Cardiac Pathology: Aneurysms

• An aneurysm is a localized, abnormal dilation of the wall of a blood vessel (or wall of the heart).
• It is commonly caused by atherosclerosis, but can also be due to a connective tissue disorder (like my favorite disorder – Marphan Syndrome!), infection, immune-mediated injury, or trauma.
  • Atherosclerotic aneurysms are due to the destruction and thinning of the vessel wall.
  • As the wall becomes weaker, blood pressure pushes on it, stretching the tissue. No new tissue develops so you’re stretching the same amount of tissue over a larger and larger area, creating a balloon-like effect.
• The most common aneurysm (and the only one discussed in class) is an abdominal aortic aneurysm.
  • These typically form below the renal arteries and above the iliac bifurcation.
• Aneurysms cause many clinically significant problems.
  • They can become extremely large, so large that they may mimic neoplasms.
     

• You might feel a palpable mass on examination.The pressure of the aneurysm can cause mass effects, compressing adjacent structures and causing pressure atrophy.
• A picture in class showed the vertebrae distorted and worn away from where an aneurysm pressed against them.
• The blood within an aneurysm does not move in the same predictable way as blood within a normal vessel. This can lead to mural thrombus formation.
  • Portions of this thrombus may embolize occluding branch vessels further downstream.
     

• The most dangerous problem with an abdominal aortic aneurysm is rupture.
  • A ruptured abdominal aortic aneurysm is fatal approximately 50% of the time because of internal hemorrhaging.
  • The wall of an aneurysm is extremely thin, so it makes sense that this could rupture.
  • Dr. Cleveland told an anecdote about her father, a doctor, who knew he had a abdominal aortic aneurysm but chose to ignore it. It ruptured (fortunately while he was at the hospital working) and his first symptom was testicular pain. She is unsure whether this is a common symptom but her father recognized it for what it was and he lived to tell the tale.

• Other types of aneurysms are syphilitic aneurysms and intracranial saccular aneurysms (“berry aneurysms”).

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