saddle pulmonary embolism

Saddle pulmonary embolism commonly refers to a large pulmonary embolism that straddles the bifurcation of the pulmonary trunk, extending into the left and right pulmonary arteries.

If large enough, it can completely obstruct both left and right pulmonary arteries resulting in right heart failure and, unless treatment is prompt, death.

With such extensive embolic burden, signs of right heart strain are usually present and include:

  • dilatation of the right ventricle (RV) (i.e. RV width > left ventricular width)
  • straightening or leftward bulging of the interventricular septum
  • enlargement of the pulmonary trunk

Contrast reflux into the azygos vein, via the superior vena cava, and hepatic veins, via the inferior vena cava, is a controversial sign of RV strain, as it often occurs in the absence of raised right-sided heart pressures.

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