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.

David Oxborough,Liam Ring,James Willis,Martin Stout,Saqib Ghani,Allan Harkness,Julie Sandoval,Guy Lloyd,Abbas Zaidi,Roxy Senior,Victor Utomi,Nabeel Sheikh,Richard Steeds,William Moody

doi:10.1530/erp-14-0004

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.

Highlights

Aortic dilatation is a common manifestation in a range of conditions such as hypertension, aortic valve disease and connective tissue disease that carries an adverse prognosis and often requires serial monitoring over long periods of time
There is an allometric relationship to body surface area (BSA) and, allometric scaling in the order of BSA0.6 provides a size-independent index that is not influenced by the age or gender
In cases where a significant correlation has been identified, we examined whether this scaling approach had removed the influence of the body size as described www.echorespract.com previously [8] and determined whether allometric scaling was appropriate [12]

Summary

Introduction

Aortic dilatation is a common manifestation in a range of conditions such as hypertension, aortic valve disease and connective tissue disease that carries an adverse prognosis and often requires serial monitoring over long periods of time. Our understanding of the normal ranges of aortic dimensions and specific echocardiographic methodology was based upon a single study [3] that was the only evidence used in the current 2005 American Society of Echocardiography guidelines on Chamber Quantification [4]. Utilisation of these data, over 20 years old, is problematic as a result of improvements in technology that have led to the widespread use of 2D rather than M-mode to perform linear measurements and a change in recommendation from measuring leading edge to leading edge to measuring the tissue–blood interface. There is still a lack of clarity pertaining to the technical minutia of the measurements with little attention of when these measurements should be acquired in the cardiac cycle or whether to use leading edge to leading edge/inner edge to inner edge methods

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