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Size Predicts Growth Rate in Small AAAs

Statin use slows growth

The growth rate of small abdominal aortic aneurysms (AAAs) increases steadily with size, according to a study published recently in Vascular Medicine.

Although ultrasound screening for large AAAs is well established as rupture preventive, there were no definitive data on smaller aneurysms. The authors of the current study thus sought to calculate the average rate of growth in these aneurysms as well as identify any risk factors for increased growth and determine appropriate screening intervals. They analyzed patients who underwent aortic ultrasound between January 2005 and January 2006 at the Belfast City Hospital Department of Radiology. All participants -- 214 men and 38 women -- had AAAs smaller than 5.5 centimeters (mean size 3.9 cm).

Statin use was the only significant predictor of AAA growth; aneurysms in patients taking statins grew 4.5 percent per year, but aneurysms in patients not taking statins grew 7.5 percent per year. The authors note that statins are known to retard atherosclerosis and that they appear to stabilize the aortic wall, thereby slowing AAA growth. Aneurysm size also predicted growth rate. The minimum time to reach 5.5 cm decreased steadily for AAAs of less than 3.5 cm, 3.5 to 3.9 cm, 4.0 to 4.4 cm, and 4.5 to 4.9 cm (61, 17, 11, and five months, respectively).

The authors write that an aneurysm of less than 3.5 cm does not require a repeat scan for five years, and those 3.5 to 3.9 cm, 4.0 to 4.4 cm, and greater than 4.5 cm should be scanned again at 17, 11, and three to six months, respectively. “It would be prudent to tailor screening intervals according to the AAA size and previous growth patterns,” the authors conclude.

Source: Badger SA, Jones C, McClements J, et al. 2011. Surveillance strategies according to the rate of growth of small abdominal aortic aneurysms. Vascular Medicine 16(6):415-421.