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

Comparisons of Two-dimensional Echocardiographic Aortic Dimensions between Chinese, Japanese, and Europeans

PURPOSE

We aimed to investigate the impacts of age, gender, and race on aortic dimensions in healthy adults.

METHODS

We analyzed data from 3 large population-based sample studies, including Chinese Echocardiographic Measurements in Normal Chinese Adults, Japanese the Normal Values for Echocardiographic Measurements Project, and European Normal Reference Ranges for Echocardiography, to compare the two-dimensional echocardiography-derived aortic diameters at different levels and to explore the effects of age, gender, and race on aortic measurements. We also compared the values corrected by body surface area (BSA) or height.

RESULTS

The results are as follows: (1) Aortic diameters showed positive correlations with age (r=0.12-0.42, P<0.05), and there were significant inter-age group differences before and after indexing to BSA (P<0.05); (2) Men had greater measurements of aortic diameters than women, with the differences being the same when indexed to height. However, indexing to BSA reversed the differences; (3) The aortic diameters at annulus (Ao-a) and sinus (Ao-s) levels were very close with minor differences between the Chinese and Japanese regardless of whether BSA was used for correction; and (4) The aortic measurements at Ao-s and proximal ascending aorta (Ao-asc) levels in the Chinese were significantly lower than in the Europeans for both genders, with the differences remaining the same even after indexing to BSA or height (P<0.05).

CONCLUSION

Aortic dimensions vary with age and gender, and there are significant differences between races or ethnicities even when stratified by gender and age. The indexation by BSA or height cannot eliminate these differences. Therefore, age-specific, gender-specific, race-specific, and nationality-specific reference values may be more appropriate at present for clinical practice to avoid misdiagnosis and misclassification of aortic dilation.

Normal Values of Aortic Root Size According to Age, Sex, and Race: Results of the World Alliance of Societies of Echocardiography Study

BACKGROUND

Accurate measurements of the aortic annulus and root are important for guiding therapeutic decisions regarding the need for aortic surgery. Current echocardiographic guidelines for identification of aortic root dilatation are limited because current normative values were derived predominantly from white individuals in narrow age ranges, and based partially on M-mode measurements. Using data from the World Alliance Societies of Echocardiography study, the authors sought to establish normal ranges of aortic dimensions across sexes, races, and a wide range of ages.

METHODS

Adult individuals free of heart, lung, and kidney disease were prospectively enrolled from 15 countries, with even distributions among sexes and age groups: young (18-40 years), middle aged (41-65 years) and old (>65 years). Transthoracic two-dimensional echocardiograms of 1,585 subjects (mean age, 47 ± 17 years; 50.4% men; mean body surface area [BSA], 1.77 ± 0.22 m²) were analyzed in a core laboratory following American Society of Echocardiography guidelines. Measurements, indexed separately by BSA and by height, included the aortic annulus, sinuses of Valsalva, and sinotubular junction. Differences among age, sex, and racial groups were evaluated using unpaired two-tailed Student's t tests.

RESULTS

All aortic root dimensions were larger in men compared with women. After indexing to BSA, all measured dimensions were significantly larger in women, whereas men continued to show larger dimensions after indexing to height. Of note, the upper limits of normal for all aortic dimensions were lower across all age groups, compared with the guidelines. Aortic dimensions were larger in older age groups in both sexes, a trend that persisted regardless of BSA or height adjustment. Last, differences in aortic dimensions were also observed according to race: Asians had the smallest nonindexed aortic dimensions at all levels.

CONCLUSIONS

There are significant differences in aortic dimensions according to sex, age, and race. Thus, current guideline-recommended normal ranges may need to be adjusted to account for these differences.

Image-based scaling laws for somatic growth and pulmonary artery morphometry from infancy to adulthood

Pulmonary artery (PA) morphometry has been extensively explored in adults, with particular focus on intra-acinar arteries. However, scaling law relationships for length and diameter of extensive preacinar PAs by age have not been previously reported for in vivo human data. To understand preacinar PA growth spanning children to adults, we performed morphometric analyses of all PAs visible in the computed tomography (CT) and magnetic resonance (MR) images from a healthy subject cohort [n = 16; age: 1-51 yr; body surface area (BSA): 0.49-2.01 m²]. Subject-specific anatomic PA models were constructed from CT and MR images, and morphometric information-diameter, length, tortuosity, bifurcation angle, and connectivity-was extracted and sorted into diameter-defined Strahler orders. Validation of Murray's law, describing optimal scaling exponents of radii for branching vessels, was performed to determine how closely PAs conform to this classical relationship. Using regression analyses of vessel diameters and lengths against orders and patient metrics (BSA, age, height), we found that diameters increased exponentially with order and allometrically with patient metrics. Length increased allometrically with patient metrics, albeit weakly. The average tortuosity index of all vessels was 0.026 ± 0.024, average bifurcation angle was 28.2 ± 15.1°, and average Murray's law exponent was 2.92 ± 1.07. We report a set of scaling laws for vessel diameter and length, along with other morphometric information. These provide an initial understanding of healthy structural preacinar PA development with age, which can be used for computational modeling studies and comparison with diseased PA anatomy.NEW & NOTEWORTHY Pulmonary artery (PA) morphometry studies to date have focused primarily on large arteries and intra-acinar arteries in either adults or children, neglecting preacinar arteries in both populations. Our study is the first to quantify in vivo preacinar PA morphometry changes spanning infants to adults. For preacinar arteries > 1 mm in diameter, we identify scaling laws for vessel diameters and lengths with patient metrics of growth and establish a healthy PA morphometry baseline for most preacinar PAs.

