Cardiomyopathy

Cardiomyopathy is the name given to a number of conditions that affect the heart muscle. The heart muscle thin, thicken or stiffen - which can make it difficult for your heart to effectively pump blood around your body. This can sometimes lead to heart failure, which causes fluid to build up in the lungs, abdomen, legs, feet or ankles.

Signs and symptoms

Cardiomyopathy can cause no symptoms for many people, particularly in its early stages. As the condition worsens, signs and symptoms of heart failure can appear, including:

• Difficulty breathing;
• Shortness of breath, particularly when exercising;
• Tiredness or fatigue;
• Swelling in the abdomen, feet, ankles or legs;
• Lung crackles, indicating fluid build-up on the lungs;
• Dizziness and fainting;
• Irregular heartbeats, and;
• Chest pain.

Causes and risk factors

The specific cause of cardiomyopathy is often not known. Causes and triggers that may lead to the development of the condition include:

• Genetics. It is possible that certain gene mutations are inherited that give people an increased risk of developing the condition. This may be the cause in about 30% of dilated cardiomyopathy cases (see below);
• Viral infections, including adenoviruses and enteroviruses, that can target particular cells within the heart. Not all people affected by these viruses will develop cardiomyopathy;
• An autoimmune response developing against your heart cells;
• Tachycardias. These are heart rates that are faster than normal. Examples of tachycardia include supraventricular tachycardia and atrial fibrillation;
• Toxic agents that specifically affect heart cells in some people. These can include chemotherapy drugs, alcohol, cocaine and other narcotics;
• Heart attacks can damage the heart muscle and sometimes cause scarring. Scar tissue can affect the way that electrical impulses flow around the heart and prevent it from beating normally, and;
• Hypertension, which can place additional strain on the heart.

Types

There are four types of cardiomyopathy: dilated, hypertrophic, restrictive and arrhythmogenic right ventricular. Each type of cardiomyopathy affects the heart muscle in a different way.

Dilated cardiomyopathy

In dilated cardiomyopathy, the heart enlarges, causing the heart muscle to stretch and become thinner. When this occurs, the heart cannot contract like it normally would, and has trouble pumping blood around the body. As the heart becomes weaker, heart failure can occur.

Dilated cardiomyopathy can also lead to irregular heartbeats, heart valve problems and blood clots in the heart due to blood pooling in its chambers and not being pumped out. This condition affects more men than women, and usually occurs between 20-60 years of age.

Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy occurs when the heart muscle walls thicken. This happens when many individual cells within the heart grow larger, and together they can block the flow of blood from ventricles.

The heart must then work harder to move blood around the body, leading to chest pain and shortness of breath. Hypertrophic cardiomyopathy is common, affecting around one in 500 people at any age.

Restrictive cardiomyopathy

Restrictive cardiomyopathy involves the heart muscle becoming stiff. This is due to abnormal heart tissue - usually scar tissue - replacing normal heart muscle. This can affect how well the heart can pump blood and can lead to heart failure and arrhythmias. Restrictive cardiomyopathy usually affects older adults.

Arrhythmogenic right ventricular cardiomyopathy

This involves changes in the heart's electrical system. Part of the healthy heart muscle tissue is replaced with scar tissue, which prevents the electrical circuitry in the heart from working properly, causing irregular heartbeats. Symptoms can include palpitations and fainting. This type of cardiomyopathy usually affects younger people, including teenagers and young adults.

A healthy heart and the four types of cardiomyopathy. 

Methods for diagnosis

In some cases, cardiomyopathy does not have any symptoms, particularly in the early stages. This is because the heart can often compensate for any problems it has by working harder. To make a diagnosis, your doctor will look at your symptoms, conduct a physical examination and perform some diagnostic tests including a chest X-ray, echocardiography, electrocardiography and blood tests. To help identify the cause of your cardiomyopathy, a biopsy of heart muscle (endomyocardial biopsy) may be performed.

Chest X-ray

A chest X-ray can show whether the cardiac muscle is enlarged, or if there is fluid build-up caused by heart failure.

Echocardiography

Echocardiography allows your doctor to see the size of your heart and also how well it is working. It can show how hard your heart is pumping blood, whether it is leaking and highlight areas of damage. This can also indicate what type of damage the heart has sustained.

Electrocardiography

Electrocardiography (ECG) is used to determine if there are any abnormalities in your heart's rhythm. This can be particularly important when diagnosing restrictive cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy.

An electrocardiography procedure. 

Stress test

A stress test involves assessing your heart while it is under stress, or beating fast. This can be done while exercising, or after taking medication that makes your hear beat faster.

