Variation in Ascending Aorta Position: An analysis by Computed Tomography

Background: There is no evidence in current literature that demonstrates the prevalence of ascending thoracic aortic variation in relation to the sternum in the general, or diseased population. This measurement has become an important factor in decision-making for Trans-Catheter Aortic Valve Implantation (TAVI) and Minimally Invasive Cardiac Surgery (MICS).

Methods: We conducted a cross-sectional study in Cape Town, South Africa. We evaluated the Thoracic CT scans of pre-selected TAVI patients (n=25) and compared these to Thoracic CT scans from the same general population (n=100). Three parameters of ascending thoracic aorta variation were measured.

Results: Mean aorta distance from sternum was 28,01 mm [95%CI: 24.56 - 31.48] in cases and 27,34 mm [95% CI: 25.49 - 29.20] in controls (p<0.001). The mean position of the aorta relative to the sternum, favoured the aorta being more than 50% of its diameter to the right, in both groups. Aorto-ventricular angle showed a mean angle (degrees) of 47.92 [95%CI: 44.36-51.23] in cases and 37.06 [95%CI: 35.03-39.09] in controls (p<0.001). A linear relationship of aorto-ventricular angle compared to age was demonstrated.

Conclusion: Statistical analysis of ascending thoracic aorta position, indicates that patients presenting for aortic valve surgery, especially older patients (>70yrs) have favourable anatomy for MICS through a right thoracotomy. The aortic distance from the sternum was larger in the exposed group > 60 years. The aorto-ventricular angle in aortic stenosis patients was 10° more than the general population, regardless of age. This angle increases linearly with age, in both groups.