Pathophysiology and Epidemiology of Aortic Dissection

Aortic dissection is characterized by disruption of the intimal layer of the aortic wall with subsequent separation of the layers of the wall. Entry tears in the intima allow for blood flow into the wall, creating a two-barrel aorta, with a true and a false lumen separated by an intimal flap (Figure 1).

Figure 1

Type B dissection includes a classic double barrel type with a true (smaller in these panels) and a false lumen (larger in these panels). The location of the arrow in (A) depicts the entry tear.

Another variant of aortic dissection, termed intramural hematoma, consists of a thrombosed false lumen, and can have an associated ulcer like projection (Figure 2).

Figure 2

Type B dissection can also include an atypical variant of intramural hematoma. If an ulcer like projection is present, as shown by the arrow in the right sided panels (November 1998 scan), evoluion can occur, resulting in a “saccular aneurysm” configuration as shown in the right sided panels from the May 1999 scan.

Aortic dissection is a devastating disease with high mortality rates when left untreated. The exact incidence of aortic dissection is relatively unknown because patients may expire before ever reaching a hospital. Furthermore, it can mask as other acute pathologies such as myocardial infarction or pulmonary embolism, leading to missed diagnoses. The estimated incidence is based on population studies and is reported to range between 2-3.5 cases per 100.000 person years, or 6000-10.000 cases in the United States each year.[1][2][3] Aortic dissection is more often observed in male patients and usually manifests in patient older than 60 years of age.[4] Lastly, The incidence of aortic dissection in the Western Hemisphere appears to be rising with the aging of the population.^[4] This chapter will focus on the classification, presentation and management of type B aortic dissections.

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