Risks associated with stent angioplasty include dislodgement and embolization, trauma to the vessel walls, fracture of the stent, and restenosis Covered stents made by fashioning expanded polytetrafluorethylene to balloonexpandable or self-expanding stents have been used in situations where the risk of vascular injury and aneurysm is considered to be high or to exclude existing vascular pathology, such as a pseudoaneurysm or dissection.52 The use of covered stents in younger patients is limited by their size and the caliber of the delivery systems currently available Covered stents approved by regulatory agencies throughout the world are now readily available.53 Newer bioabsorbable stent platforms are currently being investigated to reduce restenosis and improve vasomotion in coronary arterial lesions Such stents could prove useful in treating stenoses of small vessels in infants and children, albeit temporarily, thus allowing for normal growth without the need for later surgical stent transection or intentional stent fracture to facilitate further interventional therapy.54 Closure of Septal Defects and Vascular Occlusion The advent of shape-memory alloy has revolutionized transcatheter interventions for intracardiac and extracardiac shunts Nitinol is the most common alloy used Several devices for closing septal defects and vascular occlusion are currently available The most commonly used occluder, the Amplatzer Septal Occluder (now manufactured by Abbott Medical), has a central occluding component, with left- and right-sided discs A Dacron polyester patch sewn into the device is responsible for thrombogenicity and acute occlusion A large number of devices are available around the world that largely mimic the design of the ASO device, including the Occlutech ASD occluder, which is very popular in Europe The second most commonly used occluder in the United States is the Cardioform Septal Occluder (W.L Gore & Associates), which consists of a nitinol coil frame with Gore-Tex covering on the left- and right-sided discs This device covers the defect but does not contain a central occluding component and thus is not selfcentering like the Amplatz device The Gore Cardioform ASD Occluder, currently in clinical trial, offers a hybrid approach to ASD closure with a nitinol coil frame and Gore-Tex covering but also containing an anatomically adaptable central component that fills the defect itself Sizing of a septal defect is performed by transesophageal or intracardiac echocardiography, with or without inflating a balloon across the defect during the procedure Reported complications of such closure devices eroding through the atrial or aortic walls, and devices designed to occlude ventricular septal defects (VSDs) causing complete heart block, emphasize the importance of choosing a device of appropriate size and the ongoing need for further device development Various practice strategies, from oversizing to reduce the risk of device embolization, to appropriate sizing to reduce the risk of trauma to contiguous structures, have been used Intracardiac Interventions Valvar Heart Disease Pulmonary Valve Pulmonary Valvar Stenosis As already discussed, the initial description of balloon dilation of pulmonary valve stenosis was made by Kan and colleagues in 1982.12 Since then, the technique has been accepted as a first-line treatment for congenital valvar pulmonary stenosis.54–58 Balloon dilation is usually indicated in the presence of related cardiac symptoms (such as poor feeding in an infant or exertional intolerance in an older child), when the gradient across the stenotic valve is 40 mm Hg or more, or when there is an increase in right ventricular systolic pressure by more than half of the systemic pressure.59 However, the indications for the procedure are different in neonates with a ductal-dependent pulmonary circulation, when gradients are unreliable The presence of a dysplastic valve with ductal-dependent pulmonary blood flow (critical pulmonary stenosis) is an accepted indication for treatment The right ventricular pressure is measured, after which right ventricular angiography is performed in the lateral projection to measure the diameter of the ventriculoarterial junction at the basal attachment of the valvar leaflets The stenotic pulmonary valve is crossed using an end-hole catheter, such as a balloon-tipped catheter or a directional catheter (e.g., Judkins right coronary) A guidewire, from 0.014 to 0.035 inch in diameter, is passed through the catheter into a branch of the pulmonary artery (PA) supplying the lower lobe of either lung In neonates, the guidewire may be placed across the patent arterial duct into the descending aorta, for maximal wire “purchase.” A balloon that is between 110% and 140% of the diameter of the measured valve is passed through the sheath in the femoral vein over the wire and advanced across the pulmonary valve The balloon is rapidly inflated and deflated with dilute contrast across the stenotic valve A significant waist is typically visualized on the balloon, which resolves with further dilation, until only a mild persistent annular waist remains, consistent with the use of a balloon that is slightly larger than the valve The balloon is then withdrawn, with the guidewire still in place, and a