Effect of flow and pressure on pulmonary vessels. A semiquantitative study based on lung biopsies

Mystery still unresolved: Untouched "Blue heart" presenting at 40yrs of age

The modern-day surgical techniques and strategies have changed the outlook of patients with dextro-transposition of great arteries (d-TGA). The survival of an unrepaired d-TGA into late adulthood is difficult to explain. Even when large intracardiac shunts are present, it still remains a lethal cyanotic congenital heart disease if it is not surgically corrected soon after birth. Here, we report an extremely rare case of d-TGA presenting at 40 years of age, with moderately elevated pulmonary artery pressures and relatively stable symptoms.

Pulmonary blood flow and pulmonary hypertension: Is the pulmonary circulation flowophobic or flowophilic?

Increased pulmonary blood flow (PBF) is widely thought to provoke pulmonary vascular obstructive disease (PVO), but the impact of wall shear stress in the lung is actually poorly defined. We examined information from patients having cardiac lesions which impact the pulmonary circulation in distinct ways, as well as experimental studies, asking how altered hemodynamics impact the risk of developing PVO. Our results are as follows: (1) with atrial septal defect (ASD; increased PBF but low PAP), shear stress may be increased but there is little tendency to develop PVO; (2) with normal PBF but increased pulmonary vascular resistance (PVR; mitral valve disease) shear stress may also be increased but risk of PVO still low; (3) with high PVR and PBF (e.g., large ventricular septal defect), wall shear stress is markedly increased and the likelihood of developing PVO is much higher than with high PBF or PAP only; and (4) with ASD, experimental and clinical observations suggest that increased PBF plus another stimulus (e.g., endothelial inflammation) may be required for PVO. We conclude that modestly increased wall shear stress (e.g., ASD) infrequently provokes PVO, and likely requires other factors to be harmful. Likewise, increased PAP seldom causes PVO. Markedly increased wall shear stress may greatly increase the likelihood of PVO, but we cannot discriminate its effect from the combined effects of increased PAP and PBF. Finally, the age of onset of increased PAP may critically impact the risk of PVO. Some implications of these observations for future investigations are discussed.

Assessment of operability in d-transposition of great arteries with ventricular septal defect: A practical method

Introduction:

Pulmonary vascular disease is a risk factor in the surgical management of patients with d-transposition of great arteries (d-TGA) and a ventricular septal defect (VSD). In older infants or children with this physiology, the question of operability often arises. Cardiac catheterization in this condition can be fallacious. It is well known that oxygen reduces pulmonary arterial pressure and pulmonary vascular resistance especially where irreversible pulmonary vascular obstructive disease has still not set in. We tried to implement this effect of oxygen in correlation with echocardiography in patients with TGA-VSD physiology where operability was in question.

Methods:

Patients with d-TGA and a large post tricuspid shunt in whom operability was considered doubtful were selected for the study. We administered humidified oxygen at the rate of 10 litres/minute by mask for 48 hours in the ward or intensive care unit. After administration of oxygen we reassessed the child echocardiographically looking for signs of lowering of pulmonary vascular resistance which included increased pulmonary venous blood flow to the left atrium (LA) and right to left shunting across the VSD.

Observation:

We studied 1 patient with d-TGA and aortopulmonary window (APW), 4 patients with TGA / large VSD and 1 patient with Taussig-Bing anomaly. The age of the studied children ranged from 4 months to 3 years with a mean age of 1.1 years. After administering oxygen as described, echocardiogram showed an increase in pulmonary venous blood flow to the LA and right to left shunting across the VSD in 5 patients and increased flow reversal in aorta in presence of the APW.

Conclusion:

Patients with TGA/VSD physiology with doubtful operability can be subjected to this method of determining operability using echocardiography after administering oxygen. Although not 100% accurate in predicting long term postoperative pulmonary hypertension, this is a simple, noninvasive method that can aid in decision making in such a situation.

Pulmonary arterial hypertension in adults born with a heart septal defect: the Euro Heart Survey on adult congenital heart disease

AIM

To investigate the role of pulmonary arterial hypertension (PAH) in adult patients born with a cardiac septal defect, by assessing its prevalence and its relation with patient characteristics and outcome.

