Structural changes in the pulmonary arteries and veins in tetralogy of Fallot

Resting respiratory lung volumes are "healthier" than exercise respiratory volumes in different types of palliated or corrected congenital heart disease

AIMS

Cardiac surgery has improved life expectancy of patients with congenital heart diseases (CHDs). Exercise capacity is an important determinant of survival in patients with CHDs. There is a lack of studies focusing on the role of resting respiratory performance in reducing exercise tolerance in these patients.

OBJECTIVES

To determine the prevalence and severity of respiratory functional impairment in different types of corrected/palliated CHDs, and its impact on an exercise test.

MATERIALS AND METHODS

Retrospective single-center study involving 168 corrected/palliated patients with CHD and 52 controls. Patients CHD were divided into subgroups according to the presence of native pulmonary blood flow or total cavopulmonary connection (TCPC). All subjects performed complete pulmonary function tests and gas diffusion; patients with CHD also performed cardiopulmonary exercise test (CPX).

RESULTS

Mean values of lung volumes were within the normal range in all CHD groups. Comparing to controls, patients with the reduced pulmonary flow and with TCPC had the highest reduction in lung volumes. CPX was reduced in all groups, most severely in TCPC, and it was correlated to decreased dynamic volumes in all CHD groups except in TCPC. Younger age at intervention and number of surgical operations negatively affected lung volumes.

CONCLUSIONS

Respiratory function is within the normal range in our patients with different CHDs at rest but altered in all CHDs during exercise when cardiorespiratory balance is likely to be inadequate. Comparing the different groups, patients with reduced pulmonary flow and TCPC are the most impaired.

Purinergic receptor stimulation induces calcium oscillations and smooth muscle contraction in small pulmonary veins

KEY POINTS

We investigated the excitation-contraction coupling mechanisms in small pulmonary veins (SPVs) in rat precision-cut lung slices. We found that SPVs contract strongly and reversibly in response to extracellular ATP and other vasoconstrictors, including angiotensin-II and endothelin-1. ATP-induced vasoconstriction in SPVs was associated with the stimulation of purinergic P2Y2 receptors in vascular smooth muscle cell, activation of phospholipase C-β and the generation of intracellular Ca²⁺ oscillations mediated by cyclic Ca²⁺ release events via the inositol 1,4,5-trisphosphate receptor. Active constriction of SPVs may play an important role in the development of pulmonary hypertension and pulmonary oedema.

ABSTRACT

The small pulmonary veins (SPVs) may play a role in the development of pulmonary hypertension and pulmonary oedema via active changes in SPV diameter, mediated by vascular smooth muscle cell (VSMC) contraction. However, the excitation-contraction coupling mechanisms during vasoconstrictor stimulation remain poorly understood in these veins. We used rat precision-cut lung slices and phase-contrast and confocal microscopy to investigate dynamic changes in SPV cross-sectional luminal area and intracellular Ca²⁺ signalling in their VSMCs. We found that the SPV (∼150 μm in diameter) contract strongly in response to extracellular ATP and other vasoconstrictors, including angiotensin-II and endothelin-1. ATP-induced SPV contraction was fast, concentration-dependent, completely reversible upon ATP washout, and inhibited by purinergic receptor antagonists suramin and AR-C118925 but not by MRS2179. Immunofluorescence showed purinergic P2Y2 receptors expressed in SPV VSMCs. ATP-induced SPV contraction was inhibited by phospholipase Cβ inhibitor U73122 and accompanied by intracellular Ca²⁺ oscillations in the VSMCs. These Ca²⁺ oscillations and SPV contraction were inhibited by the inositol 1,4,5-trisphosphate receptor inhibitor 2-APB but not by ryanodine. The results of the present study suggest that ATP-induced vasoconstriction in SPVs is associated with the activation of purinergic P2Y2 receptors in VSMCs and the generation of Ca²⁺ oscillations.

