The evaluation of the aortic annulus displacement during cardiac cycle using magnetic resonance imaging

Background: The stress in the ascending aorta results from many biomechanical factors including the geometry of the vessel and its maximum dimensions, arterial blood pressure and longitudinal systolic stretching due to heart motion. The stretching of the ascending aorta resulting from the longitudinal displacement of the aortic annulus during the heart cycle has not been examined in the general population so far. The aim of the study is to evaluate this parameter using cardiovascular magnetic resonance (CMR) imaging in the general population in all age groups. Methods: The cardiac magnetic resonance images of 73 patients were evaluated. The maximum distance to which the ventriculo-aortic junction was pulled by the contracting heart (LDAA - longitudinal displacement of the aortic annulus) was measured in the cine coronal sequences. Moreover, the maximum dimensions of the aortic root and the ascending aorta were assessed. Results: The LDAA value was on average 11.6 +/- 2.9 mm (range: 3-19 mm; 95% CI: 10.9-12.3 mm) and did not differ between males and females (11.8 +/- 2.9 mm vs. 11.2 +/- 2.9 mm, p = .408). The diameter of the ascending aorta was 32 +/- 6.3 mm (range: 20-57 mm). The maximal dimension of the aortic root was 35 +/- 5.1 mm (range: 18-42 mm). There was a statistically significant negative correlation between the LDAA and the age of patients (r = -.38, p = .001). There was no significant correlation between the LDAA and aortic root dimension (r = .1, p = .409) and between the LDAA and diameter of the ascending aorta (r = .16, p = .170). Conclusions: Human aortic root and ascending aorta are significantly stretched during systole and the distance to which the aorta is stretched decreases with age. The measurement of the longitudinal displacement of the aortic annulus using the CMR is feasible and reproducible.