This was a retrospective study of all patients who had been referred for cardiovascular magnetic resonance (CMR) between 2015 and 2016 to the Department of General and Interventional Radiology and Neuroradiology at Wroclaw Medical University in Poland. In total, the cardiovascular magnetic resonance images of 89 patients were included for initial assessment. The exclusion criteria were poor quality of the images in the cine coronal view, which resulted mainly from the respiratory movement of the patient (6 patients) or arrhythmia (5 patients). Finally, 73 patients were included in the analysis.

The CMR examinations were carried out on 1.5 T Signa HDxt (General Electric Healthcare, WI, USA) with an eight phased-array coil. All measurements were performed in the ECG-gated coronal cine Fast Imaging Employing Steady-state Acquisition (FIESTA) sequences. The serial images with a nominal resolution of 1.2 × 1.2 mm and 6 mm section thickness were obtained. The images covered a 256 × 256 mm field of view.

The CMR images were analyzed in the coronal cine-MRI view. The maximum distance to which the ventriculo-aortic junction (VAJ) was pulled by the contracting heart was measured (LDAA – longitudinal displacement of the aortic annulus). First, the position of the VAJ was established in the maximum systole and diastole, then the distance between the mid-points of the VAJ in systole and diastole was measured. Moreover, the maximum dimensions of the aortic root and the ascending aorta were assessed. The methodology of the measurements is presented in Fig. 1.

All examinations were evaluated by two observers. For inter-observer variability, the same examinations were analyzed by a second observer blinded to all the measurements performed by the first observer. For intraobserver variability of longitudinal systolic stretching of the aorta, all measurements were retaken by each observer 1 week after the initial assessment.

The normality of distribution was assessed using the Shapiro-Wilk test. Based on the distribution, data are presented as mean ± standard deviation or median and range for continuous data. The categorical data are presented as frequencies. The correlations were assessed using the Pearson correlation coefficient. The means were compared using either the student’s t-test or the Mann-Whitney U test depending on the normality of the distribution. The inter- and intraobserver variabilities were assessed using the interclass correlation coefficient. The analyses were carried out using Dell Statistica 13 software (Dell, USA).

The mean age of the patients was 45.2 ± 17.3 years and 68% (50 patients) were males. The mean height of the patients was 171.3 ± 14.4 cm and mean weight was 77.2 ± 10.8 kg. The mean BMI was 26.1 ± 3.8. There were 11 patients diagnosed with arterial hypertension and one patient had diabetes mellitus. There were no patients with poor ejection fraction of the left ventricle (< 30%). The diameter of the ascending aorta was 32.0 ± 6.3 mm (range: 20-57 mm) and was comparable between the genders (males: 32.6 ± 6.9 mm vs. females: 30.7 ± 4.8 mm, p = .256). The maximum dimension of the aortic root was 35.0 ± 5.1 mm (range: 18-42 mm) and was bigger in males than females (36.4 ± 5.2 mm vs. 31.2 ± 3.4 mm, p < .001).

The longitudinal displacement of the aortic annulus (LDAA) 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 aortic arch (junction between the innominate artery and the left carotid artery) was displaced on average by 2.9 ± 0.4 mm (range: 0-6 mm; 95% CI: 2.1–3.7 mm). There was a tendency towards lower LDAA values in older patients and a statistically significant negative correlation between the LDAA and the age of patients (r = −.38, p = .001) was observed (Fig. 2). The values of the LDAA in the age groups were as follows (0-20 yrs.: 14.6 ± 2.7 mm; 21-40 yrs.: 12.1 ± 2.5 mm; 41-60 yrs.: 11.5 ± 2.6 mm; 61-80 yrs.: 9.6 ± 2.8 mm; p = .002) and are shown on Fig. 3. There was no statistically significant correlation between the LDAA and the patient’s height (r = .112, p = .092), weight (r = .096, p = .771) and BMI (r = .084, p = .501).

The longitudinal displacement of the aortic annulus was not affected by the maximum dimension of the aorta. No significant correlations 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) were found in the examined patients (Fig. 4).

The interobserver variability for the longitudinal stretching of the ascending aorta was 0.95 (95% CI: 0.92–0.97) and the intraobserver variability was 0.96 (95% CI: 0.94–0.98).

This is a small cohort study that include normal controls. An additional study assessing the LDAA in patients’ with cardiovascular diseases is necessary to evaluate the clinical relevance of the LDAA. Due to a small sample size, one cannot rule out that the significant correlation of the LDAA with age may be influenced by other confounding factors. A study on a much larger population is warranted. The measurements of the LDAA were performed on two-dimensional images. However, the aortic annulus is a three-dimensional structure that changes its position during the heart cycle. It might have influenced the accuracy of the measurements.