Download Sudden cardiac death in the young

Table 1
MODULE 17:
Cardiology
PART 10
Sudden cardiac
death in the young
by Helen O’Donnell
When a young person dies suddenly it has devastating effects.
More than 5,000 people suffer sudden cardiac death in Ireland
each year, of which 60-80 are under 35 years of age. Sudden cardiac death (SCD) is defined as ‘death due to natural causes within
an hour of the onset of symptoms, in the absence of any other
cause, and assumed or proven to have a cardiac cause’.1
Post mortem results of SCD in the young have shown a number
of underlying conditions, such as cardiomyopathy, myocarditis
and coronary heart disease.1 There are also many unexplained
deaths (approximately 20-30%) in people under 35 years of age,
where no structural abnormality is found at post mortem1 and
these are classed as sudden arrhythmic death syndrome (SADS).
Review of Irish post mortem data suggests that SCD in a population of 14-35 year olds occurs in three to four per 100,000, with
males being seven times more likely to be affected. It also suggests that in up to 50% of cases of SCD in the young, the cause
may be inherited.2 Since prospective cardiac assessment of the
general population is not currently feasible, the initial focus is to
target high-risk subgroups see Table 1.
Exercise can increase the risk of sudden death only in those
who have the conditions. It is also possible for a young person
who has one of these conditions to die suddenly doing normal
activities or during sleep.
Conditions detected on cardiac testing
Conditions that can be detected on cardiac testing include:
• Long QT syndrome (LQT)
• Cardiomyopathy – Dilated cardiomyopathy (DCM), hypertrophic
cardiomyopathy (HCM), arrhythmogenic right ventricular
cardiomyopathy (ARVC)
• Brugada syndrome
• Catecholaminergic polymorphic ventricular tachycardia (CPVT)
• Wolf Parkinson White syndrome (WPW)
• Connective tissue disorders (eg. Marfan syndrome)
• Fabry disease.
LQT: Long QT syndrome is an association of cardiac rhythm disorders
and QT prolongation or abnormal T waves on ECG.3 A patient’s resting
ECG is not always abnormal in LQT patients. Abnormal corrected QT
measurements are defined as being > 440ms in men and > 460ms in
High-risk subgroups
• History of sudden death in close family member with suspected
cardiac cause or unknown cause
• Family history of inherited cardiac disease
• Signs and symptoms that may indicate cardiac cause
Signs and symptoms
• Short of breath on exertion that happens repeatedly on less than
maximal exertion
• Chest pain with activity that limits completion of activity
• Dizziness/syncope – especially on exercise
• Exercise intolerance
• Sometimes no symptoms – could be found during routine
medical examination
• Unexplained/uncontrolled seizure-like episodes
women for a diagnosis to be made.4 Some medications may increase
the risk of arrhythmia in LQT syndrome (see: www.azcert.org).5
LQT can be acquired or congenital. The acquired type is most
often associated with repolarisation abnormalities which are
induced by drugs, ie. antiarrhythmics, some antibiotics, some
antihistamines and even some antipsychotic medications. The
prevalence of this condition is said to affect one in 5,000 of the
population, however a recently published study in newborn infants
suggests that the prevalence may be closer to one in 2,000.
Hypertrophic cardiomyopathy/obstructive cardiomyopathy: HCM/
HOCM is a genetic disease that is associated with a risk of ventricular tachyarrhythmias and sudden death, especially in young
patients.6 The heart muscle becomes thick and fibres are arranged
haphazardly increasing the risk of fatal arrhythmias. The thickened
muscle interferes with the heart’s normal contraction and relaxing, which results in reduced cardiac output. Of patients 25-30%
have the ‘obstructive’ form with relative obstruction to blood flow
from the left ventricle to the aorta. An affected individual has a
50% chance of passing this condition on to their children. Most
patients with HCM have at least one other affected relative.7
Patients are assessed on their risk of arrhythmia based on their
test results. These include:
• Hypertrophy of ≥ 3cm on ECHO
• Sudden cardiac death in first degree relatives
• Malignant genotype
• Unexplained syncope
• Significant PVCs or arrhythmia on Holter monitor.
Brugada syndrome: This is an arrhythmogenic disease that is characterised by ST elevation in the right precordial leads (V1-V3) with
incomplete or complete right bundle branch block (RBBB) pattern
on the ECG. It is associated with a high incidence of syncope and
sudden death in patients with a structurally normal heart. 8 The
patients’ resting ECG is often significantly abnormal in patients
with a high risk of arrhythmia. Gene carriers of Brugada syndrome
may be unmasked during ajmaline provocation testing.
The patient is admitted as a day case for ajmaline provocation
Sponsored by an unrestricted grant from Merck Sharp & Dohme Ireland (Human Health) Ltd.
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Continuing Education
Figure 1
testing. The procedure is explained to the patient and a written consent is obtained. A baseline ECG is recorded with V1 and V2 placed in
the second intercostal space rather than the usual fourth intercostal
space. This allows for clearer viewing of any ECG changes. The patient
is then weighed and ajmaline is administered at 1mg/kg in 100ml
infusion of sodium chloride 0.9% intravenously. The infusion is given
over 20 minutes while the patient has continuous ECG monitoring.
The infusion should be stopped at any stage if positive changes
occur. Other reasons for stopping the infusion include: frequent
premature ventricular contractions (PVCs), an arrhythmia occurring, sinus arrest, type 2 or type 3 AV block and also widening of the
QRS complex. The patient then has continuous ECG monitoring
for a further 10 minutes following completion of the infusion.
