SUDDEN CARDIAC DEATH IN YOUNG PEOPLE – THE MOST COMMON CAUSES

Heart disease is the most common cause of unexpected sudden death in all age groups. In people over the age of 40, heart disease is usually due to narrowing or “blockage” of the blood vessels which supply the heart muscle, i.e. coronary artery disease. However, in younger people, the majority of sudden deaths are due to congenital or inherited disorders of the heart muscle and irregular heart rhythms. More than 20 different conditions have been identified as causes of sudden cardiac death (SCD) in young people. However, a few conditions are responsible for most deaths.

(A) CARDIOMYOPATHIES
Cardiomyopathies are abnormalities of the heart muscle and are usually inherited. Hypertrophic cardiomyopathy (HCM) is the most common cause of sudden death in young athletes, accounting for up to 40% of athletic field deaths in the USA. The disease causes excessive unexplained thickening of heart muscle and disorganisation and disruption of the arrangement of the heart’s muscle cells. It is a hereditary disease i.e. a ‘spelling mistake’ in one of the heart genes is passed from one of the parents to the child, and can affect both men and women of any ethnic origin. The majority of sufferers with HCM have no symptoms prior to sudden death. A few may have a family history of a sudden or unexplained death and some may have signs or symptoms (chest pain, shortness of breath, palpitations, light-headedness, blackouts) of cardiac disease. However, in some cases, SCD is the first and only presenting feature of HCM. 90% of patients with HCM have an abnormal electrocardiogram (ECG). An echocardiogram (ECHO), an ultrasound scan of the heart, is also usually abnormal. There is no cure at present for HCM. However, several treatments (drugs, pacemaker, implantable defibrillators, surgery) are available in order to prevent complications and improve symptoms.

Dilated cardiomyopathy (DCM) is a disorder in which the main pumping chambers of the heart become dilated and pump less efficiently. This may result in a low output of blood from the heart which is insufficient to meet the body’s requirements. There are many different causes of DCM including viral infection, immune disorders, excessive alcohol consumption and, rarely, pregnancy. DCM is a hereditary condition in approximately 30% of cases. Symptoms are usually due to the effects of heart pump failure.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a disorder in which normal heart muscle is replaced by scar tissue and fat. This hereditary disorder affects mainly the right side of the heart but can also affect the left side. Clinical presentation is usually with symptoms of arrhythmia and occasionally with sudden death. Investigations are similar to those performed in the diagnosis of HCM. However, additional tests such as MRI scan of heart, are often required.

(B) ION CHANNELOPATHIES
Ion channelopathies are a group of hereditary disorders that affect the electrical functioning of the heart without affecting the heart’s structure. Genetic abnormalities affect “ion channels” which regulate the movement of electrical charge through the heart muscle. If these “ion channels” are not functioning normally, the electrical activity of the heart becomes abnormal and the patient becomes susceptible to arrhythmias that can cause blackouts, cardiac arrest and, in some cases, SCD.

Long QT syndrome (LQTS) is the most common and best understood type of channelopathy. In this condition, abnormalities of the potassium or sodium channels result in an electrical disturbance in heart cells called “prolonged repolarisation”. This can be seen on an ECG recording as lengthening of the time period known as the “QT interval” from which the syndrome derives its name. The most common symptoms are blackouts and, less commonly, palpitations. Potassium channel LQTS is associated with SCD which is related to exercise or when the person has been startled or awoken suddenly (‘sudden arousal’). The sodium channel form has been reported to cause death while asleep. Diagnosis is by ECG. Repeated ECG, exercise tests and 24-48 hour tape monitoring may be necessary to make the diagnosis. Genetic testing can sometimes identify carriers of the abnormal gene for LQTS. Management involves avoidance of excessive exercise or strenuous athletic activities. Therapeutic options include drugs and either pacemaker or implantable defibrillator insertion.

