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Cardiology–SON-TH 18/04/2006 10:09 Page 1 Keeping abreast of developments in an ever-changing health service CONTINUING PROFESSIONAL DEVELOPMENT is essential for nurses and midwives practising in an ever-changing healthcare environment. With this in mind WIN has taken the decision to expand its Continuing Education section for 2006 and will focus on two clinical areas which impact on all areas of the Irish health service – namely cardiology and diabetes. Cardiovascular disease and type 2 diabetes can be considered the most significant public health problems that we have faced in recent times, so much so that we are facing the MODULE 12: Cardiology prospect of a reduction in life expectancy if the dual problem is not tackled. The Cardiology Module to date has focused on: • Cardiac risk protection in people with type 2 diabetes • Women and stroke, outlining risk factors • Role of cardiac rehabilitation • Blood pressure management This month we focus on sudden cardiac death and outline the recent recommendations of the SCD taskforce. Table 1 Main causes of SCD (Report of the Taskforce on Sudden Cardiac Death) PART 5 Current thinking on sudden cardiac death by Shirley Ingram KNOWN cardiac disease causes 82.4% of out-of-hospital cardiac arrests in Scotland1 and in the US sudden death is responsible for more than 60% of adult deaths from coronary heart disease (CHD).2 An estimated 700,000 Europeans will suffer a cardiac arrest annually,3 with CHD being the major structural abnormality found in most sudden cardiac arrest victims.4, 5 Definition of sudden cardiac death (SCD) SCD is defined as:“An unexpected death due to cardiac causes that occurs within one hour of symptom onset. Cardiac arrest, usually due to cardiac arrhythmias, is the term used to describe the sudden collapse, loss of consciousness and loss of effective circulation that precedes biologic death.”6 Mechanism of SCD Analysis of holter monitor recordings has shown that out-ofhospital cardiac arrest during myocardial infarction is usually due to sustained ventricular tachycardia (VT) degenerating into ventricular fibrillation (VF).7 Ventricular arrhythmias that occur within minutes of coronary occlusion are due to the effects on the electrical properties of cardiac fibres, hypoxia, pH imbalance, potassium and calcium changes and catecholamines.4 VF can occur at any time and in any place. If untreated VF deteriorates into asystole and death follows within minutes. Only 25%-30% of out-of-hospital sudden cardiac arrest victims survive to hospital discharge.8 Recognition and treatment of these potentially lethal arrhyth- Valvular heart disease Coronary heart disease ● Anomalous coronary arteries ● Dilated cardiomyopathy ● Hypertrophic cardiomyopathy ● Right centricular cardiomyopathy ● Brugada syndrome Long QT syndrome Wolff-Parkinson White syndrome ● Catecholaminergic polymorphic VT ● Viral myocarditis ● Commotio cordis ● Drugs ● Electrocution ● ● ● ● mias in the CCU has reduced mortality; however up to 75% of fatalities occur out of hospital.9,10 Of these out-of-hospital cardiac arrests it is estimated that up to 80% occur in the home, with a spouse or other family member being the witness.11,12 Comparing research on rates of SCD in other countries to Irish mortality figures, it is estimated that 5,000 sudden cardiac deaths occur every year in Ireland, which is an average of 14 deaths a day.13 Retrospective studies of sudden death show that victims who have known heart disease usually have the risk factors for sudden death, namely: male, hypertensive, diabetic, increased low density lipo protein (LDL) cholesterol and smoke cigarettes.14,15 The incidence of sudden death has been found to be related to blood pressure, serum cholesterol, glucose intolerance, heart rate, cigarette smoking and relative weight.16 SCD in the young In recent years SCD focus has shifted to high-profile deaths in young athletes. Sudden cardiac death is traumatic for those who are left behind, especially so if the victim was a previously healthy young athlete. Thankfully this is a rare event but it has attracted public attention to SCD. The majority of these deaths are due to VF arising from abnormalities in the cardiac muscle (cardiomyopathy), cardiac muscle cell ion channels (channelopathy) or coronary arteries (congenital coronary artery anomalies). SCD can also be due to non-cardiac causes, such as drug overdose, electrocution, trauma, especially blunt chest trauma (commotio cordis), and near drowning (see Table 1).13 Prevention of sudden death Various approaches have been taken to manage the problem of sudden death worldwide, from primary prevention of heart disease; to secondary prevention of events associated with CHD, the This module is supported by MSD Ireland (Human Health) Ltd. Cardiology–SON-TH 18/04/2006 10:09 Page 2 Continuing Education Table 2 Terms of reference for SCD taskforce ● Define SCD and describe underlying causes in Ireland ● Advise on the detection and assessment of those at highest risk of SCD and their relatives ● Advise on the assessment of risk of SCD of those engaged in sports and exercise ● Advise on maximising access to BLS and AEDs ● Advise on establishment of and maintenance of surveillance systems (registry of SCD) ● Advise and make recommendations on other priority issues relevant to SCD in Ireland ● Outline a plan for implementation and monitoring of the recommendations made in the report development of cardiopulmonary resuscitation (CPR) techniques and emergency care pathways to deal with cardiac emergencies. In Ireland, the Minister for Health established the Cardiovascular Health Strategy Group in 1999 to “develop a strategic approach to reduce unavoidable death and illness caused by cardiovascular disease.”17 In 2004, the Minister established a Taskforce on Sudden