Vessel wall morphology is equivalent for different artery types and localizations of advanced human aneurysms

Aneurysm formation occurs most frequently as abdominal aortic aneurysm (AAA), but is also seen in other localizations like thoracic or peripheral aneurysm. While initial mechanisms for aneurysm induction remain elusive, observations from AAA samples show transmural inflammation with proteolytic imbalance and repair mechanisms triggered by the innate immune system. However, limited knowledge exists about aneurysm pathology, especially for others than AAA. We compared 42 AAA, 15 popliteal, 3 ascending aortic, five iliac, two femoral, two brachial, one visceral and two secondary aneurysms to non-aneurysmatic controls by histologic analysis, immunohistochemistry and cytokine expression. Muscular and elastic type arteries show a uniform way of aneurysm formation. All samples show similar morphology. The changes compared to controls are distinct and include matrix remodeling with smooth muscle cell phenotype switch and angiogenesis, adventitial lymphoid cell accumulation and M1 macrophage homing together with neutrophil inflammation. Inflammatory cytokines are up-regulated accordingly. Comparative analysis of different disease entities can identify characteristic pathomechanisms. The phenotype of human advanced aneurysm disease is observed for elastic and muscular type arteries, does not differ between disease localizations and might, thus, be a unique response of the vasculature to the still unknown trigger of aneurysm formation.

C-reactive protein predicts aortic aneurysmal disease progression after endovascular repair

OBJECTIVES

This study aims to investigate the prognostic significance of the rate of variation of C-reactive protein (CRP) levels as a predictor of aneurysmal sac and neck expansion and, therefore, of aneurysm disease progression, in patients undergoing endovascular aneurysm repair (EVAR) in the absence of endoleaks.

METHODS

192 patients following non-emergency elective EVAR for asymptomatic infra-renal abdominal aorta aneurysm (AAA) were included after a six-month period after intervention to ensure the treatment success and absence of endoleaks. Expansion of aneurysm sac or neck after the six-month stabilization term occurred in 120 (63%) and 128 (67%) patients for a mean follow-up of 53±23 months.

RESULTS

The relative CRP plasma level gradient significantly differed between the subgroups of patients according to relative sac expansion quartiles (7%, 26%, 39%, and 61%; p<0.001). In the bivariate analysis, the aorta sac diameter expansion rate progressively increased in the subgroups determined by CRP gradient quartiles (-0.5±1%, 3.6±1%, 8±2%, 10±3%; p<0.01). The median (25th; 75th quartile) CRP level rise in "rapid expanders" patients (those above the median annual sac expansion rate of 5.7%) was 51% (37%; 67%) compared with 15% (3%; 28%) in "slow- or non-expanders" (p<0.001). The multivariate age-adjusted logistic model confirmed the variation of CRP level and neck length as the only factors independently associated to sac expansion (odds ratio 4.3; 95% CI: 2.3-7.9 and 1.7; 95% CI: 1.3-2.2, respectively).

CONCLUSION

There is a significant time-related association between AAA sac diameter enlargement and CRP plasma level gradient after EVAR in the absence of endoleaks, confirming the latter as a proper marker of aneurysm disease progression and rate of expansion in these patients.