METHODS AND RESULTS

From the database of the Euro Heart Survey on adult congenital heart disease (a retrospective cohort study with a 5-year follow-up), the relevant data on all 1877 patients with an atrial septal defect (ASD), a ventricular septal defect (VSD), or a cyanotic defect were analysed. Most patients (83%) attended a specialised centre. There were 896 patients with an ASD (377 closed, 504 open without and 15 with Eisenmenger's syndrome), 710 with a VSD (275, 352 and 83, respectively), 133 with Eisenmenger's syndrome owing to another defect and 138 remaining patients with cyanosis. PAH was present in 531 (28%) patients, or in 34% of patients with an open ASD and 28% of patients with an open VSD, and 12% and 13% of patients with a closed defect, respectively. Mortality was highest in patients with Eisenmenger's syndrome (20.6%). In case of an open defect, PAH entailed an eightfold increased probability of functional limitations (New York Heart Association class >1), with a further sixfold increase when Eisenmenger's syndrome was present. Also, in patients with persisting PAH despite defect closure, functional limitations were more common. In patients with ASD, the prevalence of right ventricular dysfunction increased with systolic pulmonary artery pressure (OR = 1.073 per mm Hg; p<0.001). Major bleeding events were more prevalent in patients with cyanosis with than without Eisenmenger's syndrome (17% vs 3%; p<0.001).

CONCLUSION

In this selected population of adults with congenital heart disease, PAH was common and predisposed to more symptoms and further clinical deterioration, even among patients with previous defect closure and patients who had not developed Eisenmenger's physiology.

Enhanced expression of nitric oxide synthase in the early stage after increased pulmonary blood flow in rats

OBJECTIVE

Evidence that vasodilator nitric oxide mediates normal pulmonary vascular tone has led to the hypothesis that endothelial injury induced by congenital heart disease with increased pulmonary blood flow disrupts these regulatory mechanisms and its associated altered vascular reactivity. Therefore, we hypothesized that increased pulmonary blood flow results in altered expression of endothelial nitric oxide synthase (eNOS).

METHODS

We created an arteriovenous shunt in female Wistar (5-week-old) and measured the change of pulmonary blood flow and pressure immediately after and 1 month after the shunt operation. The protein levels of eNOS in the lung tissues of rats were assessed.

RESULTS

The shunt immediately resulted in a significant increase in pulmonary blood flow (16.5 +/- 11.8% , pulmonary artery pressure (2.3 +/- 0.7 mm Hg), and blood O(2) saturation (16.1 +/- 11.8%) in the pulmonary artery. After 4 weeks, there was a significant increase in pulmonary blood flow (30.7 +/- 1.6%), pulmonary artery pressures (4.3 +/- 1.1 mm Hg), and blood O(2) content (43.3 +/- 17.5%). Western blot analysis demonstrated that eNOS protein was increased in the shunt lung 72 h after surgery and recovered to the control level 1 week later.

CONCLUSION

This simple shunt model can induce early upregulation of eNOS expression with increased pulmonary blood flow and pulmonary artery pressure in rats.

Intravascular ultrasound imaging of the pulmonary arteries in primary pulmonary hypertension

OBJECTIVE

Intravascular ultrasound has the unique ability to provide cross-sectional images of the arterial wall. This study examined intravascular ultrasound (IVUS) images of the proximal pulmonary arteries in primary pulmonary hypertension (PPH).

METHODOLOGY

Study 1: Specimens from four patients who had died of PPH (in vitro PPH group) were compared with those of three patients who had died of subarachnoid haemorrhage but had no evidence of cardiopulmonary disease (in vitro control group). Three-centimetre segments of the following levels were examined by IVUS: pulmonary trunk, eight secondary branch arteries of the upper, middle, and lower lobes of both lungs, and the thoracic descending aorta. Study 2: Four patients with PPH (in vivo PPH group) and five patients without pulmonary hypertension and no evidence of cardiopulmonary disease (in vivo control group) were examined. The IVUS images of the apical segmental artery of the right upper lobe and the descending branch of the right pulmonary artery were studied.

