Korean J Pediatr 2010;53(12):1012-1017 • DOI: 10.3345/kjp.2010.53.12.1012 1015 3. Failure Failure occurred in a 3­ month­ old infant weighting 5.8 kg with 4 mm ductus. The patient was also diagnosed as atrial septal defect and coarctation of aorta. Initially, the 6/4 ADO device was successfully deployed in this patient and was observed in the intensive care unit. However, position of device was unstable on follow­ up echocardiography after one day. As a result, the patient was then referred for surgery. 4. Complication The mean follow­ up duration was 21.0±19.6 months (range: 3 to 82 months). Of the 114 patients with successful deployment of a device, residual shunt was noted in one patient at 3­ year echocardiographic follow­ up. The patient was a 3­ month­ old infant weighing 7.7 kg with 3 mm ductus. The PDA was closed using 6× 5 mm Nit­ Occlud®(pfm AG, Köln, Germany). There still remained a very small residual shunt of PDA at his last echocardiographic follow­ up, 3 years after the procedure. There were no complications related to vascular access, hemolysis and massive blood loss in any of the patient. However, in two patients, after the implantation of the ADO, mild narrowing of descending aorta was noted. One of the patients, 1 month­ old boy, weighing 3.2 kg, underwent transcatheter closure using 6/4 mm ADO. A peak velocity on Doppler echocardiography after the procedure was 1.5 m/sec, but the echocardiography revealed progressive narrowing of the aorta, resulting in a peak velocity ranging from 3.0 to 3.8 m/sec during follow­ up at 2 months. PTA was performed for narrowing of the aorta 3 months after the initial intervention. Aortogram showed a significant decrease in peak velocity of aorta from 3.8 m/sec to 1.5 m/sec. The other patient was a 4 month­ old girl, weighing 4.2 kg with an 8mm duct and the PDA was closed using 6/4 mm ADO. After the procedure, on the echocardiography, a peak velocity of 2.0 m/sec was seen. On the follow­ up echocardiography after Table 4. Procedural Complications (n=9/115, 8%) Complications Major complications Failure of device implantation Device embolization Residual shunt > 12 months Significant obstruction of aorta or pulmonary artery Infective endocarditis Massive blood loss Total events Minor complications Mild narrowing of left pulmonary artery Mild narrowing of descending aorta Transient weak arterial pulse Total events N (%) 0 ( 0%) 1 (0.9%) 1 (0.9%) 0 ( 0%) 0 ( 0%) 0 ( 0%) 2 (1.7%) 3 (2.6%) 2 (1.7%) 2 (1.7%) 7 ( 6%) 12 months, a peak velocity of 1.9 m/sec was seen. These patients are under close observation at outpatient clinic without further intervention so far. Three patients showed mild narrowing of left pulmonary artery, but their peak velocity on left pulmonary artery only slightly increased (range: 1.3 m/sec to 1.5 m/sec). After the procedure, 2 patients had transient weak pulse on femoral artery, which was managed by continuous infusion of heparin, and they all recovered their femoral artery pulse tension the next day (Table 4). Discussion PDA occurs in 5­ 10% of all congenital heart defects10). Once the diagnosis of the uncomplicated PDA is established, closure is recommended by surgery or catheter occlusion to avoid pulmonary overflow and prevent infective endocarditis10, 11). Transcatheter closure of PDA has been the mainstay of treatment in children and adults12). Fortescue et al. presented retrospective case series of 1808 patients with transcatheter closure of PDA in a report published in 2010. Overall PDA closure rate was 94 percent and major adverse events were 1.5 percent11). There have been only a few minor complications compared with the initial interventional data13, 14). Nevertheless, procedure­ associated complications have been still described in different age groups, and they are relatively major in infants4­ 6). Information is also inadequate regarding safety and feasibility of transcatheter closure in infants15, 16). Few studies have investigated their usefulness in children weighing less than 10 kg17, 18). Our current study is mainly focused on the clinical results in using either Nit­ Occlud®, ADO or COOK Detachable Coil® for the transcatheter closure of PDA in children weighing less than 10 kg. Completely successful closure of PDA was achieved in 98% of the patients19). This confirms the safety of transcatheter closure of PDA in children weighing less than 10 kg. In previous report by Kim et al.2), mean age of 150 patients was 38 months and mean body weight was 15 kg in our center; however, current study focused on younger and smaller patients. The incidence of PDA is higher in premature infants10). Jung20) reported that incidence in preterm infants with persistent patency of the ductus arteriosus is about 16 times more than full term infants. Delayed closure of the hemodynamically significant patent ductus arteriosus is related to the development of various morbidity in preterm infants21). Transcatheter closure of PDA can be considered as treatment option to avoid the risk of surgical ligation in these patients22). The important factors for successful procedure are vascular accessibility, morphology of ductus, availability of device, and imaging modality. First of all, the vascular accessibility is an