Aortic Wall Inflammation Predicts Abdominal Aortic Aneurysm Expansion, Rupture and Need for Surgical Repair
Background—Ultrasmall superparamagnetic particles of iron oxide (USPIO) detect cellular inflammation on magnetic resonance imaging (MRI). In patients with abdominal aortic aneurysm, we assessed whether USPIO-enhanced MRI can predict aneurysm growth rates and clinical outcomes.
Methods—In a prospective multicentre open-label cohort study, 342 patients with abdominal aortic aneurysm (diameter ≥40 mm) were classified by the presence of USPIO enhancement and were monitored with serial ultrasound and clinical follow-up for at least 2 years. The primary endpoint was the composite of aneurysm rupture or repair.
Results—Participants (85% male, 73·1±7·2 years) had baseline aneurysm diameter of 49·6±7·7 mm, and USPIO enhancement was identified in 146 (42·7%) participants, absent in 191 (55·8%) and indeterminate in 5 (1·5%). During follow-up (1005±280 days), there were 17 (5·0%) abdominal aortic aneurysm ruptures, 126 (36·8%) abdominal aortic aneurysm repairs, and 48 (14·0%) deaths. Compared to those without uptake, patients with USPIO enhancement have increased rates of aneurysm expansion (3·1±2·5 versus 2·5±2·4 mm/year, p=0·0424) although this was not independent of current smoking habit (p=0·1993). Patients with USPIO enhancement had higher rates of aneurysm rupture or repair (47·3% versus 35·6%; difference 11·7%, 95% confidence intervals 1·1 to 22·2%, p=0·0308): this was similar for each component of rupture (6.8% versus 3.7%, p=0·1857) or repair (41.8% versus 32.5%, p=0·0782). USPIO enhancement was associated with reduced event-free survival for aneurysm rupture or repair (p=0·0275), all-cause mortality (p=0·0635) and aneurysm-related mortality (p=0·0590). Baseline abdominal aortic aneurysm diameter (p<0·0001) and current smoking habit (p=0·0446) also predicted the primary outcome, and the addition of USPIO enhancement to the multivariate model did not improve event prediction (c-statistic, 0·7935 to 0·7936).
Conclusions—USPIO-enhanced MRI is a novel approach to the identification of aortic wall cellular inflammation in patients with abdominal aortic aneurysms, and predicts the rate of aneurysm growth and clinical outcome. However, it does not provide independent prediction of aneurysm expansion or clinical outcomes in a model incorporating known clinical risk factors.
Clinical Trial Registration—URL:http://www.isrctn.com/ Unique Identifier: ISRCTN76413758 EudraCT Number: 2012-002488-25
- Received March 17, 2017.
- Revision received May 17, 2017.
- Accepted June 5, 2017.
Circulation is published on behalf of the American Heart Association, Inc., by Wolters Kluwer. This is an open access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/), which permits use, distribution, and reproduction in any medium, provided that the original work is properly cited.