RESULTS

Echographic examination of formalin-fixed preparations of secondary branch sections of the pulmonary artery failed to show a clear three-layer structure in the in vitro control group (24 preparations), but a distinct three-layer structure and increased vessel wall thickness were observed in the in vitro PPH group (32 preparations). Similar findings were obtained in the in vivo study. The mean echo density of the proximal pulmonary arterial wall correlated well with the mean pulmonary arterial pressure (mPA) in the in vitro PPH, and also correlated with the mPA in the in vivo study (r = 0.960, P < 0.0001). The echo intensity of secondary branch sections of the pulmonary artery was higher in the in vitro PPH group than in the in vitro control group (180.5 +/- 27.0 vs 132.5 +/- 26.7 counts, P < 0.001); similar results were obtained in the in vivo study (144.7 +/- 23.4 vs 85.0 +/- 14.3 counts, P < 0.01).

CONCLUSIONS

These results suggest that the histological changes detected in the pulmonary artery walls in the PPH group were responsible for the increased echo intensity.

Rest and exercise hemodynamics before and after valve replacement--a combined Doppler/catheter study

BACKGROUND

Hemodynamic improvement is a common finding following valve replacement. However, despite a normally functioning prosthesis and normal left ventricular ejection fraction, some patients may show an abnormal hemodynamic response to exercise.

METHODS

In a combined catheter/Doppler study, rest and exercise hemodynamics were evaluated in 23 patients following aortic (n = 12) (Group 1) or mitral valve (n = 11) (Group 2) replacement and compared with preoperative findings. Patient selection was based on absence of coronary artery disease and left ventricular failure as shown by preoperative angiography. Cardiac output, pulmonary artery pressure, pulmonary capillary pressure, and pulmonary resistance were measured by right heart catheterization, whereas the gradient across the valve prosthesis was determined by Doppler echocardiography. Postoperative evaluation was done at rest and during exercise. The mean follow-up was 8.2 +/- 2.2 years in Group 1 and 4.2 +/- 1 years in Group 2.

RESULTS

With exercise, there was a significant rise in cardiac output in both groups. In Group 1, mean pulmonary pressure/capillary pressure decreased from 24 +/- 9/18 +/- 9 mmHg preoperatively to 18 +/- 2/12 +/- 4 mmHg postoperatively (p < 0.05), and increased to 43 +/- 12/30 +/- 8 mmHg with exercise (p < 0.05). The corresponding values for Group 2 were 36 +/- 12/24 +/- 6 mmHg preoperatively, 24 +/- 7/17 +/- 6 mmHg postoperatively (p < 0.05), and 51 +/- 2/38 +/- 4 mmHg with exercise (p < 0.05). Pulmonary vascular resistance was 109 +/- 56 dyne.s.cm-5 preoperatively, 70 +/- 39 dyne.s.cm-5 postoperatively (p < 0.05), and 70 +/- 36 dyne.s.cm-5 with exercise in Group 1. The corresponding values for Group 2 were 241 +/- 155 dyne.s.cm-5, 116 +/- 39 dyne.s.cm-5 (p < 0.05), and 104 +/- 47 dyne.s.cm-5. There was a significant increase in the gradients across the valve prosthesis in both groups, showing a significant correlation between the gradient at rest and exercise. No correlation was found between valve prosthesis gradient and pulmonary pressures.

CONCLUSION

Exercise-induced pulmonary hypertension and abnormal left ventricular filling pressures seem to be a frequent finding following aortic or mitral valve replacement. Both hemodynamic abnormalities seem not to be determined by obstruction to flow across the valve prosthesis and may be concealed, showing nearly normal values at rest but a pathologic response to physical stress.