Normal reference intervals for cardiac dimensions and function for use in echocardiographic practice: a guideline from the British Society of Echocardiography

This guideline presents reference limits for use in echocardiographic practice, updating previous guidance from the British Society of Echocardiography. The rationale for change is discussed, in addition to how the reference intervals were defined and the current limitations to their use. The importance of interpretation of echocardiographic parameters within the clinical context is explored, as is grading of abnormality. Each of the following echo parameters are discussed and updated in turn: left ventricular linear dimensions and LV mass; left ventricular volumes; left ventricular ejection fraction; left atrial size; right heart parameters; aortic dimensions; and tissue Doppler imaging. There are several important conceptual changes to the assessment of the heart’s structure and function within this guideline. New terminology for left ventricular function and left atrial size are introduced. The British Society of Echocardiography has advocated a new approach to the assessment of the aortic root, the right heart, and clarified the optimal methodology for assessment of LA size. The British Society of Echocardiography has emphasized a preference to use, where feasible, indexed measures over absolute values for any chamber size.

Normal reference intervals for cardiac dimensions and function for use in echocardiographic practice: a guideline from the British Society of Echocardiography

This guideline presents reference limits for use in echocardiographic practice, updating previous guidance from the British Society of Echocardiography. The rationale for change is discussed, in addition to how the reference intervals were defined and the current limitations to their use. The importance of interpretation of echocardiographic parameters within the clinical context is explored, as is grading of abnormality. Each of the following echo parameters are discussed and updated in turn: left ventricular linear dimensions and LV mass; left ventricular volumes; left ventricular ejection fraction; left atrial size; right heart parameters; aortic dimensions; and tissue Doppler imaging. There are several important conceptual changes to the assessment of the heart’s structure and function within this guideline. New terminology for left ventricular function and left atrial size are introduced. The British Society of Echocardiography has advocated a new approach to the assessment of the aortic root, the right heart, and clarified the optimal methodology for assessment of LA size. The British Society of Echocardiography has emphasized a preference to use, where feasible, indexed measures over absolute values for any chamber size.

Aortic root remodelling in competitive athletes

Background

Controversy remains about the cut-off limits for detecting aortic dilatation in athletes, particularly in large-sized individuals. The allometric scaling model has been used to obtain size-independent measurements in cardiovascular structures in the general population.

Aim

The purpose of this study was to validate the use of allometric scaling in the measurement of the aortic root for competitive athletes and to offer reference values.

Methods

This was a cross-sectional study that analyses the dimensions of aortic root found in the echocardiogram performed as part of pre-participation sports screening in competitive athletes between 2012–2015. Beta exponents were calculated for height and body surface area in the whole cohort. In order to establish whether a common exponent could be used in both genders the following model was assessed y = a xb*exp(c*sex). If a common exponent could not be applied then sex-specific beta exponents were calculated.

Results

Two thousand and eighty-three athletes (64% men) were included, from a broad spectrum of 44 different sports disciplines, including basketball, volleyball and handball. The mean age was 18.2 ± 5.1 years (range 12–35 years) and all athletes were Caucasian, with a training load of 12.5 ± 5.4 h per week. Indexed aortic root dimension showed a correlation with ratiometric scaling by body surface area (r: −0.419) and generated size independence values with a very light correlation with height (r: −0.084); and with the allometric scaling by body surface area (r: −0.063) and height (r: −0.070). The absolute value of aortic root was higher in men than in women ( p < 0.001). These differences were maintained with allometric scaling.

Conclusion

Size-independent aortic root dimension values are provided using allometric scaling by body surface area and height in a large cohort of competitive athletes. Aortic root values were larger in men than in women, both in absolute values and after allometric scaling. The use of these indexed aortic reference ranges can be useful for the early detection of aortic pathologies.

