- The term cardiomyopathy means a disorder of heart muscle. Often the cause is unknown, but several underlying causes/associations have been identified.
- Whatever the root cause, the disorder often manifests in one of four ways, and this largely determines the treatment approach and outcome. A common presenting pattern is heart failure, but sudden death is well documented.
- The condition cannot be cured, but can be managed, usually medically, though surgery may be used for hypertrophic obstructive cardiomyopathy (HOCM), and transplantation may be considered for some intractable forms. The longterm outcome is dependant on the underlying cause, with the best prognosis being for peripartum cardiomyopathy.
- Prevention is not really possible, though lifestyle modification could theoretically prevent the onset and advance of coronary artery disease, which, if untreated, becomes one of the common causes of cardiomyopathy.
In plain language, the term "cardiomyopathy" simply means "something wrong with the muscle of the heart" - in other words, the cardiomyopathies are disorders or diseases of heart muscle.
Two main classification systems are used: one system classifies according to known causes; the other sorts cardiomyopathies into categories according to anatomy and physiology. This second system is much more useful, as it links to treatment, and is internationally accepted.
This system will be used here, and recognises five main categories:
1. Dilated cardiomyopathy – (DCM)
In this condition there is enlargement of one or both ventricles, and the thickness of the muscle wall can vary from excessively thick to very thin. In extreme cases, all four chambers of the heart may be enlarged. The incidence of DCM seems to vary widely, but some studies suggest that more than 14% of the elderly population have some degree of DCM.
2. Hypertrophic cardiomyopathy (HCM)
Here there is abnormal, often localised, thickening of the heart muscle. This is a genetic disorder resulting in abnormal patterns of muscle cells in the heart, often affecting mainly the interventricular septum, which is the wall separating the two ventricles. The left ventricle is usually affected by this bulging septum, which takes up some of the cavity, thereby reducing the volume of blood the ventricle can hold and pump out.
The ventricle also may become stiffened and unable to relax completely to permit normal filling, and this can further reduce the volume of blood it can hold. When the upper part of the interventricular septum is affected, it often causes the mitral valve to leak. HCM is estimated to affect 1 in every 500 persons.
3. Restrictive cardiomyopathy (RCM)
In this condition, the ventricles are not dilated, but show impaired filling. While this is not as common a condition as HCM, it is a common cause of death in Africa, Asia and South/Central America, and is mainly linked to the high incidence of endomyocardial fibrosis in these regions.
4. Arrhythmogenic right ventricular cardiomyopathy (RVCM)
This is an unusual condition in which part or all of the right ventricular wall muscle is replaced with fatty or fibrous tissue. As little or no normal heart muscle remains, the ventricle cannot function normally.
5. Unclassified cardiomyopathies
This category exists for types that do not fit into any of the above categories, and the two best-known examples are:
- Endocardial fibroelastosis (EFE) – this occurs mainly in infants under one year, often together with other congenital heart disease. Survival is poor, and transplantation is often required.
- Left ventricular compaction – a rare entity, due to problems arising in the foetus.
1. Dilated cardiomyopathy
In this condition there is enlargement of one or both ventricles, and the thickness of the muscle wall can vary from excessively thick to very thin. In extreme cases, all four chambers of the heart may be enlarged.
The commonest causes of DCM are:
- Ischaemia (coronary artery disease)
- Heart valve disease
- Viral CM
- Genetic CM – a late manifestation of hypertrophic obstructive cardiomyopathy, or HOCM (see later)
2. Hypertrophic cardiomyopathy (HCM)
As already stated, this is a fairly common genetic condition, and can occur in varying degrees of severity. The heart muscle is thickened, often only in parts, and there may be dysfunction of the mitral valve as well.
There are non-genetic causes of hypertrophy, notably hypertension and aortic stenosis. Fabry’s disease is a storage disease which may lead to HCM, however this is an extremely rare condition.
3. Restrictive cardiomyopathy (RM)
Often the cause of RM is not known, although it may have a familial tendency. It may be caused by infiltrative diseases such as amyloidosis and haemochromatosis. Chemotherapy and radiotherapy have also been implicated. A large number of cases have scarring of the heart muscle, such as with endomyocardial fibrosis (EMF) and Loeffler’s endocarditis.
EMF is associated with extreme poverty and persistent parasitic infestations. Loeffler's is associated with persistently raised levels of specific white cells in the blood.