Exploration of the pulmonary circulation. Festschrift to Professor Donald Heath

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Plexogenic arteriopathy

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Intimal thickening of peripheral pulmonary vein: Analysis of 139 consecutive autopsy cases

Intimal thickening of the peripheral pulmonary veins collected from 139 autopsy cases (ages ranging from 1 to 96 years) was examined morphologically. The peripheral pulmonary veins were classified as medium-sized veins, small veins, and postcapillary venules. Intimal thickening, graded into four levels from (-) to (+++), increased with age in all three types of the peripheral veins. The severity of intimal thickening was age-dependent. In mediumsized veins, smooth muscle cells were recognized in the intima of all ages, though the amount of collagen fiber in the intima increased with age. In small veins, slight fibrosis and a few smooth muscle cells were seen in the subendothelial regions in autopsy cases up to 20 years of age. Thereafter, collagenous thickening was common. In postcapillary venules, edematous or dense collagenous thickening was a common feature of the intimal thickening in the autopsy cases over 20 years old. In those between 1 and 20 years of age who succumbed to left ventricular failure, intimal thickening was more severe than in those of the same age range in this study. The pathogenesis and the clinical significance of age-associated intimal thickening of the pulmonary veins has not been elucidated yet.

Prediction of favourable responses to long term vasodilator treatment of pulmonary hypertension by short term administration of epoprostenol (prostacyclin) or nifedipine

Eighteen patients with moderate to severe pulmonary hypertension were studied, nine with intracardiac shunts and nine without. The effects of an incremental infusion of epoprostenol (prostacyclin) (0.5-8 ng/kg per minute) or sublingual nifedipine (20-30 mg) were compared with the response to three months' treatment with oral nifedipine. Both epoprostenol and sublingual nifedipine caused a fall in pulmonary vascular resistance and pressure and a rise in cardiac output. Patients with intracardiac shunts had higher systemic blood flows than those without shunts. Exercise in the shunt group was accompanied by systemic desaturation and hyperventilation. Analysis of individual results showed that the size of the response was inversely related to the severity of the pulmonary vascular disease. A good long term response to nifedipine seemed to be as readily predicted by the resting control values for haemodynamic variables as by values after short term treatment. A favourable response was likely if the pretreatment mean pulmonary artery pressure was less than 50 mm Hg, the ratio of total pulmonary to systemic resistance was less than 0.7, or the ratio of mean pulmonary artery pressure to systemic artery pressure was less than 0.6. Short term vasodilator protocols may do harm. If such studies are carried out, an adequate dose range must be tried before the long term efficacy of an individual drug can be forecast.

Factors that influence the outcome of primary pulmonary hypertension

Factors predicting life expectancy in primary pulmonary hypertension have not been well defined. Thirty four cases of primary pulmonary hypertension that had been followed up until death or for at least five years were reviewed retrospectively. Patients were divided into three groups: 18 patients who died within five years of presentation to hospital; 12 who survived more than five years; and four who improved and who lived for more than five years. The age at onset was similar in the three groups and, like symptoms and sex, did not predict life expectancy. Right heart failure during the course of the disease was associated with a poor outcome. Radiographic evidence of cardiac enlargement and evidence of right heart strain on electrocardiogram at presentation was also predictive of survival for less than five years. Pulmonary arteriolar resistance was higher and cardiac output lower in those with the shortest survival times. There was no relation between pulmonary artery pressure and length of survival. Systemic resistance varied directly with pulmonary resistance and served to maintain systemic pressure. Presentation in or after pregnancy and patency of the foramen ovale were associated with longer survival. In four patients there was evidence of regression of the disease by cardiac catheterisation and lung histology. Primary pulmonary hypertension is a heterogeneous condition in which life expectancy varies widely.

New method for measuring intimal component of pulmonary arteries

Current methods for assessing the intima of pulmonary arteries produce measurements of intima and artery size that are affected by the constriction or collapse of the arteries and the generally patchy distribution of intimal abnormality. Our new method measures intimal area and defines artery size as the total length of the internal elastic lamina; these measurements are unaffected by the constriction or collapse of the arteries and are easily and directly obtained from histological sections, using a light microscope with a camera lucida attachment in conjunction with a microcomputer linked to a digitising board. The measurements produced are consistently repeatable. We considered that the extent of intimal change in a pulmonary artery was most readily understood when expressed not as an area measurement but in the form of an "intima index", in which intimal area is calculated as a proportion of the area enclosed by the internal elastic lamina in its theoretically unwrinkled state. Values for intima index range from greater than 0 to less than or equal to 1, indicating minimal through to total occlusion of the artery lumen. Although values for the intima index increased as artery size decreased in the subjects studied, there was no consistent overall correlation between intima index and artery size for different subjects. We therefore concluded that subjects should be compared by calculating mean intima indexes for arteries subdivided into groups according to size.

