A memo for you, who could be a sufferer or a saver
Sudden cardiac arrest (SCA) is a sudden and unexpected loss of heart function, breathing and consciousness. When it happens, blood stops flowing to the brain and other vital organs, and the person will die if appropriate resuscitation is not given within minutes.
And what makes it worse is that this typically happens without any warning signs. Globally, sudden and unexpected cardiac death is a very common cause of death.
● Campus: Despite older people being more likely to be struck by SCA, children and teenagers are not free from the risk. According to the Sudden Cardiac Arrest Foundation, more than 7,000 youth under the age of 18 experience SCA each year in the U.S., with survival rates less than 10%. The annual incidence of SCA for U.S. high school students is 0.63 per 100,000 while for student athletes, the rate is 1.14 per 100,000. 
● Workplace: Workplaces are where adults typically spend two thirds of their everyday lives. At work, SCA strikes around 10,000 people, accounting for 15% of workplace fatalities, as indicated by a report from the US Occupational Health and Safety Administration. The incidence rate is higher in high-risk emergency jobs such as firefighters and police.
● Sports places: Although regular exercise is a good way to strengthen heart functions and prevent cardiovascular problems in the long term, improper physical exertion does increase immediate risk of SCA. It is especially dangerous for those who have already had a pre-existing or undiagnosed heart condition but do not know about it.
In most cases, the underlying mechanism of SCA is ventricular fibrillation (VF), in other words, abnormal heart rhythm. An AED, or Automated External Defibrillator, can automatically analyze and detect cardiac arrhythmias of SCA patients, and advise the rescuer of the need to deliver a shock for defibrillation.
The number is astonishing - 90% of out-of-hospital cardiac arrest victims die. But if prompt cardiopulmonary resuscitation (CPR) and defibrillation is provided in the first minute, the chance of survival rises up to 90%. After that, every minute delay leads to about 10% drop of in survival chances.
However, an unfortunate fact is that it usually takes ambulances 7-12 minutes on average to arrive on a scene. This means that for sudden cardiac arrest survival, there is no time to lose.
 Heart Diseaseand Stroke Statistics - 2018 Update, American Heart Association.
 ERC Guidelines for Resuscitation 2015, European Resuscitation Council.
 Report on Cardiovascular Diseases in China 2014, China National Center for Cardiovascular Diseases
 Toresdahl, B. G.,Rao, A. L., Harmon, K. G., & Drezner, J. A. (2014). Incidence of sudden cardiac arrest in high school student athletes on school campus. Heart Rhythm, 11(7), 1190-1194.