Management of tetralogy of Fallot with unilateral absence of pulmonary artery: an overview

Tetralogy of Fallot with unilateral absence of pulmonary artery (PA) is a rare congenital anomaly that has been reported in isolated case reports and small case series. There is no well-defined treatment algorithm for these patients, and repair has been associated with high mortality, although survival is improving in the more recent era. Recent reports suggest strict case selection criteria based on PA dimensions and size of the left ventricle.

Abnormal spirometry after the Fontan procedure is common and associated with impaired aerobic capacity

Impaired exercise capacity is common after the Fontan procedure and is attributed to cardiovascular limits. The Fontan circulation, however, is also distinctively vulnerable to unfavorable lung mechanics. This study aimed to define the prevalence and physiological relevance of pulmonary dysfunction in patients with Fontan physiology. We analyzed data from the Pediatric Heart Network Fontan Cross-Sectional Study to assess the prevalence and pattern of abnormal spirometry in Fontan patients (6-18 yr old) and investigated the relationship between low forced vital capacity (FVC) and maximum exercise variables, including peak O2 consumption (Vo2peak), among those who demonstrated adequate effort (n = 260). Average ages at the time of exercise testing and Fontan completion were 13.2 ± 3.0 and 3.5 ± 2.2 yr old, respectively. Aerobic capacity was reduced (Vo2peak: 67.3 ± 15.6% predicted). FVC averaged 79.0 ± 14.8% predicted, with 45.8% having a FVC less then the lower limit of normal. Only 7.8% demonstrated obstructive spirometry. Patients with low FVC had lower Vo2peak (64.4 ± 15.9% vs. 69.7 ± 14.9% predicted, P < 0.01); low FVC independently predicted lower Vo2peak after adjusting for relevant covariates. Among those with Vo2peak < 80% predicted (n = 204/260), 22.5% demonstrated a pulmonary mechanical contribution to exercise limitation (breathing reserve < 20%). Those with both low FVC and ventilatory inefficiency (minute ventilation/CO2 production > 40) had markedly reduced Vo2peak (61.5 ± 15.3% vs. 72.0 ± 14.9% predicted, P < 0.01) and a higher prevalence of pulmonary mechanical limit compared with patients with normal FVC and efficient ventilation (36.1% vs. 4.8%). In conclusion, abnormal FVC is common in young patients after the Fontan procedure and is independently associated with reduced exercise capacity. A large subset has a pathologically low breathing reserve, consistent with a pulmonary mechanical contribution to exercise limitation.

Chronic effects of pulmonary artery stenosis on hemodynamic and structural development of the lungs

Pulmonary artery (PA) stenosis is a difficult obstructive defect to manage since clinicians cannot know a priori which obstructions to treat and when. Prognosis of PA stenosis and its chronic effects on lung development are poorly understood. This study aimed to characterize the hemodynamic and structural effects of PA stenosis during development. Fourteen male Sprague-Dawley rats underwent left PA (LPA) banding at age 21 days, and 13 underwent sham operation. Hemodynamic and structural impacts were studied longitudinally at 20, 36, 52, 100, and 160 days. Chronic LPA banding resulted in a significant reduction in LPA flow ( P < 0.0001) and size of both proximal LPA ( P < 0.0001) and distal LPA ( P < 0.01), as well as a significant increase in flow and size of the right PA ( P < 0.05) throughout development. Flows and sizes adapted such that normal levels of wall shear were restored after banding. At 160 days, LPA banding resulted in a significant decrease in left lung volume and an increase in right lung volume but no significant differences in total lung volume. There was an elevation of proximal LPA pressure as well as right ventricular hypertrophy in the banded animals. The banded lung exhibited arterial disorganization, loss of vessels, and enlargement of its bronchial arteries, whereas the contralateral lung showed signs of vascular pathology. There are consequences on development of both lungs in the presence of an LPA stenosis at young age. These results suggest that early intervention may be necessary to optimize left lung growth and minimize right lung vascular pathology.

