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Definition of cardiomyopathy
Cardiomyopathy is heart muscle disease,often of unknown cause. There are three
types1. Dilated cardiomyopathy2. Hypertropic obstructive cardiomyopathy
(HOCM)3. Restrictive cardiomyopathy
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Dilated CardiomyopathyThe heart is dilated and has impaired function.The coronary arteries are normal. Probablecauses of dilated cardiomyopathy include :
AlcoholViral infection (echovirus, coxsackievirus, andenteroviruses most likely)Untreated hypertension
Autoimmune diseaseThyrotoxicosisDrugs (cocaine, doxorubicin, cyclophosphamide,lead)Haemochromatosis
Acquired immune deficiency syndrome (AIDS)
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Investigation
Chest radiographyThis may show :Enlarged cardiac shadowSigns of pulmonary oedema (upper lobe blooddiversion, interstitial shadowing at the bases)Pleural effusions
ElectrocardiographyElectrocardiography may highlight :TachycardiaPoor R wave progression across the chest leads
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EchocardiographyPoints to consider with echocardigraphy include :
Can the dilated ventricles be easily visualized?Can the regurgitant valves be seen?Occasionally, intracardiac thrombus may be seen.Transthoracic echocardiography is not a reliable methodfor diagnosing this but it can be accurately diagnosed by
transoesophageal echocardiography.
Cardiac catheterizationThis is important to exclude coronary artery disease (themost common cause of ventricular dysfunction).
Blood testsViral titres may be useful and also thyroid function tests.
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Management
The management plan follows four basic steps (thesame applies for any other case of cardiac failure):
1. Search for and treat any underlying cause (e.g.stopalcohol)
2. Treat cardiac failure (diuretics, ACE inhibitors, nitrates)3. Treat any arrhythmias (digoxin or amiodarone for atrialfibrillation, amiodarone for ventricular arrhythmias)
4. Anticoagulate with warfarin to prevent mural thrombi.
If the cardiac failure does not respond to the abovesteps and the patient is suitable candidate then cardiactransplantation is a possible option.
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Hypertrophic obstructivecardiomyopathy
This disorder is characterized by asymmetricalhypertrophy of the cardiac septum-the cardiacseptum is hypertrophied compared to the freewall of the left ventricle.Hypertrophic obstructive cardiomyopathy isinherited as an aotusomally dominant trait withequal sex incidence.The myocytes of the left ventricle areabnormally thick when examinedmicroscopically.
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Clinical features
There are four main symptoms :1. Angina (even in the absence of coronary artery
disease)-due to the increased oxygen demands of the
hypertrophied muscle2. Palpitations-there is an increased incidence of atrialfibrillation and ventricular arrhythmias in this condition
3. Syncope and sudden death-which may be due to leftventricular outflow tract obstruction by the
hypertrophied septum or to a ventricular arrhythmia4. Dyspnoea-due to the stiff left ventricle, which leads toa high end-diastolic pressure and can therefore lead topulmonary oedema.
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It can be difficult to differentiate between HOCMand aortic stenosis on examination. Use thefollowing features to help :Pulse slow rising in aortic stenosis, jerky orwith a normal upstroke in HOCM.Thrill and murmur both found in the secondright intercostal space in aortic stenosis and atthe left lower sternal edge in HOCM.Variation of the murmur with Valsava manoeuvre this does not occur in aortic stenosis, but the
murmur of HOCM is increased because thevolume of the left ventricle is reduced by themanoeuvre and therefore the outflow obstructionworsens.
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Diagnosis and investigations
Electrocardiography
This is usually abnormal in HOCM. The mostcommon abnormalities are T wave and STsegment abnormalities; the signs of leftventricular hypertrophy may also be present.
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Continuous ambulatory electrocardiography
The presence of ventricular arrhythmias iscommon in patients who have HOCM and is a
cause of sudden death. It is thought that thepresence of ventricular arrhythmias on anambulatory ECG monitor is a risk factor forsudden death and that an antiarrhythmic agent
should be commenced. These tests are usuallyperformed as part of a yearly screeningprogramme for these patients.
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Echocardiography
This is the most useful investigation because itconfirms the diagnosis and can be used toassess the degree of outflow tract obstruction.
Characteristic echocardiography findingsinclude :
Asymmetrical hypertrophy of the septum.
Abnormal systolic anterior motion of the anteriorleaflet of the mitral valve.Left ventricular outflow tract obstrustion.
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Prognosis
Children who are diagnosed when they are
under 14 years of age have a poor prognosisand a high incidence of sudden death. Adultshave a better prognosis, but they also have ahigher mortality rate than the general population.
Another outcome is progressive cardiac failurewith cardiac dilatation.
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Management
Drug management As with aortic stenosis, vasodilators should beavoided because they worsen the gradientacross the obstruction.Therefore patients whohave HOCM should not receive nitrates. -blockers ( -adrenoceptor antagonists) areused because their negative inotropic effect actsto decrease the contractility of the hypertrophiedseptum and reduce the outflow tract obstruction.
Antiarrhythmic agents are important in patientswho have ventricular and atrial arrhythmias.
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Dual-chamber pacing
This reduces the outflow tract gradient by pacingthe heart from the right ventricular apex and
therefore altering the pattern of septal motion.New devices incorporate both a dual-chamberpacemaker and a cardioverter defibrillator totreat malignant ventricular arrhythmias inpatients with HOCM.
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Surgery
Surgery is used only when all other
treatments have failed. A myomectomy isperformed on the abnormal septum. Thereis a new catheter technique to infarct the
septum by occluding the septal artery.
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Restrictive cardiomyopathy
This is the least common of the cardiomyopathies indeveloped countries. The ventricular walls areexcessively stiff and impede ventricular filling, thereforeend-diastolic pressure is increased. The systolic function
of the ventricle is increased.Possible causes of restrictive cardiomyopathy include :Storage diseases (e.g.glycogen storage diseases)Infiltrative diseases (e.g.amyloidosis, sarcoidosis)
SclerodermaEndomyocardial diseases (e.g.endomyocardial fibrosis,hypereosinophilic syndrome, carcinoid)
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Clinical features
The main features are :Dyspnoea and fatigue due to poor cardiac
outputPeripheral oedema and ascitesElevated jagular venous pressure with apositive Kussmauls sign (increase in
jugular venous pressure duringinspiration).
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Management
There is no specific treatment and the
condition usually progresses towardsdeath relatively quickly, most patients donot survive beyond 10 years afterdiagnosis.
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