Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 67-year-old businessman is evaluated during a routine health examination. He has a 30 pack-year history of smoking, but quit 5 years ago. He consumes two or more alcoholic beverages on most days. He is asymptomatic, but performs no regular physical exercise. He takes no medications.

On physical examination, his blood pressure is 148/92 mm Hg and heart rate is 78/min and regular. His pulses are full, he has no bruits, and results of his lung, heart, abdominal, and rectal examinations are unremarkable.

Total serum cholesterol is 240 mg/dL (6.2 mmol/L), HDL cholesterol is 40 mg/dL (1.0 mmol/L), and triglyceride level is 100 mg/dL (1.1 mmol/L). Results of other serum laboratory studies are normal.

An abdominal ultrasound for screening purposes demonstrates an infrarenal abdominal aortic aneurysm measuring 4 cm in diameter.

In addition to treatment of this patient’s hyperlipidemia and hypertension and discussion about his at-risk drinking, which of the following is the best management option?

A) Abdominal CT with intravenous contrast
B) Antithrombotic therapy
C) Follow-up ultrasound in 6 to 12 months
D) Placement of an endovascular stent graft

Answer and critique

The correct answer is C) Follow-up ultrasound in 6 to 12 months. This item is available to MKSAP 15 subscribers as item 15 in the Cardiovascular Medicine section.

Abdominal aortic aneurysms are an important and treatable cause of mortality, and risk factors such as male sex, smoking history, and aging have been well established. This patient has an asymptomatic small infrarenal aortic aneurysm found on appropriate screening for a man older than 65 years who had previously smoked. Larger aneurysms expand more rapidly, and the rate of growth is important in clinical decision-making regarding intervention. Therefore, the larger the aneurysm is at index detection, the sooner follow-up surveillance should be performed. Two large prospective studies have documented the safety of semi-annual surveillance in patients with aneurysms from 4.0 to 5.4 cm in diameter. Data from the UK Small Aneurysm Trial suggest that a surveillance interval of 24 months may be more appropriate for aneurysms smaller than 4 cm.

An abdominal CT scan with intravenous contrast would clearly demonstrate the aneurysm; however, it would not affect current treatment for this patient and would expose him to unnecessary radiation and the risks of an iodinated contrast agent.

There is no indication for antithrombotic therapy in the treatment of this patient’s aneurysm. However, antiplatelet therapy should be considered for cardiovascular primary prevention. Data from several large trials, taken together, suggest benefit of aspirin in middle-aged men for prevention of a first myocardial infarction.

In asymptomatic patients, repair is indicated for aneurysms with a transverse diameter of 5.5 cm or larger, or those demonstrating an expansion rate of more than 0.5 cm/year. In this patient with a 4-cm aneurysm, there is no indication for either surgical or endovascular repair at this time, and the focus should be on surveillance and medical therapy.

This patient has hyperlipidemia and hypertension, and treatment for these conditions is indicated regardless of the aneurysm. Evidence from small randomized trials suggests that statins may inhibit aneurysm expansion. Observational human data suggest that angiotensin-converting enzyme (ACE) polymorphisms may predispose to risk of aneurysm formation, making ACE inhibitors potentially attractive for treatment of hypertension in patients with risk factors for aortic aneurysm. Animal studies with ACE inhibitors and angiotensin-receptor blockers have shown a decrease in the rate of aneurysm expansion, but this has not been demonstrated in humans.

Key Point

• For asymptomatic abdominal aortic aneurysms 4.0 to 5.4 cm in diameter, an ultrasound surveillance interval of 6 months has been shown to be safe.

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