Overview

Dilated cardiomyopathy (DCM) is a disease of the heart muscle (myocardium). It belongs to a group of diseases of the myocardium which are all defined by structural and functional abnormalities of the ventricles.

DCM usually begins in the left ventricle. Over time the ventricle stretches and its walls grow thinner to the point where the heart cannot pump the blood as effectively anymore. For some people, dilated cardiomyopathy can be totally asymptomatic, but due to its diversity it can also present as a life-threatening condition. DCM is a common cause of heart failure, irregular heart rhythms (arrhythmias), blood clots and sudden death.(2)

What makes the DCM stand out is the extensive list of causes behind it. The common causes include infections and gene mutations, but there are also DCMs associated with alcohol, long term tachycardia or many other underlying conditions such as autoimmune diseases, coronary artery disease, heart attack, high blood pressure, diabetes, hemochromatosis, end-stage kidney disease, sarcoidosis, neuromuscular diseases, etc. (4,5)

Take a look at the most common causes in the following table:

‍

Prevalence & Risk factors

The annual incidence of DCM is estimated at five to eight cases per 100,000 population, with a prevalence of 36 cases per 100,000 population (to give you a better idea, the estimated prevalence in the US is around 1:2500). However, these figures may underestimate the incidence of the disease, as many patients remain undiagnosed due to incomplete expression of the disease. (1)  

A person is more prone to develop dilated cardiomyopathy in presence of several risk factors:

• High blood pressure (2)
• Personal history of cardiovascular disease (CVD)
• Family history of either DCM, heart failure or sudden cardiac death (2)
• Autoimmune diseases such as SLE or celiac disease (2,4)
• Endocrine dysfunction such as thyroid dysfunction, pheochromocytoma or Cushing’s syndrome (4)
• Underlying conditions like hemochromatosis, diabetes or sarcoidosis (2, 4)
• Illegal drug use (2)
• High alcohol intake (2)
• Untreated tachycardia (4)

‍

Genetics

To date, genetic studies of familial dilated cardiomyopathy (FDC) have implicated more than 60 genes in the pathogenesis of DCM. (9) Most FDCs are inherited in an autosomal dominant fashion, but autosomal recessive, X-linked and mitochondrial inheritance have also been reported. Although many genes have been identified to date, it is estimated that they represent only about half of the genetic causes of FDC. (6) Of the mutations described so far, the most common are mutations in genes encoding structural proteins of the cell (e.g. titin, dystrophin, emerin, sarcomere proteins, cytoskeleton, etc.). (7)

Signs & Symptoms

According to the existing data, dilated cardiomyopathy is not age-dependent, however it is most often manifested between 30 and 40 years of age. (7) 

As the disease progresses over time and the heart’s ability to pump blood declines, several specific symptoms may appear: (7)

• Fatigue
• Weakness
• Signs of left-sided heart failure, such as:

1. Exertional and/or resting shortness of breath (dyspnoea)
2. Cough
3. Paroxysmal nocturnal dyspnoea
4. Orthopnoea (shortness of breath felt when a person lies on their back, causing them to sleep in a sitting position)

If the right ventricle is also affected patients often develop signs of congestion in the venous system:

• Swelling of the legs 
• Hepatosplenomegaly
• Ascites

In addition to the already listed symptoms, others such as palpitations, chest pain, presyncope and syncope are also sometimes described.

If the condition is left untreated, it may lead to other health problems. These complications include:

• Heart failure
• Heart valve regurgitation (back-flow of the blood through one of the valves)
• Arrhythmias
• Sudden cardiac death
• Blood clots and thromboembolic events 

‍

Diagnosis

The diagnosis of dilated cardiomyopathy and the search for its etiology is difficult, but at the same time essential as a large part of the wide range of underlying causes is partly or completely reversible. (8) Number of tests and specific methods may be used in the process: 

• Family and personal medical history anamnesis
• Physical exam by a doctor
• Blood analysis
• ECG
• Echocardiogram
• Exercise stress test
• Imaging methods such as the chest X-ray, CT or MRI
• Cardiac catheterization
• Genetic screening

‍

Therapy

If the etiology of DCM is known, treatment is focused on it. Under normal circumstances, treatment can help relieve or eliminate symptoms, improve blood circulation and prevent further damage to the heart. (2) On occasion, the heart reverse remodelling can also be achieved. (9) 

In general, the following methods are most commonly (but not always) used: (2)

‍

Prevention

Studies suggest that dilated cardiomyopathy is caused by genetic mutations in up to one third of patients. Although preventive measures may not prevent the disease in these cases altogether, healthy lifestyle habits can help prevent or significantly reduce the complications. (2) 

Patients with DCM or in high risk of developing it are advised to: (2)

• Maintain an ideal body weight
• Include regular exercise recommended by a doctor
• Limit the alcohol intake
• Give up smoking and any illegal drugs
• Follow a heart-healthy diet (a lot of fruits and vegetables, minimum of salt intake, reducing total fat intake, especially saturated fat)
• Manage mental stress
• Get good quality sleep

‍

Prognosis

The prognosis of patients has improved significantly in the last decades with the development of approaches in the treatment of heart failure. Nevertheless, previous studies have shown that after the age of 60, DCM is the second most common cause of heart transplantation after ischaemic heart disease, accounting for 39% of all heart transplants. (9) 

It appears that the prognosis of patients depends on many factors, such as:

• The possibility of reverse remodelling of the cardiac compartments
• The severity of heart failure symptoms
• The degree of myocardial fibrosis
• The presence of significant disease complications such as atrial fibrillation or thromboembolism

Despite major progress in treatment, heart failure remains the leading cause of death in patients with dilated cardiomyopathy. (9)

‍

Recommendations

• If you are overweight, try to lose weight and afterwards maintain your ideal body weight. Even a small weight loss can be beneficial.
• Choose a diet rich in fruits, vegetables, and low-fat dairy products, and low in meats, sweets, and refined grains.
• Try to manage stress and try to always get a good quality sleep
• Give up smoking and any illegal drugs
• Limit your alcohol intake to the minimum
• If you have a family history of cardiomyopathy, always consult your cardiovascular health with your physician

‍