Singapore฀Med฀J฀ 2006;฀47(9)฀:฀763 ABSTRACT Introduction: The aim of this study was to determine predictors of failed closure of patent ductus arteriosus (PDA) following a single course of indomethacin in symptomatic preterm infants. Methods: This prospective observational study was carried out on 60 preterm infants weighing less than 1,750 g with symptomatic PDA confirmed by echocardiography. At a median age of 7.0 days (interquartile range 4.0), they were given indomethacin of 0.1 mg/kg/day intravenously daily for six days. Closure of PDA was reassessed by echocardiography upon completion of therapy. Results: The PDA of 40 percent (n=24) of these infants remained patent. Forward logistic regression analysis showed that the only significant predictors of failed PDA closure in these infants were: PDA size (adjusted odds-ratio [OR] is 7.0; 95 percent confidence interval [CI] of OR is 2.0, 24.8; p-value is 0.002), birth weight (adjusted OR is 0.996; 95 percent CI of OR is 0.993, 1.000; p-value is 0.03) and platelet count (adjusted OR is 0.987; 95 percent CI is 0.975, 1.000; p-value is 0.045). Gestational age, maternal age and left atrium/aorta ratios were not significant predictors. Conclusion: Larger PDA, lower birth weight and lower platelet count were significant predictors of high failure in indomethacin therapy given late at one week of life. Keywords: indomethacin therapy, patent ductus arteriosus, preterm infants Singapore Med J 2006; 47(9):763-768 INTRODUCTION Patent ductus arterious (PDA), a common problem in preterm infants, is associated with a number of Department฀of฀ Paediatrics Faculty฀of฀Medicine Hospital฀Universiti฀฀ Kebangsaan฀ Malaysia Jalan฀Yaacob฀Latif Cheras Kuala฀Lumpur฀56000 Malaysia Boo N Y, MRCP, FRCPE, FRCPG Professor of Neonatology Mohd-Amin I, MD, MMed Registrar Bilkis A A, MD, MMed Paediatric Cardiologist Yong-Junina F, BScMedSci, MBChB, MMed Paediatric Cardiologist Correspondence฀to: Professor Nem-Yun Boo Department of Paediatries International Medical University Jalan Rasah Seremban 70300 Malaysia Tel: (60) 6 767 7798 Fax: (60) 6 767 7709 Email: nemyun_boo@ imu.edu.my complications including prolonged requirement for ventilatory support, increased risks of infections, bronchopulmonary dysplasia and heart failure (1-3) . Indomethacin, an inhibitor of synthesis of prostaglandins, has been found to be a very useful drug for closure of PDA in preterm infants (4,5) . However, despite treatment with this drug, failure of closure has been reported to be as high as 21% (6) . Based on univariate analyses, a number of potential risk factors have been identified to be associated with failed closure of PDA using indomethacin. Review of the literature published between 1966 and 2002 via MEDLINE showed that there is only one multivariate analysis reported on significant predictors associated with failed closure of PDA following treatment with indomethacin (7) . In that study, late treatment with indomethacin, larger size of PDA, and lower gestational age were some of the significant predictors identified, after controlling for various confounders (7) . As PDA is associated with high morbidity and mortality, surgical closure should be considered early in cases when medical treatment fails. The objective of the present study was to determine the significant predictors of failed closure of PDA following a single course of indomethacin, so that infants who required surgical ligation could be identified earlier to minimise associated complications. METHODS This was a prospective observation study carried out in the neonatal intensive care unit (NICU) of Hospital Universiti Kebangsaan Malaysia over a 33-month period, between January 1, 2002 and September 30, 2004. The study protocol was approved by both the hospital’s scientific and ethics committees. During the study period, any infants suspected to have symptomatic PDA (defined as presence of a systolic heart murmur and/or easily palpable popliteal pulses associated with tachycardia >160 beats/minute) were evaluated using echocardiography. Echocardiography was performed by one of Original฀Article Predictors of failed closure of patent ductus arteriosus with indomethacin Boo N Y, Mohd-Amin I, Bilkis A A, Yong-Junina F