4. Right ventricular cardiomyopathy (RVCM)
In this unusual condition, there is replacement of heart muscle by fibrous or fatty tissue. Most often the cause is not known, but it may run in families, implying some form of genetic cause. Up to 30% of cases have a familial component. RVCM is a common cause of sudden death in young adults, especially athletes, in north Italy. A number of specific gene abnormalities linked to this condition have been identified.
The term "athlete’s heart" is often used to describe the normal response to intensive exercise shown by all muscle (including heart muscle): here the heart muscle is thickened, at the expense of the cavity size, which may be markedly decreased. Under these conditions, there is an increased risk for rhythm disturbances.
If an athlete has an underlying cardiomyopathy, heavy physical exertion carries a high risk of lethal arrhythmias. Many European sports organisations now advise screening of serious athletes to exclude underlying cardiomyopathies in order to prevent sudden death during sports activities.
The two main types in this category are:
- Endocardial fibroelastosis – this is found mainly in infants, and whose exact cause is unknown. It is thought to be a tissue response to injury caused by several proposed factors such as myocarditis, viral infections and maternal auto-immune disease.
- Left ventricular non-compaction – a rare abnormality due to faulty arrangement of heart muscle cells occurring in the foetus.
The other classification system lists the known causes of cardiomyopathies, and is shown for completeness, but is not as useful, practically, as the first system detailed above:
- Ischaemic - this presents usually as DCM, due to heart attacks
- Valvular CM - because of valve disease, the ventricle cannot function normally
- Hypertensive CM - leads to left ventricular hypertrophy and heart failure
- Inflammatory CM - viral and other infections, and autoimmune disorders
- Metabolic CM - storage and nutritional disorders
- General systemic disease - this includes leukaemia
- Muscular dystrophy - this includes Duchenne muscular dystrophy
- Neuromuscular disorders
- Toxic reactions - for example to drugs, toxins or radiation
- Peripartum CM - a specific condition associated with pregnancy
Symptoms and signs
The symptoms associated with this group of diseases are more dependent on the pathological subtype (i.e. dilated, hypertrophic or restrictive) than on the specific cause. However, it is important to look for such causes as they may potentially be treatable and may sometimes shed some light on the prognoses.
1. Dilated cardiomyopathy
This usually presents with symptoms of left-sided heart failure. These include inappropriate shortness of breath (dyspnoea) and decreased effort tolerance.
So-called right-sided symptoms (a tender, swollen abdomen, legs that swell etc.) sometimes predominate.
Less common presentations are dysrhythmias (abnormal cardiac rhythm) leading to syncope (falls due to brief loss of consciousness) or, rarely, sudden death. Systemic emboli (blood clots that affect a part of the body distant from the heart), which can present as a stroke or other medical problems, are sometimes the first sign.
2. Hypertrophic cardiomyopathy
This has distinctly different symptoms. Although shortness of breath may occur, more classic and prominent features include chest pain (angina-like in origin), palpitations (awareness of an abnormal heart beat) and syncope.
This form of cardiomyopathy has been strongly linked to sudden unexpected deaths occasionally seen in apparently healthy young adults. The classic scenario is that of a young, fit athlete collapsing and dying suddenly and unexpectedly on a sports field or even in a swimming pool.
3. Restrictive cardiomyopathy
This has a very non-specific presentation that may include swelling of the legs (oedema), a tender enlarged liver, free fluid in the abdomen (ascites) and eventually congested neck veins. Many other cardiac conditions have similar presentations, often resulting in (initially at least) misdiagnoses.
Your doctor will ask about your symptoms and perform a physical examination. Certain physical signs (such as heart murmurs and chamber enlargement) should alert an examining doctor to the possible presence of a cardiomiopathy.
An astute doctor can potentially diagnose a dilated or hypertrophic cardiomyopathy (although not with absolute accuracy). It can be very difficult (sometimes practically impossible) to diagnose a restrictive cardiomyopathy on clinical grounds alone.
The following special investigations will help make the correct diagnosis:
- Chest X-ray. This will show any enlargement of the heart and major blood vessels in the chest. Accumulation of fluid in the lungs (indicating heart failure) will also be shown.
- Electrocardiogram (ECG). There are no changes diagnostic of cardiomyopathy, but rhythm disorders, coronary artery disease and muscle thickness may be identified.
- Echocardiogram. This form of ultrasound gives information about the functioning of the heart and its valves, and the thickness of the muscle walls. It can also be used to measure the cardiac output (pumping ability) and the pressures within the heart.
