Aortic isthmus

Last revised by Dr Rohit Sharma on 14 Jun 2020

The aortic isthmus is the part of the aorta just distal to the origin of the left subclavian artery at the site of the ductus arteriosus.

This portion of the aorta is partly constricted in the fetus because of the lack of flow within the aortic sac and ascending aorta. It marks the partial separation of fetal blood flow derived from the right and left ventricles.

History and etymology

Derived from the Ancient Greek ισθμος (isthmos) meaning a neck of land 3.

Related pathology

  • most common anatomical area of traumatic thoracic aortic injuries in patients surviving long enough to be imaged 1
  • the site of the ductus diverticulum which is an anatomical variant of the aorta that should be differentiated from an aortic pseudoaneurysm in the setting of trauma 2
  • the aortic isthmus index (isthmus flow index) is used in obstetric Doppler as a marker of raised placental resistance and fetal growth restriction 4

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Cases and figures

  • Figure 1: thoracic aorta
    Drag here to reorder.
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