Patent ductus arteriosus and muscular ventricular septal defects are similar communications to secundum atrial defects in that they are surrounded by normal vessel or muscular ventricular septum. More recent concentric devices, modified from the design of the Amplatzer Septal Occluder device, have now provided the clinical opportunity for transcatheter closure in patients with such defects.
Patent ductus arteriosus is a failure of closure of a vascular channel present before birth; it normally closes in the first 2 d of life. Overcirculation of the lungs results when this vessel remains open, and this can cause damage to the pulmonary vasculature, overwork the heart, or predispose the patient to bacterial endocarditis. Closure is primarily recommended to reduce the workload of the heart, specifically when spontaneous closure is considered no longer likely (beyond 1-2 yr of age) (14). Like operative closure of a secundum atrial septal defect, surgical closure of a patent ductus arteriosus is a low-risk procedure that has been performed for decades (15). Transcatheter closure of such defects is considered to carry a risk at least as low as the major invasive approach.
Successful transcatheter closure of a small patent ductus arteriosus was performed before the design of successful commercially available devices. Specifically, a coil occlusion of a patent ductus arteriosus was first performed at the University of
Minnesota in 1972. Filling the aortic ampulla with stainless steel coils and their attached Dacron fibers or "hanging" a coil across the narrowest part of a patent ductus arteriosus produced reliable closure. However, the first embolization coils were not attached to a delivery wire, and the coil sometimes embolized into the pulmonary circulation. This technique was most effective when the narrowest diameter of the patent ductus was <3 mm (16). At that time, a retrievable device that would occlude larger ductus was considered highly desirable.
The Amplatzer Ductal Occluder is shaped and plug sized to the aortic ampulla, with an aortic retention disk designed to prevent embolization through the ductus (Fig. 2). The device is delivered by the venous route; delivery catheters can be small (5-8 French) because of the small collapsed device diameter. This simple modification of a self-expanding stent was extremely successful in producing complete occlusion of even a large patent ductus arteriosus. In the phase II FDA trial, there was over 97% complete closure at 6 and 12 mo. Furthermore, there was only a 2.3% incidence of serious and major adverse events (including one embolization that required surgical removal and one death of a child, not device related, with a chromosomal trisomy) (17). Premarket FDA approval of the Amplatzer Ductal Occluder device was granted in January 2003.
Muscular ventricular septal defects typically occur in the lower, thicker ventricular septum. Procedural closure is recommended for the same indications as both atrial septal defects and patent ductus arteriosus, that is, eliminating overwork of the heart and overcirculation to the lungs. However, unlike the other two defects, it is generally considered that surgery to close muscular ventricular septal defects is not a nontrivial or low-risk option.
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