it happens, and how you can protect yourself.

- Simon Andrew

Not a heart attack?

What is the difference between a sudden cardiac arrest (SCA) and a heart attack?

SCA happens when the heart develops an abnormal rhythm and can't pump blood. A heart attack occurs when blood flow to part of the heart is blocked.

Most heart attacks do not lead to sudden cardiac arrest, though a small percentage of people with heart attack will develop sudden cardiac arrest. But when sudden cardiac arrest occurs, heart attack is a common cause.

Here is an article showing how trail runner Philip van Wyk experienced a heart attack which did not develop into cardiac arrest.

What are the causes?

The biggest cause of cardiac arrest is any process that lessens oxygen delivery to the heart muscle.

This can be due to the heart beating too fast (not enough time for the heart muscle to receive blood flow). It is important to remember that the heart pumps blood to the all the other organs, and does not get its oxygen from the blood flowing through it. The heart has its own circulation which flows between beats.

Other causes include:

Blockage of the heart's blood supply.

Thickening of the blood, as happens with dehydration.

Loss of red blood cells, for example through severe trauma.

Changes that cause chemical reactions required to keep the body working normally to fall outside of their most efficient range, such as changes in blood acidity (pH) and temperature.

As we exercise, the heart is able to change the rate and volume of blood that can be circulated every minute. Each cell requires oxygen in order to be able to make energy as efficiently as possible (aerobic).