Cardiac Death13 (see Table 2 for terms of reference). The taskforce report, Reducing the Risk: A Strategic Approach, was launched in March this year.13 In the pre-hospital setting, prevention of SCD is based on improving the links in what the American Heart Association calls ‘the chain of survival’.18 The vital links in the chain are early access to emergency medical services (EMS), early CPR, early defibrillation and early access to advanced cardiac life support. Early access Timely access to EMS is vital. In Ireland, the contact number for the EMS is 999 or 112. The 112 number is in line with the Council of Europe recommendation to have a universal phone number throughout Europe. The taskforce recommends that all emergency vehicles should have signage to alert the public to these phone numbers and that pre-ambulance arrival advice, including telephone-assisted CPR, be provided to a national standard. Early CPR Prior to the development of current techniques in resuscitation, cardiac arrest was treated in the operating room using open thoracotomy, direct internal cardiac massage with defibrillation, and was only available for those patients in surgery at the time of arrest. The development of closed chest CPR in 1960 proved a turning point in the management of cardiac arrest post-MI. By 1974, CPR was endorsed by influential bodies such as the American Heart Association. The effectiveness of closed chest cardiac massage and mouthto-mouth ventilation has been advocated worldwide and the technique has altered little since the pioneering days. The aim of prompt resuscitation has not changed since the early days of its creation. The aim is to enable the body to spontaneously support its own oxygenation and to return the patient to their pre-arrest status in heart and central nervous system function, and retain healthy brain function. To be effective, CPR must be commenced within four to six minutes from the time of collapse. There is a body of evidence showing that bystander CPR, provided promptly at the scene of an out-of-hospital cardiac arrest significantly improves long-term survival.19,20 The international liaison committee on resuscitation (ILCOR) states that a trained lay rescuer who is ready and willing may be the most important determinant of survival from sudden cardiac arrest.21 40 WIN May 2006 Early defibrillation Pre-hospital cardiac care has improved with the introduction of semi-automatic defibrillators that can identify ventricular fibrillation and provide counter shocks. Ideally defibrillation should be performed within four minutes of the onset of VF. Defibrillation depolarises the myocardium and allows the sino-atrial node to resume its function as the pacemaker of the heart. The automated external defibrillator (AED) was developed to increase the availability of early defibrillation. Figures from the Mater University Hospital, Dublin found that in the vicinity of an AED, 54% of victims survived to hospital discharge compared to 1.6% in areas where no AED was available.22 The taskforce recommends that all ambulances, regardless of purpose, should carry an AED and it makes detailed recommendations on ‘first responder’ programmes incorporating hospital, community and home programmes. Secondary prevention of SCD Secondary prevention may take the form of cardiac rehabilitation (CR) and the Cardiovascular Health Strategy Group17 recommends that “every hospital that treats patients with heart disease should provide a cardiac rehabilitation service”. Cardiac rehabilitation includes education on the management of angina and the signs and symptoms of MI. Cardiac rehabilitation is an appropriate environment in which to enhance this education by providing CPR training.When asked about their interest in learning CPR, 46%23 and 58%24 of previously untrained patients in coronary care units said they would participate in CPR training. The fact that cardiac patients are at high risk of cardiac arrest should not preclude them from being able to help others. Such patients live in the community as everyday citizens and many of them will have relatives with cardiovascular disease. Ingram et al (in press) recommend that cardiac patients be involved in CPR training as it poses them no adverse psychological consequences and may increase participation in CPR training by cardiac patients’ relatives. The taskforce recommends that secondary prevention programmes including CR services should continue to be developed and family members of those who have suffered a cardiac event should be offered basic life support and AED training, with CR programmes being “ideally placed” to provide such training. With regard to young SCD victims, the taskforce recommends that in cases of SCD < 40 years, assessment of first-degree relatives should be undertaken by GPs with cardiology referral if indicated. For the safety of those engaged in sports and exercise, it recommends that a protocol for risk assessment be agreed by the major sports and medical organisations, the Irish Cardiac Society and Irish College of GPs, to include questionnaires and medical follow up if required. The taskforce acknowledges that it is important to encourage participation in exercise as a healthy lifestyle choice. While healthcare providers play an important role, it is vital that the lay public plays its part in the prevention of sudden cardiac death by learning to recognise the warning signs, accessing the emergency medical services and commencing CPR.The taskforce recommendations will hopefully lead to a decrease in the tragedy that is SCD. As stated by Beck,25 “The heart wants to beat, and often it needs only a second chance.” Shirley Ingram is a cardiac rehabilitation co-ordinator at the Cardiac Rehabilitation Department, AMNCH, Tallaght, Co Dublin References on request from [email protected] (quote: Ingram S.WIN 2006; 14(5): 39-41