Diagnosis - Cardiomyopathy

Cardiomyopathy means ‘a disease of the heart muscle’. There are several different types, the main ones being:

1. Dilated cardiomyopathy
2. Ischaemic cardiomyopathy (due to coronary artery disease)
3. Hypertrophic cardiomyopathy

What is dilated cardiomyopathy?
Dilated cardiomyopathy (DCM) is a disease of the heart muscle that causes the heart to become enlarged and to pump less strongly. Unlike ischaemic cardiomyopathy, the coronary arteries are usually normal. The reasons why the heart muscle weakens are uncertain, but the process is probably slow and only presents with symptoms when quite advanced.

As a result the muscle of the heart becomes weak, thin, or floppy and is unable to pump blood efficiently around the body: this is called heart failure. This causes fluid to build up in the lungs, which therefore become congested, and results in a feeling of breathlessness. Sometimes there is also fluid accumulation in the tissues and organs of the body, usually the legs and ankles, and the liver and abdomen.

What causes dilated cardiomyopathy?
In the majority of cases of DCM the cause is not known. The condition is then termed idiopathic (no identifiable cause) dilated cardiomyopathy. There are, however, some factors that are accepted to cause or contribute to disease in individual circumstances.

Genetic/familial
All our heart proteins are coded by genes that we inherit from our parents. In the last decade, careful screening of families of DCM patients has shown mild abnormalities in at least a third of relatives, most of whom have no symptoms. There are as yet no good predictors as to who in a family might develop DCM. Family screening, with simple non-invasive ECG and echo tests, is usually offered to close relatives when a patient is first diagnosed with DCM. Gene tests are being developed but no simple test exists at present.

Viral infection
People encounter many viruses every day and, normally, the body’s immune system is very efficient at intercepting these viruses and neutralising them. However, a virus may in rare cases affect the heart of a normal person, often without other symptoms of the viral infection itself. This is called viral myocarditis and is commonly caused by a group of viruses called Coxsackie B viruses but the majority of people do not have any permanent damage to their heart. However, DCM may occur when the virus severely damages the heart during the initial infection, or perhaps when the virus triggers the body’s own defence system (immune system) to attack and damage the heart (see auto-immune disease below).

Excessive alcohol consumption and exposure to toxic agents
Excess consumption of alcohol is known to be a cause of DCM. If excessive alcohol intake is stopped before serious damage to the heart has occurred, then the heart can recover. In some cases, however, the damage is too great and the DCM persists for life. Irrespective of the cause of their disease, patients with an established DCM are advised to abstain from alcohol or at least to limit consumption to minimal amounts.

Other chemicals (e.g. anti-cancer therapies such as herceptin) have been reported to cause cardiomyopathy in some cases. It is difficult to predict who will develop this side effect, and heart function can return to normal with good medical therapy.

Pregnancy
Rarely, women in mid to late pregnancy or soon after delivery can develop DCM. In this setting, the condition is termed peripartum cardiomyopathy and occurs in approximately one in 10,000 pregnancies. Some of these women may have DCM due to one of the other causes outlined above, but coincidence makes the disease first obvious during pregnancy, probably because of the extra demands placed on the heart. This type of DCM may persist long after pregnancy has ended.

In true peripartum cardiomyopathy, the condition resolves within six to eight weeks of the delivery in 50 - 60% of cases, but may recur in a subsequent pregnancy. The cause of the occurrence or recurrence of peripartum cardiomyopathy is unknown.

For those women with DCM who become pregnant unexpectedly, it is also important to consider with your doctor stopping tablets such as ACE inhibitors and beta-blockers (see below) as they may damage the foetus - consult your doctor immediately.