The structure and composition of the pulmonary circulation in congenital heart disease

Pulmonary artery stiffness in fetuses with tetralogy of Fallot

PURPOSE

This study evaluated the elastic characteristics of the pulmonary trunk and distal branches in fetuses diagnosed with tetralogy of Fallot (TOF) using Doppler echocardiography.

METHODS

Data on 42 fetuses diagnosed with TOF and 84 gestational age-matched normal fetuses were prospectively collected from the Second Xiangya Hospital of Central South University between August 2022 and January 2023. The severity of TOF was classified into three categories based on the z-score of the pulmonary annulus diameter: mild (z-score ≥-2), moderate (-4

RESULTS

Compared with the normal group, the MPA-PAS in fetuses with TOF was significantly higher, while the DLPA-PAS and DRPA-PAS were notably lower (all P<0.05). The MPA-PAS of fetuses with severe TOF was higher than that of those with mild and moderate TOF (all P<0.05). However, there were no significant differences in the DLPA-PAS or DRPA-PAS among fetuses with mild, moderate, and severe TOF (all P>0.05).

CONCLUSION

Fetuses diagnosed with TOF exhibited increased vascular stiffness in the MPA and reduced stiffness in the distal pulmonary artery (PA). Larger-scale follow-up studies are required to elucidate the relationships between these changes in vascular stiffness and PA development in patients with TOF.

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Key Words

• Fetus
• Pulmonary arterial elasticity
• Pulmonary arterial stiffness
• Tetralogy of Fallot
• Ultrasonic cardiography

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Affiliation(s)

Yushan Liu Department of Ultrasound Diagnosis, Second Xiangya Hospital, Central South University, Changsha, China
Ran Xu Department of Urology, Second Xiangya Hospital, Central South University, Changsha, China
Dan Zhou Department of Ultrasound Diagnosis, Second Xiangya Hospital, Central South University, Changsha, China
Yang Yang Department of Ultrasound Diagnosis, Second Xiangya Hospital, Central South University, Changsha, China
Ganqiong Xu Department of Ultrasound Diagnosis, Second Xiangya Hospital, Central South University, Changsha, China
Shi Zeng Department of Ultrasound Diagnosis, Second Xiangya Hospital, Central South University, Changsha, China

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Structural abnormalities of the pulmonary trunk in tetralogy of Fallot and potential clinical implications: a morphological study

OBJECTIVES

The purpose of this study was to determine whether intrinsic histological abnormalities of the pulmonary trunk (PT) are present from birth and interact with palliative surgery and/or repair.

BACKGROUND

Little is known about PT histology in patients with tetralogy of Fallot (TOF), especially in the era of surgical intervention in childhood.

METHODS

We studied 39 formalin-fixed necropsy heart specimens with TOF and compared them with 17 normal control heart specimens. Sections of the PT and aorta were studied by light microscopy using various stains; histological findings were graded according to severity.

RESULTS

Among the TOF group (1 fetus, 11 infants, 14 children, and 13 adults), 11 patients had undergone palliative and 10 patients had undergone reparative surgery at a median age of 8 years (range 2.5 to 18 years). Histological changes of grade 2 or higher were present in 59% (medionecrosis), 36% (fibrosis), 56% (cystlike formation), and 56% (abnormal elastic tissue configuration) of TOF patients. Total histology grading scores were higher in TOF hearts (median 6, range 1 to 9) compared with controls (median 1, range 0 to 6; p < 0.0001). Histological abnormalities were present among infants (median score 3.5, range 1 to 9) and after palliative surgery (median score 5, range 2 to 9) or repair (median score 7.5, range 4 to 9).

CONCLUSIONS

Marked histological abnormalities in the PT of hearts with TOF exist compared with controls. These changes were present from infancy and among patients who had undergone palliative or reparative surgery, although operations in this cohort were performed late. Our data suggest that structural abnormalities of the PT, similar to these recently shown in the aorta, are intrinsic.

Structural abnormalities of great arterial walls in congenital heart disease: light and electron microscopic analyses

BACKGROUND

Great arteries in congenital heart disease (CHD) may dilate, become aneurysmal, or rupture. Little is known about medial abnormalities in these arterial walls. Accordingly, we studied 18 types of CHD in patients from neonates to older adults.

METHODS AND RESULTS

Intraoperative biopsies from ascending aorta, paracoarctation aorta, truncus arteriosus, and pulmonary trunk in 86 patients were supplemented by 16 necropsy specimens. The 102 patients were 3 weeks to 81 years old (average, 32+/-6 years). Biopsies were examined by light (LM) and electron (EM) microscopy; necropsy specimens by LM. Positive aortic controls were from 15 Marfan patients. Negative aortic controls were from 11 coronary artery disease patients and 1 transplant donor. Nine biopsies from acquired trileaflet aortic stenosis were compared with biopsies from bicuspid aortic stenosis. Negative pulmonary trunk controls were from 7 coronary artery disease patients. A grading system consisted of negative controls and grades 1, 2, and 3 (positive controls) based on LM and EM examination of medial constituents.

CONCLUSIONS

Medial abnormalities in ascending aorta, paracoarctation aorta, truncus arteriosus, and pulmonary trunk were prevalent in patients with a variety of forms of CHD encompassing a wide age range. Aortic abnormalities may predispose to dilatation, aneurysm, and rupture. Pulmonary trunk abnormalities may predispose to dilatation and aneurysm; hypertensive aneurysms may rupture. Pivotal questions are whether these abnormalities are inherent or acquired, whether CHD plays a causal or facilitating role, and whether genetic determinants are operative.

