Impact of methodology and the use of allometric scaling on the echocardiographic assessment of the aortic root and arch: a study by the Research and Audit Sub-Committee of the British Society of Echocardiography

Abstract

The aim of the study is to establish the impact of 2D echocardiographic methods on absolute values for aortic root dimensions and to describe any allometric relationship to body size. We adopted a nationwide cross-sectional prospective multicentre design using images obtained from studies utilising control groups or where specific normality was being assessed. A total of 248 participants were enrolled with no history of cardiovascular disease, diabetes, hypertension or abnormal findings on echocardiography. Aortic root dimensions were measured at the annulus, the sinus of Valsalva, the sinotubular junction, the proximal ascending aorta and the aortic arch using the inner edge and leading edge methods in both diastole and systole by 2D echocardiography. All dimensions were scaled allometrically to body surface area (BSA), height and pulmonary artery diameter. For all parameters with the exception of the aortic annulus, dimensions were significantly larger in systole (P<0.05). All aortic root and arch measurements were significantly larger when measured using the leading edge method compared with the inner edge method (P<0.05). Allometric scaling provided a b exponent of BSA0.6 in order to achieve size independence. Similarly, ratio scaling to height in subjects under the age of 40 years also produced size independence. In conclusion, the largest aortic dimensions occur in systole while using the leading edge method. Reproducibility of measurement, however, is better when assessing aortic dimensions in diastole. There is an allometric relationship to BSA and, therefore, allometric scaling in the order of BSA0.6 provides a size-independent index that is not influenced by the age or gender.

Normal Reference Intervals for Cardiac Dimensions and Function for Use in Echocardiographic Practice: A Guideline from the British Society of Echocardiography

“…Consequently, there is a vast array of data from which reference limits can be derived. NORRE, along with earlier work by Oxborough et al, demonstrated that aortic root dimensions are best correlated to height and not BSA (10,61). This is a change from the currently accepted practice and will have potential benefits in overweight individuals.…”

“…This will make echo surveillance with sequential measurements of a dilating aorta more reproducible. Aortic dimensions obtained in diastole are consistently smaller than corresponding measurements made in systole (10,61). If the aorta in question is approaching the point at which intervention is required, the BSE suggests that corroborative measurements are made with an additional imaging modality.…”

“…This dimension is neither the outer nor the inner size of the aorta, but has resulted in reference values and cut-offs for therapy (such as aortic root replacement) that are embedded in contemporary guidance (60). Conversely, there is evidence that measurements of the aortic root using the IE-IE methodology is more readily obtained and more reproducible (61). Previous BSE guidance has advocated the IE-IE technique, and therefore, to maintain consistency, the current guidance advises ongoing use of this approach.…”

Establishment of reference values of the caudal vena cava by fast‐ultrasonography through different views in healthy dogs

“…Normality was visually evaluated for The association between body weight (BW) and echocardiographic measurements has been reported in several studies 27,28 and is best described using allometric scaling in dogs, cats, humans and rhesus monkeys. [27][28][29][30] Therefore, we used allometric scaling to calculate references values for the various CVC measurements according to BW. The use of allometric scaling for echocardiographic dimensions in dogs has been described extensively.…”

Our obsession with normal values

“…Handling mean and SD can be simplified by using Z -scores, which have gained popularity in particular in pediatric cardiology, where rapidly and substantially changing body sizes in infants and adolescents must be dealt with ( 10 ). Z -scores are based on mean value and SD of a given parameter, which can be indexed to a variable such as body surface area, height or powers of such variables ( 11 ). The formula for the Z -score of a particular measurement x is Z -score = ( x − x mean )/SD, where x mean is the mean value and SD is the standard deviation of that parameter in a population of normals of that age and/or body size.…”