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PEDIATRICS Vol. 105 No. 3 March 2000, pp. 528-532
,,,,
From the * Department of Pediatrics, University of Southern
California, Women's and Children's Hospital Los Angeles; Childrens
Hospital Los Angeles; and § Los Angeles County and University of
Southern California Medical Center, Los Angeles, California.
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ABSTRACT |
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Abstract
Methods
Results
Discussion
Conclusion
References
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Objective. Angiographic visualization of systemic to pulmonary collaterals (SPC) has been documented in premature infants needing prolonged ventilatory support. Noninvasive identification of such communications in premature infants was reported recently. The purpose of this study was to describe: 1) incidence, 2) clinical findings and implications, and 3) short-term follow-up of SPC diagnosed by echocardiography in very low birth weight (VLBW) infants admitted to the neonatal intensive care unit.
Methods. From December 1, 1994 to August 31, 1996, 196 infants with birth weight <1500 g were admitted to the neonatal intensive care unit; 133 of them received serial echocardiographic evaluations at 1 to 2 days, at 2 weeks, and at 1, 2, and 3 months of life. Follow-up echocardiograms were scheduled at 6 months and 1 year of age for patients with SPC persisting at 3 months of age.
Results. SPC were demonstrated in 88 patients (66%) at 1 to 90 days of life (mean 28 days). In most cases, the SPC originated at the distal aortic arch or the proximal descending aorta. Ten patients (11%) were treated for congestive heart failure. The symptoms improved and anticongestive therapy was discontinued in 9. One patient with persistent congestive heart failure underwent therapeutic cardiac catheterization and 1 prominent SPC was embolized.
Conclusions. The incidence of SPC in VLBW infants is much higher than previously reported. We postulate that SPC are bronchopulmonary communications that enlarge and/or proliferate in response to a given stimulus. These communications are associated with increased time on positive pressure ventilation and length of stay in the hospital. SPC may lead to pulmonary edema and should be searched for in VLBW infants with a more complicated course. Echocardiographic examination with color Doppler performed in premature infants to evaluate left to right shunts should include careful search for systemic to pulmonary collaterals.echocardiography, systemic to pulmonary collaterals, aortopulmonary collaterals, prematurity, pulmonary edema.
Left to right shunts impose additional difficulties in
managing sick premature infants.1 Early diagnosis and
closure of patent ductus arteriosus (PDA) in particular, during the
course of hyaline membrane disease, may be important because ductal
closure has been shown to increase lung compliance2 and
early intervention may help prevent bronchopulmonary
dysplasia.1 Echocardiography with color flow Doppler has
been an important tool in the bedside evaluation for the presence of
PDA in infants with respiratory disease.
PDA is not the only cause of extracardiac left to right shunt in
infants. In previous studies, systemic to pulmonary collaterals (SPC)
have been demonstrated by angiography in 26 infants requiring prolonged
ventilatory support; surgical ligation was performed in 1 and coil
embolization in 3 with clinical improvement in all 4.3-5
Noninvasive detection of such collateral circulation by color flow
Doppler was recently reported.6-8
SPC have been classified as congenital or acquired.9,10
Congenital SPC have been described in patients with congenital heart
disease, typically pulmonary atresia with ventricular septal
defect,9,11 or as an isolated occurrence.8
The acquired variety may be secondary to chronic alveolar hypoxia and
has been described in patients with inflammatory, neoplastic, or
traumatic lung disease.12-14
The purpose of this study was to evaluate the incidence, clinical
findings and implications, and short-term follow-up of SPC in very low
birth weight (VLBW) infants.
From December 1, 1994 to August 31, 1996, 196 infants with birth
weight <1500 g were admitted to the neonatal intensive care unit at
Los Angeles County and University of Southern California Medical
Center. Sixty-three patients were excluded because of early death,
congenital heart disease, abnormal ventricular function, or incomplete
echocardiographic studies. The remaining 133 patients comprise our
study population.
All infants entering the study received serial echocardiographic
evaluations at 1 to 2 days; 2 weeks; and at 1, 2, and 3 months of life.
Follow-up echocardiograms were scheduled at 6 months and 1 year of age
for patients with collaterals persisting at 3 months of age. All
studies were performed with a Hewlett-Packard Sonos 1000 Ultrasound
system equipped with a dual 5- to 7.5-MHz transducer for imaging,
continuous and directional spectral and color Doppler mapping. Special
attention was placed in the imaging and color Doppler interrogation of
the aortic arch and head and neck vessels. Ascending aorta (Ao) and
left atrial (LA) dimensions were obtained from the parasternal long
axis view of the heart to calculate the LA/Ao ratio, a commonly used
ratio to evaluate LA dilatation. An LA/Ao ratio of >1.3 is considered
consistent with LA dilatation.15
Demographic data and cardiopulmonary parameters were obtained from
medical records.
