Download Current thinking on sudden cardiac death

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