Optimization of adenoviral vector-mediated gene transfer to pulmonary arteries in newborn swine

Efficient pulmonary vascular gene transfer in neonates would aid in understanding the pathophysiology of, and ultimately allow the development of specific therapies for, pulmonary vascular diseases. The purpose of this study was to optimize efficiency, and evaluate the duration, of catheter-based adenoviral vector-mediated pulmonary artery gene transfer in newborn pigs. An adenovirus vector encoding LacZ was infused via percutaneously placed catheters that were advanced to segmental pulmonary arteries under fluoroscopic guidance. Optimal viral dose and duration of expression were determined by histochemical evaluation of gene transfer efficiency 72 hr, 2 weeks, and 1 month after gene delivery. The effect of protamine on the efficiency of gene transfer was studied by assaying transgene protein in lung at 72 hr. The optimal viral dose was 2 x 10(10) plaque-forming units (PFU). Seventy-two hours after infusion, expression predominated in medium-sized artery endothelial cells, 40% of which expressed beta-galactosidase. At 2 weeks, the distribution of expression had changed such that the majority of transduced cells were seen not in arteries but in gas exchange units of lung. No histochemical evidence of transgene expression was seen 1 month after virus infusion. The addition of protamine to virus infusate resulted in a fivefold increase in transgene protein product in lung tissue assayed 72 hr after gene transfer. Adenoviral vector-mediated gene transfer in neonatal swine results in high-efficiency transduction of arterial endothelial cells. However, the time course of gene transfer is not significantly prolonged compared with the adult. The addition of protamine results in a significant improvement in transduction efficiency, permitting lower doses of virus.

Ventilatory response to exercise in patients with major aortopulmonary collateral arteries after definitive surgery

Patients with pulmonary atresia and major aortopulmonary collateral arteries (MAPCAs) may be at risk for both ventilatory impairment and abnormal pulmonary circulation after definitive surgery. We measured the ventilatory response to exercise in 16 patients with MAPCAs after definitive surgery (group A) and compared the results with those in 16 patients with tetralogy of Fallot with pulmonary atresia and without MAPCAs after definitive operation (group B), with 24 patients with tetralogy of Fallot after one-stage repair without previous palliation (group C), and with 48 healthy subjects (group D). Pulmonary function and treadmill exercise tests were performed. Arterial blood gases were also analyzed and the dead space to tidal volume ratio calculated. In group A, the vital capacity, diffusion capacity, and peak oxygen uptake were lowest (p <0.001), whereas the ventilatory equivalent for carbon dioxide was highest and its value at peak exercise correlated with age at time of surgery (r = 0.73, p <0.002). The arterial oxygen tension decreased progressively in group A and its value at peak exercise inversely correlated with the mean pulmonary artery pressure in all patients (r = -0.75, p <0.001). The arterial carbon dioxide tension decreased significantly at peak exercise in controls but showed no change in group A. The dead space to tidal volume ratio decreased during exercise in patients without MAPCAs and in controls but increased in group A, and the dead space to tidal volume ratio at peak exercise was inversely correlated with vital capacity in all patients (r = -0.77, p <0.001). Diffusion capacity independently predicted arterial carbon dioxide tension and dead space ventilation during exercise. Marked restrictive ventilatory impairment with low diffusion capacity along with a pulmonary obstructive change contributed to the abnormal pulmonary gas exchange during exercise in group A. Earlier repair of MAPCAs may prevent the progression of the impaired ventilatory response to exercise in these patients.

Evaluation of pulmonary artery histopathologic findings in congenital heart disease: an in vitro study using intravascular ultrasound imaging

OBJECTIVES

This study aimed to 1) compare in vitro intravascular ultrasound images of human pulmonary arteries with corresponding histologic sections, and 2) correlate the relation between intravascular ultrasound findings and Heath-Edwards pathologic grade of pulmonary vascular changes.

BACKGROUND

The pathologic assessment of the pulmonary vascular bed is essential for diagnosis and management of congenital heart disease with pulmonary hypertension.

