Patent ductus arteriosus treatment in the premature newborn: clinical and surgical analisys

Locali, Rafael Fagionato; Matsuoka, Priscila Katsumi; Gabriel, Edmo Atique; Bertini Júnior, Ayrton; La Rotta, Carlos Arnulfo; Catani, Roberto; Carvalho, Antônio Carlos de Camargo; Buffolo, Enio

doi:10.1590/S0066-782X2008000500007

Abstracts

BACKGROUND: The surgical treatment of patency ductus arteriosus is indicated when the clinical intervention fails. However, this treatment may have some complications. OBJECTIVE: To analyze clinical and surgical aspects involved on the treatment of patency ductus arteriosus in premature newborn. METHODS: Twenty two premature newborns, submitted to surgical treatment for patency ductus arteriosus from January, 2000 to June, 2006, were evaluated. There were 77,3% female patients, the mean birth weight was 952,5g and the mean gestational age was 27 weeks. The use of vasoactive drugs, indometacin, echocardiograph parameters and complications, in the pre and postoperative periods were evaluated. RESULTS: In this casuistic 59,1% patients needed intratracheal intubation at birth, 77,3% needed surfactants, 59,1% used vasoactive drugs preoperative. The mean doses of indometacin were 3,43, with dose range 0,1 to 0,25 mg/Kg/day. The mean caliber of arterial duct patent was 1,96 mm. The surgical procedure was carried out through extrapleural approach in 59.1% of the patients, the mean time of postoperative intubation was 30,9 days, and 50% of the patients used vasoactive drugs postoperative. There were 18,1% postoperative complications (postoperative non-fatal complications). CONCLUSION: More than the half of the patients needed intratracheal intubation at birth, surfactant use and vasoactive drugs in the preoperative period. There was greater prevalence of the extrapleural approach during the surgery. In the postoperative period, there was less demand of vasoactive use and there was not deaths related to the surgical procedure.

Ductus arteriosus, patent; infant, premature; heart defects, congenital

FUNDAMENTO: O tratamento cirúrgico da persistência de canal arterial é indicado quando a intervenção clínica fracassa. No entanto, esse tratamento não é livre de complicações. OBJETIVO: Analisar aspectos clínicos e cirúrgicos envolvidos no tratamento da persistência do canal arterial, em recém-nascidos prematuros. MÉTODOS: No período de janeiro de 2000 a junho de 2006, foram analisados 22 recém-nascidos prematuros submetidos a tratamento cirúrgico para persistência de canal arterial. Do total de pacientes, 77,3% eram do sexo feminino, com peso médio ao nascimento de 952,5 g e idade gestacional média de 27 semanas. O uso de agentes vasoativos, indometacina, parâmetros ecocardiográficos e complicações, nos períodos pré e pós-operatórios, foi avaliado. RESULTADOS: Na casuística avaliada, 59,1% dos pacientes necessitaram de intubação orotraqueal ao nascimento; 77,3%, de surfactante; e 59,1% usaram agentes vasoativos no pré-operatório. O número médio de aplicações de indometacina foi de 3,4, com dosagem variando de 0,1 a 0,25 mg/kg/dia. O calibre médio do canal arterial foi de 1,96 mm. O procedimento cirúrgico foi realizado por abordagem extrapleural em 59,1% dos casos, e no pós-operatório o tempo médio de intubação foi de 30,9 dias, com emprego de agentes vasoativos em 50% dos pacientes. Observaram-se 18,1% de complicações pós-operatórias não-fatais. CONCLUSÃO: Mais da metade dos pacientes necessitou de intubação orotraqueal ao nascimento, emprego de surfactante e agentes vasoativos no período pré-operatório. Houve maior prevalência de abordagem extrapleural durante o ato operatório. No período pós-operatório, houve menor demanda de agentes vasoativos e não houve óbitos diretamente relacionados ao procedimento cirúrgico.

Persistência do conduto arterioso; prematuro; cardiopatias congênitas

ORIGINAL ARTICLE

Universidade Federal de São Paulo (Unifesp) - São Paulo, SP - Brazil

Mailing address

SUMMARY

BACKGROUND: The surgical treatment of patent ductus arteriosus is indicated when the clinical intervention fails. However, this treatment may present some complications.

OBJECTIVE: To analyze clinical and surgical aspects involved in the treatment of patent ductus arteriosus in the premature newborn.

METHODS: Twenty-two premature newborns, submitted to surgical treatment for patent ductus arteriosus from January 2000 to June 2006, were evaluated. Of the 22 newborns, 77.3% were females, mean birth weight was 952.5 g and the mean gestational age was 27 weeks. The use of vasoactive drugs, indomethacin, echocardiographic parameters and complications were evaluated in the pre- and postoperative periods.

RESULTS: In this sample, 59.1% of the patients needed intratracheal intubation at birth, 77.3% needed surfactants and 59.1% used preoperative vasoactive drugs. The mean number of indomethacin doses was 3.43, with dose ranging from 0.10 to 0.25 mg/Kg/day. The mean caliber of the patent ductus arteriosus was 1.96 mm. The surgical procedure was carried out through extrapleural access in 59.1% of the patients; the mean time of postoperative intubation was 30.9 days and 50% of the patients used postoperative vasoactive drugs. There were 18.1% of postoperative complications (non-fatal postoperative complications).

CONCLUSION: More than 50% of the patients needed intratracheal intubation at birth, surfactant use and vasoactive drugs in the preoperative period. There was a higher prevalence of the extrapleural approach during surgery. In the postoperative period, there was a lower need for vasoactive drugs and there were no deaths related to the surgical procedure.

Key words: Ductus arteriosus, patent; infant, premature; heart defects, congenital.

Introduction

The arterial canal functions as a vital arterial conduit during intrauterine life that is vital for the satisfactory development of the fetus, as it diverts more than half of the cardiac output for the systemic and the umbilical-placental circulation^1,2. At birth, in the presence of the blood rise of the oxygen pressure, a constriction of this canal occurs, concomitantly with the dilation of the pulmonary circulation, thus establishing a new circulatory pattern in the newborn (NB)^1,2.

However, in premature NB, this mechanism of arterial canal closing does not occur in 50% of the cases, resulting in a congenital cardiac defect called patent ductus arteriosus (PDA)^1-4. Therefore, there is an increase in the pulmonary flow in detriment to the systemic perfusion, due to the left-right shunt⁴. This hemodynamic alteration causes a left ventricular overload, myocardial dysfunction and respiratory failure⁴. Additionally, severe complications that are associated or concomitant to PDA are necrotizing enterocolitis, renal failure, bronchopulmonary dysplasia and intraventricular hemorrhage^4-10.

The clinical therapy of PDA is mainly based on the administration of indomethacin, an agent that is a prostaglandin-synthesis inhibitor, associated to fluid restriction and diuretics⁴. However, in situations where the PDA is refractory to the clinical management, its surgical ligation is indicated, aiming at attenuating its hemodynamic complications^4,11-13. Although this surgical intervention presents satisfactory results, it is not complication-free. Therefore, the aim of this study is to show the clinical and surgical aspects involved in the treatment of PDA in premature newborn infants.

Methods

A retrospective analysis of the clinical and surgical aspects of 22 newborn infants, with gestational age below 32 weeks, who were submitted to the surgical treatment of patent ductus arteriosus during January 2000 to June 2006 was carried out. These patients were originally from the Federal University of São Paulo Hospital São Paulo and Hospital Santa Catarina. All NB that presented other concomitant heart diseases and/or incomplete medical files were excluded.

Of the patients that were included in the study, 5 (22.7%) were males and 17 (77.3%) were females; the mean gestational age at birth was 27 weeks (ranging from 23 to 32 weeks) and mean weight was 952.5 g (ranging from 485 to 1,765 g). Birth by normal delivery had occurred in 4 (18.1%) cases and the diagnosis of PDA was carried out clinically in 8 (36.3%) and by echocardiogram in 14 (63.7%) cases.

The mean diameter of the arterial canal was 1.96 mm (0.2 3.2 mm). Of all the patients, only 4 (18.1%) did not undergo the clinical management with indomethacin, considering that their clinical condition required immediate surgical approach. The mean number of indomethacin applications was 3.4, with the dose varying from 0.1 to 0.25 mg/Kg/day, administered orally. However, this drug was not effective in any of the cases of this surgical series, regarding the closing of the canal.

Based on the reviewed data, information on the pre-, intra- and postoperative periods of each patient were obtained. These data included the need for orotracheal intubation (OTI) and ventilation parameters, surfactant administration, use of vasoactive drugs, access pathway and surgical technique, postoperative complications, re-operations, hospital stay duration and deaths.

All these reviewed parameters were evaluated under the aspect of analyses of prevalence.

Results

The surgical procedure was carried out exclusively at the surgical center, with the patient under general anesthesia. The surgical access of choice was the left posterolateral thoracotomy and the intrapleural approach was used in 9 (40.9%0 of the patients, with a mean operation time of 58 minutes (20 to 120 minutes). In this series, only one patient was submitted to the arterial canal clamping, whereas the others were submitted to its ligation.

The complications observed in this series were bronchopulmonary dysplasia in 2 patients, congestive heart failure and surgical wound infection in 1 patient. No cases of renal failure or necrotizing enterocolitis were observed; however, all patients presented intraventricular hemorrhage, although there were no consequences for the central nervous system. Three deaths, which were unrelated to the surgical procedure, occurred due to septic shock with a pulmonary infectious source and 1 patient needed to be re-operated due to clamping loosening. The mean time of OTI during the hospital stay was 30.9 days (1 to 91 days) and the mean duration of hospital stay was 89 days (17 to 332 days). The chest drain in the patients with an intrapleural approach was removed after a mean time of 1.8 days (1 to 2 days) after the surgery. Complementary data of the results are shown in charts 1 and 2.

Discussion

The decrease in the mortality rates of premature, low-weight newborn infants is one of the milestones of modern Medicine and reflects the development and the quality of assistance given during the pregnancy and labor management. It is known that a premature patient, even when free of other comorbidities, presents neuropsychomotor development (NPMD) retardation, which requires a stringent follow-up by the healthcare team¹⁴.

However, it is also known that this group of patients presents an increased risk of malformations and congenital diseases, mainly cardiovascular ones. The study by Rivera et al¹⁵, published in 2007, shows a prevalence of congenital heart disease of 13.2:1,000 live births, which is higher than that reported by Guitti¹⁶, in 2000, of 5.5:1,000 live births. In premature infants, the presence of heart disease significantly impairs the NPMD, in addition to failure to thrive. It is under these considerations that one must analyze the patent ductus arteriosus.

Our cohort shows a predominance of the female sex 977.3%), which corresponds with the prevalence of PDA described in the literature. Due to lung immaturity, surfactant was administered to 77.3% of the patients and OTI was carried out in 59.1% of the cases. It is known that PDA influences adequate pulmonary function; however, Van Woerkom et al, in a study of low-weight NB infants submitted to PDA ligation, did not observe short-term improvement in the patients' ventilation parameters¹⁷. This fact was confirmed by Carboni & Ringel¹⁸, Farstad & Bratlid¹⁹ in their results.

The mean diameter of the PDA was 1.96 mm. Literature data show that PDA severity can be expressed as a ratio between the sizes of the left atrium and aortic root > 1.47 or a transversal diameter of the largest canal > 1.5 mm, in the presence of a left-right shunt^20,21.

Therefore, most of the patients in the present study presented disease with important clinical and/or hemodynamic implication. However, the patients with a transversal diameter < 1.5 mm, although they did not have severe PDA, according to the aforementioned criteria, presented unfavorable clinical conditions, which also represented high risk.

The number of doses of indomethacin used in this study is in accordance with the doses administered in other studies^4,22. However, the closing of the arterial canal was not observed following this treatment protocol. This might be explained by the fact that, in the present study, indomethacin was administered orally, which has been proven to be less effective than the intravenous administration of the drug.

Additionally, this drug has also been studied as prophylaxis for intraventricular hemorrhage in patients with PDA^23,24. A meta-analysis designed by Fowlie et al, in 2003¹⁴, showed the efficacy of indomethacin in preventing this complication. Nevertheless, whether the prophylactic effect in intraventricular hemorrhage is secondary to the closing of PDA by indomethacin is debatable²².

All of the patients presented intraventricular hemorrhage, a fact that, in literature, is associated to the presence of PDA^4-10. However, this fact might be simply due to prematurity itself, as this group of patients is more susceptible to this type of brain injury, regardless of other morbidities¹⁴. Hence, we agree with the results by Brooks et al²², when they state they did not observe an association between PDA and intraventricular hemorrhage and other comorbidities.

The surgical procedure was carried out at the surgical center, in all patients, without any intercurrent events. It is known that this surgical procedure can be performed at the Intensive Care Unit (ICU); however, the risks of infection and complications, which are inherent to the operative intervention, are in fact better controlled and prevented at the surgical center⁴. Similar results were reported by Gould et al⁴, in a study where the authors compared interventions performed at the ICU and those performed at the surgical center⁴. The study results were based on the possible complications inherent to the transportation of the NB to the operating room.

In addition to the conventional surgery, i.e., the left posterolateral or axillary thoracotomy with canal ligation, the thoracoscopy can be employed, as well as the mini-thoracotomy with extrapleural access and the interventionist catheterism^25-30.

In fact, the development of several techniques for the treatment of PDA aims at attaining the least trauma, risk, cost and higher effectiveness than the conventional treatment.

The extrapleural approach is the access of choice for reaching the arterial canal, as it prevents the need for introducing a chest drain and thus, results in a lower risk of postoperative infection and pain. However, considering the anatomical variability of the parietal pleural thickness, even when the dissection is performed very carefully, many times it is not possible to preserve its integrity and the intrapleural access is followed.

The chest drain, when employed, remained in our patients for a mean period of 1.8 days. This is in accordance with the information reported by Gould et al⁴. However, these authors do not discuss the type of surgical access was employed, whether it was intra or extrapleural.

Among the observed postoperative complications, the main one was bronchopulmonary dysplasia, which presented as a consequence of the PDA, although some studies do not show such association^4,20. The deaths described were not due to the surgical procedure, as they occurred 30 days after the intervention, but they reflect the severity of the picture in the newborn. The mortality rate of 13.6% is in accordance with that reported in literature, with similar data^4,20.

In summary, the data presented here show the experience of our Service in the treatment of PDA, explicating the clinical and surgical management. In fact, the inclusion criteria are restricted and well-delimited, so if anything is lost regarding the number of patients, it is gained in terms of sample homogeneity. However, it is important to mention that, as demonstrated by our experience, when treating a newborn patient with PDA, one must keep in mind that a prolonged postoperative period should be expected, with a mean intubation time > 3 weeks and, therefore, with a higher risk of hospital infection and sepsis.

Potential Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Sources of Funding

There were no external funding sources for this study.

Study Association

This study is not associated with any graduation program.

References

1. Thebaud B, Michelakis ED, Wu XC, Moudgil R, Kuzyk M, Dyck JR, et al. Oxygen-sensitive Kv channel gene transfer confers oxygen responsiveness to preterm rabbit and remodeled human ductus arteriosus: implications for infants with patent ductus arteriosus. Circulation. 2004; 110 (11): 1372-9.
2. Heyman MA, Rudolph A. Control of the ductus arteriosus. Physiol Rev. 1975; 55: 62-78.
3. Clyman RI. Ibuprofen and patent ductus arteriosus. N Engl J Med. 2000; 343: 728-30.
4. Gould DS, Montenegro LM, Gaynor JW, Lacy SP, Ittenbach R, Stephens P, et al. A comparison of on-site and off-site patent ductus arteriosus ligation in premature infants. Pediatrics. 2003; 112 (6 Pt 1): 1298-301.
5. Uchita S, Imai Y, Takanashi Y, Hoshino S, Seo K, Terada M, et al. Surgical management of patent ductus arteriosus in low body weight infants. Jpn J Thorac Cardiovasc Surg. 1998; 46: 1088-92.
6. Van de Bor M, Verloove-Vanhorick SP, Brand R, Ruys JH. Patent ductus arteriosus in a cohort of 1338 preterm infants: a collaborative study. Paediatr Perinat Epidemiol. 1988; 2: 328-36.
7. Redline RW, Wilson-Costello D, Hack M. Placental and other perinatal risk factors for chronic lung disease in very low birth weight infants. Pediatr Res. 2002; 52: 713-9.
8. Evans N, Kluckow M. Early ductal shunting and intraventricular haemorrhage in ventilated preterm infants. Arch Dis Child Fetal Neonatal. 1996; 75: 183-6.
9. Dykes FD, Lazzara A, Ahlmann P, Blumenstein B, Schwartz J, Brann AW. Intraventricular haemorrhage: a prospective evaluation of etiopathogenesis. Pediatrics. 1980; 66: 42-9.
10. Noerr B. Current controversies in the understanding of necrotizing enterocolitis. Part 1. Adv Neonatal Care. 2003; 3: 107-20.
11. Burke RP, Jacobs JP, Cheng W, Trento A, Fontana GP. Video-assisted thoracoscopic surgery for patent ductus arteriosus in low birth weight neonates and infants. Pediatrics. 1999; 104: 227-30.
12. Wagner HR, Ellison RC, Zierler S, Lang P, Purohit DM, Behrendt D, et al. Surgical closure of patent ductus arteriosus in 268 preterm infants. J Thorac Cardiovasc Surg. 1984; 87: 870-5.
13. Little DC, Pratt TC, Blalock SE, Krauss DR, Cooney DR, Custer MD. Patent ductus arteriosus in micropreemies and full-term infants: the relative merits of surgical ligation versus indometacin treatment. J Pediatr Surg. 2003; 38: 492-6.
14. Fowlie PW, Davis PG. Prophylactic indomethacin for preterm infants: a systematic review and meta-analysis. Arch Dis Child Fetal Neonatal. 2003; 88: 464-6.
15. Rivera IR, da Silva MA, Fernandes JM, Thomaz AC, Soriano CF, de Souza MG. Congenital heart diseases in the newborn: from the pediatrician's request to the cardiologist's evaluation. Arq Bras Cardiol. 2007; 89 (1): 6-10.
16. Guitti JCS. Epidemiological characteristics of congenital heart diseases in Londrina, Paraná South Brazil. Arq Bras Cardiol. 2000; 74 (5): 400-4.
17. Van Woerkom R, Govindaswami B, Cleary J, Weyler J, Vanhaesebrouck P. Patent ductus arteriosus ligation in very low birthweight infants: is there benefit? Pediatr Res. 2001: A32.
18. Carboni MP, Ringel RE. Ductus arteriosus in premature infants beyond the second week of life. Pediatr Cardiol. 1997; 18: 372-5.
19. Farstad T, Bratlid D. Pulmonary effects of closure of patent ductus arteriosus in premature infants with severe respiratory distress syndrome. Eur J Pediatr. 1994; 153: 903-5.
20. Kluckow M, Evans N. Early echocardiographic prediction of symptomatic patent ductus arteriosus in preterm infants undergoing mechanical ventilation. J Pediatr. 1995; 127: 774-9.
21. Skinner J, Alverson D, Hunter S, eds. Echocardiography for the neonatologist. London: Churchill Livingstone, 2000.
22. Brooks JM, Travadi JN, Patole SK, Doherty DA, Simmer K. Is surgical ligation of patent ductus arteriosus necessary? The Western Australian experience of conservative management. Arch Dis Child Fetal Neonatal. 2005; 90: 235-9.
23. Fowlie PW. Intravenous indometacin for preventing mortality and morbidity in very low birth weight infants. Cochrane Database Syst Rev. 2000;(2):CD000174.
24. Coombs RC, Morgan ME, Durbin GM, Booth IW, McNeish AS. Gut blood flow velocities in the newborn: effects of patent ductus arteriosus and parenteral indometacin. Arch Dis Child. 1990; 65: 1067-71.
25. Salerno PR, Jatene MB, Santos MA, Ponce F, Bosísio IBJ, Fontes VF, et al. Patent ductus arteriosus (PDA) closure with minithoracotomy: technique and results. Rev Bras Cir Cardiovasc. 2000; 15 (3): 234-7.
26. Souto GLL, Tinoco RC, Tinoco ACA, Caetano CS, Souza JB, Paula AG, et al. Ligadura videotoracoscópica da persistência do canal arterial. Rev Bras Cir Cardiovasc. 2000; 15 (2): 154-9.
27. Atik FA, Jatene FB, Costa PH, Atik E, Barbero-Marcial M, Oliveira SA. Surgical treatment of coil embolization to the pulmonary artery after an attempt at percutaneous closure of patent ductus arteriosus. Arq Bras Cardiol. 2004; 83 (1): 80-2.
28. Atik E. Cateterismo cardíaco intervencionista na cardiologia pediátrica: o posicionamento médico quanto às aplicações atuais e perspectivas. Arq Bras Cardiol. 2002; 79: 443-5.
29. Jatene FB, Assad RS, Pêgo-Fernandes P, Jatene MB, Monteiro R, Rocha e Silva R. Video-assisted surgery for closure of patent ductus arteriosus. Study in sheep and initial clinical experience. Arq Bras Cardiol. 1994; 63: 469-72.
30. Simões LC, Pedra CA, Esteves CA, Camargo R, Braga SL, Loureiro P, et al. Percutaneous closure of ductus arteriosus with the amplatzer prosthesis: the Brazilian experience. Arq Bras Cardiol. 2001; 77 (6): 520-31.

Patent ductus arteriosus treatment in the premature newborn: clinical and surgical analysis

Rafael Fagionato Locali; Priscila Katsumi Matsuoka; Edmo Atique Gabriel; Ayrton Bertini Júnior; Carlos Arnulfo La Rotta; Roberto Catani; Antônio Carlos de Camargo Carvalho; Enio Buffolo

Publication Dates

Publication in this collection
27 May 2008
Date of issue
May 2008

History

Accepted
22 Jan 2008
Received
02 Sept 2007
Reviewed
20 Dec 2007

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

[1] 1. Thebaud B, Michelakis ED, Wu XC, Moudgil R, Kuzyk M, Dyck JR, et al. Oxygen-sensitive Kv channel gene transfer confers oxygen responsiveness to preterm rabbit and remodeled human ductus arteriosus: implications for infants with patent ductus arteriosus. Circulation. 2004; 110 (11): 1372-9.

[2] 2. Heyman MA, Rudolph A. Control of the ductus arteriosus. Physiol Rev. 1975; 55: 62-78.

[3] 3. Clyman RI. Ibuprofen and patent ductus arteriosus. N Engl J Med. 2000; 343: 728-30.

[4] 4. Gould DS, Montenegro LM, Gaynor JW, Lacy SP, Ittenbach R, Stephens P, et al. A comparison of on-site and off-site patent ductus arteriosus ligation in premature infants. Pediatrics. 2003; 112 (6 Pt 1): 1298-301.

[5] 5. Uchita S, Imai Y, Takanashi Y, Hoshino S, Seo K, Terada M, et al. Surgical management of patent ductus arteriosus in low body weight infants. Jpn J Thorac Cardiovasc Surg. 1998; 46: 1088-92.

[6] 6. Van de Bor M, Verloove-Vanhorick SP, Brand R, Ruys JH. Patent ductus arteriosus in a cohort of 1338 preterm infants: a collaborative study. Paediatr Perinat Epidemiol. 1988; 2: 328-36.

[7] 7. Redline RW, Wilson-Costello D, Hack M. Placental and other perinatal risk factors for chronic lung disease in very low birth weight infants. Pediatr Res. 2002; 52: 713-9.

[8] 8. Evans N, Kluckow M. Early ductal shunting and intraventricular haemorrhage in ventilated preterm infants. Arch Dis Child Fetal Neonatal. 1996; 75: 183-6.

[9] 9. Dykes FD, Lazzara A, Ahlmann P, Blumenstein B, Schwartz J, Brann AW. Intraventricular haemorrhage: a prospective evaluation of etiopathogenesis. Pediatrics. 1980; 66: 42-9.

[10] 10. Noerr B. Current controversies in the understanding of necrotizing enterocolitis. Part 1. Adv Neonatal Care. 2003; 3: 107-20.

[11] 11. Burke RP, Jacobs JP, Cheng W, Trento A, Fontana GP. Video-assisted thoracoscopic surgery for patent ductus arteriosus in low birth weight neonates and infants. Pediatrics. 1999; 104: 227-30.

[12] 12. Wagner HR, Ellison RC, Zierler S, Lang P, Purohit DM, Behrendt D, et al. Surgical closure of patent ductus arteriosus in 268 preterm infants. J Thorac Cardiovasc Surg. 1984; 87: 870-5.

