Presence of Blood Clot Tied to Accelerated AAA Progression

By David Douglas

February 05, 2020

NEW YORK (Reuters Health) - The maximal diameter of an abdominal aortic aneurysm (AAA) and the presence of an intraluminal thrombus (ILT) are both independent predictors of faster aneurysm growth, according to a new study.

"Such findings provide another piece of information to use in determining the prognosis of patients with this potentially dangerous condition, and people from the research and clinical community need to be aware of the importance of a thrombus in patients with abdominal aortic aneurysm." Dr. Chengcheng Zhu of the University of California, San Francisco, told Reuters Health by email.

Patients with AAAs larger than 5.5 cm are normally referred for elective repair, Dr. Zhu and colleagues note in Radiology. Smaller AAAs are most commonly followed with serial imaging, but a considerable number of them end up rupturing.

ILT is present in the majority of aneurysms close to the repair threshold and in a considerable number of smaller aneurysms, the researchers say, suggesting potential as a marker of rapid AAA growth and rupture.

To investigate, the team studied data on 225 male patients with AAA who between 2004 and 2008 underwent contrast material-enhanced CT at baseline and CT or black-blood MRI at follow-up.

At baseline, the median size of the AAA was 3.8 cm and 127 patients (54.7%) had ILT. This group had AAAs with significantly larger baseline diameters (median, 4.1 cm vs. 3.4 cm) and faster annual growth rates (median, 2.0 mm vs. 1.0 mm).

In addition, small AAAs (with a diameter of 3-4 mm) with ILTs had growth rates a significant 1.9 times greater than their counterparts without ILT. The corresponding rate for AAAs from 4 to 5 mm in diameter was 1.2 times greater (P=0.06).

Baseline diameter and ILT were both independently tied to aneurysm growth rate in multivariable analysis, with standardized regression coefficients of 0.43 (P=0.001 and 0.15 (P=0.02, respectively.

Dr. Zhu said in a statement, "If in patients with a thrombus the aneurysm grows twice as fast, then shortening the surveillance interval could be considered."

He and his colleagues conclude, "Our finding supports the role of ILT in predicting AAA progression and suggests that identification of ILT is important in AAA screening and surveillance imaging for better risk stratification and surveillance interval optimization."

SOURCE: Radiology, online January 28, 2020.