Brugada syndrome is rare in the Western world and seems to be much more common amongst young men in South East Asia. The syndrome can present with blackouts, palpitations or SCD. Diagnosis is by ECG. Occasionally the ECG may be entirely normal at rest and the characteristic changes may only be evident after the administration of a specific drug (such as flecainide). The outlook for some patients with Brugada syndrome can be poor. In selected patients a defibrillator can be implanted to protect patients from sudden death.

Other ion channelopathies include catecholaminergic polymorphic ventricular tachycardia, progressive cardiac conduction defect (Lev-Lenegre’s syndrome) and idiopathic ventricular fibrillation.

(C) CONGENITAL HEART DISEASE
This group of conditions includes abnormalities of the structure of the heart which have been present since birth.

Congenital coronary artery anomalies are characterised by an abnormal arrangement of arteries supplying the heart muscle. One or more arteries may be either missing or have an abnormal origin jeopardising the muscle they supply.

Valvular and more complex diseases are a group of conditions characterised by abnormalities of the heart’s valves which may occur as an isolated abnormality or in association with other abnormalities of the heart’s structures. Mitral valve prolapse is a relatively common condition but is only rarely associated with arrhythmias and SCD. Aortic valve stenosis is often described as a risk factor for SCD. Athletes who have had more complex congenital heart malformations (for example, tetralogy of Fallot) repaired in infancy are at risk of fatal cardiac arrhythmias.

(D) MYOCARDITIS
Myocarditis is the term used to describe inflammation of the heart muscle. It is usually due to a viral illness although it may occur as a complication of other medical conditions or as a result of exposure to drugs. Viral myocarditis is usually a mild condition although severe cases can result in heart pump failure and sudden death. Many patients feel feverish and have generalised aches and pains as with any other viral illness. Complete rest and cessation of all sporting activity until symptoms have subsided will reduce the risk of sudden death. Most patients improve within several weeks without any complications.

(E) CONNECTIVE TISSUE DISEASE
Connective tissue disorders are inherited conditions, which affect the structures that give strength, support and elasticity to the walls of the heart and major blood vessels.

Marfan syndrome affects many organ systems. Signs and severity of the condition vary greatly. Diagnosis in most cases is made by physical examination. The major life threatening complication affects the aorta which is the major vessel arising from the heart. Loss of strength and elasticity of the wall of the aorta leads to enlargement of the aorta that may eventually result in either a tear or rupture of the wall of the vessel often with fatal consequences. Aortic enlargement can also result in impaired function of the aortic valve. Other heart valves, e.g. mitral valve, may also be affected. Specific sports guidelines have been issued for patients with Marfan syndrome.

Ehler-Danlos syndrome is another example of a connective tissue disorder which affects the heart and blood vessels in a similar way to Marfan syndrome.

(F) CONDUCTION DISEASE
Conduction diseases include abnormalities that affect the way electrical impulses are conducted through the heart.

Wolff-Parkinson-White (WPW) syndrome is an uncommon cause of sudden death. It results from an additional or “accessory” electrical pathway between the upper and lower pumping chambers of the heart. Most patients have no symptoms and the condition is usually only detected on a routine ECG. A few patients have symptoms, the most frequent of which is recurrent palpitations. SCD is a rare complication of WPW syndrome.

(G) OTHER CAUSES

Occasionally premature narrowing or “blockage” of the blood vessels which supply the heart muscle (coronary heart disease) may develop in a young individual. This is usually associated with recognised risk factors such as cigarette smoking, high blood pressure, diabetes and high cholesterol. Prescription, over-the-counter and illegal drugs, especially if taken in excessive amounts, can have potentially dangerous side effects including arrhythmias and SCD. Sudden death may be caused infrequently by non-cardiac conditions such as epilepsy (fits), severe asthma attacks and pulmonary embolism (a clot in the lungs). Pulmonary embolism has received much media attention recently due to its association with prolonged immobility during long-haul air travel.