Open lung biopsies in congenital heart disease for evaluation of pulmonary vascular disease. Predictive value with regard to corrective operability

For evaluation of pulmonary vascular disease 140 open lung biopsies were performed in 137 patients with congenital heart disease in order to decide whether the state of the lung vessels would allow corrective surgery. As far as possible follow-up was obtained in patients who underwent a cardiac repair. From the study of these biopsy specimens it appeared that medial hypertrophy of pulmonary arteries and changes in pulmonary veins should not be considered an impediment for a corrective operation as long as more advanced changes are absent. The same is true for intimal thickening due to longitudinal smooth muscle, post-thrombotic changes or cellular proliferation. Concentric-laminar intimal fibrosis forms no contra-indication as long as it is mild but, if severe, it is likely that hypertensive pulmonary vascular disease will progress in spite of cardiac repair. In the presence of fibrinoid necrosis or plexiform lesions correction of a cardiac anomaly should not be attempted. The presence of dilatation lesions is more disputable but probably, as long as they are scarce and not accompanied by fibrinoid necrosis or plexiform lesions, corrective surgery may be attempted. This becomes very dubious when they are more numerous.

Histometrical investigation of the pulmonary artery in severe hepatic disease

Histological changes of the pulmonary vasculature in comparison with that of the portal vein in necropsy cases of severe hepatic injury that had not been associated with clinical pulmonary hypertension were analysed qualitatively and quantitatively. The main changes of the intra-hepatic portal vein were dilatation (88.3 per cent), thickening of the wall (58.5 per cent) and thrombi (22.3 per cent). The changes of the pulmonary vasculature were limited to muscular type arteries, which showed dilatation (31.9 per cent), thickening of the wall (30.9 per cent) and thrombi (10.6 per cent). Association of wall thickening of the portal vein and the small pulmonary artery was observed in 30.9 per cent, these associations being statistically significant. Coincidence of thrombus formation in the portal vein and pulmonary vasculature was observed only in 4.3 per cent, which was not statistically significant. After the circumferences of the internal and external elastic laminae of small pulmonary arteries and the cross-sectional area of the media were measured, the anatomical radius and wall thickness of each artery were calculated according to Furuyama 's method. The relations between the anatomical radii and wall thickness of small pulmonary arteries in controls and hepatic cirrhosis groups were investigated by analysis of covariance to compare the equality of the two corresponding regression lines. The wall thickness and the ratio of wall thickness to the anatomical radius of small pulmonary arteries were significantly larger in the cirrhotic group than in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Smooth muscle content of pulmonary arterial media in pulmonary venous hypertension compared with other forms of pulmonary hypertension

The number of smooth muscle cells per unit of surface area of the media of muscular pulmonary arteries was assessed and expressed as an index of medial smooth muscle density. The relative medial thickness of these arteries was also established. Subjects were ten children and ten adults in each of the following conditions: normal, congenital cardial defects with a left-to-right shunt (CCD), primary pulmonary hypertension (PPH), and mitral stenosis (MS); ie, 80 persons in all. The density of medial smooth muscle is generally the same in normal control subjects and in patients with CCD or PPH and is independent of the medial thickness. The index is also the same in children with MS, but significantly reduced in adult patients with MS, apparently by a prominent contribution of collagen and edematous ground substance to the structure of the media. This may explain, at least to some extent, the discrepancy often observed in adult patients with MS, of a very thick media associated with mild elevation of pulmonary arterial pressure. The present study leaves open the possibility that other factors, decisive for this elevation of pressure, are involved. The differences in medial structure may also account for some hemodynamic differences between adults and children with MS.

