K14 - Cardiomyopathy.pptx

8/12/2019 K14 - Cardiomyopathy.pptx

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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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K14 - Cardiomyopathy.pptx