SUDDEN CARDIAC DEATH AND THE USE OF AUTOMATED EXTERNAL DEFIBRILLATORS

Sudden cardiac arrest is one of the leading causes of death worldwide. There are approximately 100,000 sudden cardiac deaths each year in the UK and approximately 6,000 each year in Ireland. The majority of victims have no warning as they have no prior symptoms. During sudden cardiac arrest the heart abruptly stops pumping usually due to an electrical malfunction called ventricular fibrillation. The victim collapses, stops breathing and quickly loses consciousness due to a lack of blood flow and oxygen to the brain. Death quickly ensues unless a normal heart rhythm can be restored within a few minutes. Once ventricular fibrillation has developed, time is the most crucial factor that determines the chances of successful resuscitation.

The only effective treatment for ventricular fibrillation is defibrillation, a term used to describe the application of a high energy electric shock to the chest of the victim in an attempt to restart the heart. Unfortunately, most people in the UK and Ireland live and work in places where it takes considerably more than 5 minutes for an ambulance to arrive. Add to this the time required to call for help, to reach the individual, to assess the situation and deliver the first shock, and it soon becomes clear why today less than 5% of victims survive sudden cardiac arrest outside hospital. During ventricular fibrillation, every minute counts. It has been estimated that for every minute that goes by without defibrillation, the chance of survival decreases by about 10%. Conversely, studies have shown that survival rates as high as 74% can be achieved if defibrillation is given within 3 minutes.

Following any sudden medical emergency, onlookers sometime comment on their sense of frustration at not being able to help. This feeling of helplessness is inevitably more profound if the victim dies. However, there are tasks an onlooker can perform which might help improve the likelihood of a successful outcome. Summoning the emergency medical services might seem a logical first step but this simple task can sometimes be overlooked in such a stressful situation. Cardiopulmonary resuscitation (CPR) is a skill that involves manual chest compressions and “mouth to mouth” rescue breathing. CPR by itself is unlikely to restart a heart that has stopped. However, CPR may make the difference between life and death because it helps to maintain blood flow and oxygen to the brain until defibrillation has restored a normal heart rhythm. In effect, CPR can be considered to be a “holding measure” until more advanced treatment is possible.

Sudden cardiac arrest is one of the leading causes of death worldwide. There are approximately 100,000 sudden cardiac deaths each year in the UK and approximately 6,000 each year in Ireland. The majority of victims have no warning as they have no prior symptoms. During sudden cardiac arrest the heart abruptly stops pumping usually due to an electrical malfunction called ventricular fibrillation. The victim collapses, stops breathing and quickly loses consciousness due to a lack of blood flow and oxygen to the brain. Death quickly ensues unless a normal heart rhythm can be restored within a few minutes. Once ventricular fibrillation has developed, time is the most crucial factor that determines the chances of successful resuscitation.

The only effective treatment for ventricular fibrillation is defibrillation, a term used to describe the application of a high energy electric shock to the chest of the victim in an attempt to restart the heart. Unfortunately, most people in the UK and Ireland live and work in places where it takes considerably more than 5 minutes for an ambulance to arrive. Add to this the time required to call for help, to reach the individual, to assess the situation and deliver the first shock, and it soon becomes clear why today less than 5% of victims survive sudden cardiac arrest outside hospital. During ventricular fibrillation, every minute counts. It has been estimated that for every minute that goes by without defibrillation, the chance of survival decreases by about 10%. Conversely, studies have shown that survival rates as high as 74% can be achieved if defibrillation is given within 3 minutes.

Following any sudden medical emergency, onlookers sometime comment on their sense of frustration at not being able to help. This feeling of helplessness is inevitably more profound if the victim dies. However, there are tasks an onlooker can perform which might help improve the likelihood of a successful outcome. Summoning the emergency medical services might seem a logical first step but this simple task can sometimes be overlooked in such a stressful situation. Cardiopulmonary resuscitation (CPR) is a skill that involves manual chest compressions and “mouth to mouth” rescue breathing. CPR by itself is unlikely to restart a heart that has stopped. However, CPR may make the difference between life and death because it helps to maintain blood flow and oxygen to the brain until defibrillation has restored a normal heart rhythm. In effect, CPR can be considered to be a “holding measure” until more advanced treatment is possible.

