Cardiomegaly

Cardiomegaly is a catch-all term to refer to enlargement of the heart, and should not be confused with causes of enlargement of the cardiomediastinal outline, or enlargement of the cardiac silhouette. 

Pathology

Etiology

There are many etiologies for cardiomegaly:

• congestive heart failure
• ischemic heart disease
• hypertension (with left ventricular hypertrophy)
• valvular disease
  • mitral regurgitation
  • tricuspid regurgitation
  • aortic stenosis
  • aortic regurgitation
  • subacute bacterial endocarditis
• cardiomyopathy
  • idiopathic cardiomyopathy
  • alcoholic cardiomyopathy
  • hypertrophic cardiomyopathy
  • drugs (numerous drugs are cardiotoxic)
• congenital heart disorders
  • ASD
  • VSD
  • PDA
  • coarctation of the aorta
  • Ebstein anomaly
  • tetralogy of Fallot
• pulmonary disease (leading to right-sided enlargement)
  • pulmonary embolism
  • COPD
  • cor pulmonale
  • primary pulmonary hypertension
• myocarditis
• systemic disease/physiology
  • normal “athletic” heart
  • pregnancy
  • renal failure
  • anemia
  • scleroderma
  • systemic lupus erythematosus
  • sickle cell disease
  • rheumatoid arthritis
  • Marfan syndrome
  • post-radiation

Radiographic features

In most cases, merely 'eye-balling' a chest x-ray will be sufficient in detecting cardiomegaly (as the heart is either clearly normal in size or clearly abnormally enlarged). In equivocal cases, the cardiothoracic ratio (CTR) can be easily calculated on a PA chest x-ray. The CTR measures the width of the cardiac silhouette and the thoracic cavity; a ratio greater than 0.5 is an abnormal finding.

Specific cardiac chamber enlargement can be recognized by cardiac contour changes, new or different interfaces with adjacent lung, and/or displacement of adjacent mediastinal structures. These are discussed separately:

• right atrial enlargement
• right ventricular enlargement
• left atrial enlargement
• left ventricular enlargement

Differential diagnosis

• other causes of an enlarged cardiac silhouette