The correlation between blood pressure and morphometric findings in children with congenital heart disease and pulmonary hypertension

The lungs of 68 children with malformations of the heart or the great vessels which could cause pulmonary hypertension were obtained at autopsy. We analysed the media of muscular pulmonary arteries morphometrically and calculated the area ratio (area media/total area of the vessel). As hemodynamic parameter we used the systolic blood pressure ratio (pulmonary/systemic). Additionally we employed the mean pressure of the pulmonary artery in 38 cases. We analysed the correlation between hemodynamic and morphometric parameters and obtained a product moment correlation of 0.7. There was a linear correlation between the area and pressure ratios. Younger children showed a higher relative thickness of the media than older children with comparable pressure ratios. After dividing the children into three age groups, we obtained an even higher correlation (r = 0.90 in the oldest group). We found these correlations not only in cases with left-to-right shunt but also in children with other heart defects. There was also a good correlation between the quantitatively measured data and the qualitative Heath and Edwards classification.

Lung biopsy specimens in the evaluation of pulmonary vascular disease

Open lung biopsy specimens in 72 patients were submitted for evaluation of pulmonary vascular disease. In nine instances, the specimens were inadequate for this purpose. Essentially, there were three indications for taking a lung biopsy specimen. The first was unexplained pulmonary hypertension with 40 patients in this category; plexogenic pulmonary arteriopathy was diagnosed in 14, and chronic pulmonary thromboembolism in 12. Others included pulmonary venoocclusive disease in two patients; two other patients had pulmonary vascular lesions in their lung biopsy specimens, indicative of chronic hypoxic pulmonary hypertension; and ten patients had severe arterial as well as venous alterations that could have been caused by obstruction to pulmonary venous flow as well as by fibrosis of lung tissue. Since we realized this possible source of error, we have submitted these two alternative possibilities to the clinician. In a heterogeneous group of eight patients, the nature of acquired or congenital heart disease remained doubtful in spite of extensive clinical investigation. In several instances, the biopsy specimen contributed to establishing the diagnosis of the cardiac condition. Finally, in a group of 15 patients with known congenital cardiac disease and pulmonary hypertension, whose state of pulmonary vasculature was considered borderline as far as the possibility of corrective surgery of the cardiac defect was concerned, lung biopsy specimens helped to determine the feasibility of surgery. The results show that in a restricted group of patients with pulmonary vascular disease, a biopsy of the lung has a place in establishing the nature and severity of the vascular alterations.

Congenital absence of the pulmonary valve

The clinical, radiological, electrocardiographic, and haemodynamic findings in 7 patients with the syndrome of congenital absence of the pulmonary valve with ventricular septal defect are reported. Findings included a pansystolic murmur and a low-pitched delayed diastolic murmur at the left sternal border with no pulmonary valve closure sound, an rsR' pattern in V1 on the electrocardiogram, and a chest x-ray showing a large heart and gross dilatation of the main, left or right pulmonary arteries but normal or reduced vascularity of the peripheral lung fields. Cardiac catheterization showed a left-to-right shunt at ventricular level in every case, though in one the shunt was bidirectional. Despite right ventricular systolic pressures at least 75 per cent of systemic level in every patient, the pulmonary artery pressure was invariably normal. Pulmonary stenosis was shown to exist at infundibular level, at valve ring level, or at both. Selective right ventricular angiography was diagnostic: the main and right or left pulmonary arteries were aneurysmally dilated and there was an abrupt transition in calibre between these vessels and their immediate branches; enlargement of the right pulmonary artery caused distortion and downward displacement of the left atrium in 4 patients; in 2 there was a flat ;diaphragm' in the pulmonary valve position.The diagnosis was confirmed in 3 patients by necropsy. The pulmonary valve was represented by at most a rudimentary fringe of tissue. Histological examination of the pulmonary arteries in one patient showed a correlation between the dilatation of the artery and the structure of its wall.

Haemodynamic studies after repair of ventricular septal defect

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