Effects of prostaglandin E1 given in low doses on the histopathology of the arterial duct

Low-dose prostaglandin E1 is safe and effective for critical congenital heart disease: is it time to revisit the dosing guidelines?

INTRODUCTION

Prostaglandin E1 is used to maintain ductal patency in critical congenital heart disease (CHD). The standard starting dose of prostaglandin E1 is 0.05 µg/kg/minute. Lower doses are frequently used, but the efficacy and safety of a low-dose regimen of prostaglandin E1 has not been established.

METHODS

We investigated neonates with critical CHD who were started on prostaglandin E1 at 0.01 µg/kg/minute. We reviewed 154 consecutive patients who were separated into three anatomical groups: obstruction to systemic circulation, obstruction to pulmonary circulation, and inadequate mixing (d-transposition of the great arteries). Treatment failure rates and two commonly reported side effects, respiratory depression and seizure, were studied.

RESULTS

A total of 26 patients (17%) required a dose increase in prostaglandin E1. Patients with pulmonary obstruction were more likely to require higher doses than patients with systemic obstruction (15/49, 31% versus 9/88, 10%, p = 0.003). Twenty-eight per cent of patients developed respiratory depression and 8% of patients needed mechanical ventilation. Prematurity (<37 week gestation) was the primary risk factor for respiratory depression. No patient required dose escalation or tracheal intubation while on transport. No patient had a seizure attributed to prostaglandin E1.

CONCLUSIONS

Prostaglandin E1 at an initial and maintenance dose of 0.01 µg/kg/minute was sufficient to maintain ductal patency in 83% of our cohort. The incidence of respiratory depression requiring mechanical ventilation was low and was mostly seen in premature infants. Starting low-dose prostaglandin E1 at 0.01 µg/kg/minute is a safe and effective therapy for critical CHD.

Abnormally extended ductal tissue into the aorta is indicated by similar histopathology and shared apoptosis in patients with coarctation

BACKGROUND

The pathogenesis of coarctation of the aorta (CoA) has not been clearly elucidated. It is hypothesized that CoA patients have abnormal extension of ductal tissue into the aorta which plays some pathogenic role. The aim of this study was to investigate the extension of ductal tissue into the aorta in CoA patients by comparative analysis of ductal and aortic tissue histopathology, smooth muscle cell (SMC) phenotypes and apoptosis.

METHODS

Fifteen cases of surgically resected specimens including coarctation segment (CS), ductus arteriosus (DA) and transition zone (TZ) were histologically reviewed. SMC phenotypes were determined by immunohistochemistry for myosin heavy chain isoforms SM1, SM2, SMemb and α-smooth muscle actin. Apoptotic cell death was estimated by the TUNEL method.

RESULTS

A considerable amount of ductal tissue was found in CS and TZ in all investigated cases. CS showed a histologic pattern similar to that of closing DA. CS showed the least differentiated SMC phenotype and TZ intima displayed SMC phenotype more similar to that of DA than that of the normal aorta. TUNEL-positive cell deaths were frequently found in the media of both CS and DA, but absent in TZ.

CONCLUSIONS

Abnormal extension of ductal tissue into the aorta in CoA patients was indicated by similar histology and shared apoptosis. SMC phenotypic modulation may be involved in the formation of CoA. Our results strongly support the hypothesis that abnormal extension of ductal tissue in the aorta plays a crucial role in the pathogenesis of CoA.

Insufficient intimal thickening and scarcity of cell deaths may play a significant role in the pathogenesis of the persistently patent ductus arteriosus in the preterm infant

BACKGROUND

Functional closure and subsequent remodeling of the ductus arteriosus (DA) are essential for postnatal adaptation. Very preterm infants often fail to accomplish this process spontaneously. Histologic studies on human DA have shown that the closing ductus exhibits progressive intimal thickening and cell death of muscle media, which was verified by recent animal studies.

AIMS

To analyze the histologic findings of preterm infants' DA in relation to their clinical parameters and to investigate the histologic difference between preterm and term DAs.

METHODS

Histology of 14 preterm DAs and 13 term DAs obtained from surgery was analyzed. We examined hematoxylin and eosin staining and van Gieson staining for the elastic tissue. Cell death was determined with the in situ apoptosis detection technique.

RESULTS

The histologic findings of preterm DAs showed apparent correlations with clinical parameters, especially birth weight. Preterm DA histology was significantly different from that of term DAs in the extent and degree of intimal thickening. Cytolytic necrosis where TUNEL-positive cell deaths were prominent was observed mainly in term DAs.

CONCLUSIONS

The results of this study indicate that insufficient intimal thickening and scarcity of cell deaths in the DA may play a significant role in the pathogenesis of the persistently patent DA in preterm infants.

Differentiation, dedifferentiation, and apoptosis of smooth muscle cells during the development of the human ductus arteriosus

Differentiation of vascular smooth muscle cells (SMCs) is characterized by several molecular transitions. As differentiation proceeds, proteins of the cytoskeletal and contractile apparatus, such as alpha-smooth muscle actin, smooth muscle myosin, calponin, and heavy caldesmon, and the expression of the membrane-related protein smooth muscle phosphoglucomutase-related protein increase, whereas the expression of other proteins, such as fibronectin splice variants with extradomains A (EDA) and B (EDB), decreases. In this study, we investigated the differentiation of the SMCs of the ductus arteriosus during the development of intimal thickening. Ascending and descending aortas of the same age were used for comparison because these vessels lack intimal thickening. In the fetal ductus arteriosus, a relatively early differentiation of the contractile apparatus was observed compared with the ascending and descending aortas. EDA and EDB expression was already low, being similar in the ductus and descending aorta and even lower in the ascending aorta. In the neonatal ductus, SMCs of the media and outer intima were well differentiated and comparable with SMCs of the ascending aorta. Dedifferentiated SMCs, with a low expression of cytoskeletal and contractile proteins and a high expression of EDA and EDB, were found in regions in the inner intima that show features of progression of intimal thickening and in areas of cytolytic necrosis in the media. With a technique using in situ end labeling of DNA fragments, we found extensive apoptosis in the area of cytolytic necrosis and to a lesser extent in these areas of the inner intima. In conclusion, SMCs of the fetal ductus arteriosus have an advanced differentiation of the contractile apparatus compared with the adjacent aorta. Reexpression of fetal characteristics is seen in a number of cells in inner intima and media of the neonatal ductus arteriosus. The finding of apoptosis in these areas suggests that dedifferentiation and apoptosis are associated processes that may play a role in vascular remodeling.