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 that impose a chronic pressure overload. There may also be right ventricular dysfunction. Causes are related to intrinsic myocardial damage.

Clinical presentation

Presenting symptoms are nonspecific and are secondary to elevated venous filling pressures as well as decreased end-organ perfusion secondary to a progressive decrease in cardiac output:

• dyspnea

  • exacerbated by supination, bending forward at the waist, and exertion

• fatigue, early satiety, cough

• peripheral edema

Physical examination is likewise nonspecific but may reveal a laterally displaced apical impulse, auscultatory S3, jugular venous distension, dependent auscultatory crackles in the basilar lung segments, and pitting-dependent peripheral edema.

Pathology

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

Etiology

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) 

• infectious (myocarditis)

  • viral (e.g. coxsackievirus, echovirus, adenovirus)

  • bacterial (e.g. diphtheria, mycoplasma, listeria)

• infiltrative disease

  • sarcoid

  • amyloid

• endocrine/metabolic derangements

  • uremia, hypocalcemia, hypophosphatemia

  • thyrotoxicosis, thiamine deficiency (i.e. "wet" beriberi)

• toxic

  • amphetamines, cocaine, ethanol, phenylpropanolamine, clozapine

  • zidovudine, statins, anabolic steroids

  • antimony, cobalt

• chemotherapy

  • anthracyclines (e.g. doxorubicin, daunorubicin)

  • mitoxantrone

  • checkpoint inhibitors

• others

  • peripartum

  • muscular dystrophies

• autoimmune

  • late-onset cardiomyopathy in Chagas disease

• idiopathic

  • idiopathic dilated cardiomyopathy

• familial

  • familial dilated cardiomyopathy ¹

Associations

• intra-cardiac thrombus

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 ventricular chamber dilation

  • ​elevation in left ventricular mass and volumes

    • may be inferred by an LV end-diastolic diameter above 5.9 cm (males) or 5.3 cm (females)

    • ventricular wall thickness may be normal or reduced (<0.6 cm)

  • ventricle may appear spherical with a decreasing length: width ratio

    • normal left ventricular long: short axis ratio ~1.5

• secondary mitral regurgitation 

  • mitral annular dilation, failure of leaflet coaptation, stretching of subvalvular apparatus

• systolic dysfunction

  • left ventricular ejection fraction will decrease, with a normal or reduced stroke volume

• diastolic dysfunction

  • left atrial dilation implies a degree of chronicity

• right ventricular dysfunction

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 ⁴.

Late enhancement MR images may demonstrate areas of fibrosis within the myocardium, characteristically in the mid- or subepicardial myocardium, allowing differentiation from ischemic cardiomyopathy ¹.

Differential diagnosis

Conditions mimicking the clinical presentation or imaging appearance of dilated cardiomyopathy include:

• ischemic cardiomyopathy/left ventricular aneurysm

• non-compaction cardiomyopathy

• left ventricular dilatation due to valvular heart disease

On plain radiographs consider:

• large pericardial effusion