Closure of Muscular Ventricular Septal Defects With The AMPLATZER™ Muscular VSD Occluder

Inclusion Criteria: * Patients with hemodynamically significant muscular VSD's (demonstrated by echocardiography or angiography), either isolated or in conjunction with other congenital heart defects * Age \< 18 years old Exclusion Criteria: * Less than 4 mm distance from the semilunar (aortic and pulmonary) and atrioventricular valves (mitral and tricuspid) * Patients with severely increased pulmonary vascular resistance above 7 woods units and a right-to-left shunt and documented irreversible pulmonary vascular disease * Patients with perimembranous (close to the aortic valve) VSD * Patients \< 3 kg * Patients with sepsis (local/generalized) * Patients with gastritis, gastric ulcer, duodenal ulcer, bleeding disorders etc. and other contraindications to aspirin therapy unless other anti-platelet agents can be administered for 6 months * Inability to obtain informed consent