METHODS

We evaluated and compared intravascular ultrasound images with histologic findings at identical sites in 40 pulmonary artery segments from 17 autopsy studies: group 1 = 7 patients with pulmonary hypertension (Heath-Edwards grade I to V, 20 segments); group 2 = 10 patients without cardiopulmonary disease (20 segments).

RESULTS

In group 2, the pulmonary artery wall echo consisted of a single layer. In group 1, 1) all segments of pulmonary arteries from patients with pulmonary hypertension showed a three-layered appearance; 2) in patients with mild pulmonary hypertension (Heath-Edwards grades I and II), intravascular ultrasound demonstrated increased thickness of the echoluscent zone due to medial hypertrophy with no intimal reaction; 3) patients with severe pulmonary hypertension (Health-Edwards grade III or higher) had intravascular ultrasound findings of increased medial thickness and a bright inner layer from intimal hyperplasia; 4) percent wall thickness derived from intravascular ultrasound showed a significant correlation with that determined by histologic examination (r = 0.89, p = 0.0001, n = 20).

CONCLUSIONS

Changes observed with intravascular ultrasound imaging correlate well with histopathologic grade. Thus, intravascular ultrasound may have significant utility in the evaluation of pulmonary vascular morphology in patients with pulmonary hypertension.

Lung function in children and adolescents with tetralogy of Fallot after intracardiac repair

We studied lung function in 41 patients, aged 6-27 years, 1-5 years after intracardiac surgical repair (ICR) of tetralogy of Fallot (TOF) and about 5 years after the establishment of the Pediatric Cardiac Center in Prague. The measurements included vital capacity (VC), total lung capacity (TLC), functional residual capacity (FRC), residual volume (RV), forced expiratory flows (FEF), specific airway conductance (SGaw), lung recoil pressure (Pst), and specific static lung compliance (SC1st). Single or multiple abnormal lung function parameters were found in 83% of patients. Lung function was not related to shunting operations prior to ICR, hemoglobin concentration, and hematocrit, and had no specific pattern. Pst at 100% TLC and 90% TLC declined with increasing age at ICR and at lung function testing, while SC1st rose, as did the ratio FRC/TLC. Fifteen patients were studied before and after surgery. Single or multiple lung function tests were abnormal in 93% before and in 84% after ICR. After ICR the ratios FRC/TLC and also RV/TLC, FEF at 25% VC, and FEF at 60% TLC were less frequently abnormal, while Pst at 100% TLC and at 90% TLC, as well as SGaw and TLC, were more frequently abnormal after ICR. The results indicated a regression of smaller airway obstruction and lung hyperinflation after ICR. The evolution of abnormally compliant (emphysematous) lungs with growth of the patients might be a sign of permanent sequelae of early lung damage from abnormal pulmonary hemodynamics.

Pulmonary developmental anomaly associated with Klippel-Feil syndrome and anomalous atrioventricular conduction

We report the findings in a patient with Klippel-Feil syndrome and associated agenesis of right upper and middle lobes, hypoplasia of the right lower lobe of the lung, and Lown-Ganong-Levine syndrome. To our knowledge, such an association has not been previously described.

Cardiorespiratory function after correction of tetralogy of Fallot. Modifying effect of previous shunt operation

Of 28 patients with total surgical correction of tetralogy of Fallot in adult life, 22 had previously undergone Blalock-Taussig shunt operation. Possible modifying effects of the shunt on pulmonary ventilation and perfusion and on exercise tolerance were investigated with spirometry, radiospirometry and bicycle ergometry. The observed ventilatory volumes and capacities and diffusing capacity were significantly lower than the predicted values. Vital capacity was significantly reduced in patients with adverse NYHA or haemodynamic classification. Between the various NYHA or haemodynamic groups no statistically significant difference was demonstrable in pulmonary function or diffusing capacity or in airway resistance. Ventilatory obstruction was found also in patients without previous shunt. Other lung function tests showed no significant difference between the shunt and the non-shunt group. Nor was distribution of lung perfusion significantly affected by shunt. No correlation was seen between lung function and bicycle ergometric findings. However, in non-shunt patients who had ventilatory obstruction or impaired diffusing capacity, exercise tolerance was significantly higher than in patients who had had palliative shunt.

