Diseases of Blood Vessels

             A.     Aortic Dissection (aka dissecting hematoma)

·         You may have thought we totally switched gears from hypertension, but Hypertension is actually a risk factor for this major disease of blood vessels called aortic dissection. 

·         Another risk factor is connective tissue abnormality, like in Marfan syndrome.

o        Marfan Syndrome is an autosomal dominant genetic disorder in which there is a mutation in the gene for fibrillin, which is needed to make elastic tissue.  This causes the person to make poor elastic tissue, and therefore have a loss of integrity of blood vessel walls.  This may affect some individuals with Marfan’s so that the elastic tissue in the tunica media is in disarray in the aorta and they are predisposed to aortic dissections b/c of this loss of wall resilience.  This condition of weakened blood vessel wall integrity in Marfan’s is known as cystic medial degeneration.  (Note: there are no cysts present.  A cyst is an epithelial lined cavity.  This name is derived from the small spaces that are present b/c of the elastic tissue fragmentation, so it is more “cyst-like”).

o        Individuals with Marfan’s are also predisposed to another condition, mitral valve prolapse, which will be a topic of discussion next week!...just wait!

·         The jury is still out whether atherosclerosis is a risk factor for aortic dissection. (Some sources say yes, and others say no!)

·         So, what happens during an aortic dissection?

o        There is a tear in the muscular wall of the aorta (specifically, the tunica intima) and a channel begins to form that is filled with blood.  This channel, or hematoma, has a few options:

§         It usually ends by another tear that will allow the blood back into the aortic bloodstream. This is also known as a double barrel lumen.  (this has the best prognosis of all the following options!)

§         It can also tear deeper into the tunica adventitia and enter the mediastinum à this leads to massive hemorrhage à can lead to death

§         Or it can tear and enter into the pericardial sac à cardiac tamponade à compromises cardiac filling à death

·         Clinically, what does a patient present with?

o        Ripping, tearing chest pain that may mimic an acute myocardial infarction that goes along the track of the dissection.

o        Side note: Our beloved Three’s company roomie John Ritter passed away after suffering an aortic dissection.
 

B. Vasculitis Syndromes

·         There is a whole group of disorders, however we will only be talking about one in particular. 

·         In general, vasculitis is inflammation of the vessel walls.

·         The 2 most common causes are:

1)       Direct infection by infectious organisms (bacterial, viruses & fungi) à Tx: antibiotics

2)       An immune-mediated inflammation (with immune complex formation) à Tx: immunosuppressants.
 

§         In Kawasaki’s disease, we can make the diagnosis by just looking for antiendothelial cell antibodies.

§         Or we can identify the anti-neutrophil cytoplasmic autoantibodies (ANCAs) our body produces and correlate them with specific types of vaculitis:

·         P-ANCA is directed against myeloperoxidase à present in microscopic polyangitis

·         C-ANCA is directed against proteinase 3 à present in Wegener’s granulomatosis. 

3)       You must be able to distinguish the cause of the vasculitis to make an appropriate treatment regimen!  You wouldn’t give someone with a bacterial infxn an immunosuppressant, or else you wouldn’t end up helping the person fight off the infxn at all!

·         Let’s actually talk about one of the diseases: Giant Cell arteritis, aka Temporal Arteritis.

o        The most common vasculitis syndrome.

o        The cause is unknown, but there may be some genetic link due to increased prevalence of HLA-DR4. 

o        The presence of CD4+ T cells in the inflammatory area suggests some kind of T-cell mediated immune response.  And of course, this is a granulomatous inflammatory disease, so there is characteristic presence of multinucleated Giant cells, hence the name ;0)

o        It affects mostly arteries of the head & neck, like the branches of the carotid artery, like the ophthalmic and temporal arteries, hence the other name temporal arteritis!

o        The classic presentation: 50+ year old female with severe headaches and radiating facial pain.  About 50% of the patients also have ocular symptoms (b/c involves the ophthalmic artery!) and 50% of the patients may also present with flu-like symptoms (like muscle pain, joint stiffness à this is called polymyalgia rheumatica).  Craniofacial pain, like pain on chewing, and fever may also be present.

o        Diagnosis is by biopsy and staining, i.e elastic stains, of the arteries involved.

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