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Ann Thorac Surg 1997;64:511-515
© 1997 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Morphologic Features of the Normal Aortic Arch in Neonates, Infants, and Children Pertinent to Growth

Department of Cardiovascular Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands

Accepted for publication February 8, 1997.

	Abstract

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Background. The aorta in newborns rapidly adapts by growth to postnatal circulatory conditions. The question arises what structural features are associated with growth and whether differences occur between the various segments.

Methods. Nineteen specimens have been studied: seven from babies less than 1 month, seven from 1 month to 1 year, and five from 1 to 4 years. In each baby the diameter of the aortic segments and its branches were measured. Histologically the number of elastin lamellae was counted, and furthermore, collagen density was quantified at several measurement sites.

Results. The diameter of each segment increases rapidly after birth and more so than that of the descending aorta, except for the brachiocephalic artery and its branches and the left common carotid artery, albeit not at the same rate. The ascending aorta is the only segment that shows a decrease in the ratio of elastin lamellae to diameter. Collagen density was always highest in the descending aorta.

Conclusions. These observations show that postnatal growth of the thoracic aorta is associated with distinct structural remodeling soon after birth; these observations are of clinical relevance in case of aortic arch abnormalities.

	Introduction

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
The aorta in newborn babies rapidly adapts to postnatal circulatory conditions, which shows angiographically as an increase in diameter of the distal part of the transverse arch and in widening of the isthmus [1]. It has been claimed that an increase in internal diameter of the ascending aorta is paralleled by an increase in the so-called packing density of the elastin lamellae [2]. This raises the question as to what are the basic structural features present at the time of adaptive vascular growth (ie, in the perinatal period and early infancy). Understanding these aspects is relevant, as an abnormal aortic wall structure has been documented in patients with hypoplastic transverse arch [3] and growth after end-to-end repair for obstructive arch anomalies remains controversial [4–6].

This study was undertaken to clarify the relationship between the diameter and the length of the various segments of the thoracic aorta and the microscopic features pertinent to growth.

	Material and Methods

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Heart Specimens
The study is based on 19 heart specimens, together with the thoracic aorta, of mature newborn babies, infants, and children. There were no cardiovascular abnormalities. The specimens were grouped together according to age. Seven were obtained from babies less than 1 month of age (male/1 day, n = 2; female/1 day, n = 3; male/5 days, n = 1; female/25 days, n = 1), seven from 1 month to 1 year (male/1 month, n = 1; male/3 months, n = 3; male/4 months, n = 1; male/5 months, n = 1; female/8 months, n = 1), and five from 1 to 4 years (male/1 year, n = 3; male/2 years, n = 1; female/4 years, n = 1).

All specimens were obtained from the Cardiovascular Registry and all had been fixed in 4% formalin for a considerable length of time.

Morphometry
The external diameters of the various segments of the thoracic aorta were measured as displayed in Figure 1. The descending aorta was measured at 2.5 cm distal to the insertion of the arterial duct or its ligament. The external diameters of the brachiocephalic artery, the right subclavian artery, the right and the left common carotid artery, and the left subclavian artery were measured at 5 mm from their origin. To compensate for age, the diameter of each segment was divided by that of the descending aorta and expressed as a ratio. The length of the proximal and distal transverse arch and that of the aortic isthmus were taken as shown in Figure 1.

View larger version (24K): [in this window] [in a new window]   Fig 1. . Diagram of the thoracic aorta showing the various segments and the sites of measurements. (dist. TA = distal transverse arch; ist. = isthmus; prox. TA = proximal transverse arch.)

Collagen Density
The total amount of collagen was quantified with the use of a microdensitophotometer, using sections stained with picrosirius red F3BA [8]. The measurements were performed on a Vickers M85 scanning and integrating microdensitometer. In each section 20 randomly selected frames, within the middle part of the media, were screened. The values obtained were corrected for variations in thickness of the sections and staining concentrations, using a reference section. The average was calculated and expressed as a percentage of total collagen in relation to total protein.

Statistical Analysis
Statistical analysis was performed as a mean ± the standard deviation. Data were analyzed by analysis of variance. Post-hoc intergroup comparisons were performed using Fischer's protected least significant difference test. A priori level of significance was set at a p value of less than 0.05.

	Results

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Morphometry
The values obtained are shown in Table 1. The average absolute diameter of each segment increased significantly with age. Once diameters were expressed as a ratio (diameter divided by the diameter of the descending aorta) a different pattern was observed (Table 2). A significant increase was observed in the two youngest age groups (<1 month and between 1 month and 1 year) with respect to the ascending aorta, the proximal and distal transverse arch, the aortic isthmus, the left common carotid artery, and the left subclavian artery. In the brachiocephalic artery and its branches, the ratio did not increase significantly in this period. The diameter of the ascending aorta was larger than that of the descending aorta at all ages (ratio <1). In the proximal and distal transverse arch, the ratio became larger than 1 only after 1 month of age and the aortic isthmus ratio reached that number only after 1 year of age (Table 2).

Histology
The number of elastin lamellae in each segment is shown in Table 3. In all segments of aorta, except the right subclavian artery, the number of elastin lamellae was significantly higher in the cases of 1 month and beyond, compared with the youngest specimens. Once expressed as a ratio (number of elastin lamellae divided by that of the descending aorta) only the ascending aorta showed a significantly higher number and only in specimens of less than 1 month (Table 3).