Strain differences in response of Sprague-Dawley and Long Evans Hooded rats to the teratogen nitrofen

Administration of nitrofen (2,4-dichloro-4'-nitrodiphenyl ether) during organogenesis in rodents produces neonatal lethality accompanied by lung hypoplasia, diaphragmatic hernias, heart anomalies, and hydronephrosis. Different strains of rats, Long Evans Hooded (LEH) and Sprague-Dawley (SD), are reported to have different malformation responses to prenatal exposure, which could be due to true strain differences, to different levels and times of exposure, or to the use of different methods for detecting visceral malformations. In the present study, LEH, SD, and "virus-antibody-negative" SD (VAN-SD) rats were identically exposed to 0, 6.25, 12.5, or 25 mg/kg/day of nitrofen by gavage in corn oil on days 6 15 of gestation. At term, half of the litter was examined by the Wilson method of razorblade sectioning and the remainder by a modified Staples method of fresh visceral examination. The two methods were equally sensitive for detecting diaphragm, kidney, and lung anomalies, whereas heart malformations were more frequently identified with fresh visceral examination. The frequency of total malformations did not vary across strains at any dose, but there were substantial differences in the pattern of malformations in each strain. SD and VAN-SD rats responded similarly for all malformations, but had significantly higher incidences of diaphragm and lung anomalies than LEH rats. Conversely, LEH rats had significantly elevated levels of kidney anomalies compared to SD and VAN-SD rats, whereas frequency of heart malformations was low and comparable across strains. These results suggest that true strain differences exist in the pattern of malformation produced by prenatal exposure to nitrofen that may be based on genetic differences in embryonic susceptibility.

Resting lung function in children after repair of tetralogy of Fallot

Children with tetralogy of Fallot had pulmonary function tests (PFT) after intracardiac repair (ICR). According to the age at time of ICR and to the existence or not of palliative surgery preceding ICR, they were divided into three groups. Group 1 had ICR at a mean of one year one month of age (range four months to one year seven months), that is, during the active period of postnatal lung growth. Groups 2 and 3 had ICR later in childhood, that is, respectively, at four years seven months (range two years nine months to 11 years 9 months) and at five years four months (range two years seven months to 11 years five months). In group 3, ICR was preceded by palliative surgery. The PFT at rest included measurement of lung volumes (functional residual capacity), vital capacity (VC), dynamic or static compliance (CL), total pulmonary resistance, lung transfer factor for CO (TLCO) and blood gases. Group 1 had normal lung function suggesting that early repair of TOF saves lung development. In groups 2 and 3, significant decrease in VC(p less than 0.01) and CL (p less than 0.01) were found suggesting impaired alveolar growth. Additional defect in TLCO (p less than 0.01) in group 3 suggested that palliative surgery induces abnormal vascular growth. Thus, the present functional results suggest repair of TOF during the two first years of life, ie, the active period of postnatal lung growth.

Hypoplasia of the intrapulmonary arteries in children with right ventricular outflow tract obstruction, ventricular septal defect, and major aortopulmonary collateral arteries

Postmortem injection studies have been carried out on the pulmonary vasculature of four children dying with pulmonary atresia and ventricular septal defect or severe tetralogy of Fallot with major aortopulmonary collateral arteries, in which nearly all bronchopulmonary segments had more than one source of blood supply. Despite regional variations in the source of blood supply, there was remarkable uniformity of arterial size and number within the respiratory unit throughout each case. In all cases, there was a normal number of arterial pathways, but both pre- and intraacinar arteries were considerably smaller than normal. The need for early operative intervention to ensure growth of pre- and particularly intraacinar arteries is emphasized.

