COVID-19: Find information on how we’re keeping you safe here.

To top

What are the causes of cardiac arrest?

There are several possible underlying causes of the fast abnormal heart rhythms that cause cardiac arrest. The most common reason is coronary disease, a narrowing of the arteries that supply the heart, including sudden blockages that cause a heart attack. This can then cause these unstable cardiac rhythms. Coronary disease is the most common cause of cardiac arrest over the age of 35.

Most people who have a cardiac arrest under the age of 35 have abnormal hearts because of conditions that they have been born with. These are often undetected. Conditions include cardiomyopathies (diseases of the heart muscle), electrical abnormalities, heart valve disease and an abnormal position of one of coronary arteries (one of the blood vessels supplying blood to the heart).

Cardiac arrest in athletes and screening

Cardiac arrests are more common in athletes because exercise can increase the likelihood of these unstable cardiac rhythms in people with underlying abnormalities of the heart. In response to this some sports programmes have started screening athletes for cardiac disorders before they undertake competitive sport.

In the UK, the Football Association has a prominent long running screening programme which involves assessing whether players have any symptoms, past medical history or any family history of medical problems and in addition includes testing with an ECG and echocardiogram as first line routine cardiac investigations. This screening programme has recently published its long term outcomes 1 .

Although screening can’t pick up all underlying conditions, some can be detected and steps taken to reduce the risk for that individual.

What can be done if there is a high risk of cardiac arrest

In people who are thought to have a high risk of these lethal arrhythmias there is the option of offering implantation of a cardiac defibrillator. This is a small device that is usually fitted under the skin like a pacemaker, which detects if a lethal rhythm occurs and then can deliver energy to shock the heart out of that rhythm. This provides patients with a safety net which means that they can survive a cardiac arrest even if there is no immediate help at hand.

Patients are also offered lifestyle advice and usually medication to minimise the risk of these abnormal rhythms happening.


  1. Outcomes of Cardiac Screening in Adolescent Soccer Players (Malhotra A, Mayet J, Varnava A et al. NEJM 2018;379:524-534)

Written by Professor Jamil Mayet, Consultant Cardiologist at OneWelbeck Heart Health, specialising in hypertension and the heart, covid and the heart, cardiac screening, chest pain assessment and the athlete’s heart.