Scaling to produce size-independent indices of echocardiographic derived aortic root dimensions in elite Rugby Football League players

The assessment of aortic root dimensions is important in cardiac pre-participation screening. Scaling of cardiac dimensions removes the impact of body size allowing meaningful inter/intra group comparisons. Developing appropriate scaling approaches, scaling variables and extending the application to major vessels is warranted so underlying pathology can be detected and managed appropriately. The study aims to define relationships between aortic root dimensions and body surface area/height. Two hundred and twenty elite Rugby Football League athletes were recruited. All participants completed anthropometric assessments, a 12-lead ECG and echocardiogram. Aortic root was measured at the aortic annulus, sinus of valsalva, sinotubular junction and the proximal ascending aorta. Linear and allometric scaling were performed on the relationship between aortic measurements and body surface area/height. Absolute aortic root measurements fell within normal population data (mean ± standard deviation (range): aortic annulus: 22 ± 2 (17-28) mm, sinus of valsalva: 28 ± 3 (20-38) mm, sinotubular junction: 22 ± 3 (14-33) mm, proximal ascending aorta: 22 ± 3 (15-31) mm). Linear scaling to height produced size-independent indices at all aortic measurement sites (P < 0.05). Conversely, linear scaling using body surface area did not produce size-independent indices at any site (P > 0.05). Allometric scaling, using both body surface area and height, produced size-independent indices at all sites (P < 0.05). We recommend linearly scaling aortic root dimensions to height in elite Rugby Football League athletes and discourage the use of body surface area as a linear scaling quantity. Allometric scaling is also effective when using both body surface area and height.

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

BACKGROUND

Clinical assessment of intravascular volume status is challenging. In humans, ultrasonographic assessment of the inferior vena cava diameter, directly or as a ratio to the aortic diameter is used to estimate intravascular volume status.

OBJECTIVES

To ultrasonographically obtain reference values (RV) for caudal vena cava diameter (CVCD ), area (CVCa ) and aortic ratios using 3 views in awake healthy dogs.

ANIMALS

One hundred and twenty-six healthy adult dogs from clients, students, faculty, or staff.

METHODS

Prospective, multicenter, observational study. Two observer pairs evaluated CVCD by a longitudinal subxiphoid view (SV), a transverse 11th-13th right hepatic intercostal view (HV), and a longitudinal right paralumbar view (PV). Inter-rater agreements were estimated using concordance correlation coefficients (CCC). For body weight (BW)-dependent variables, RVs were calculated using allometric scaling for variables with a CCC ≥ 0.7.

RESULTS

The CCC was ≤0.43 for the CVC/aorta ratio at the PV and ≤0.43 in both inspiration and expiration for CVC at the SV. The RVs using allometric scaling for CVCa at the HV for inspiration, expiration, and for CVCD at the PV were 6.16 × BW0.762 , 7.24 × BW0.787 , 2.79 × BW0.390 , respectively.

CONCLUSIONS AND CLINICAL IMPORTANCE

The CVCD , measured at the HV and PV in healthy awake dogs of various breeds has good inter-rater agreement suggesting these sites are reliable in measuring CVCD . Established RVs for CVCD for these sites need further comparison to results obtained in hypovolemic and hypervolemic dogs to determine their usefulness to evaluate volume status in dogs.

Our obsession with normal values

Normal values provide the background for interpretation of quantitative imaging data and thus are essential information for daily routine. Nevertheless, the ways how normal values are obtained, presented and interpreted, often do not receive the attention they deserve. We review the concepts of normalcy, the implications of typical normal ranges including the types of distribution of normal data, the possibilities to index for confounding biological factors like body surface area and the limitations of the very concept of normal values, demonstrating that there are no easy statistical solutions for difficult clinical problems.

The Complex Phenotype of the Athlete's Heart: Implications for Preparticipation Screening

Preparticipation screening is vital to exclude inherited cardiac conditions that have the potential to cause sudden cardiac death in seemingly healthy athletes. Recent research has questioned traditional theories of load-induced, dichotomous cardiac adaptation. We therefore considered whether a one-size-fits-all approach to screening can account for interindividual differences brought about by sporting discipline, training volume, ethnicity, body size, sex, and age.

Right to Left Ventricular Diameter Ratio ≥0.42 is the Warning Flag for Suspecting Atrial Septal Defect in Preschool Children: Age- and Body Surface Area-Related Reference Values Determined by M-Mode Echocardiography

It is not always easy to observe and screen atrial septal defects (ASD) using echocardiography. In addition, there are no established echocardiographic reference indices for screening patients with ASDs. We retrospectively reviewed our database and recruited 151 isolated ASD patients and 2769 healthy subjects. In total, 307 echocardiographic studies were performed for ASD patients. Surgical repairs were done in 75 of the ASD patients. The ratio of right to left ventricular end-diastolic dimensions (RVD/LVD), which was determined by M-mode echocardiography, was used as an index of RV dilatation. After obtaining age- and body surface area (BSA)-related RVD/LVD nomograms in healthy subjects, we calculated the z-scores of RVD/LVD for all subjects and obtained the optimal cut-off values to differentiate patients with ASD from healthy subjects. The optimal cut-off values were high in neonates and gradually decreased with an increase in the age and BSA, but were almost constant in children aged >4 years or whose BSA was >0.65 m(2). The cut-off values of RVD/LVD for suspected ASD were ≥0.42 in children aged >4 years or those whose BSA was >0.65 m(2). Those for an ASD operation were ≥0.46 in those whose BSA > 0.65 m(2). The RVD/LVD determined by M-mode echocardiography is a useful index to evaluate RV dilatation in patients with ASDs. The RVD/LVD ≥ 0.42 is the warning flag for suspecting ASD in preschool children and that ≥0.46 may be a clinical important sign to determine ASD operation.