[13] 13. Little DC, Pratt TC, Blalock SE, Krauss DR, Cooney DR, Custer MD. Patent ductus arteriosus in micropreemies and full-term infants: the relative merits of surgical ligation versus indometacin treatment. J Pediatr Surg. 2003; 38: 492-6.

[14] 14. Fowlie PW, Davis PG. Prophylactic indomethacin for preterm infants: a systematic review and meta-analysis. Arch Dis Child Fetal Neonatal. 2003; 88: 464-6.

[15] 15. Rivera IR, da Silva MA, Fernandes JM, Thomaz AC, Soriano CF, de Souza MG. Congenital heart diseases in the newborn: from the pediatrician's request to the cardiologist's evaluation. Arq Bras Cardiol. 2007; 89 (1): 6-10.

[16] 16. Guitti JCS. Epidemiological characteristics of congenital heart diseases in Londrina, Paraná South Brazil. Arq Bras Cardiol. 2000; 74 (5): 400-4.

[17] 17. Van Woerkom R, Govindaswami B, Cleary J, Weyler J, Vanhaesebrouck P. Patent ductus arteriosus ligation in very low birthweight infants: is there benefit? Pediatr Res. 2001: A32.

[18] 18. Carboni MP, Ringel RE. Ductus arteriosus in premature infants beyond the second week of life. Pediatr Cardiol. 1997; 18: 372-5.

[19] 19. Farstad T, Bratlid D. Pulmonary effects of closure of patent ductus arteriosus in premature infants with severe respiratory distress syndrome. Eur J Pediatr. 1994; 153: 903-5.

[20] 20. Kluckow M, Evans N. Early echocardiographic prediction of symptomatic patent ductus arteriosus in preterm infants undergoing mechanical ventilation. J Pediatr. 1995; 127: 774-9.

[21] 21. Skinner J, Alverson D, Hunter S, eds. Echocardiography for the neonatologist. London: Churchill Livingstone, 2000.

[22] 22. Brooks JM, Travadi JN, Patole SK, Doherty DA, Simmer K. Is surgical ligation of patent ductus arteriosus necessary? The Western Australian experience of conservative management. Arch Dis Child Fetal Neonatal. 2005; 90: 235-9.

[23] 23. Fowlie PW. Intravenous indometacin for preventing mortality and morbidity in very low birth weight infants. Cochrane Database Syst Rev. 2000;(2):CD000174.

[24] 24. Coombs RC, Morgan ME, Durbin GM, Booth IW, McNeish AS. Gut blood flow velocities in the newborn: effects of patent ductus arteriosus and parenteral indometacin. Arch Dis Child. 1990; 65: 1067-71.

[25] 25. Salerno PR, Jatene MB, Santos MA, Ponce F, Bosísio IBJ, Fontes VF, et al. Patent ductus arteriosus (PDA) closure with minithoracotomy: technique and results. Rev Bras Cir Cardiovasc. 2000; 15 (3): 234-7.

[26] 26. Souto GLL, Tinoco RC, Tinoco ACA, Caetano CS, Souza JB, Paula AG, et al. Ligadura videotoracoscópica da persistência do canal arterial. Rev Bras Cir Cardiovasc. 2000; 15 (2): 154-9.

[27] 27. Atik FA, Jatene FB, Costa PH, Atik E, Barbero-Marcial M, Oliveira SA. Surgical treatment of coil embolization to the pulmonary artery after an attempt at percutaneous closure of patent ductus arteriosus. Arq Bras Cardiol. 2004; 83 (1): 80-2.

[28] 28. Atik E. Cateterismo cardíaco intervencionista na cardiologia pediátrica: o posicionamento médico quanto às aplicações atuais e perspectivas. Arq Bras Cardiol. 2002; 79: 443-5.

[29] 29. Jatene FB, Assad RS, Pêgo-Fernandes P, Jatene MB, Monteiro R, Rocha e Silva R. Video-assisted surgery for closure of patent ductus arteriosus. Study in sheep and initial clinical experience. Arq Bras Cardiol. 1994; 63: 469-72.

[30] 30. Simões LC, Pedra CA, Esteves CA, Camargo R, Braga SL, Loureiro P, et al. Percutaneous closure of ductus arteriosus with the amplatzer prosthesis: the Brazilian experience. Arq Bras Cardiol. 2001; 77 (6): 520-31.

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