Until recently, the act of defibrillation required considerable skill and training and was largely restricted to medical and specialist nursing staff. However, the recent introduction of the automated external defibrillator (AED) has meant the average citizen, following a brief period of training, should be able to easily perform defibrillation. Indeed, a report has shown that bystanders with no defibrillator training have been able to use an AED in actual cardiac arrest situations.

AEDs are designed for simplicity of use. Having recognised that cardiac arrest has occurred, the operator simply attaches two large adhesive electrodes to the chest wall. Audible voice prompts guide the operator through the steps of defibrillation and CPR. The electrodes, once attached to the chest wall, automatically analyse the heart rhythm and, where necessary, prompt the operator to provide a defibrillation shock to the victim’s heart so as to restore normal heart rhythm; several shocks may be necessary to restore normal function. AEDs are designed to recognise only ventricular fibrillation and certain other ventricular arrhythmias where the heart is beating too fast. It is almost impossible to shock inappropriately using an AED.

Advances in AED technology has made possible attempted defibrillation outside hospital for a much wider range of people in the community than previously – “first responder defibrillation”. First responder attempted defibrillation is vital as the time from collapse to defibrillation is the single greatest determinant of survival. The Resuscitation Council in the UK has published guidelines which state that AEDs should be available where the time to shock from collapse is likely to be more than 5 minutes. In many communities training and equipping lay people as first responders can reduce this collapse-to-shock interval. The evidence for improved survivability is so overwhelming that the Department of Health in the UK has embarked on a “Defibrillators in Public Places Initiative”. This has led to an increased provision of AEDs at public locations where large numbers congregate, such as airports, railway stations, shopping complexes and sports grounds. The intention is that lay personnel, often trained workers at the site, should be able to operate these AEDs.

One of the aims of the Cormac Trust is to provide AEDs to communities within County Tyrone. Tyrone has a largely rural-based population and only one remaining acute hospital in Omagh. The vast majority of the approximately 160,000 people who live in Tyrone therefore live in places where it takes an ambulance more than 5 minutes to arrive. By providing towns and villages with AEDs and training lay people within these communities in their use, it is hoped that lives might be saved as victims of sudden cardiac arrest may be defibrillated more quickly.

The Philips HeartStart First Aid Defibrillator (supplied by Cardiac Services, Belfast) is a small, lightweight AED that is reliable and easy to use. Clear voice instructions guide the operator through the steps of CPR and defibrillation. In May 2005, the Cormac Trust embarked on a programme of providing communities in Tyrone with the HeartStart AED. A skilled hospital resuscitation officer is providing lay people in these communities with training in both resuscitation skills and use of the defibrillator. The first training session took place in Cormac’s home town of Eglish on May 30 2005. Since then, over 300 lay people have been trained and 49 defibrillators provided to various communities in Tyrone. The process of training people and providing defibrillators is ongoing and it is the Trust’s intention that the programme will be rolled out to all communities in Tyrone within the next 12 months. Local sporting clubs have largely facilitated organisation of the scheme at a local level. As of September 19 2005, AEDs have been provided to the following towns and communities:

Despite the large numbers of people who die as a result of a cardiac arrest, it is still a relatively rare occurrence. With this in mind the training provided by the Cormac Trust programme includes a range of other simple, effective skills that the lay rescuer can utilise. These include recognition of the signs of a possible cardiac event, care of the unconscious patient, dealing with a choking patient and dealing with serious bleeding. The skills taught are simple, effective measures to reduce the risk of victim death. As all of the above situations have the potential to degenerate into a cardiac arrest if not handled promptly, a timely intervention by the lay person can help to prevent this from happening.

In addition to the training, there has been an offer of support from the Resuscitation Department in the Tyrone County Hospital (TCH) in Omagh. Any emergency situation will be stressful for the individual concerned; having an outlet for feedback and discussion of the situation will usually help to alleviate this stress. An important aspect of any training programme is structure and organisation of continuing training. As such, the Resuscitation Department of the TCH has indicated a willingness to provide further support and advice, to ensure this initiative provides ongoing benefit to the community for many years to come.