Cardiac arrests explained

Dr Mike KnaptonOur Associate Medical Director, Dr Mike Knapton, answers some frequently asked questions about cardiac arrest.

Monday 19 March 2012

Chest clip monitorOver the last few days, the British Heart Foundation has been inundated with calls about the health of Premiership footballer Fabrice Muamba, who collapsed suddenly on Saturday. We hope Fabrice makes a full recovery but only his doctors will have a true understanding about his current condition and what might have caused his collapse.

However, here are some of the questions we’ve been answering.

1. What is a cardiac arrest?

A cardiac arrest is when your heart stops pumping blood around your body.  You are unresponsive and won’t be breathing normally. Immediate CPR and defibrillation is needed to have any chance of survival.

A cardiac arrest is very different to a heart attack. Most heart attacks are caused by coronary heart disease, which is when one or more coronary arteries narrow due to a gradual build-up of fatty material within their walls. If this material becomes unstable, a piece may break off and lead to a blood clot forming.  This clot can block a coronary artery, starving part of your heart of oxygen-carrying blood causing damage to your heart muscle - this is a heart attack.

2. What can cause a cardiac arrest?

Doctor uses stethoscopeThe most common cause of cardiac arrest is a life threatening abnormal heart rhythm called ventricular fibrillation. It occurs when the electrical activity of the heart becomes so chaotic the heart stops pumping and quivers, or fibrillates, instead.

Heart attacks cause the majority of cardiac arrests in the UK. However, there are lots of other things which can trigger a cardiac arrest. Without proper screening, many of these conditions go unnoticed. For example, a hereditary disease called Hypertrophic Cardiomyopathy is the most common cause of sudden death in young people. It causes the heart muscle to become excessively thick and makes the heart vulnerable to ventricular fibrillation.

Other causes include:

  • You lose a large amount of blood or fluid
  • A lack of oxygen
  • Your body being very hot or very cold

3. How can screening help?

Lots of heart conditions are inherited and looking at someone’s family history can help flag up any potential problems. Cardiac screening involving a test called an electrocardiogram (ECG) can then help diagnose most cardiac abnormalities, but not all.

Around 500 young people die suddenly each year with apparently no explanation or cause of death. Often an inherited heart condition is to blame. Our Genetic Information Service on 0300 456 8383 can provide information if someone in your family has been diagnosed with, or has died from, what is suspected to be an inherited heart condition.

4. How important is CPR and defibrillation during cardiac arrest?

Vinnie JonesIf someone has a cardiac arrest they will not survive without prompt CPR, which could be Hands-only CPR, and a defibrillator. A defibrillator is a life-saving machine that can give the heart a controlled electrical shock during a cardiac arrest. For every minute that passes without defibrillation chances of survival decrease by about 10 percent.

If someone has collapsed, call 999 straight away. If you’re unsure or unconfident about giving full CPR, including rescue breathes, try Hands-only CPR instead. The technique involves calling 999 and then pushing hard and fast in the centre of the casualty’s chest to the rhythm of the Bee Gees, Staying Alive, until professional help arrives.