dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is defined as left ventricular chamber dilation with decreased systolic function (FEVG <40%) in the absence of coronary artery disease or conditions which impose a chronic pressure overload. There may also be right ventricular dysfunction. Causes are related to intrinsic myocardial damage.


The ventricles are dilated and poorly contractile with normal or reduced wall thickness. The atria may also have a similar appearance and function.


Although a variety of etiologies can result in dilated cardiomyopathy which are listed below. Some are classified as separate entities. (See WHO 1995 classification of cardiomyopathies)


Radiographic features

Plain radiograph

Chest radiographs commonly show an enlarged left ventricle and atria with pulmonary edema. Associated pleural effusions may also be seen.

Ultrasound: echocardiography

The degree of left ventricular dilatation is highly variable and depends on the stage of disease and severity of left ventricular dysfunction.

  • global chamber dilation with increased sphericity
    • ​elevation in left ventricular mass and volumes
      • may be inferred by a measured elevation in LV end-diastolic internal diameter
        • the LVIDd upper limit of normal is 5.9 cm in males and 5.3 cm in females
      • wall thickness may be normal (between 0.6 cm and 1.2 cm) or reduced
    • the ratio between the long and short axes of the left ventricle may decrease to 1 in severe cases
      • a normal LV has an LAX/SAX ratio around 1.5
      • consequent mitral annular dilation and failure of coaptation leading to mitral regurgitation is common
  • perturbation of systolic function
  • diastolic dysfunction
    • with progressively higher E/e' ratio (correlates with left atrial pressure) as filling pressures elevate
Cardiac MRI

In idiopathic dilated cardiomyopathy, the left heart is markedly dilated and thinned, and mid-wall enhancement, especially in the septum, is present in more than 50% of patients .

Late enhancement MR images may demonstrate areas of fibrosis within the myocardium, characteristically in the mid- or subepicardial myocardium, allowing differentiation from ischemic cardiomyopathy.

Differential diagnosis

On plain radiographs consider: