ABSTRACT
Introduction Transcatheter closure of muscular ventricular septal defects (VSDs) first achieved practical potential with the improvement in design of double umbrella closure devices. These double umbrella device modifications subsequently led to the first and only transcatheter device approval to date by the FDA for ventricular septal defect closure (CardioSEAL device). The original Lock Clamshell Occluder (CR Bard, Boston, MA) consisted of two opposing, self-expanding umbrellas, scaffolded by single spring-loaded stainless steel arms and covered in a Dacron meshwork. The original design allowed for operator and device strategies that
1. maximized device apposition to the septal surfaces with least stress placed on the myocardium and device
2. provided greatest potential to conform to defect anatomy, with least distortion of surrounding myocardium
3. lessened interference with adjacent structures 4. allowed for post-deployment device auto-adjustment 5. increased the potential for complete closure, and
decreased the time to accomplish such 6. increased MRI compatibility, and 7. lessened the use of potentially corrosive metallic com-
ponents with the goal of increased biocompatibility and bioabsorption.