Coronary angiograph

A coronary angiograph is used to give an image of the coronary arteries, which supply the heart with blood, and of the pumping function of the heart. A special dye is injected into the arteries near the heart, and then images are taken. The way the dye shows up in the images show how the dye travels through the heart and nearby blood vessels.

Ejection fraction

The ejection fraction is the amount of blood that is ejected out of the left ventricle with each heartbeat. This measurement can give an indication of how well the heart is pumping blood and indicate if there is evidence of heart failure.

Endomyocardial biopsy

An endomyocardial biopsy is a very small piece of tissue taken from the heart and examined under a microscope. This can be used to see whether any changes in cells have occurred. It can be particularly useful for identifying if your cardiomyopathy was caused by a viral infection.

Types of treatment

Treatment of cardiomyopathy aims to help you to manage your condition while living a fulfilling life. A main focus of treatment is to identify and treat any underlying condition that has caused your cardiomyopathy.

Treatments can include lifestyle changes, medications, surgery or medical devices.

Lifestyle changes

Some lifestyle changes include regular light physical activity, reducing excess body fat, not smoking, eating a healthy diet that is low in fat and salt, limiting alcohol intake and getting adequate rest. If heart failure worsens due to cardiomyopathy, your doctor may recommend a daily limit on the amount of fluids you drink.

Medications

To treat the various forms of cardiomyopathy, a combination of medications may be required. Depending on your symptoms, some medications can include:

Diuretics

Diuretics, such as frusemide, remove excess fluid from your body by making you urinate more often. Sometimes, diuretics can also cause your body to lose natural minerals, including magnesium and potassium, so your doctor may monitor the levels of these in your blood and prescribe supplements if needed.

Angiotensin-converting enzyme (ACE) inhibitors

ACE inhibitors are vasodilators that can reduce blood pressure by widening blood vessels. This can ease the strain on the heart and lead to a reduction in your body's salt and water retention. Some examples include enalapril, lisinopril and captopril.

Beta-blockers

These medications work by slowing your heart rate and reducing your blood pressure. Some examples include carvedilol, metoprolol and bisoprolol.

Digoxin

Digoxin, also known as digitalis, helps your heart to pump more effectively by increasing the strength of your heart muscle contractions. Digoxin also tends to slow down the heart rate and regulate a normal rhythm.

Additional medications

Along with your cardiomyopathy medications, your doctor might also prescribe other medications. These can include a statin (a cholesterol-lowering medication) if required, nitrates for chest pain, or blood-thinning medications (warfarin) to prevent blood clots.

Surgery and medical devices

In some cases of cardiomyopathy, surgery or medical devices may be needed. These can include:

Implantable cardioverter-defibrillators (ICDs)

These are small electrical devices surgically placed in your chest. The ICD can pace your heart to a normal rhythm, or automatically defibrillate (shock) your heart if you develop a dangerous rhythm.

Left ventricular assist devices (LVDs)

These are heart pumps that are surgically inserted and attached to a damaged heart. Powered by an external battery pack, they can be used as a substitute for a heart transplant, or while you wait for a donor heart to become available.

Septal myectomy

A septal myectomy is used for people with hypertrophic cardiomyopathy. This involves open heart surgery to remove part of the thickened wall of the heart to improve blood flow from the heart.

Heart transplant

In some cases, when other treatments are not successful, a donor heart may be required.

Potential complications

Some complications associated with cardiomyopathy include:

Heart failure

Heart failure is a condition in which your heart is unable to pump enough blood around your body. This can lead to blood 'damming up' behind the heart, causing fluid to collect in your lungs or other body tissue.

Stroke

A stroke is when a blood clot blocks a blood vessel in your brain. During heart failure, blood may travel more slowly through the heart. This can lead to the formation of clots and increase your risk of having a stroke.

Kidney failure

Reduced blood flow caused by cardiomyopathy can cause your kidneys to fail. If you suffer significant kidney damage, you may require dialysis.

Heart valve problems

If your heart becomes enlarged, or the pressure within your heart becomes very high, your heart valves may not work properly.

Prognosis

Cardiomyopathy is a life-threatening condition. In some cases, with correct treatment, symptoms can subside and heart function can improve. Depending on your condition, lifestyle changes, medication, or occasionally surgery can help give you a better quality of life.

Prevention

It is not possible to prevent inherited forms of cardiomyopathy, but it is possible to live a healthy lifestyle and limit risk factors of the condition occurring. This can involve exercising regularly, limiting alcohol, and avoiding viral and toxic agents that can damage your heart. It is also important to treat any conditions that can lead to cardiomyopathy, such as hypertension, as soon as they are identified.

Genetic testing in those with a family history of cardiomyopathy can allow for early detection and treatment.