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Published on: January 15, 2022
Lower Aorto-Iliac Bifurcation Position and Incident Cardiovascular Disease: A Multi-Ethnic Study of Atherosclerosis
Nketi I Forbang1, Matthew A Allison1,2, Michael H Criqui1
1Department of Family Medicine and Public Health, University of California, San Diego, La Jolla, California, USA.
Insights
A lower aorto-iliac bifurcation position, while indicating adverse vascular aging, did not independently predict future cardiovascular disease events. This finding suggests complex aortic mechanics may influence outcomes.
Area of Science:
- Vascular aging and cardiovascular disease risk assessment.
- Biomechanical properties of the aorta and their clinical implications.
Background:
- A lower aorto-iliac bifurcation position shifts downward with age.
- This position is linked to vascular aging and cardiovascular disease (CVD) risk factors.
- Its association with actual CVD events was previously unknown.
Purpose of the Study:
- To investigate the independent association between aorto-iliac bifurcation position and incident CVD events.
- To determine if a lower bifurcation position predicts coronary heart disease (CHD), CVD, or all-cause mortality (ACM).
Main Methods:
- Utilized abdominal computed tomography scans to measure aorto-iliac bifurcation distance (AIBD).
- Employed Cox proportional hazard analysis to assess risk associated with lower AIBD.
- Followed 1,711 participants for a median of 10 years for incident CHD, CVD, and ACM.
Main Results:
- A lower AIBD (1st quartile) showed a trend towards increased risk for CHD and CVD.
- Participants with the lowest bifurcation position had a significantly higher risk of all-cause mortality (ACM).
- After adjusting for CVD risk factors, the association with ACM was no longer significant.
Conclusions:
- A lower aorto-iliac bifurcation position is not an independent predictor of future CVD events.
- This position serves as a marker for adverse vascular aging.
- Aortic atherosclerosis and stiffness may explain the lack of independent association with CVD events.
Background:
With increasing age, a downward shift of the aorto-iliac bifurcation relative to the lumbar spine occurs. A lower bifurcation position is an independent marker for adverse vascular aging and is associated with increased burden of cardiovascular disease (CVD) risk factors; however, the associations between lower bifurcation position and CVD events remain unknown.
Methods:
Abdominal computed tomography scans were used to measure the aorto-iliac bifurcation distance (AIBD, distance from the aorto-iliac bifurcation to the L5/S1 disc space). Cox proportional hazard analysis was used to determine the independent hazard of a lower bifurcation position (smaller AIBD) for incident coronary heart disease (CHD, defined as myocardial infarction, resuscitated cardiac arrest, or sudden cardiac death), CVD (CHD plus stroke or stroke death), and all-cause mortality (ACM).
Results:
In the 1,711 study participants (51% male), the mean AIBD was 26 ± 15 mm. After a median follow-up of 10 years, 63 (3.7%) developed CHD, 100 (5.8%) developed CVD, and 129 (7.5%) were deceased. Compared to the 4th quartile of AIBD (highest bifurcation position), participants in the 1st quartile (lowest bifurcation position) had increased risk for CHD (hazard ratio (HR) = 1.5, 95% confidence interval (CI): 0.8-3.0, P = 0.2), CVD (HR = 1.8, 95% CI: 0.9-2.7, P = 0.1), and ACM (HR = 2.2, 95% CI: 1.3-3.6, P = 0.01). After adjustments for CVD risk factors, the HR for ACM was no longer significant.
Conclusion:
Despite being an independent marker for adverse vascular changes in the aorta, a lower aorto-iliac bifurcation position was not independently associated with future CVD events. The opposing effects of atherosclerosis and stiffness in the aorta may, in part, explain our null findings.