	Comment

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

What could be the explanation for these phenomena? One could hypothesize that the increased volume of blood to be conveyed by the ascending aorta and aortic arch after birth causes the increase in diameter. The significant increase in diameter of the left subclavian artery also suggests redistribution of blood toward this vessel. Indeed, it is generally accepted that arterial growth (ie, diameter) relates to blood flow [9–11]. This is nicely illustrated also by comparing the ascending aorta and the pulmonary trunk. During the gestational period—in general terms—left ventricular output is less than that of the right ventricle, but these differences gradually increase and at the time of birth both ascending aorta and pulmonary trunk have almost similar diameters and a similar configuration of elastin lamellae [12, 13].

However, the present study also shows that the number of elastin lamellae is not determined on the basis of flow only, as the descending aorta has significantly less elastin lamellae than the ascending aorta despite an almost equal diameter at birth. Moreover, as pointed out before, after birth the ascending aorta shows a rapid relative decrease in the number of elastin lamellae, which surely cannot be attributed to a decrease in flow. It is tempting, therefore, to consider other rheologic factors as well. For instance, after birth the peak blood velocity in the ascending aorta changes from approximately 90 cm/s in fetuses to approximately 140 cm/s at 6 months of age [13, 14]. At the same time the absolute output from the left ventricle increases with body growth. However, within the aorta flow velocity and oscillation decrease with increasing distance from the pumping chamber, whereas the pressure pulse increases [15]. Hence, one may speculate that these factors contribute to the genesis of elastin lamellae, but because of the differences between the ascending and descending aorta, these factors also cause a relative decrease in the number of elastin lamellae in the ascending aorta compared with that in the descending aorta.

Our observations of normal growth characteristics reveal distinct remodeling of the ascending aorta and the aortic arch soon after birth, that is before 1 month of age. In this particular period the potential for growth and, most likely, adaptation to secondary changes, such as those induced by congenital heart defects, is high. These observations, therefore, may serve as reference once confronted with abnormalities of the aortic arch.

	Acknowledgments

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
During the course of this study Dr Machii was a Research Fellow from the Kitasato University, Faculty of Medicine, Kanagawa, Japan. We thank Marsha I. Schenker for excellent secretarial assistance.

	Footnotes

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Address reprint requests to Dr Machii, Division of Cardiovascular Surgery, Ebina General Hospital Cardiovascular Center, 1519 Kawaraguchi, Ebina, Kanagawa 24304, Japan.

	References

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 

1. Clarkson PM, Brandt PWT. Aortic diameters in infants and young children: normative angiographic data. Pediatr Cardiol 1985;6:3–6.[Medline]
2. Van Meurs-Van Woezik H, Klein HW, Markus-Silvis L, Krediet P. Comparison of the growth of the tunica media of the ascending aorta, aortic isthmus and descending aorta in infants and children. J Anat 1983;136:273–81.[Medline]
3. Becker AE. Segmental aortic hypoplasia or how to interpret the flow concept. Int J Cardiol 1988;20:247–55.[Medline]
4. Lacour-Gayet F, Bruniaux J, Serraf A, et al. Hypoplastic transverse arch and coarctation in neonates. Surgical reconstruction of the aortic arch: a study of sixty-six patients. J Thorac Cardiovasc Surg 1990;100:808–16.[Abstract]
5. Siewers RD, Ettedgui J, Pahl E, Tallman T, del Nido PJ. Coarctation and hypoplasia of the aortic arch: will the arch grow? Ann Thorac Surg 1991;52:608–14.[Abstract]
6. Brouwer MHJ, Cromme-Dijkhuis AH, Ebels T, Eijgelaar A. Growth of the hypoplastic aortic arch after simple coarctation resection and end-to-end anastomosis. J Thorac Cardiovasc Surg 1992;104:426–33.[Abstract]
7. Wolinsky H, Glagov S. A lamellar unit of aortic medial structure and function in mammals. Circ Res 1967;20:99–111.[Abstract/Free Full Text]
8. James J, Bosch KS, Zuyderhoudt FMJ, Houtkooper JM, Van Gool J. Histophotometric estimation of volume density of collagen as an indication of fibrosis in rat liver. Histochemistry 1986;85:129–33.[Medline]
9. Kamiya A, Togawa T. Adaptive regulation of wall shear stress to flow changes in the rabbit carotid artery. Am J Physiol 1980;239(Heart Circ Physiol 8):H14–H21.
10. Langille BL, Bendeck MP, Keeley FW. Adaptations of carotid arteries of young and mature rabbits to reduced carotid blood flow. Am J Physiol 1989;256(Heart Circ Physiol 25):H931–9.
11. Guyton JR, Hartley CJ. Flow restriction of one carotid artery in juvenile rats inhibits growth of arterial diameter. Am J Physiol 1985;248(Heart Circ Physiol 17):H540–6.
12. Heath D, Wood EH, DuShane JW, Edwards JE. The structure of the pulmonary trunk at different ages and in cases of pulmonary hypertension and pulmonary stenosis. J Pathol Bacteriol 1959;77:443–56.[Medline]
13. Reed KL, Meijboom EJ, Sahn DJ, Scagnelli SA, Valdes-Cruz LM, Shenker L. Cardiac Doppler flow velocities in human fetuses. Circulation 1986;73:41–6.[Abstract/Free Full Text]
14. Light LH, Cross G. Convenient monitoring of cardiac output and global left ventricular function by transcutaneous aortovelography—an effective alteration to cardiac output measurements. In: Spencer MP, ed. Cardio Doppler diagnosis, Vol 1. The Hague: Martinus Nijhoff Publishers, 1984:69–80.
15. McDonald DA. Blood flow in arteries, 2nd ed. London: Edward Arnold, 1974:351–88.

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This Article Abstract Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Anton E. Becker Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Machii, M. Articles by Becker, A. E. Search for Related Content PubMed PubMed Citation Articles by Machii, M. Articles by Becker, A. E.