Chain mediation of the aortic path in the relationship between Body Mass Index and abdominal aortic diameter

Abstract

Introduction: The aorta, sensitive to excess weight, can undergo structural changes associated with cardiovascular risks. Studying its segments would allow a better understanding of the relationship between Body Mass Index (BMI) and distal aortic morphology.

Objective: To analyze the relationship between BMI and abdominal aortic diameter, considering the thoracoabdominal aortic segments as mediators.

Materials and Method: A cross-sectional study using secondary data from 801 adults assessed by chest computed tomography. The independent variable was BMI. The dependent variable was abdominal aortic diameter. The mediators were the diameters of six aortic segments. The Hayes PROCESS 6 model was applied with chain mediation analysis and bootstrap resampling (5000 samples). A directed acyclic graph was constructed to support the causal structure.

Results: BMI was not directly related to the abdominal aorta. It was significantly related to the aortic sinus of valsalva (B=14.159, p<0.001) and sinotubular junction (B=0.4686, p=0.0036), but not to the mid-ascending aorta (B=-0.0715, p=0.757). It also showed a significant positive effect on the mid-descending aorta (B=0.4837, p<0.001), which, together with the aorta at the diaphragm (B=0.6110, p<0.001), influenced the abdominal aortic diameter (B=0.1570 and B=0.6113, p<0.001). In the mediation analysis, the most relevant indirect effects were: BMI→aortic sinus of Valsalva→mean descending aorta→aorta at the diaphragm→abdominal aorta(effect=0.1807,95%CI[0.0878, 0.2778]), BMI→mean ascending aorta→mean aortic arch→mean descending aorta→abdominal aorta(effect=0.0611), and BMI→mean descending aorta→abdominal aorta(effect=0.0759,95%CI[0.0306, 0.1343]).

Conclusions: The impact of BMI on the abdominal aorta does not occur in an isolated or linear manner, but rather is mediated through a series of interconnected anatomical structures.