Assessment of Biomarkers and Predictive Model for Short-term Prospective Abdominal Aortic Aneurysm Growth-A Pilot Study

Background: Abdominal aortic aneurysms (AAAs) are currently followed with serial ultrasound or computed tomography scanning diameter measurements, but evidence shows that AAA expansion is mostly discontinuous and quite unpredictable in any given patient. A reliable predictive model of AAA growth and/or rupture risk could help individualize treatment, follow-up protocols, and cost-effectiveness. Our objective is to set a predictive model of short-term prospective AAA growth, after clinical, serologic, and anatomic data. Methods: A prospective pilot cohort was designed. We recruited 96 consecutive, asymptomatic, infrarenal, atherosclerotic AAA patients. We registered clinical data (age, gender, cardiovascular risk factors, comorbidity, and statin intake), baseline aortic diameter, prospective 1-year AAA growth, and the concentration of metalloprotease-2, metalloprotease-9, cystatin C, alpha(1)-antitrypsin, myeloperoxidase, monocyte chemoattractant proteine-1, homocysteine, D-dimer, plasmine-antiplasmin complex (PAP), and C-reactive protein in peripheral blood at the time of baseline assessment. With all these data, we elaborated predictive models for 1-year AAA growth assessed both as a continuous variable (mm/year) and a dichotomic one (defined as stability, if AAA growth rate was <= 2 mm/year, versus expansion, if AAA growth rate was >2 mm/year), using simple and multiple linear and logistic regression. Results: The multivariate model confirmed the independent impact of D-dimer levels and chronic renal failure (CRF) on increasing AAA growth rates. Every increase by 1 ng/mL in the plasma concentration of D-dimer was related to a mean 1-year increase of 0.0062 mm in the AAA growth. Likewise, CRF increased the 1-year prospective AAA growth by a mean of 2.95 mm. When we assessed AAA growth as a dichotomic variable, the increase in the peripheral concentrations of PAP slightly increased the risk of AAA expansion (odds ratio [OR]: 1.01; 95% confidence interval [CI]: 1.00-1.02), but the presence of CRF increased the risk dramatically (OR: 14,523.62; 95% CI: 0-7.39E+40). Conclusions: Plasma D-dimer and PAP levels seem promising biomarkers of short-term AAA activity. CRF is an important independent prognostic factor of AAA expansion. The dichotomic classification of AAA growth, as stability versus progression, can be useful in the development of management models and their clinical application.