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Module 3: Abnormal 4-chamber view

Abnormalities of position

There are two classifications for abnormalities of position:

1. The overall position in the chest

  • Heart in the right chest
    • Displaced right (abnormal angle of the interventricular septum)
    • Dextrocardia (normal angle of the interventricular septum)
  • Heart in the midline

2. The deviation of the cardiac axis

  • Displaced leftwards (interventricular septum >70 degrees)
    • Right sided intrathoracic mass
    • Cardiac defect, especially tetralogy of Fallot
    • Hypoplastic left lung
  • Displaced rightwards (interventricular septum <20 degrees)
    • Left sided intrathoracic mass
    • Hypoplastic right lung

 Left atrial isomerism

A heart in the midline can be associated with complex cardiac defects or chromosomal abnormalities. In this case of left atrial isomerism the heart is in the midline with the apex pointing out of the front of the chest. There is cardiomegaly, atrioventricular septal defect and complete heart block.