1016 YA Park, et al. • Clinical outcomes of transcatheter closure of PDA in small children important variable. There is a high potential of thrombosis forma­ tion or interruption in femoral vessel related to vascular access, because the diameter of the femoral vessel in infants is small. Also, a more invasive approach such as cut­ down of femoral vessel may be necessary during catheterization. Second, in addition to measurement of the diameter, the morphology of the ductus should also be assessed by echocardiography before procedure is performed. With careful regard to anatomic details and cautious planning of device deployment, procedural risks can be minimized and success rates can be maximized. Third, the miniaturization of device is also an important variable. Catheter manipulations within the heart have to be minimized to prevent injury and to avoid causing arrhythmias and hemodynamic instability. There is also the possibility of narrowing of adjacent aorta from protrusion of the aortic retention disc3). Further development in device can potentially improve the scope of catheter closure for ducts in preterm infants. Recently, Amplatzer duct occluder (ADO) II, a new device designed by the AGA Medical (Golden Valley, Minnesota) show successful PDA closure and decrease the risk in small patients23). Finally, the imaging modality is also an important factor. Because it is difficult for very small infants to maintain their vital signs such as body temperature and respiration without assistance, the procedure by the bedside maybe more suitable than at the catheterization laboratory. If portable imaging modality can be used during procedures, the risk of transcatheter closure for PDA will decrease in small infants. Surgical ligation of PDA remains the treatment of choice in small children. Surgical morbidity, cost, and hospital length of stay have been decreased by the technique of video­ assisted thoracoscopic ligation of the PDA24). However, through our current study transcatheter closure for PDA of infants has somewhat established its safety and efficacy. Carefully selected group of infants may be offered transcatheter closure as a treatment option with great caution. With careful planning and improvement of imaging modality, transcatheter closure for PDA can be successfully accomplished in preterm infants. Furthermore, transcatheter closure of PDA can be accepted as the gold standard of treatment in patients of PDA weighing less than 10 kg in the near future soon. Acknowledgment The authors are grateful to Professor John Linton, International Health Care Center, Yonsei University Health System for language consultation. References 1) Porstmann W, Wierny L, Warnke H. Closure of persistent ductus arteriosus without thoracotomy. 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