Spatial disorder of collagens in the great vessels, associated with congenital heart defects

Surgical ablation of the cardiac neural crest from the chicken embryo results in persistent truncus arteriosus (PTA) and a change in the elastic laminae of the great vessels, wherein elastin and the elastin microfibril show significant spatial disorder. The purpose of this study was to test the hypothesis that the interstitial collagens would also be disordered in the elastic laminae of chicken embryos with PTA. The birefringence characteristics of interstitial collagen were examined to evaluate spatial ordering. The results showed that collagen in the elastic laminae assumed an orderly configuration of well-defined fiber bundles in the great vessel walls of control embryos, whereas vessels from embryos with PTA lacked any distinct spatial order. Collagens type I and III were localized in the vessel walls. Type III collagen was the principal collagen of the elastic laminae, but was absent from the intima of all vessels. In the elastic laminae of vessels from control embryos, collagen type III showed well-defined fiber bundles whereas embryos with PTA had diffuse collagen type III in poorly defined laminae that were not separated by discrete layers of smooth muscle cells. Collagen type I was a minor component of the elastic laminae but formed robust pericellular fiber bundles throughout the media and intima. Collagen type I fibers appeared to be coarsened and less uniform in the vessels from embryos with PTA.

Impaired elastic matrix development in the great arteries after ablation of the cardiac neural crest

The cells that form the aorticopulmonary septum in the avian embryo have been shown to be similar to the cells that form the walls of the great vessels in two ways: both are derived from the cardiac neural crest and both are able to synthesize an elastogenic matrix in the early embryo. Because of these similarities, and because ablation of the cardiac neural crest causes congenital defects of the outflow tract that are related to failure of proper septation, it was hypothesized that such an ablation also would cause the walls of the great vessels to be defective. The purpose of this study was to compare the elastic matrix in the mediae of the great vessels of normal embryos with those from which the cardiac neural crest had been ablated. The results show that the elastic matrix in the great vessels of the experimental embryos was impaired 1) in the rate of downstream propagation of the initiation of elastogenesis among younger embryos, incubation days 4-8 and 2) in the spatial configuration of the elastic matrix among the older embryos, incubation days 16-20. These results may provide a biological explanation for the elastin defect that affects the pulmonary artery of many patients with cyanotic congenital heart defects.

Pulmonary vascular and alveolar development in tetralogy of Fallot: a recommendation for early correction

Using quantitative morphometric techniques, we analysed pulmonary arterial and alveolar development in the lungs of seven children aged 1.2-12 years who died during or soon after repair of tetralogy of Fallot. One child had a residual ventricular septal defect and survived for five months. One other child had had a previous Waterston-Cooley anastomosis (Waterston shunt). Postmortem lung volume in relation to body surface area was generally below normal for age, the alveoli were small, and the total alveolar number was below normal in five of the seven cases. Microscopically, airway and alveolar structure appeared normal. The preacinar arteries were larger and the intra-acinar arteries were smaller than normal for age. The preacinar elastic pulmonary arteries appeared to contain less elastin and in both preacinar and intra-acinar muscular arteries the media was thinner than normal, although muscle was normally distributed along the arterial pathway. Eccentric areas of intimal fibrosis were small and uncommon. The bronchial arteries were generally more prominent than usual both macroscopically and microscopically, but no abnormal bronchopulmonary connections were present. After corrective surgery a residual ventricular septal defect and pulmonary hypertension were associated with arterial medial hypertrophy, and this change was also found in the right lung of a normotensive patient who had had a Waterston shunt. This group probably represents the most favourable clinical picture of tetralogy in patients who usually survive but, even so, pulmonary arterial and alveolar development was abnormal. The structural findings are discussed in relation to the functional outcome in patients with tetralogy who have survived. Repair of the abnormality during the first two to three years of life is recommended.

Elastin and collagen accumulation in rabbit ascending aorta and pulmonary trunk during postnatal growth. Correlation of cellular synthetic response with medial tension

Absolute and relative quantities of elastin, collagen, and DNA in anatomically defined segments of rabbit ascending aorta (AA) and pulmonary trunk (PT) were compared at intervals from birth to 2 months of age. Identical in size, weight, and composition at birth, the vessels maintained similar lengths and diameters at each age but diverged markedly in weight and scleroprotein content after 1 week. By 2 months, 3 times as much elastin and 1.7 times as much collagen had accumulated in the AA as compared to the PT. By contrast, the increase in total DNA content was the same for both segments. Differences in total fibrous protein accumulation, total elastin accumulation, and elastin content relative to DNA paralleled differences in estimated total medial tangential tension. Proportions of elastin and collagen relative to dry weight increased markedly only between 4 and 2 weeks of age and not thereafter despite continuing rapid growth, steadily increasing medial tension, and increasing total scleroprotein content. Thus, medial cells were capable of adapting their quantitative scleroprotein synthetic response to differences in medial tension throughout growth but established a fixed qualitative response within 2 weeks.

Histology, extensibility, and chemical composition of pulmonary trunk in persons living at sea-level and at high altitude in Peru

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