Cardiomyopathy

• What is Cardiomyopathy
• Statistics on Cardiomyopathy
• Risk Factors for Cardiomyopathy
• Progression of Cardiomyopathy
• Symptoms of Cardiomyopathy
• Clinical Examination of Cardiomyopathy
• How is Cardiomyopathy Diagnosed?
• Prognosis of Cardiomyopathy
• How is Cardiomyopathy Treated?
• Cardiomyopathy References

What is Cardiomyopathy

Cardiomyopathy is disease affecting the heart muscle. Most cardiomyopathies affect the left ventricle of the heart, which is the largest chamber responsible for pumping blood throughout the entire body. Although many conditions can affect the heart muscle, by definition, cardiomyopathy only includes primary abnormalities of the myocardium. Thus, the term does not include acute myocardial ischaemia (lack of oxygen), or hypertensive or valvular disorders of the heart.

There are four main types of cardiomyopathy:

• Dilated cardiomyopathy (DCM): Ventricular dilation;
• Hypertrophic cardiomyopathy (HCM): Hypertrophy or thickening of the myocardium.
• Restrictive cardiomyopathy (RCM): Impaired ventricular filling.
• Arrhythmogenic right ventricular cardiomyopathy: Unlike for other types of cardiomyopathy, the right ventricle is mainly involved. This type is commonly associated with abnormal heart rhythms.

Statistics on Cardiomyopathy

Myocardial (heart muscle) dysfunction occurs very commonly, usually due to other diseases such as coronary artery disease, high blood pressure, and diseases of the heart valves. Disease originating in the heart muscle itself (cardiomyopathy) is much rarer.

It is thought that around one in 500 Australians suffer from cardiomyopathy. The most common type is dilated cardiomyopathy.

Risk Factors for Cardiomyopathy

In most cases, the cause of cardiomopathy is not known. However, in some cases, cardiomyopathy can be shown to be related to the following factors:

Dilated cardiomyopathy

• Genetics: About 20-30% of cases of dilated cardiomyopathy are thought to run in families. The exact genes involved are unknown;
• Viral infection of heart muscle (myocarditis), from coxsackie virus B and others;
• Alcohol and other toxins, including the chemotherapy drug doxorubicin;
• Pregnancy;
• Other diseases: Haemochromatosis, sarcoidosis, systemic lupus erythematosus (SLE), systemic sclerosis and muscular dystrophy have all been associated with dilated cardiomyopathy.

Hypertrophic cardiomyopathy

About 50% of cases are familial (i.e. inherited). The type of inheritance is called autosomal dominant which means the abnormal gene only needs to be passed from one parent for offspring to get the disorder. The genes involved are associated with the heart’s contractile mechanism so that when they are abnormal the muscle becomes thick and overactive. HCM may also be associated with other diseases such as Friedrich’s ataxia and Noonan’s syndrome.

Restrictive cardiomyopathy

• Amyloidosis (and other infiltrative disease): This is the most common form of restrictive cardiomyopathy where abnormal proteins accumulate in the heart muscle;
• Sarcoidosis: This is a systemic disorder of unknown cause that causes granulomas to form in various tissues including the heart muscle;
• Radiation fibrosis;
• Endomyocardial fibrosis (a disease occurring mainly in Africa and tropical areas);
• Loeffler’s endocarditis (a disease causing fibrosis and thickening of cardiac muscle).

Progression of Cardiomyopathy

As the cardiomyopathy becomes worse, patients will begin to suffer from arrhythmias (abnormal heart rhythms) and cardiac failure. Patients are at risk of sudden death due to ventricular arrhythmias. In addition, cardiac failure may progress to be life threatening therefore requiring transplantation.

Symptoms of Cardiomyopathy

Your doctor will ask you numerous questions about your symptoms and family history to elicit information in order to diagnose this disorder.

Often patients with cardiomyopathy may have close relatives with the disorder or family history of sudden or premature death. If you have a close relative who was previously well and died suddenly it may be worth seeing a doctor to investigate the possibility of these disorders.

Each of the cardiomyopathies often presents with symptoms of right or left heart failure or arrhythmias (irregularities in your heart beat). Right heart failure may cause tiredness, swelling of the ankles and nausea. Left heart failure causes fatigue, and breathlessness on exertion, or at night. Arrhythmias, on the other hand, may be experienced as palpitations or with tiredness, faniting or dizzy spells.

The first symptom of DCM is often shortness of breath that may be wrongly attributed to a chest infection. HCM, on the other hand, freqently initially presents with chest pain which can mimick that present in angina.

