Download Understanding cardiomyopathy

MODULE 11:
Cardiology
More people in Ireland die from diseases of the circulatory
system than from any other condition. Ireland is still above the
EU average for premature deaths from coronary heart disease
and three out of four deaths in those under 65 are the result of
heart attack, stroke or another disease of the circulatory
system.
The WIN Continuing Education module for 2005 is focusing on
various aspects of cardiac nursing. The articles are aimed at
assisting nurses to understand, care for and educate patients
who present with cardiac conditions.
To date this module has addressed the pathogenesis of
PART 8
Understanding
cardiomyopathy
by Lisa Browne and Mary Mooney
CARDIOMYOPATHY is a disease of the heart muscle, whereby the
myocardium weakens and loses its ability to pump or receive
blood effectively. This predisposes the person to varying degrees
of cardiac failure. In addition, persons with cardiomyopathy are
often at increased risk of arrhythmia and sudden cardiac death.
This article will address the incidence, pathogenesis and the treatment options available to those with cardiomyopathy.
Ischaemic and non-ischaemic cardiomyopathy
There are various types of cardiomyopathies; these broadly fall
into two main categories namely ischaemic or non-ischaemic in
origin.
Ischaemic cardiomyopathy typically refers to heart muscle
damage, which results directly from obstructive coronary disease.
Patients with this disease may have had a prior myocardial infarct
or have significant obstructive coronary disease causing symptoms of angina. Typically these individuals display symptoms of
heart failure caused by myocardial ischaemia. The management
of these patients has already been addressed in this series and
includes revascularisation, secondary prevention and symptom
management of heart failure.
There are four main types of non-ischaemic cardiomyopathy,
namely dilated, hypertrophic, restrictive and arrhythmogenic
right ventricular cardiomyopathy. Cardiomyopathy can also be
caused by many other pathologies including hypertension, infection, alcohol and various genetic and idiopathic causes.
Dilated cardiomyopathy (DCM)
Dilated cardiomyopathy (DCM) is characterised by the presence
coronary heart disease, the in-hospital management of patients
who present with conditions including STEMI, NSTEMI and
unstable angina, and the pathogenesis of cardiac failure.
This month we focus on cardiomyopathy – a disease of the
heart muscle. Upcoming articles will focus on the management
of patients with atrial fibrillation, pacemakers and other
implantable devices and gender issues in cardiology.
At the end of the module you will have the opportunity to
complete some self-test questions to enable you to identify
what you have learned each month. It is therefore advisable that
you keep the entire series of articles for reference.
of dilatation of one or both ventricles. This weakens the heart’s
pumping ability.The heart tries to compensate with this pumping
limitation by stretching and increasing its contractile force. This
compensatory mechanism eventually fails leading to both systolic and diastolic dysfunction, predisposing to symptoms of
congestive heart failure.
In addition, this progressive dilatation of both ventricles can
predispose to valvular regurgitation, the formation of mural
thrombus and atrial and ventricular arrhythmias.
Causes
In most cases the disease is idiopathic. However several factors
have been associated with its occurrence including chronic excessive alcohol consumption, viral infections, which lead to
inflammation of the heart muscle (myocarditis), undiagnosed and
or untreated hypertension and familial or genetic factors. In some
20% of patients, screening of relatives will reveal evidence of the
condition.2
Management
The management of patients with DCM focuses primarily upon
the relief of both the symptoms and the progression of heart failure. In addition, efforts are made to treat and prevent
complications of this disease. Simple life style changes with
dietary salt reduction; alcohol cessation and symptom limited
exercise training can improve clinical symptoms. Pharmacological
management is comparable to the treatment of heart failure in
general, with ace inhibitors, beta-blockers and diuretics.
Prognostic predictions for patients with DCM are difficult. In
many cases the diagnosis is only made when the disease has
reached an advanced stage and some 50% of these patients will
die within two years.2 For these individuals, heart transplantation
offers the only hope of long-term survival and is considered for
patients who are unresponsive to medical therapy.
Peripartum cardiomyopathy (PPCM)
Peripartum cardiomyopathy (PPCM) is a form of DCM, which
develops in the last month of pregnancy or within five months of
delivery. The cardiomyopathy may or may not have been preexisting and exacerbated by the pregnancy.
In the severe forms, women may present with acute heart failure and marked fluid retention requiring positive inotropic
support, a ventricular assist device or even transplantation. Ven-
Continuing Education
tricular function generally improves but there is a higher risk of
recurrence with subsequent pregnancies.5
Hypertrophic cardiomyopathy (HCM)
Hypertrophic cardiomyopathy (HCM) is a complex and relatively common genetic cardiac disorder affecting approximately
one in every 500 individuals in the adult general population.1 It is
a familial or inherited disease caused by mutation in one of 10
genes each encoding protein components of the cardiac sarcomere.
Diagnosis
The diagnosis is most commonly made by echocardiography,
which depicts diffuse or segmental left ventricular wall thickening (greater or equal to 15mm). Abnormalities in systolic and
diastolic function causes functional limitation with chest pain,
dyspnoea and syncope.
