Effect of intraluminal thrombus on growth rate of abdominal aortic aneurysms.

BACKGROUND: Abdominal aortic aneurysm (AAA) includes variety of morphologies with changing properties. Growth rate is one of the most important factors directly linked to the risk of rupture. Intraluminal thrombus (ILT) covering aortic wall is found in majority of AAAs. Yet, its role in biomechanical processes in AAA remains unclear. From one point of view ILT can serve as protective factor in reducing wall stress of AAA and thus slow down the growth. Modern concept of multilayered ILT proved active inflammatory processes inside, that can significantly affect the quality of the wall and thus lead to the higher growth rate and higher risk of rupture. The goal of this study was to analyze effect of ILT on growth rate of AAA and support one these theories.

METHODS: Retrospective study of CT angiography scans of AAA of 26 patients was performed. 40 pairs of consecutive scans have been analyzed. Periods between two scans varied. Maximal infrarenal diameter of AAA and size of ILT were measured. AAAs were split into 4 groups according to their intial diameter. Growth rate was calculated for each AAA and linked to the relative size of ILT These values were statistically evaluated.

RESULTS: Negative correlation between relative size of ILT and growth rate was found (p=0.042062). This significant result proved that thicker thrombus slowed down the growth of AAA and vice versa, smaller relative size of ILT was linked to higher growth rate.

CONCLUSIONS: This finding shows importance of ILT as one of the key factors influencing biomechanical processes inside an AAA. Results of this study may contribute to the further research of this topic.