Cardiac arrest - What are the symptoms?

If you have a cardiac arrest, you will black out (become unconscious). If you were standing up, you will fall to the ground. This is because too little blood is getting to your brain and the rest of your body.

Before a cardiac arrest you may:

Feel sick
Feel dizzy
Get pains in your chest
Find it hard to breathe.

To confirm that someone is having a cardiac arrest, a doctor or paramedic will check if they have a pulse. They may also look at the rhythm of their heart using an electrocardiogram (ECG). The ECG shows the electrical activity in the heart as a line on a moving graph or screen. Doctors look at the size, shape and spacing of the line to see what's happening to the heartbeat.[1]

When there is no heartbeat (or pulse), no blood pressure and no electrical activity in the heart, the ECG line is flat. This is called asystole. It usually means that the heart hasn't had any oxygen for some time. But it is still sometimes possible to get a normal heartbeat back. If asystole continues for five to 10 minutes, a person is usually declared dead.

References

Meek S, Morris F. ABC of clinical electrocardiography: introduction II: basic terminology. BMJ. 2002; 324: 470-473.

Glossary

blood pressure: Blood pressure is the amount of force exerted by the blood on the walls of the vessels that carry it. You can think of it like the water pressure in your home: the more pressure you have, the faster and more forcefully the water flows out of the shower. Blood pressure is measured in millimetres of mercury (written as mm Hg). When your blood pressure is taken, the measurement is given as two numbers, for example 120/80 mm Hg. The first, higher, number is called the systolic pressure, and the second, lower, number is the diastolic pressure. The systolic number is the highest pressure that occurs while the heart is pushing blood into the arteries. The diastolic number is the lowest pressure that happens when the heart is relaxing and is not pushing the blood.

This information does not replace medical advice. If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.