The classic clinical symptom of aortic dissection is the sudden onset of excruciating tearing or stabbing pain, usually beginning in the anterior chest, radiating to the back between the scapulae, and moving downward as the dissection progresses. The most common cause of death is rupture of the dissection into the pericardial, pleural, or peritoneal cavity. Retrograde dissection into the aortic root also can cause fatal disruption of the aortic valvular apparatus or compression of the coronary arteries. Common clinical presentations stemming from cardiac involvement include tamponade, aortic insufficiency, and myocardial infarction. Other complications are related to extension of the dissection to the great arteries of the neck and the renal, mesenteric, or iliac arteries, any of which may become obstructed. Similarly, compression of spinal arteries can cause transverse myelitis.
In type A dissections, rapid diagnosis and institution of intensive anti-hypertensive therapy coupled with surgical plication of the aortic intimal tear can save 65% to 85% of the patients. However, the mortality rate approaches 70% in patients who present with hemorrhage or symptoms related to distal ischemia, and the overall 10-year survival rate is only 40% to 60%. Most type B dissections can be managed conservatively; patients have a 75% survival rate whether they are treated with surgery or with anti-hypertensive medication only.
Aneurysmsarecongenitaloracquireddilationsoftheheartorbloodvesselsthatinvolvetheentirewallthickness.Complicationsarerelatedtorupture,thrombosis,andembolization.
Dissectionsoccurwhenbloodentersthewallofavesselandseparatesthevariouslayers.Complicationsariseasaresultofruptureorobstructionofvesselsbranchingofftheaorta.
AneurysmsanddissectionsresultfromstructuralweaknessofthevesselwallcausedbylossofSMCsorweakeningoftheECM,whichcanbeaconsequenceofischemia,geneticdefects,ordefectivematrixremodeling.
Vasculitis is a general term for vessel wall inflammation. The two most common pathogenic mechanisms of vasculitis are immune-mediated inflammation and direct vascular invasion by infectious pathogens. Infections also can indirectly precipitate immune-mediated vasculitis (e.g., by generating immune complexes or triggering cross-reactivity). In any given patient, it is critical to distinguish between infectious and immunologic mechanisms because immunosuppressive therapy is appropriate for immune-mediated vasculitis but could exacerbate infectious vasculitis. Physical and chemical injury, including that due to radiation, mechanical trauma, and toxins, also can cause vasculitis.
Some 20 primary forms of vasculitis are recognized, and classification schemes attempt (with variable success) to group them according to vessel diameter, role of immune complexes, presence of specific autoantibodies, granuloma formation, organ specificity, and even population demographics (
Table 10.4
Fig. 10.22
The possible clinical manifestations are protean, but they largely depend on the specific vascular bed that is affected. Besides findings referable to the affected tissue(s), there are usually also signs and symptoms of systemic inflammation, such as fever, myalgia, arthralgias, and malaise. There is considerable clinical and pathologic overlap among these entities, as will be evident from the discussion of individual forms below.
The main immunologic mechanisms underlying noninfectious vasculitis are as follows: