Background
Aortic size is known to vary significantly by age and body size and to be an important predictor of cardiovascular diseases. The aim of this study was to determine reference values for proximal thoracic aorta diameters, using the inner edge technique and two-dimensional transthoracic echocardiography.
Methods
Diameters of the aortic annulus, sinuses of Valsalva, sinotubular junction, arch, and ascending aorta and the angle of insertion of the aorta were measured in 500 subjects (231 women; mean age, 48 ± 18 years) with normal echocardiographic findings, retrospectively enrolled. The relations of age and body size with aortic measurements were investigated using bivariate and multiple linear regressions.
Results
Measurements were highly feasible (83% for the aortic arch, 100% for the other segments). All aortic diameters significantly related to age, weight and body surface area, while height was correlated only with annular diameter. In predictive models adjusted for gender, older age was associated with increased aortic diameters ( R 2 values ranged from 0.36 for the sinotubular junction to 0.52 for the sinuses of Valsalva). Adjustments for height and weight led to significant improvements ( R 2 values ranged from 0.43 for the sinotubular junction to 0.58 for the sinuses of Valsalva). Similar correlations were observed for men and women. Angle was found to be dependent only on age and gender. Reproducibility analysis showed good to excellent accordance between repeated measurements.
Conclusions
The results of this study show the effect of aging on the proximal thoracic aorta and emphasize the importance of accounting for gender and body size when assessing aortic size. The obtained reference ranges will help standardize the assessment of aortic dimensions by applying inner edge convention and facilitate comparisons with other imaging techniques.
Aortic size is known to vary significantly by age and body size and to be an important predictor of cardiovascular diseases. Therefore, the accurate assessment of aortic size is a key component in guiding clinical and therapeutic decisions. The establishment of reference ranges and normative equations, taking into account aging and anthropometric data, is of undoubted importance in clinical practice for diagnosis, prognosis, monitoring, and identifying the best timing for surgery. Normal values of proximal aortic diameters and area have been reported using different imaging techniques, from the pioneer studies based on M-mode echocardiography, to the more recent ones obtained using cardiac computed tomographic (CT) imaging and magnetic resonance imaging (MRI). However, the intermodality comparison is limited by several methodologic discrepancies, including the site of measurement, the considered cardiac phase, and the fact that CT and MRI measurements are made using the inner edge–to–inner edge method, whereas echocardiographic studies are mainly based on the leading edge convention.
Although two-dimensional (2D) transthoracic echocardiographic (TTE) imaging can be used to quantify the inner edge–to–inner edge diameter of the thoracic aorta, available normative ranges relate to the leading edge approach, and large series of normal values with the inner edge–to–inner edge method are lacking. Also, the new ultrasound 2D TTE equipment and transducers allow the accurate evaluation of the proximal aorta at different levels, and not only of the aortic root.
Accordingly, our aims were to derive normal 2D TTE reference values of thoracic aortic size at different levels in a large series of adult subjects with normal echocardiographic findings and to investigate the influence of aging, gender, and body size on these measurements.
Methods
Study Population
A total of 500 consecutive subjects, referred to Centro Cardiologico Monzino IRCSS between 2007 and 2012, were retrospectively included in the study in the presence of normal echocardiographic findings according to recent guidelines. Patients were referred for echocardiographic evaluation in the presence of routine cardiac evaluation, heart murmurs, suspicion of coronary artery disease, rhythm disturbances, and other causes. Among the study population, 70 individuals (14%) had mild systemic arterial hypertension, defined as a documented history of mild high blood pressure (systolic blood pressure, 140–160 mm Hg; diastolic blood pressure, 90–100 mm Hg), without any abnormality on echocardiographic examination and specifically no left ventricular hypertrophy.
The study design aimed to include ≥25 subjects per gender and per age decade. Exclusion criteria were poor-quality 2D echocardiographic images; obesity (body mass index ≥ 30 kg/m 2 ); diabetes; coronary, valve, and congenital heart diseases; renal diseases; and previous cardiac percutaneous or surgical intervention.
Echocardiographic Imaging and Measurements
All patients underwent standard echocardiographic examinations, following the protocol of our laboratory. Examinations were performed using iE33 (Philips Medical Systems, Andover, MA), or Vivid 7 (GE Vingmed Ultrasound AS, Horten, Norway) ultrasound systems equipped with the appropriate 2D transthoracic probe.
Data sets were retrieved from the picture archiving and communication system of our institution in the Digital Imaging and Communications in Medicine format and processed offline. In detail, the diameters of the proximal aorta were measured at the following sites ( Figure 1 ): (1) the aortic valve annulus, as the distance between the hinge points of the right and noncoronary leaflets; (2) the diameter at the sinuses of Valsalva (SoV); (3) the sinotubular junction (STJ); (4) the ascending aorta, as the maximum diameter visualized; and (5) the aortic arch, as the diameter in correspondence of the junction of the far wall of the left subclavian artery with the aorta. Also, the angle of insertion of the aorta on the left ventricle was considered by tracing the anterior-septal wall midaxis and evaluating the angle formed with the aortic long axis passing through the leaflet coaptation point.
