Cardiomyopathies & Myocarditis


Cardiomyopathy is defined as a structural or functional abnormality of the myocardium that is not secondary to structural heart disease, hypertension, or pulmonary vascular disease. Cardiomyopathies are usually classified as follows:

Dilated cardiomyopathy

This is the most common cause of cardiomyopathy in children. It may be secondary to myocarditis, coronary artery disease, and many other conditions. In familial cases, an autosomal dominant transmission is the most frequent pattern of inheritance. Autosomal recessive, X-linked and mitochondrial inheritance have also been described.


The heart in dilated cardiomyopathy is globular and is grossly dilated. The myocardium is pale and mottled and the endocardium is thin. Histologically, there is myocyte hypertrophy and degeneration and interstitial fibrosis as compared to myocarditis, in which there is myocyte necrosis and lymphocytic infiltration.


Systolic dysfunction is manifested by decreased shortening and ejection fractions which leads to increased end-diastolic volume and pressure. The blood flow to kidneys is diminished with resultant salt and water retention and worsening of CHF. Myocardial fibrosis may lead to ventricular arrhythmias secondary to the development of reentry circuits in the ventricles.

Clinical presentation

CHF signs and symptoms develop as the cardiac output decreases. These include decreased exercise tolerance and dyspnea with exertion. Infants present with poor feeding, diaphoresis during feeding, and failure to thrive. Palpitation and syncope are sometimes the earliest presentation of DCM.

Making the diagnosis


If cardiac decompensation is present, intravenous inotropic agents such as dobutamine and dopamine (in renal doses) may be useful. Amrinone and milrinone also have positive inotropic effect and also reduce the afterload. When the patient is clinically stable, oral digoxin, ACE inhibitors and B-blockers (carvedilol) may be started. Diuretic therapy is useful for removing excess fluid. Patients with acute and severe decompensation may require ventricular assist devices or extracorporeal membrane oxygenation. Heart transplantation may be considered if all other measures fail.