Student's t test was used to compare continuous data, and
SPC were identified by echocardiography in 88 of the 133 infants
included in the study (66%). There was no significant difference in
birth weight, gestational age, sex, or diagnosis of chronic lung
disease (defined as oxygen dependency at 36 weeks' postconceptional age), between the patients with SPC and those without evidence of SPC
(Tables 1 and
2). Therapy with surfactant for
respiratory distress syndrome and hemodynamically significant PDA
requiring treatment with indomethacin and/or surgery were significantly
more frequent in patients with SPC (P values of .009 and
.01, respectively; Table 2). The need for postnatal steroids for lung
disease was higher in the patients with SPC (P = .038).
The period of time on positive pressure ventilation and the length of
stay in the hospital were also significantly longer in the group of
infants with SPC (P values of .05 and .02, respectively)
compared with infants without SPC. Ten of the 88 infants with SPC
manifested clinical signs of heart failure; 9 required medical therapy
only, with digoxin and diuretics; the medications were discontinued at
3 to 4 months of age; the remaining 1 infant required coil embolization
of 1 collateral for persistent signs of heart failure.
TABLE 1 TABLE 2
METHODS
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Discussion
Conclusion
References
2 test for nominal data. A P value
of <.05 was considered significant.
RESULTS
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Methods
Results
Discussion
Conclusion
References
Demographic Data
Cardiorespiratory Data
Echocardiography
Cardiac contractility and structure were normal in all patients included in the study. A PDA was diagnosed in 82 (62%) patients during the first echocardiographic examination.
When present, the SPC were best visualized at their origin from the thoracic aorta and/or head-and-neck vessels, by color imaging of the long axis of the aortic arch and its branches and proximal descending aorta. The aortic arch is best imaged from the suprasternal and/or high parasternal approaches. On the echocardiographic studies performed from 1 to 90 days of life (mean 28 days), the color Doppler interrogation revealed 1 to 3 sources of abnormal continuous flow from the undersurface of the distal aortic arch or the anterior wall of the proximal descending aorta (Fig 1A and 1B) in 88 patients (66%), and from both, the proximal descending aorta and the origin of the innominate artery in 1 of these infants. This continuous flow was not seen entering the intrapericardial pulmonary arteries, and therefore, was not consistent with a PDA. Pulsed Doppler interrogation showed continuous flow (Fig 1C) consistent with systemic to pulmonary flow.
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The abnormal flow was first detected in 2 cases during the first examination, and during the second examination in the other 86 patients. LA dilatation, with a LA/Ao ratio of 1.4 to 1.8 was noted in 20/88 in the absence of PDA. Color Doppler identified 2 or 3 SPC in 9/88 patients.
Cardiac Catheterization
One patient showed persistent signs of congestive heart failure despite medical management and underwent cardiac catheterization at 60 days of life. Normal pulmonary artery pressure, normal ventricular systolic function, and multiple SPC from the proximal descending aorta, proximal right head and neck vessels, and intercostal arteries (Fig 2), were demonstrated. Only 1 vessel, originating from the proximal descending aorta, was considered large enough (diameter at its aortic origin was 2.2 mm) for embolization and was successfully embolized with Gianturco coils (2-mm × 2-cm coils, Cook Company, Bloomington, IN).
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Follow-up
In 39 of the 88 patients with collaterals, the abnormal communications were not visualized during subsequent follow-up evaluation at 3 months of age. Of the 49 infants with persistent SPC, 28 returned for the evaluation at 6 months of age. All these infants were asymptomatic and were not on supplemental oxygen; the echocardiogram demonstrated small collaterals in 11/28 patients. Nine of the 11 infants returned at 1 year of age for follow-up evaluations, only 2/9 had evidence of tiny collaterals, and the echocardiograms were otherwise within normal limits in all these infants.
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DISCUSSION |
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Our study represents the first longitudinal evaluation of SPC in VLBW infants. SPC were demonstrated by echocardiogram in 66% of VLBW infants. Eleven percent of these infants required treatment for congestive heart failure. One patient with persistent signs of heart failure underwent successful coil embolization of one collateral.
