Causes of Sudden Cardiac Death

What causes cardiac arrest?

The rate and rhythm of your heart are controlled by an electrical system. When the heart’s electrical system is not working correctly, it can give rise to abnormal heart rhythms called arrhythmias. Arrhythmias can cause the heart to beat fast, slow, or irregularly. Not all arrhythmias are life-threatening; most are not, but some can cause the heart to stop pumping blood effectively around the body, leading to cardiac arrest. Ventricular Fibrillation (VF) is an example of a dangerous arrhythmia. This is an arrhythmia where the heart’s lower chambers (ventricles) beat fast and irregularly, ‘fibrillate’. When the heart fibrillates, it can no longer perform its pumping function, preventing oxygen from reaching the vital parts of the body. The brain no longer receives oxygen and this leads to loss of consciousness. No oxygen in the heart muscles leads to a cardiac arrest.

What conditions can lead to cardiac arrest?

The cardiac diseases associated with cardiac arrest differ depending on the person’s age.

In younger people, cardiac arrest affects apparently healthy people. Deaths are rare and are caused by several different heart diseases, which are often difficult to diagnose during life and after death. The most common underlying cardiac conditions associated with cardiac arrest in younger people are inherited heart diseases that affect the heart’s electrical system, congenital heart diseases, cardiomyopathies, and myocarditis. Yet, half of the sudden cardiac death cases during the fourth decade of life are related to coronary artery diseases, especially acute coronary syndrome or else known as a heart attack.²

In older populations, there is a clear predominance of coronary artery disease as a cause of sudden cardiac death. Other common conditions include cardiomyopathies (heart muscle diseases) and valvular disorders.²

Listed below are some heart conditions that can cause dangerous arrhythmias and lead to cardiac arrest if they are severe or remain untreated.¹

heart attack (often due to coronary heart disease)
cardiomyopathies (disease of the heart muscle)
inherited heart diseases that affect the heart’s electrical system, such as Brugada or Long QT syndrome.
congenital heart diseases – heart conditions or defects a person is born with.
heart valve diseases – one or more of your heart valves does not work correctly.
myocarditis – an inflammation of the heart muscle.

If you have any of these conditions, we recommend that you discuss with your healthcare provider methods to reduce your risk.

Yet some non-heart conditions can lead to cardiac arrests, such as:

severe bleeding (losing a large amount of blood)
hypoxia – a severe drop in oxygen levels
electrolyte disturbances (disturbances of minerals in your blood)
drug overdoses
intoxication from other causes.

Are there any risk factors that increase the risk of sudden cardiac death?

The same factors that increase the risk of heart disease can also raise the risk of sudden cardiac arrest. Some of those factors include: ¹

a personal or family history of coronary artery disease
a previous episode or a family history of sudden cardiac arrest
a personal or family history of inherited heart diseases that affect the heart’s electrical system or heart problems present at birth.
smoking
high blood pressure.
high blood cholesterol.
obesity
diabetes
inactive lifestyle
age – the risk of sudden cardiac arrest increases with age
using illegal drugs such as cocaine or amphetamines
low potassium or magnesium levels
chronic kidney disease

If you have any risk factors, talk to your doctor for personalised advice about improving your risk profile.

When should I have my first cardiovascular disease (CVD) risk assessment?

Systematic global CVD risk assessment is recommended in individuals with any major vascular risk factor (i.e. family history of premature cardiovascular disease, familial hypercholesterolaemia, cardiovascular risk factors such as smoking, arterial hypertension, diabetes, raised lipid levels, obesity, or comorbidities increasing CVD risk).

Systematic or opportunistic CVD risk assessment in the general population in men >40 years of age and in women >50 years of age or postmenopausal with no known atherosclerotic cardiovascular disease risk factors may be considered.

Can sudden cardiac death affect athletes?

Sudden cardiac death in athletes is rare (about one to three in 100,000).³ Males are affected more often than women. Most professional athletic programs will screen potential athletes for the most common causes of sudden cardiac death.

In younger athletes, most sudden cardiac deaths occur in patients with structurally normal hearts, according to autopsies. ³

Commotio cordis is the occurrence of a sudden dangerous arrhythmia, such as ventricular fibrillation, which can lead to cardiac arrest after a chest blow. Athletes with thin, compliant chest walls with no apparent cardiovascular disorder can be affected. Usually, something small and hard (e.g., a baseball or hockey puck) strikes the left side of the chest during a critical face of the heartbeat. Other causes include inherited heart diseases that affect the heart’s electrical system, heart muscle diseases, or inflammation.

In older athletes, sudden cardiac death is typically caused by coronary artery disease.⁴

What are the most common symptoms of cardiac arrest?

In more than half of the cases, cardiac arrest strikes without prior symptoms.

Symptoms before cardiac arrest may include:

a racing heartbeat.
chest pain.
shortness of breath.
dizziness.
fainting.

These symptoms are signs of potentially dangerous heart conditions that can lead to cardiac arrest and sudden cardiac death.

When should I suspect that someone is experiencing cardiac arrest?

The most common signs of cardiac arrest are:

Sudden loss of responsiveness – the person doesn’t respond – even if you tap them hard – and doesn’t move or speak.
The person isn’t breathing or is only gasping for air.

If you suspect a person is experiencing cardiac arrest, you should immediately call for help, call an ambulance and start CPR.

References

Adabag AS, Luepker RV, Roger VL, et al. Sudden cardiac death: epidemiology and risk factors. Nature reviews Cardiology 2010;7(4):216-25. doi: 10.1038/nrcardio.2010.3 [published Online First: 2010/02/10]
Zeppenfeld K, Tfelt-Hansen J, de Riva M, et al. 2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Eur Heart J 2022;43(40):3997-4126. doi: 10.1093/eurheartj/ehac262 [published Online First: 2022/08/27]
Maron BJ, Haas TS, Ahluwalia A, et al. Demographics and Epidemiology of Sudden Deaths in Young Competitive Athletes: From the United States National Registry. The American journal of medicine 2016;129(11):1170-77. doi: 10.1016/j.amjmed.2016.02.031 [published Online First: 2016/10/25]
Harmon KG, Asif IM, Maleszewski JJ, et al. Incidence, Cause, and Comparative Frequency of Sudden Cardiac Death in National Collegiate Athletic Association Athletes: A Decade in Review. Circulation 2015;132(1):10-9. doi: 10.1161/CIRCULATIONAHA.115.015431 [published Online First: 2015/05/16]