- Exercise testing. This can record how the heart functions during physical activity. If a patient cannot exercise, other methods can be used to simulate exercise.
- Cathetersiation. This angiogram shows the chambers of the heart, as well as the flow through the coronary arteries. During the angiogram, accurate pressure readings can me made to assess heart function.
- Specific diagnostic tests for suspected underlying causes may include blood tests (e.g. thyroid functions or viral studies) and genetic tests (for HOCM).
The treatment of cardiomyopathy is dependent not only on the specific subtype of cardiomyopathy (i.e. dilated, hypertrophic or restrictive), but also on its cause if known. Any identified reversible causes (e.g. thyroid dysfunction) must be treated.
The degree of heart involvement and complications present will also determine the treatment. Many patients are in heart failure, so the treatment here will focus on this mainly. The management of these conditions is usually undertaken with specialist supervision.
1. Dilated cardiomyopathies
Different types of treatment are used to improve symptoms (i.e. the patient's quality of life), slow or reverse the deterioration of heart function and reduce mortality.
These types of treatment include:
- Treatment of the underlying causes where identified, e.g. total abstinence from alcohol.
- Vasodilator therapy: drugs that dilate (increase the diameter) of the arteries both improve the symptoms of cardiac failure and decrease the rate of further heart enlargement. Unless contraindicated, all patients with dilated cardiomyopathies should be on such drugs. The classes of drugs that are currently very popular are the so-called ACE-inhibitors (e.g. Tritace, Renitec and many others) and AT2 receptor blockers.
- Beta-blockers: In recent years, there has been great interest in the potential benefit of these drugs, previously thought to be harmful. Used correctly, these drugs have been shown to increase life expectancy in people with dilated cardiomyopathies. Examples include carvedilol and metoprolol.
- Drugs used to treat the symptoms of cardiac failure: Resistant cardiac failure usually requires diuretic therapy (i.e. water pills) and digoxin (which improves the way in which the heart contracts).
- Drugs used to treat the complications of dilated cardiomyopathy: These include anticoagulation (to keep the blood from clotting where thrombi are found) and specific anti-arrhythmic therapy.
- Dual chamber pacing (two pacemaker leads are inserted into the heart, one into the atrium or upper chamber and the other into the ventricle or lower chamber to facilitate synchronised contraction of the heart) and implantable cardioverter-defibrillators (a lead is placed into the heart that may record an abnormal cardiac rhythm and initiate a local electric shock to restore the normal rhythm) are treatments only available in very specialised centres. An implantable cardioverter-defibrillator effectively automatically puts the heart back into the correct rhythm if a potentially fatal arrhythmia occurs.
- Heart transplantation: Dilated cardiomyopathy is currently the commonest reason worldwide for this potentially lifesaving procedure.
2. Hypertrophic cardiomyopathies
Few forms of therapy have been shown to alter the natural progression of this disease.
Therapies used include:
- Beta-blockers: These drugs are the mainstay of treatment and are most useful in alleviating the chest pain associated with the disease.
- Calcium-blockers: This class of drugs alleviates symptoms in some people.
- Anti-arrhythmic drugs: Low-dose amiodorone is used in some cases, especially if there is a moderate risk of sudden death.
- Surgery: Septal myomectomy, which means the surgical removal of parts of the thickened or hypertrophied septum or other thickened heart muscle. (As a result of the thickening of the heart muscle, blood flow out of the heart may be obstructed and the surgical removal of the muscle may alleviate the obstruction.) In a patient whose condition is severe enough to warrant this type of surgery, there is usually accompanying mitral valve dysfunction (leak), so that the valve is also replaced at the same time. Heart transplantation is reserved for end-stage heart failure.
- Catheter interventions: In the past, alcohol was injected directly (via a catheter in the heart) into the arteries feeding the thickened septum. This caused the heart muscle to die (i.e. induced a heart attack in that thickened part of the heart). This procedure is now discarded in favour of medical management plus corrective surgery when appropriate.
- Implantable cardioverter-defibrillators: These are beneficial for people who previously suffered a life-threatening dysrhythmia.
3. Restrictive cardiomyopathy
There is unfortunately no specific therapy for this disease. Where this is secondary to a known disorder (e.g. sarcoidosis), treatment of the underlying cause may help.
Treatment of the heart is aimed at reducing congestion and heart failure, e.g. the use of diuretics and calcium-channel blockers. Heart transplantation remains the only hope in severe intractable cases.