Ajmaline has a half life of 10 minutes, therefore following completion of the infusion, the drug is metabolised out of the system
within 10 minutes. The patient is then monitored for a further 10
minutes as a precaution. Blood pressure is checked at the beginning of the procedure and then every five minutes until the
procedure is completed. If a patient has Brugada syndrome, there is
a one in 100 risk of developing a cardiac arrhythmia. Other minor
side effects of the medication are feelings of tingling in the mouth
and jaw area, hot flushes or the sensation to pass urine. These usually subside within 10 minutes following drug administration.
CPVT: Catecholaminergic polymorphic ventricular tachycardia is
an arrhythmogenic disorder of the heart characterised by a reproducible form of polymorphic ventricular tachycardia induced
by physical activity, stress or catecholamine infusion, which can
deteriorate into ventricular fibrillation.9 Resting ECG is normal or
near-normal in patients with CPVT. Diagnosis is made on exercise
testing and epinephrine provocation testing.
WPW: Wolff Parkinson White syndrome is a condition in which
there is an extra electrical pathway in the heart which can lead
to tachycardia. Resting ECG is usually abnormal in patients with
WPW with the presence of a ‘delta’ wave.
Anderson-Fabry disease: More commonly known as Fabry disease
this is a rare X-linked recessive metabolic disease that can affect a
lot of systems within the body. Cardiac involvement varies. If it is
present its severity will worsen with age. This includes left ventricular hypertrophy (LVH), ischaemic heart disease (IHD), conduction
abnormalities, myocardial infarction (MI), arrhythmias and mitral
valve insufficiency.10 It accounts for around 3% of unexplained LVH
in middle aged men.11 Up to 2% of patients diagnosed with hypertrophic cardiomyopathy have been found to have Fabry disease as
the underlying cause.
Evaluation
• Detailed family pedigree (at least three generations – see Fig 1)
• Routine examination
• Detailed history
• ECG
• ECHO
• EST
• Holter monitor (24-48 hours)
• Ajmaline test (looking for Brugada syndrome).
Family history
A detailed family pedigree will identify symptomatic individuals
in the immediate and extended family and may highlight any sudden deaths that have occurred, which may have been attributed
to something else, eg. drowning or sudden death in suspected
epilepsy which may have occurred due to an arrhythmia. Fam-
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Family pedigree with three generations
ily pedigree review also gives a clear picture of family members
who may be at risk and need to be screened. Information on at
least three generations should be collected, where possible. When
someone has been diagnosed with one of these conditions all first
degree relatives should be advised to go for screening.
Treatment
• Not everyone who inherits these conditions will die suddenly
• If a person is diagnosed with the condition they will be assessed
according to their risk
• If a person is at risk they can be treated with either medication
or an implantable cardiac defibrillator (ICD).12
The Cardiac Risk in Younger Persons (CRYP) Centre
The CRYP centre aims to assess individuals or families who have
had a sudden death within their family and also young people
with symptoms that may indicate an underlying cardiac cause. A
counselling service is also available for families if required. In Ireland, SCD in the young occurs approximately once a week and for
the families it is devastating. Post mortems can show any structural
abnormalities within the heart, ie. cardiomyopathy, but electrical
conditions cannot be detected after death and are known as ‘SADS’.
The nurse can play an important role in educating and counselling
individuals and family members during this difficult period.
With new research constantly developing and new and
improved ICDs being made, the future remains bright. With close
observation and specialist management a person diagnosed with
one of these conditions may live a long and healthy life.
Helen O’Donnell is a CNM II at the Cardiac Risk in Younger Persons (CRYP) Centre,
Tallaght Hospital, Dublin
Many thanks to Dr Deirdre Ward, consultant cardiologist, AMNCH, for her help with this article
References
1. Task Force for Sudden Cardiac Death, 2004
2. Morris VB, Keelan T, Leen E et al. Sudden cardiac death in the young: a 1 year post mortem analysis in the Republic of Ireland. Ir J Med Sci 2009; 178(3): 257-261
3. Khan IA. Long QT syndrome: Diagnosis and management. Am Heart J 2002; 143: 7-14
4. Roden DM. Long-QT syndrome. NEJM 2008; 358: 169-176
5. http://www.azcert.org
6. Maron BJ, Shen W, Link MS et al. Efficacy of implantable cardioverter defibrillators for the
prevention of sudden death in patients with hypertrophic cardiomyopathy. NEJM 2000;
342 (6): 265-273
7. McKenna WJ, Behr ER. Hypertrophic cardiomyopathy: management, risk stratification
and prevention of sudden death. Heart 2002; 87: 169-176
8. Brugada P, Brugada J. Right bundle branch block, persistent ST-segment elevation and
sudden cardiac death: a distinct clinical and electrocardiographic syndrome. J Am Coll
Cardiol 1992; 20: 1391-1396
9. Bhuiyan ZA,Van den Berg MP, Van Tintelen PJ et al. Expanding Spectrum of Human RYR2Related Disease. New Electrocardiographic, Structural and Genetic Features. Circulation
2007; 116(14): 1569-1576
10. Russell M. Fabry disease – understanding a rare genetic disorder. Br J Dermatol Nurs
2004; 8(2): 14-16
11. Banikazemi M, Bultas J, Waldeck S et al. Agalsidase- Beta therapy for advanced Fabry
disease – a randomized trial. Ann J Med 2007; 146: 77-86
12. Priori SG, Schwartz PJ, Napolitano C et al. Risk stratification in long-QT syndrome. NEJM
2003; 348: 1866-1874
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