Congenital pulmonary vein stenosis: structural changes in a patient with normal pulmonary artery wedge pressure

A male infant is described who died at 13 months of age with stenosis of all extrapulmonary veins except the left upper vein. The pulmonary artery wedge pressure was normal, the first time this is reported in this condition. At autopsy, there were structural changes of the pulmonary arteries and veins in all lobes with or without pulmonary vein stenosis. Arterial changes-muscle extension, medial hypertrophy and decreased arterial size--analyzed quantitatively were found to be similar in all lobes. Venous medial hypertrophy was more marked in obstructed lobes. These anatomic changes are presumably due to fixed venous obstruction in the pulmonary lobes drained by stenotic veins and to high flow in the left upper lobe.

Changes in pulmonary blood flow affect vascular response to chronic hypoxia in rats

We banded the left pulmonary artery in rats to investigate, in the same animal, the effect of both increased and decreased flow on the lung vasculature and to determine how these hemodynamic states modify the structural changes produced by a 2-week exposure to hypobaric hypoxia. In unanesthetized rats, pressures were recorded from the main pulmonary artery and aorta via indwelling catheters, cardiac output was calculated by the Fick principle, and pulmonary and systemic vascular resistance estimated. Technetium-99m macroaggregated albumin was injected and radionuclide activity counted separately over the right and left lungs as a measure of flow. At postmortem, right and left ventricles of the heart were weighed and the lungs injected to permit analysis of arteriograms and morphometric assessment of structural changes in the pulmonary vascular bed. Flow in the left lung was reduced to one-fifth normal in rats with left pulmonary artery bands. In "room air" rats, pressure proximal to the left pulmonary artery band and in the right lung was slightly higher than in nonbanded controls, but not as high as in nonbanded or banded hypoxic rats. Changes in flow and pressure in both lungs of "room air" rats with left pulmonary artery bands were associated with a mild degree of extension of muscle into peripheral pulmonary arteries normally nonmuscular, medial hypertrophy of normally muscular arteries, and reduced arterial density. These three structural changes were present in both lungs of "hypoxic" rats but were much more severe. High flow in the right lungs of "hypoxic rats" with left pulmonary artery bands worsened only the degree of extension. Decreased flow and pressure in the left lungs of these animals prevented both the extension and the medial hypertrophy of hypoxia, but not the severe reduction in arterial density. It seems that the latter may occur as a direct response to low oxygen tension, whereas extension and medial hypertrophy are influenced by altered flow and pressure, respectively.

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.

Lung biopsy in congenital heart disease: a morphometric approach to pulmonary vascular disease

Fifty patients with congenital heart disease, ages 2 days-30 years (median 12 months) at cardiac surgery, underwent lung biopsy to assess pulmonary vascular disease (PVD). Twenty-six had ventricular septal defects (VSD), 17 d-transposition of the great arteries (D-TGA), and seven, defects of the atrioventricular canal (AVC). Quantitative morphologic data was correlated with hemodynamic data. Three new grades of PVD were observed. Abnormal extension of muscle into peripheral arteries (grade A) was found in all patients; all had increased pulmonary blood flow. In addition, 38 of 50 patients had an increase in percentage arterial wall thickness (grade B); this correlated with elevation in pulmonary artery (PA) pressure (r = 0.59). Another 10 of 50 patients had, in addition to A and B, a reduction in the number of small arteries (grade C); nine of 10 were patients with elevated PA resistance greater than 3.5 mu/m2 (P less than 0.005). All three patients with Heath-Edwards changes of grade III or worse also had grade C. Reduction in peripheral arterial number probably precedes obliterative PVD and may identify those patients in whom, despite corrective surgery, PVD will progress.

