Dilated cardiomyopathy (DCM) is the most common form of heart muscle disease in children accounting for approximately 55–60 % of all childhood cardiomyopathies. Outcomes are difficult to predict and depend on cause, severity and age at presentation.

It is a relatively rare condition in general paediatric population with a reported incidence of 0.57 cases per 100,000 in the United States and 2.6 cases per 100,000 in Finland. Infants can present with a history of irritability, poor feeding leading to failure to thrive, increased breathing effort, pallor, decreased urine output and sweating on activity. Older children tend to present with reduced exercise tolerance, shortness of breath on minimal exertion, recurrent chest infections and chronic cough. Presentation of DCM can also sometimes be in the form of arrhythmia with symptoms of syncope, palpitations, and seizures and in some cases the first presentation can be a cardiac arrest.

Signs of heart failure include tachycardia, prolonged capillary refill time, gallop rhythm, heart murmur (functional mitral regurgitation), elevated jugular venous pressure, hepatomegaly, peripheral oedema and tachynopea. Diagnosis of cardiomyopathy is made easier once a cardiac diagnosis is suspected. Chest radiograph and ECG are required; however, the principal investigation is echocardiography, which confirms the diagnosis, assesses degree of dysfunction and rules out structural underlying causes. It is vitally important to diagnose treatable causes of cardiomyopathy (see other chapters); however, in most cases the cardiomyopathy screen is negative. Rarely, DCM can be secondary to metabolic, storage, neuromuscular, endocrine, and mitochondrial disorders. Blood tests may include: lactate, glucose, ammonia, amino acids, carnitine, acylcarnitine, cholesterol, triglycerides, thyroid function, full blood count, creatinine kinase, thiamine, selenium, calcium, vitamin D and parathyroid hormone. Urine should be checked for amino-acids, organic acids and glycosamineglycans to further exclude metabolic disease. DCM may be due to previous myocarditis and it may be useful to check viral titres against enterovirus especially coxsackie B, parvovirus B19, human herpes virus 6, adenovirus, rubella and HIV. Dilated cardiomyopathy can be familial, and it is estimated that 20–30 % of children with DCM have a relative with the disease. However, unlike hypertrophic cardiomyopathy, DNA mutation analysis is not currently useful clinically and is of low yield.

Angiography, CT, or cardiac magnetic resonance imaging is preformed when there is diagnostic uncertainty in ruling out anomalous coronary artery from the pulmonary artery. Cardiac catheterisation and haemodynamic studies are also used to assess pulmonary vascular resistance to help assess suitability for heart transplantation. Myocardial biopsy is controversial and not without risk; however, it can help to investigate cause of myocardial dysfunction (e.g., myocarditis).

Whatever the cause, management of dilated cardiomyopathy is to give supportive relief which may include positive pressure ventilation and inotrope support. Phosphodiesterase III inhibitors (e.g., milrinone) are particularly helpful as they reduce afterload and improve ventricular contractility without increasing myocardial oxygen consumption. Diuretics should also be started; furosemide is often required intravenously as well as oral spironolactone. Any reversible causes of cardiomyopathy must be aggressively treated, e.g., vitamin D deficiency. When stability has been reached, the child is converted to oral diuretics, ACE-inhibitors and beta-blockers such as carvedilol. The child should also be anticoagulated with aspirin or warfarin to reduce the risk of thrombosis forming in the ventricle with risk of embolus. Detailed discussion of management is beyond the scope of this chapter. In some cases, children fail to thrive and deteriorate despite medical support and cardiac transplantation should be considered.