Korean J Pediatr 2010;53(12):1012-1017 • DOI: 10.3345/kjp.2010.53.12.1012 1013 procedure, there are limitations in transcatheter closure of PDA in small children. There is the difficulty in advancing the tighter curves through the right heart with a large tubular sheath in small children4). Left pulmonary artery stenosis due to protrusion of device into the left pulmonary artery has been detected with the greater frequency in the smaller children5­ 7). The procedure was generally recommended only for children weighing over 7 to 8 kg because the size of the patients’ femoral vessel was relatively smaller than the size of the required delivery system. In the past when a larger device was used, the procedure was only recommended for patients weighing over 10 to 12 kg8). We reviewed our experience to determine the efficacy and safety of transcatheter PDA closure in infants weighing less than 10 kg, with regard to rates of success and complications. Materials and methods 1. Subjects A total of 314 patients underwent transcatheter occlusion of PDA at Severance Cardiovascular Hospital from January, 2003 to December, 2009. Among them, 115 (37%) patients (male 49, female 66), weighing less than 10 kg, were enrolled in this study. We retrospectively analyzed medical records, echocardiographic findings, angiographic findings, hemodynamic data and follow­ up results of these patients. 2. Echocardiographic and cardiac catheterization parameters After confirming left to right shunting through the PDA, the size of PDA was measured on color Doppler echocardiography. The left ventricular end­diastolic dimension (LVEDD) was measured in each patient on M­ mode echocardiogram. Hemodynamic studies were performed, and the ratio of pulmonary blood flow to systemic flow (Qp/Qs ratio) was obtained in each patient during cardiac catheterization. Aortograms were obtained in the right anterior oblique 30 degree and lateral view. The maximum diameter of the narrowest portion of the ductus was measured on frozen image and balloon occlusion sizing was performed, if needed. The residual shunt was identified by aortogram, 10 to 15 minutes after the implantation of the device. 3. Follow-up protocol Chest X­ ray and transthoracic echocardiography were conducted at 24 hours after the procedure to evaluate the shape and position of the device. The patients underwent clinical evaluation and echocardiography at 1 week, 1, 3, 6 and 12 months after the procedure and then annually thereafter. All patients were followed according to this protocol. Major complications investigated during the research included failure of device implantation, embolization of device, residual shunt, significant obstruction of aortic arch or left pulmonary artery, infective endocarditis and massive blood loss. Mild narrowing (peak velocity under the 1.5 m/sec) of left pulmonary artery or aorta and transient weak arterial pulse were regarded as minor complications. A peak velocity over the 1.5 m/ sec of the left pulmonary artery or descending aorta was considered as acquired stenosis. The difference in the LVEDD before and after PDA closure was evaluated. 4. Statistical analysis All data are expressed as mean±standard deviation. A P­ value less than 0.05 was considered as statistically significant. Comparisons of mean LVEDD between before and after procedure were done using the paired T­ test. Results 1. Characteristics of subjects The patients’ mean age was 9.1±5.9 months (range: 1­ 36 months), 49 were male and 66 were female, the mean weight was 7.6±1.8 kg (range: 3.2­ 10 kg). The mean diameter of PDA was 3.2±1.4 mm (range: 1.2 to 8 mm), the mean pulmonary blood flow to systemic flow (Qp/Qs) ratio was 2.0±0.9, and the mean fluoroscopic time was 13.4±3.8 minutes. The mean procedure time was 48.6±23.0 minutes (range: 12 to 115 minutes) (Table 1). The patients who were performed concomitant procedure such as percutaneous transluminal angioplasty (PTA) or percutaneous pulmonary valve angioplasty (PPV) have also been included in the study. PDA was presented as an isolated lesion in 75 (63%) patients, associated heart lesions were as follows: ventricular septal defect (VSD, n=13), atrial septal defect (ASD, n=11), coarctation of aorta (CoA, n=9), congenital aortic valve stenosis (AS, n=3), hypoplastic left pulmonary artery (n=3) and endocardial cushion defect (n=1). Table 1. Characteristics of the Patients (n=115) Variables Age (month) Male:Female Body weight (kg) Diameter of ductus (mm) Qp/Qs ratio* Fluoroscopy time (min) Procedure time (min) *the ratio to pulmonary blood flow to systemic flow †mean±SD Data† 9.1±5.9 (1-36) 49:66 (1:1.3) 7.6±1.8 (3.2-10) 3.2±1.4 (1.2-8) 2±0.9 13.4±3.8 (8-36) 48.6±23.0 (12-115)