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 2-barrel aorta, with a true and a false lumen separated by an intimal flap (Figure 1A). An alternative but associated presentation is that of an appearance with a thrombosed false lumen, an atypical variant known at intramural hematoma (Figure 1B)→. 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 die 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 to 3.5 cases per 100 000 person years, or 6000 to 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 patients older than 60 years.[4] Lastly, the incidence of aortic dissection in the Western Hemisphere appears to be rising with the aging population.[4] This chapter will focus on the classification, presentation, and management of type B aortic dissections (TBAD).

Figure 1A

Type B dissection includes the classic “double barrel” aorta (A) but can also consist of an atypical variant of intramural hematoma (B, upper panels). If an ulcer-like projection is present, as shown by the arrow in the upper panels in (B),evolution can occur, resulting in a “saccular aneurysm” configuration as shown by the location of the arrow in the lower panels.

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Figure 1B

Type B dissection includes the classic “double barrel” aorta (A) but can also consist of an atypical variant of intramural hematoma (B, upper panels). If an ulcer-like projection is present, as shown by the arrow in the upper panels in (B),evolution can occur, resulting in a “saccular aneurysm” configuration as shown by the location of the arrow in the lower panels.