1. Dilated cardiomyopathies
The majority of patients with dilated cardiomyopathies (80%) will survive for five years after the initial diagnosis has been made, but will suffer progressively increasing symptoms and decreasing quality of life.
Predictors of mortality (factors that increase the risk of death) include:
- Severe heart failure
- Massive cardiac enlargement
- Poor contractility and wall motion abnormalities in the heart muscle
- Syncope attacks (fainting)
- Male sex and advanced age
Death may result from either progressive heart failure or from dysrhythmias, which cause sudden death. This may be the eventual cause of death in up to half of people with this condition. On the other hand, people may live for many years with only mild to moderate symptoms, adequately alleviated (but not cured) by medical means.
2. Hypertrophic cardiomyopathies
The major concern in this condition is sudden cardiac death, often without warning. Predicting which people are at particular risk is an imperfect art.
The following factors are, however, considered risk factors for sudden cardiac death with hypertrophic cardiomyopathies:
- Genetic factors: Certain mutations (e.g. troponin T) are associated with a high risk, even when little heart enlargement is evident. Other (beta-myosin light chain) mutations carry relatively low risk, despite significant heart enlargement.
- A family history of sudden cardiac death.
- Previous cardiac arrest (heart beat and blood circulation suddenly stopped).
- Dangerous cardiac rhythm disturbances on ambulatory ECG (ECG leads are attached to the patient and the heart rhythm is recorded over a period of 24 or 48 hours). Dangerous dysrhythmias include sustained ventricular tachycardia or multiple episodes of nonsustained ventricular tachycardia.
- Recurrent syncopal attacks.
- Pronounced cardiac enlargement.
Most deaths occur in young patients during strenuous physical exertion and in the early hours of the morning.
Some people with a hypertrophic cardiomyopathy may later develop thinning of the heart wall and may eventually have signs and symptoms very similar to a dilated cardiomyopathy. These people sometimes succumb to progressive cardiac failure and not dysrhythmias (sudden death).
3. Restrictive cardiomyopathies
The outcome of this subtype of cardiomyopathy varies greatly according to the underlying causes, being resistant to most types of treatment. People with amyloidosis (one of the underlying causes) have a grave prognosis, whereas those with haemochromatosis fare much better when adequately managed.
The idiopathic form of the disease (endomyocardial fibrosis) has a slow but steady progression to more severe heart failure. Medical and surgical treatment can, at best, only relieve symptoms. Heart transplantation (when available) prolongs life.
A special mention must be made of peripartum cardiomyopathy, which has the best prognosis – 94% survival at 5 years.
It remains unlikely that preventative measures currently or in the near future will play a major role in the control of these diseases.
Measures that may decrease the chances of developing a dilated cardiomyopathy are:
- Refraining from excessive alcohol intake.
- Refraining from physical exercise during viraemia (that is, when viral particles are found in the blood, e.g. during the early phases of flu).
- Early diagnosis and treatment of hypertension.
Hypertrophic cardiomyopathies are largely genetic diseases and current measures cannot prevent the development of this affliction. Genetic testing in selected individuals (family members of affected persons) can lead to carrier detection (of the mutations) and early diagnosis. A person may be diagnosed as having ‘hypertrophic cardiomyopathy’ many years before actual heart enlargement develops. Different mutations have been associated with differences in prognosis, or outcome.
Few forms of restrictive cardiomyopathy are preventable. One possible exception is the condition haemochromatosis (a disorder of iron metabolism), where appropriate control of the disease (by regularly taking off quantities of blood which reduces the amount of iron in the body, and treatment with desferoxamine) may prevent cardiac involvement.
When to call your doctor
The symptoms of the spectrum of cardiomyopathies (dilated, hypertrophic or restrictive) are not specific, but the following are definitely indications that you should consult your doctor:
- Unexplained shortness of breath
- Chest pains
- Unexplained fainting
- Previous unexplained cardiac arrest
- A family history of sudden cardiac deaths among young adults
- A family history of known cardiomyopathies
Family members of patients with documented hypertrophic cardiomyopathy can be screened by either echocardiography and/or genetic testing. Echocardiography is usually repeated at regular intervals, especially in high-risk families. Although these measures may not necessarily prolong life in all affected individuals, they may in certain individuals lead to further special investigations such as ambulatory ECG monitoring and guide prophylactic anti-dysrhythmic measures which may potentially improve the quality of life in most and prolong life significantly in some.
Reviewed by Dr A.G. Hall (B.Soc.Sc.(SW), MB,Ch.B), June 2007