Clinical Examination of Cardiomyopathy

Your doctor will carefully examine your entire cardiovascular system to make the diagnosis of these disorders. The character of the pulse and abnormal and extra heart sounds are important signs to be elicited. The doctor will also examine your abdomen and lower limbs to look for swelling which occurs with right heart failure. This is because the heart is unable to pump blood so the back pressure leads to pooling of blood in interstitial tissues. Another important part of the examination is evaluating the JVP which is a particular vein present in your neck. This also helps the doctor to decide whether heart failue is present.

How is Cardiomyopathy Diagnosed?

The commonly used tests for investigating heart disease are chest x-ray, electrocardiogram (ECG), and echocardiogram (a test looking at the structure and function of the heart).

Prognosis of Cardiomyopathy

Dilated cardiomyopathy

This has a poor prognosis. Fifty percent of patients die within 2 years; 25% of patients survive longer than 5 years. The two most common causes of death are progressive cardiac failure and arrythmia.  

Hypertrophic cardiomyopathy

The overall annual mortality from sudden death is 3-5% in adults and at least 6% in children and young adults. However, severity of disease and prognosis varies widely according to the genetic features involved. Certain genes are associated with a worse prognosis.

Restrictive cardiomyopathy

The worst prognosis is in patients with cardiac amyloidosis, in whom disease may recur after transplantation. Overall this disease has a poor diagnosis with many patients dying within a year of the diagnosis.

Arrhythmogenic right ventricular cardiomyopathy

This condition often leads to heart failure and sudden cardiac death as people are often unaware they have this condition as it is assymptomatic.

How is Cardiomyopathy Treated?

While heart failure and other features of cardiomyopathy can be treated, the only real cure for most forms of the disease is cardiac transplantation. This is usually only considered in severe cases, and in some situations, the disease may return after transplantation. Treatment of the symptoms of cardiomyopathy includes treatment of heart failure, arrhythmias, angina and emboli with standard pharmacological agents. Treatment will vary depending on the severity of your symptoms. Lifestyle factors such as avoiding competetive sportining activities in patients with HCM, are also other important aspects of management.

Heart failure is treated by medications acting on the kidneys (diuretics), on the blood vessels (ACE inhibitors, calcium channel blockers), and on the heart (beta-blockers, digoxin). In fact, most of these medications have effects on many different parts of the body. Cardiac rehabilitation is also important in patients with mild to moderately severe heart failure. Electrical leg stimulation may be useful in patients with more severe heart failure who are unable to exercise due to severe dyspnoea. Arrhythmias are treated by drugs acting on electrical properties of the heart muscle, or by the insertion of a pacemaker. Angina is treated by a range of drugs that open up the arteries and improve blood flow to the heart muscle (nitrates, beta-blockers, calcium channel blockers). Emboli arising from the heart are prevented by blood thinners such as aspirin and warfarin in patients at risk.

Severe cases of DCM and RCM may necessitate cardiac transplantation but this is limited by the amount of available donors. In the former case overall survival results are good. HCM can also be treated partly by surgical methods to remove some of the obstructing musclular septum.

In addition to the above treatments it is likely your doctor will offer screening of your close relatives to ensure they do not suffer from the same condition. this will include physical examination by a cardiologist, ECG and echocardiography testing at regular intervals throughout their life. Your doctor will also explain risks involved in apssing the condition on to your offspring.

Cardiomyopathy References

1. Cotran RS, Kumar V, Collins T. Robbins Pathological Basis of Disease Sixth Ed. WB Saunders Company 1999. pp578-584.
2. Kumar P, Clark M. Clinical Medicine. Fifth Ed. WB Saunders, 2004. pp810-815.
3. Longmore, Wilkinson, Rajagopalan. Oxford Handbook of Clinical Medicine. 6th Edition. Oxford University Press. 2004. p156.
4. McTaggart D. Hypertrophic Cardiomyopathy- An important cause of unexpected sudden cardiac death, Pulse News. Launceston, Tasmania, 2005.
5. Oakley C. Aetiology, diagnosis, investigation, and management of the cardiomyopathies. BMJ 1997;315:1520-1524
6. Talley NJ, O’Connor S. Clinical examination. Fourth Ed. MacClennan & Petty, 2001. pp 81-82.
7. The Cardiac Society of Australia and New Zealand. Guidelines for the Diagnosis and Management of Familial Dilated Cardiomyopathy. Available [online] at URL:http://www.csanz.edu.au/guidelines/practice/Familial_Dilated_Cardiomyopathy.pdf
8. The Cardiac Society of Australia and New Zealand. Guidelines for the Diagnosis and Management of Hypertrophic Cardiomyopathy. Available [online] at URL: http://www.csanz.edu.au/guidelines/practice/Hypertrophic_Cardiomyopathy.pdf