Chapter 11: Aortic Emergencies

INTRODUCTION

Patients with aortic emergencies often present with vague symptoms, but rapid diagnosis of abdominal aortic aneurysm (AAA) and acute aortic dissection is essential. In these patients POCUS has been found to be feasible, accurate, and lifesaving.^1–3

AAA is a relatively common disease in patients over 50 years of age.^4–6 Rupture of an AAA has a high mortality and resulted in nearly 10,000 deaths in the United States in 2017.⁷ The incidence of aortic dissection has been estimated at 6000–10,000 cases per year in the United States. Estimates of in-hospital mortality of aortic dissection approach 30%, but some studies suggest that two to three times as many patients die from aortic dissection than from ruptured AAA, often prior to diagnosis.^8,9

Misdiagnosis of ruptured AAA and aortic dissection is commonly due to their nonspecific presentations.^10–12 Mortality due to AAA can be decreased if the diagnosis is made prior to rupture or if the diagnosis is made rapidly after rupture has occured.^2,13–17 Similarly, the outcome in patients with aortic dissection is dependent on rapid diagnosis and treatment, since mortality increases about 1–2% every hour if untreated.⁸

Computed tomography (CT) is very accurate for detecting AAA, aortic dissection, and thoracic aortic aneurysm, but it is unreasonable to use CT to screen all patients with the potential for these diagnoses. POCUS, on the other hand, can be used as a low-threshold, rapid screening test whenever an aortic emergency is on the differential diagnosis.

CLINICAL CONSIDERATIONS

ABDOMINAL AORTA

AAA occurs in 2–5% of the population over 50 years of age and about 10% of men over 65 years of age who have risk factors for vascular disease.^18–24 The prevalence is even higher in patients with first-degree relatives who have an AAA and those with peripheral vascular disease.^25,26 AAA is about four times more prevalent in men than in women.^27–29

The risk of AAA rupture is directly related to the largest diameter of the aneurysm and increases dramatically in those greater than 5 cm. Estimates of rupture risk are as follows: less than 2% per year for aneurysms less than 4 cm, 1–5% per year for those 4–5 cm, 3–15% per year for those 5–6 cm, 10–20% per year for those 6–7 cm, and 20–50% per year for those greater than 7 cm.^30–35 Other factors such as continued smoking, uncontrolled hypertension, and emphysema increase the risk of rupture.^36,37 Also, women have a higher risk for rupture than men with the same-size aneurysm.^30,38–40 Current guidelines for elective treatment of AAA suggest operative repair of aneurysms 5.5 cm or larger.^41,42

Most patients with an AAA are asymptomatic until rupture occurs. Delayed or missed diagnosis occurs because ...