The purpose of this study is to evaluate the safety and efficacy of the Nit-Occlud -PDA Occlusion System for transcatheter closure of PDA with minimum angiographic diameter less than 4 mm, and to compare one year safety and efficacy outcomes with recommended OPCs.

The purpose of this clinical investigation is to evaluate whether transcatheter occlusion of PDAs with a minimum vessel diameter of 4 mm or smaller, by means of permanent implantation of the Nit-Occlud Spiral Coil for PDA Occlusion, is safe and effective.

The device used for this purpose is a set of two items named "Nit-Occlud - PDA Occlusion System":

• Nit-Occlud coils, 2 types: flexible (3 sizes) and medium (3 sizes)
• Introducer Sheath, F4 or F5 85cm.

The intended use of the device is the percutaneous, transluminal closure of PDA with an internal diameter or 4mm and smaller in patients who comply with the selection criteria.

The investigation will continue until the sponsor receives FDA approval for commercial distribution and implantation of the system, or until the project is terminated by the sponsor or by the investigators.

The objectives of this study are:

1. To determine the safety of the spiral coil by monitoring and reporting deaths and adverse events associated with the device and device placement.
2. To determine the effectiveness of the spiral coil by evaluating clinical and echocardiographic occlusion rates.

Inclusion Criteria:

• PDA with 4 mm or smaller minimum diameter by color Doppler
• Patent weight > 5 Kg, Age 6 months to 21 years (Patients older than 21 years may have device implant and be included in a study registry.)
• Previous treatment by surgery or Nit-Occlud device with residual PDA noted at least 6 months after the procedure
• Angiographic minimum PDA diameter (D1) less than 4 mm. (Patients with angiographic diameters larger than 4 mm and smaller or equal to 5 mm may have device implant and be included in a study registry.)

Exclusion Criteria:

• Associated cardiac anomalies requiring surgery
• Known bleeding or blood clotting disorders
• Ongoing febrile illness
• Pregnancy
• Pulmonary hypertension/increased pulmonary vascular resistance (>5 Wood Units)
• Known hypersensitivity to contrast medium