Interventional Catheterization Procedures Balloon Dilation Balloon dilation is performed to relieve stenosis of valves, vessel walls, surgically created pathways, or intracardiac structures such as a fenestration in the atrial septum There have been significant advances in the size, profile, design, and materials used in balloon catheters, facilitating their use in various applications Design of coaxial balloons has reduced the time required for inflation and deflation, with only transient hemodynamic compromise The size of the balloon used for a particular procedure not only depends on the diameter of the lesion to be dilated, but also on the diameter of the contiguous and noncontiguous normal anatomic structures The use of an oversized balloon increases the chance of a successful dilation of the lesion but also increases the risk of trauma to the target lesion and to contiguous anatomic structures Balloons have been used to treat valvar stenosis when fusion of the leaflets along their zones of apposition is responsible for reduction in the area of the effective valvar orifice The principle of creating a controlled tear or split in the commissure, but not in the leaflet, thus improving excursion of the leaflets, provides a larger area of effective orifice and thus relieves the stenosis Because the valve is abnormal, competence may be affected to various degrees after balloon dilation Pulmonary, aortic, mitral, and tricuspid valves have all been treated by balloon valvuloplasty for different diseases However, the technique is not useful in treating valves associated with significant hypoplasia at the basal hinge point of the leaflets Dilation of semilunar valves is performed commonly for congenital lesions, and dilation of atrioventricular valves is performed almost exclusively for acquired lesions The technique used in performing balloon valvuloplasty also forms the basis for angioplasty and implantation of stents High-pressure balloons have been more recently used in dilating highly resistant lesions, such as calcified conduits, postoperative anastomotic stenosis, or native pulmonary arterial stenosis.42,43 Cutting balloons have been used in substrates that do not respond to standard balloon angioplasty, such as severe pulmonary arterial stenosis or recurrent pulmonary venous stenosis, with encouraging results.44 Balloon-in-balloon catheters, known as BIB catheters (NuMed), have been very useful in implanting stents in the aorta, pulmonary arteries, and conduits.45 The inner balloon is an additional tool to help confirm the position before deployment of the stent, and the serial dilation helps to reduce stent malposition and foreshortening The use of two balloons simultaneously for valvuloplasty was first introduced for dilation of the mitral valve.46 It provides a large effective diameter of the combined balloons and has been used in pulmonary valvuloplasty in adults who have a large diameter of the pulmonary outflow tracts.47 Stability of the balloon during inflation depends on choice of a balloon of correct length and diameter, appropriate selection of a stiff guidewire, obtaining appropriately distal position for the guidewire, and achieving a rapid sequence of inflation and deflation Stability could be further aided by using techniques to reduce stroke volume, such as rapid ventricular pacing, mainly but not exclusively for lesions in the systemic circulation In balloon valvuloplasty, the size of the balloon is chosen based on the size of the target valve annulus measured In pulmonary valvoplasty, the balloon size is usually 120% to 140% of the measured diameter of the valve at the basal hinge points of the leaflets In aortic valvoplasty, the size is usually 80% to 100% of the diameter at the hinges of the leaflets A serial approach to aortic valvuloplasty with interval reassessment of residual gradient and degree of valvar incompetence can prevent the development of an adverse outcome.48 Size for dilating coarctation of the aorta equals the diameter of the distal transverse arch, prior to the development of hypoplasia or stenosis, or a size is chosen not greater than four times the diameter of the lesion but less than the diameter of the descending aorta at its position close to the diaphragm The length of the balloon should not be so short as to produce instability during inflation or make capture of the lesion difficult and not too long to cause trauma to the proximal or distal structures (including the adjacent tricuspid valve, as is the case with pulmonic valvuloplasty) The size of the patient should be taken into consideration in choosing the correct balloon Balloons are filled with dilutions of contrast medium 1:3 and 1:5 with saline, chosen based on balloon size and location, as well as patient thickness, and should be de-aired thoroughly to reduce the risk of air embolism, should the balloon rupture If the margins of the balloon, at its ends, are parallel, it suggests that inflation is at nominal pressure, and any further inflation can increase the risk of rupture After successful dilation, hemodynamics and angiography should be repeated to evaluate results and assess complications Further evaluation by echocardiography, cross-sectional imaging, or lung perfusion scan is imperative to decide long-term management Stent Angioplasty Stents are capable of maintaining patency of vessels and prevent elastic recoil after balloon dilation There have been major advances in stent technology, and their impact can be easily observed in congenital cardiology Typically, stents are cut from stainless steel tubes with a laser or made from platinum alloy wires welded together Stents can be expanded on balloons or be self-expanding when made of shape-memory alloy (nitinol) and delivered from a constraining sheath Self-expanding stents are used in patients who, or structures which, have already achieved their potential for growth and typically offer benefit in regions of dynamic stress (e.g., femoral artery) Balloon-expandable stents can be redilated within limits, each distinct to the specific model of stent chosen, and may be used in children and adults The design of the cells may be open, such as the ev3 LD series (Medtronic, Inc.), avoiding jailing or covering of neighboring arterial branches, closed, such as the Palmaz Genesis or XL series (Cordis), or a hybrid of these two designs, such as the Formula series (Cook Medical) The properties of materials considered favorable for use in congenital cardiology are those with a low profile, good radial strength and flexibility, and ability to withstand cyclic compressive stresses of the cardiovascular system The diameter of the stent should also have the potential to reach maximal dimensions of the vessel wall, as seen in a typical adult However, in small infants, a premounted biliary stent or coronary arterial stent may be used in circumstances of severe hemodynamic compromise, despite their limited final maximal diameter This is especially true in patients in whom subsequent surgical revision (e.g., conduit replacement) is inevitable; moreover, intentional transcatheter stent fracture is an increasingly viable potential.49,50 Stents are implanted using balloons of appropriate size through long, large-bored, sheaths to reach the lesion Stents may be premounted on the balloons or may need to be crimped on to the balloon manually or by using a crimping device The length of the balloon should always be equal to or longer than the length of the stent but ideally not by much, to avoid “dog boning,” which can shorten a desired stent's length The diameter of the balloon determines the final diameter of the stent Stability of the stent during deployment can be improved by using the BIB catheters, extra-stiff wires, long sheaths, and rapid right ventricular pacing to reduce stroke volume.51 The luminal surface of the stent endothelializes in 8 to 10 weeks, and patients may need to take antiplatelet agents or, in some situations, anticoagulants during this period to prevent in-stent thrombosis and restenosis ... There have been major advances in stent technology, and their impact can be easily observed in congenital cardiology Typically, stents are cut from stainless steel tubes with a laser or made from platinum alloy wires... of these two designs, such as the Formula series (Cook Medical) The properties of materials considered favorable for use in congenital cardiology are those with a low profile, good radial strength and flexibility, and ability to withstand cyclic