Sudden Cardiac Arrest in the Young

In younger people, Sudden Cardiac Arrest claims around 12 lives each week in the U.K. alone.

Sudden Cardiac Arrest in a young person can be caused by:

• heart disease, including cardiomyopathy, congenital heart disease, myocarditis, genetic connective tissue disorders, mitral valve prolapse or conduction disease
• medication-related causes
• commotio cordis, or
• other causes.

These are explained below:

Heart disease

Heart disease is the most common cause of an unexpected sudden death in all age groups. In people aged 30 or over, the heart disease is usually due to 'furring' or 'blockages' of the blood vessels that supply the heart, i.e. coronary artery disease. But in younger people and in children the cause is much more often something other than coronary artery disease. The main causes are listed below. Some of these are inherited conditions. Some are detected easily while the person is alive, while others may go unnoticed until a tragic sudden death occurs.

Cardiomyopathies

These are abnormalities of the heart muscle and are usually inherited.

The most common is hypertrophic cardiomyopathy (hypertrophy=to grow abnormally large + cardio=heart + myopathy = diseased muscle). This disease is often hereditary, and the walls of the ventricle are larger than they should be. This makes the pumping chamber of the heart smaller, and the heart has to work harder to pump blood out of the heart. As well, the thickened muscle narrows the space for the blood to flow through the aortic valve and to the rest of the body. During exercise, this decreased blood flow can irritate the heart muscle itself and cause ventricular fibrillation, collapse, and sudden death.

Other cardiomyopathies include arrhthmogenic right ventricular cardiomyopathy (ARVC) and dilated cardiomyopathy (DCM).

Congenital heart disease

This group includes abnormalities of the structure of the heart which have been present since birth. Some of them may be inherited conditions. They include:

• Valvular and more complex disease: Abnormality of the heart's valves that can be associated with other abnormalities of the heart's structures such as 'a hole in the heart'.
• Anomalous coronary arteries : When there is an abnormal arrangement of the arteries that supply blood to the heart muscle. Normally, the coronary arteries lie on the surface of the heart. Anomalous arteries dive into the heart muscle itself and may be blocked when the heart muscle that surrounds the abnormally placed artery squeezes aggressively, as with exercise, shutting off blood supply to part of the heart. This irritates the electrical system and can cause ventricular fibrillation and sudden death.

Myocarditis

Myocarditis is inflammation of the heart's muscle. It is usually due to a viral infection although it can be a complication of other medical conditions or exposure to drugs. It is not inheritable.

Genetic connective tissue disease

These are inheritable conditions affecting the structures that give support, strength and elasticity to the walls of the major blood vessels and, to a lesser extent, the heart muscle - for example Marfan's Syndrome and Ehler-Danlos Syndrome. These can cause sudden death by arrhythmias or due to the sudden rupture of a major blood vessel such as the aorta (the major blood vessel that leaves the left side of the heart and supplies blood to the body).

Mitral valve prolapse

The mitral valve can sometimes be 'floppy' in appearance. This will show up on an echocardiogram (ECG). This is very common and affects around 1 or 2 in every 20 people. It is usually an asymptomatic and benign condition. In some rare cases mitral valve prolapse can be inherited in a family and can then be associated with arrhythmias and sudden death.

Conduction disease

This includes abnormalities in the way that the electrical impulses are conducted through the heart due to disease (for example as in myotonic dystrophy), or because there are additional or 'accessory' pathways as in Wolff-Parkinson-White (WPW) Syndrome.

Medication-related causes

Prescription, over-the-counter and illegal drugs can have potentially dangerous but usually rare side effects, particularly if too much is taken (an overdose). These effects include arrhythmias (disturbance in the heart's rhythm) and sometimes a sudden death.

Commotio Cordis

Commotio Cordis is a rare but potentially catastrophic phenomenon that can result in sudden cardiac arrest. Commotio Cordis can occur when a blunt, but often relatively mild blow to the area of the chest directly over the heart occurs during a precise moment of the heart's cycle, leading to sudden cardiac arrest. Examples of the blunt object may include: rugby ball, netball, football, hockey ball, fist, shoulder or knee.

The heart responds to the blow with an interruption of the electrical impulse, thus sending the heart into ventricular fibrillation. This causes insufficient blood flow, loss of oxygen to tissues and may result in death. The location of the blow; timing of the blow in the cardiac cycle; and the force of the blow all contribute to a Commotio Cordis incident.

In the USA there has been a National Commotis Cordio Registry in existence since 1996.

Since the register began there have been over 180 cases recorded. The victim is typically a sporty male, age 14 years. These figures are estimated to be conservative as public awareness of the condition is poor.

Commotio Cordis is in fact the leading cause of death among baseball players in the USA and the second leading cause of death in all athletes after cardiomyopathies.

Other causes

Research suggests that sudden death may be caused infrequently by conditions such as fits (epilepsy) and severe asthma attacks. Pulmonary embolus (a clot to the lungs), has become better known recently due to its association with staying immobile for long periods during air travel. It can cause a sudden collapse and a rapid death.

Sudden Arrhythmic Death Syndrome (SADS)

In some cases of sudden cardiac arrest - no cause can be found, despite examination of the heart by an expert cardiac pathologist. The cause of death is therefore described as 'unascertainable'. This is called Sudden Arrhythmic Death Syndrome, or SADS.

Pre-participation athletic physical examination is a useful tool to screen children and adolescents for their risk of sudden cardiac arrest as many of these cases are precipitated by sporting activity. In some countries such as Italy, screening is mandatory for all competitive sports players. There are no such recommendations in place in the UK.

Valuable work is currently being carried out by the charity Cardiac Risk in the Young campaigning for better cardiac screening in the under 35's.

The only effective treatment for SCA is defibrillation within 4-6 minutes using an Automated External Defibrillator (AED) as part of the chain of survival.

For further information, please email: info@thedefibcentre.co.uk or call us on 0800 634 9745.