Quantitative structural study of pulmonary circulation in the newborn with aortic atresia, stenosis, or coarctation

Study of the structural features of the pulmonary circulation in various types of congenital heart disease makes it possible to correlate function and structure in the fetal and newborn lung. We applied quantitative morphometric techniques to the injected and inflated lungs of newborn infants who had died with obstruction to left ventricular outflow from aortic atresia, stenosis, or coarctation. The structure and development of the pulmonary circulation was judged by the number of arteries and veins and their size and wall structure, with particular attention to vessels within the respiratory unit. The study established for the first time that the structure of the pulmonary circulation is modified by the antenatal abnormalities in blood flow that occur through the heart and great vessels in the presence of congenital heart disease. Fetal multiplication of intra-acinar arteries in aortic atresia and stenosis is increased as also is the muscularity of both pre- and intra-acinar arteries and veins, muscle extending into smaller and more peripheral vessels than is normal at birth. When the pulmonary circulation is normal before birth but arterial pressure and flow are abnormally increased at birth, as in coarctation with patent ductus and ventricular septal defect, an increase in arterial diameter and muscularity is apparent within the first week of life.

Quantitative structural study of pulmonary circulation in the newborn with pulmonary atresia

The lungs of eight newborn infants who had died from pulmonary atresia were studied by quantitative morphometric techniques. It was established for the first time that the abnormal pattern of blood flow through the heart and great vessels in a fetus with pulmonary atresia is associated with impaired lung development as shown by arteries that are too few, too small, and with an abnormally thin muscle coat, although the distribution of muscle along the arterial pathway is normal. Differences between the cases in the degree of impairment of lung development could be detected and related to the degree of reduction in pressure and flow before birth in the individual case. Although blood flow through the pulmonary circulation is small before birth lung development seems sensitive to any further reduction.

Cyanotic congenital heart disease

This review describes the evolving concepts of diagnosis and management of patients with cyanotic congenital heart disease. Early palliative surgical procedures were followed by reparative operations and are now to a large extent replaced by these operations which are designed to relieve the problem. Collaboration of the team of cardiologists, surgeons, radiologists, anesthesiologists and nurses has made the many developments possible. The teamwork has not only widened the scope of what can be accomplished but has also extended the opportunities for beneficial reparative surgery down to the first weeks and months of life. Precise diagnosis and meticulous operative and perioperative care by the team are essential elements of success. Long-term follow-up and regular analyses of results have led to continuing improvements. Although these patients were born to be blue, their color and their outlook have been changed during these last 3 decades to something close to rosy.

Quantitative structural analysis of pulmonary vessels in isolated ventricular septal defect in infancy

Structural changes in the pulmonary circulation were studied in the lungs of 5 infants dying with ventricular septal defect. Applying precise quantitative morphological techniques to the pulmonary vessels, it was possible to correlate pathological change with clinical and haemodynamic findings, and to identify two patterns of response. Three of the infants (group I) ppresnted in cardiac failure with a large pulmonary blood flow, dilated and tortuous pulmonary arteries, and fewer intra-acinar vessels than normal. Medial hypertrophy was moderate and affected chiefly the larger arteries, i.e. those with a diameter greater than 200 mum. The other 2 infants (group 2) had a high pulmonary vascular resistance with an intermittent right-to-left shunt. The pulmonary arteries were of normal size and the reduction in the number of the arteries was less striking. Medial hypertrophy was greater than in the first group and affected all sizes of artery including those less than 200 mum in diameter. In both groups, muscle extended further along the axial pathway. Muscular hypertrophy was found also in the vein wall in most cases and, as with the arteries, was more severe in those with a higher pulmonary vascular resistance. The findings illustrate the variation in pulmonary vascular response in infants with a ventricular septal defect. It is suggested that in patients with a ventricular septal defect, arterial muscularity usually regresses after birth and a left-to-right shunt develops; secondary hypertrophy of the media then develops in reaponse to the shunt. Our findings also suggest, however, that in some infants arterial muscle fails to regress postnatally so that pulmonary blood flow is never high and a right-to-left shunt develops soon after birth.