Electrical instability from myocardial disarray and fibrosis can
predispose to arrhythmias and sudden death. Obstruction to the
left ventricular outflow tract is found in about one third of
patients,1 caused by anterior or posterior movement of the mitral
valve leaflet. Patients with outflow tract obstruction are termed as
having hypertrophic obstructive cardiomyopathy (HOCM).
The clinical course of HCM is variable with many patients
remaining stable over long periods and up to 25% of patients
achieving normal longevity.1
This clinical course may, however, be interrupted for many
patients with the progression of symptoms, heart failure and
complications, including embolic stroke, particularly in those with
concurrent atrial fibrillation.
Sudden and unexpected death is now recognised as the most
devastating complication of this disease and may occur as the initial disease presentation, frequently seen in adolescents or in
young adults. Furthermore, the presence of outflow obstruction is
a strong predicator of disease progression to HCM related death.
Management
The main goal of treatment is to alleviate symptoms and to prevent sudden death. Beta-blockers are effective in reducing heart
rate and myocardial oxygen demand, thereby improving symptoms and exercise tolerance.
Paroxysmal or established atrial fibrillation develops in approximately 25% of cases, often necessitating the use of
anti-arrhythmic and anticoagulation therapy. Patients with this
condition should be assessed to determine their risk of sudden
death.
Individuals at highest risk include those with:1
● Prior cardiac arrest
● Family history of premature cardiac death
● Evidence of non-sustained ventricular tachycardia on holter
● Unexplained syncope, particularly during exercise
● Severe left ventricular wall thickening of 30mm or more (normal
< 13mm).
Individuals deemed high risk are considered for implantable
cardioverter defibrillators and require specific exercise prescription. Young people with HCM should be restricted from intense
competitive sports to reduce the risk of sudden death; in addition
they should be advised to refrain from heavy lifting or activity
involving burst exertion.
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WIN September 2005
Restrictive cardiomyopathy (RCM)
Restrictive cardiomyopathy (RCM) is rare, and characterised by
restrictive filling, reduced diastolic volume with near normal systolic function. It may be idiopathic but is generally caused by
another disease process, which leads to myocardial infiltration.
Known causes include a build-up of protein in the heart muscle
(amyloidosis), or excess iron in the blood stream (haemochromatosis).
Management strategies focus on treating the underlying cause,
improving symptoms of congestive heart failure and preventing
the development of mural thrombus with anticoagulation.
Arrhythmogenic right ventricular cardiomyopathy (ARVC)
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is
generally a familial disease. It is characterised by progressive dysplasia, due to fatty and fibrofatty myocardial infiltration of the
right ventricle.3
It manifests clinically with ventricular arrhythmias originating
from the right ventricle or in sudden death. Patients’ ECGs typically depict T-wave inversion in leads V1-V3 with right bundle
branch block. In addition, there may be a terminal notch on the
QRS complex called an ‘epsilon’ wave.
ARVC is one of the major causes of sudden cardiac death in
young people and is commonly precipitated by exercise. Treatment strategies for patients diagnosed with this condition
involves antiarrhythmic therapy with beta-blockers or amiodarone. Radio-frequency ablation may be attempted, however, it
is often necessary to use an implantable cardioverter defibrillator
because of the inherent high risk of sudden cardiac death.
Cardiomyopathy is a particularly poignant cardiac condition.
After coronary heart disease, cardiomyopathies represent the second largest group of patients who die suddenly from a cardiac
cause.
In many cases, a diagnosis of cardiomyopathy is only made
when symptoms are advanced or at post mortem. While the disease can manifest at any age, sudden death is more common in
adolescence or in young adults.
Treatment strategies for those with symptoms are generally
comparable with the treatment of heart failure. Due to the strong
familial relationship, close family members of those affected
should be referred for screening. This for the most part involves
resting and exercise ECG, ECHO and ambulatory holter monitoring, with other screening tests available at specialist cardiac
centres.
Genetic study of this complex cardiac disease is evolving, with
many causative gene mutations already identified. Future study in
this area may facilitate earlier diagnosis and more definitive
mutation screening of families.
Lisa Browne is a chest assessment nurse at the Mater Hospital, Dublin and Mary
Mooney is a lecturer in cardiovascular nursing at TCD
References
1. ACC/ESC American College of Cardiology / European Society of Cardiology Clinical
Expert Consensus Document on hypertrophic Cardiomyopathy. European Heart Journal
2003; 24, 1965-1991
2. Swanton RH Pocket Consultant, Cardiology. Fifth edition. Blackwell Publishing 2003
3. Zipes DP et al Sudden Cardiac Death. Circulation, 1998; 98; 2334-2351
4. Dalla Volta D (ed) Cardiology. McGraw-Hill, London, 1999
5. ESC Expert consensus document on the management of cardiovascular disease during
pregnancy, European Heart Journal 2003, 24: 761-781