During the early stages of development the lungs have a single source of blood supply; the vascular plexus forming in the lung buds is connected to segmental arteries arising from the dorsal aorta.16 By the 40th day of gestation, both, the right ventricle via the pulmonary arteries, and the segmental arteries arising from the dorsal aorta17 perfuse both lungs, until the segmental arteries disappear at about the 50th day.13 At 9 to 12 weeks of gestation, the bronchial arteries appear, frequently originating from the thoracic aorta and the first intercostal arteries18; accessory bronchial arteries, branches of the subclavian or innominate arteries, have also been described.19 The pulmonary arteries supply the terminal respiratory unit and the bronchial arteries supply the conducting airways, bronchi, and the nonrespiratory bronchioles. The bronchial arteries also supply the vasa vasorum of the pulmonary arteries, veins, and other structures such as pericardium and visceral pleura.18
Systemic to pulmonary connections between the bronchial arteries and the pulmonary circulation, also known as bronchopulmonary anastomoses, have been demonstrated in the normal lung, including neonates, at the arterial, precapillary, and capillary levels; however no significant shunt is normally present between the two systems.20-22 In certain pulmonary and cardiac diseases, blood flow through the bronchial arterial system is increased, resulting in bronchial arterial enlargement and proliferation as demonstrated in lungs from patients with tuberculosis, chronic infections, bronchiectasis and Tetralogy of Fallot.21 Abnormal bronchopulmonary communications may also result from dilatation of the normal bronchopulmonary connections during recanalization of a thrombosed pulmonary artery, and penetration by vascular endothelium of pulmonary and bronchial arteries in granulation tissue.20
Botenga21 postulated that the primary stimulus for the development of wide bronchopulmonary shunts arise from hypoxia of alveolar and interstitial lung tissue. The high incidence of SPC, and their origin from the thoracic aorta, intercostal arteries, and head and neck vessels, indicates that they may be bronchopulmonary anastomoses, which are functional, more conspicuous, and/or more susceptible to enlargement and proliferation in response to a given stimulus. Angiographic studies, performed in infants with persistent pulmonary edema, also demonstrated a high incidence of collaterals.5 The significant difference in the need for surfactant and indomethacin therapy in infants with SPC (Table 2) suggests that alveolar and interstitial lung tissue hypoxia stimulus for the development of bronchial collaterals may play a role in the genesis of SPC in VLBW infants.
The 66% incidence of SPC in our patients is much higher than the 4% reported in a previous publication.8 The marked difference is probably attributable to the fact that our study was prospective, looking specifically for the aortic origin of the SPC in the views mentioned above. Shaughnessy et al8 found their cases during routine echocardiographic evaluations for PDA, which included "the use of color flow Doppler analysis around the pulmonary arteries;" in addition, their population included larger preterm infants.
Although SPC have been identified in previous studies by angiography in infants,3-5 noninvasive demonstration of these communications in premature infants was reported only recently.6-8 The present study reaffirms the capability of echocardiography to demonstrate the abnormal collaterals, obviating the need for invasive diagnostic studies, and leaving cardiac catheterization for those patients in whom embolization is deemed necessary.
The significance of the left to right shunt is difficult to evaluate in patients with smaller SPC and without clear evidence of congestive heart failure. Although we found no evidence of volume overload in the majority of our patients, any degree of left to right shunt may contribute to interstitial or alveolar edema in patients with increased endothelial permeability from hyaline membrane disease.1,22 This left to right shunt may, at least in part, be responsible for the significantly longer duration on positive pressure ventilation and length of stay in the hospital in the group of patients with SPC (Table 2). Our short-term follow up, however, indicates a tendency for the SPC to get smaller and disappear during the first year of life. We believe that our study is the first detailed evaluation of the incidence and natural history of SPC in VLBW infants.
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CONCLUSION |
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Methods
Results
Discussion
Conclusion
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A high incidence of SPC was demonstrated in this group of VLBW infants without congenital heart disease. The presence of SPC is associated to increased need for postnatal steroids for lung disease, increased time on positive pressure ventilation, and length of stay in the hospital. Echocardiographic examination with color flow Doppler performed in premature infants to evaluate left to right shunts should include careful search for SPC. The role of diuretics to decrease lung fluid needs additional consideration.
Serial echocardiography may give valuable information in patients with persistent congestive heart failure in whom transcatheter embolization or surgical intervention may be indicated.
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ACKNOWLEDGMENT |
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We thank Dr Joan Hodgman for her insightful comments and help in the preparation of this manuscript.
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FOOTNOTES |
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This article is in memory of Robert A. deLemos, MD
a superb
teacher, dedicated researcher, and compassionate physician.
Received for publication Dec 29, 1998; accepted Jun 4, 1999.
Reprint requests to (R.J.A.) Los Angeles County and University of Southern California Medical Center, Women's and Children's Hospital, 1240 N Mission Rd, Room L-919, Los Angeles, CA 90033. E-mail: archerman{at}hsc.usc.edu.
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ABBREVIATIONS |
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PDA, patent ductus arteriosus; SPC, systemic to pulmonary collaterals; VLBW, very low birth weight; Ao, ascending aorta; LA, left atrium.
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REFERENCES |
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This article has been cited by other articles:
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  R. Ramanathan Pharmacology Review: Bronchopulmonary Dysplasia and Diuretics NeoReviews, June 1, 2008; 9(6): e260 - e267. [Abstract] [Full Text] [PDF]
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 K. R. Stenmark and V. Balasubramaniam Angiogenic Therapy for Bronchopulmonary Dysplasia: Rationale and Promise Circulation, October 18, 2005; 112(16): 2383 - 2385. [Full Text] [PDF]
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