An Older Man With a Large Abdominal Aortic Aneurysm

During an interval examination, a new pulsatile mass is detected slightly above the umbilicus of a 72-year-old man with chronic obstructive pulmonary disease (COPD). He has not noticed any abdominal pain or any other new symptoms.

HISTORY
The patient has had COPD for many years. He has chronic dyspnea on exertion and at rest and a morning cough that produces sputum. He uses a variety of inhalers but does not require oxygen therapy. His forced expiratory volume in 1 second is 1.5 L.

In addition, he has essential hypertension, which is reasonably well controlled with low doses of an angiotensin-converting enzyme inhibitor and a diuretic. He denies angina but is unable to climb 1 flight of stairs.

PHYSICAL EXAMINATION
No bruits are associated with the pulsatile mass. Pulses in the lower extremities are symmetrical and reasonably strong.

LABORATORY AND IMAGING STUDIES
The hemogram is normal; the serum chemistry panel reveals a normal glucose level and a stable creatinine level of 2.3 mg/dL. The ECG shows nonspecific ST-T changes and voltage criteria for left ventricular hypertrophy but no evidence of ischemia or previous myocardial infarction. An abdominal ultrasound examination reveals an abdominal aortic aneurysm (AAA) of 6.5 cm in diameter. Follow-up pulmonary function and cardiac stress tests are scheduled for the following week.

Answer and discussion on next page.

Poll Results

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CORRECT ANSWER: D
AAAs are found in 6% of men aged 65 years; the incidence increases by 6% per decade. "Clinically relevant" AAAs (larger than 4 cm) occur in 1% of men aged 65 years; the incidence increases by 2% to 4% per decade.¹

The chief clinical relevance of AAA is the catastrophic complication of rupture, which occurs in roughly one-third of cases. Once an AAA ruptures, the prognosis is extremely grim: most persons do not reach a hospital, and of those who do, half do not survive emergency surgery. The overall survivorship of the event is about 10% to 15%.²

THE TAKE-HOME MESSAGE:
Intervention is warranted when an abdominal aortic aneurysm expands to 5.5 cm or larger. For patients who are poor candidates for open surgical repair, a reasonable alternative consists of endovascular repair and risk factor modification.

Natural history. Rupture of the aneurysm is extremely unlikely as long as the diameter is less than 5.5 cm. However, AAAs expand inexorably over time, and the rate of expansion accelerates exponentially as the diameter increases.^1,3 Modification of risk factors (diabetes, hypertension, and hyperlipidemia) probably can slow the expansion rate somewhat, but this alone does not seem to be adequate therapy. Smoking cessation can significantly slow the expansion rate in AAA. Ultimately, however, if a patient lives long enough, questions of whether, when, and how to prevent rupture of the AAA by surgery will need to be addressed.

Intervention. Clinical evaluation by palpation and assessment of symptoms (choice B) is neither sensitive nor specific enough to monitor patients with AAA. In fact, most cases of AAA are, and remain, asymptomatic even as the aneurysm expands toward a dangerous diameter.

The size of this patient’s AAA already puts him at extreme risk for rupture; thus, he is a candidate for some form of intervention, if possible. Recent data have clarified the selection of a procedure on the basis of the patient’s operative and long-term mortality risk. In large trials, 30-day mortality with elective surgery is between 3% and 6%; in higher-risk patients who have impaired renal function (such as this man), the risk of 30-day operative mortality is 10% to 15%.⁴ Because this patient is at higher risk for operative mortality, immediate surgery with open repair would not be offered by most experts; thus, choice A is not correct.

Endovascular repair (choice D) using a stent-graft system placed via the femoral artery was initially thought to be an excellent compromise between monitoring and early surgical repair.⁵ Ongoing trials have confirmed the equivalence in long-term total and aneurysm-related mortality with this technique.^6,7

This case is problematic. The aneurysm is large and poses a significant risk of rupture. However, the risk of a major vascular procedure is very high in light of this patient’s borderline pulmonary function, elevated creatinine level, and unknown cardiac status (because he is unable to climb steps, further evaluation of his cardiac status would be needed). This leaves conservative therapy and endovascular repair (choice D) as alternatives, and recent studies^8,9 have delineated the expected results.

In a randomized trial that compared endovascular repair with expectant management in patients who were physically ineligible for open repair, endovascular repair was associated with significantly lower aneurysm-related mortality than no repair; however, it was not associated with a reduction in all-cause mortality.⁹ Disadvantages of endovascular repair were graft-related complications and reinterventions and financial cost. The comorbid cardiac and pulmonary conditions that prevented open repair in the study population also affected ongoing mortality to the degree that total mortality at 7 years was equivalent. Thus, although "regular surveillance" if interpreted as simple conservative management is acceptable, the best compromise in this patient would be lessening his risk of aneurysm rupture with endovascular repair and ongoing management of his comorbidities.

Outcome of this case. Endovascular repair was accomplished without morbidity. At 3-year follow-up, the patient’s creatinine level and pulmonary function are stable.

References:

REFERENCES:

1.

Powell JT, Greenhalgh RM. Clinical practice. Small abdominal aortic aneurysms.

N Engl J Med.

2003;348:1895-1901.

2.

Brown LC, Powell JT. Risk factors for aneurysm rupture in patients kept under ultrasound surveillance. UK Small Aneurysm Trial Participants.

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1999;230:289-296.

3.

Lederle FA, Wilson SE, Johnson GR, et al; Aneurysm Detection and Management Veterans Affairs Cooperative Study Group. Immediate repair compared with surveillance of small abdominal aortic aneurysms.

N Engl J Med.

2002;346: 1437-1444.

4.

Brady AR, Fowkes FG, Greenhalgh RM, et al. Risk factors for postoperative death following elective surgical repair of abdominal aortic aneurysm: results from the UK Small Aneurysm Trial participants.

Br J Surg.

2000;87:742-749.

5.

Lederle FA. Abdominal aortic aneurysm-open versus endovascular repair.

N Engl J Med.

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6.

United Kingdom EVAR Trial Investigators, Greenhalgh RM, Brown LC, et al. Endovascular versus open repair of abdominal aortic aneurysm.

N Engl J Med.

2010;362:1863-1871.

7.

United Kingdom EVAR Trial Investigators, Greenhalgh RM, Brown LC, et al. Endovascular repair of aortic aneurysm in patients physically ineligible for open repair.

N Engl J Med.

2010;362:1872-1880.

8.

Kent KC. Endovascular aneurysm repair-is it durable?

N Engl J Med.

2010; 362:1930-1931.

9.

De Bruin JL, Baas AF, Buth J, et al; DREAM Study Group. Long-term outcome of open or endovascular repair of abdominal aortic aneurysm.

N Engl J Med.

2010;362:1881-1889.