[Dimensions of the proximal thoracic aorta from childhood to adult age: reference values for two-dimensional echocardiography. Ligurian Group of SIEC (Italian Society of Echocardiography)]

Abstract

Background: Two-dimensional echocardiography (2-DE) represents the main tool for detecting and monitoring abnormalities of proximal thoracic aorta. However, previous studies performed to assess the reference values of aortic diameters using this technique are few and, often, involve a small number of subjects. Furthermore, such a study has not been performed on an Italian population.

Methods: To assess the reference values and the growth curves of the dimensions of the proximal thoracic aorta in an Italian population, we measured aortic diameters at the level of the anulus, of the sinuses of Valsalva and of the supraaortic ridge, by using 2-DE, in 134 healthy volunteers (78 males, 56 females), aged 35 +/- 16 years (range 5-76). Sex, age, weight, height, body surface area (BSA), heart rate, systolic and diastolic blood pressure were analyzed as determinants of proximal thoracic aorta diameters. In addition, to compare the specificity of the reference values, we have obtained with those provided by literature, we studied another independent group of 23 healthy volunteers, aged 32 +/- 15 years (range 11-65).

Results: In our study population, mean values and range of aortic 2-DE diameters were 2.1 +/- 0.3 cm (range 1.3-2.9) at the level of the anulus, 2.6 +/- 0.4 cm (range 1.7-3.7) at the level of the sinuses of Valsalva and 2.4 +/- 0.4 cm (range 1.5-3.4) at the level of the supraaortic ridge. At multivariate regression analysis, sex and age emerged as the only independent determinants of the aortic root diameters (r2 = 0.35, 0.43, and 0.52 for aortic diameter at the level of anulus, sinuses of Valsalva, and supraaortic ridge, respectively). On average, aortic root dimensions at the level of the anulus, of the sinuses of Valsalva and of the supraaortic ridge in females were 1.5 mm, 2.8 mm, and 1 mm, respectively, smaller than those of males of comparable age, height and weight. The growth curves showed that proximal thoracic aorta increases in size in the first 30 years of life; thereafter, it remains relatively constant in size up to 55 years, after which the proximal thoracic aorta tends to enlarge gradually. The ratios of sinuses of Valsalva to annular diameter and of supraaortic ridge to annular diameter (1.27 +/- 0.17 and 1.17 +/- 0.16, respectively) were found to be indexes of aortic root dimension independent of sex and age. No correlation was found between aortic root dimensions and systolic blood pressure. M-mode echocardiography systematically overestimated 2-DE aortic diameters at the level of the anulus, as well as at the level of the sinuses of Valsalva and of the supraaortic ridge (+0.8 +/- 0.04 cm, +0.2 +/- 0.04 cm, and +0.4 +/- 0.04 cm, respectively, p < 0.0001 for all). In the control population, our reference values demonstrated a specificity significantly higher than that of the main reference values reported in literature (97 +/- 2% versus 62 +/- 4%, p < 0.0001).

Conclusions: Our study provides a prospectic, systematic and detailed analysis of 2-DE proximal thoracic aorta diameters in a wide group of healthy Italian subjects. Our data show that: 1) 2-DE aortic root dimensions are influenced by sex and age but not by body size or blood pressure; 2) the ratios of sinuses of Valsalva to annular diameter and of supraaortic ridge to annular diameter are indexes of aortic root dimension which are independent of age and sex; 3) M-mode diameter systematically overestimates 2-DE diameters of the aortic root; and 4) Italian population based reference values showed higher specificity than values provided by literature.