Cardiac Catheterization in Congenital Heart Disease: Pediatric and Adult - Part 8 doc

CHAPTER 25 Coarctation and systemic arterial stents 654 over the wire. If an adequate angiogram cannot be obtained by either of these techniques, a second, small retrograde catheter should be introduced. A freeze-frame “road map” of this angiogram of the ductus is stored for reference use. After the angiogram has been obtained, an end-hole catheter with a smooth tip is advanced over the wire very gently, through the ductus and into the distal branch pulmonary artery. Once the catheter is in the distal pulmonary artery, the original floppy, torque-controlled, guide wire that was used to manipulate across the ductus is replaced with the stiffest possible exchange length guide wire that the delivery balloon/stent that will be used to deliver the stent to the ductus, will accommodate. The exact length of the stent used in the PDA is deter- mined from the angiogram of each particular ductus. Ideally the stent must cover, and extend slightly past both ends of the ductus but, at the same time, should not extend too far into the lumen of either the pulmonary artery or the aorta. Once the delivery wire is secure through the ductus and well into a distal pulmonary branch, the second angiographic catheter is positioned adjacent to the aortic end of the ductus. The correct stent/balloon is chosen and prepared on the catheterization table and the prostaglandin infusion is stopped. The patient is observed closely for at least 30 minutes, and assuming no acute or severe deterioration of the patient during that time, the aortogram is repeated. Usually the ductus constricts and changes in configuration rapidly once the infusion of prostaglandin is stopped. Occasionally the rebound con- striction of the ductus is very severe and very rapid which, in turn, necessitates either the reinstitution of the prostaglandin infusion or the rapid introduction of, and the implant of, the stent. The ductus tissues are friable, so the balloon/stent introduction must be very gentle and very precise, and the stent must pass easily through the ductus. Because of these factors, some operators prefer to prepare the balloon stent and position the stent/balloon across the ductus before stopping the prostaglandin infusion and then wait for the prostaglandin to wear off with the deflated balloon/stent already in place across the ductus. The second catheter adjacent to the aortic end of the ductus is essential at this stage of the procedure in order to allow very rapid and precise final positioning of the stent within the ductus just before deployment. With any deterioration of the patient, or after 30 minutes, the angiogram is repeated, the stent/balloon position adjusted, and the balloon/stent is inflated to its advertised pressure or until all indentations in the balloon/stent have disappearedawhichever comes first. The balloon is deflated immediately and rapidly. With a properly implanted stent, the patient immediately will oxy- genate better and stabilize as soon as the balloon is deflated. The balloon is withdrawn carefully out of the stent/ductus and with the wire still through the stent and ductus, the aortogram is repeated to visualize the adequacy of the coverage of the stent in the ductus and the new flow to the pulmonary arteries. If there are any areas of the ductus, particularly at either end of the ductus, which are not covered by the stent, a second (or more) stent(s) is/are implanted during the same catheterization. The additional stent(s) is/are placed overlapping the first stent and covering all of the ductal tissues entirely. Any “exposed” ductus tissue is notorious for constricting and closing completely, even with a stent in the remainder of the ductus. For the implant of an additional stent immediately after the implant of the first stent, all of the catheters and wires are already in place and minimal further manipulation or time in the catheterization laboratory is necessary for the implant of an additional stent. Once the ductus is covered adequately and the patient is stable, the delivery wire is withdrawn from the stent and the catheter withdrawn. The infants are maintained on 21 mg aspirin per day. Stenting of the ductus in patients with pulmonary atresia with intact ventricular septum In infants with pulmonary atresia and intact ventricular septum, along with the opening of the pulmonary valve, a systemic to pulmonary “shunt” can be performed in the catheterization laboratory by implanting a stent in the ductus arteriosus. The stenting of the ductus is addressed after the pulmonary valve has been perforated and dilated successfully. This allows the delivery and implant of the stent into the ductus arteriosus through a venous route and the use of a smaller catheter system in the artery. When a stent is to be implanted in the ductus during the catheterization, before any intervention on the ductus and if not administered earlier when the lines were established, the patient is administered heparin systemically. After the pulmonary valve has been perforated and dilated, the final balloon dilation catheter for the pulmonary valvotomy is removed over the guide wire. Following the perforation and balloon dilation of an atretic pulmonary valve, a long guide wire usually has already been advanced through the ductus creating a “through-and-through” route from a femoral vein, through the right heart and ductus, down the descending aorta and out through a femoral artery sheath/catheter. If the through-and-through “rail” wire was not established during the valve perforation/dilation, the “rail” is established at this time with an exchange length wire which the proposed balloon catheter for stent delivery will accommodate. The balloon dilation catheter used for the pulmonary valve is replaced with a long 4- or 5-French end-hole catheter, which is advanced through the venous sheath, over the original guide wire and into the pulmonary CHAPTER 25 Coarctation and systemic arterial stents 655 artery or ductus (wherever the end of the wire is positioned). If the tip of the prograde venous catheter is in the pulmonary artery, it is manipulated through the ductus into the descending aorta and maneuvered through and out of the femoral artery sheath with the help of a torque- controlled wire. Occasionally the prograde catheter in the pulmonary artery cannot cross the ductus easily into the descending aorta. In that circumstance a floppy tipped wire and then a snare catheter is maneuvered from the aorta, through the ductus and into the pulmonary artery. A soft tipped wire is advanced through the venous catheter prograde into the main pulmonary artery and is snared with a Microvena™ snare (ev3, Plymouth, MN), which has been passed through the retrograde catheter into the main pulmonary artery. The snared prograde wire and the prograde venous catheter are withdrawn through the ductus and out through the femoral arterial sheath with the retrograde snare. Once both ends of the catheter are available outside of the body, the original floppy tipped exchange wire is removed and replaced with a stiff exchange wire of the maximum wire diameter that the particular coronary stent/balloon catheter or other pre-mounted stent/balloon that will be used for implanting the stent in the ductus, requires. This wire is secured outside of the body at both the arterial and venous ends. An equally effective alternative is to advance the floppy tipped wire from the retrograde catheter through the ductus and into the main pulmonary artery and to introduce the snare catheter into the pulmonary artery from the venous route. The retrograde wire then is withdrawn through the right heart and out through the venous sheath to complete the through-and-through wire. Even when previously visualized very adequately, a repeat aortogram with the injection adjacent to the ductus is performed either through a Tuohy™ adapter attached to the hub of the catheter over the through-and-through wire or through a separate prograde or retrograde catheter positioned in the descending aorta adjacent to the ductus. This angiogram of the ductus is imperative because of spasm or distortion of the ductus caused by the various wire/catheter manipulations through it. The diameter and length of the ductus are remeasured very accurately. As with the implant of a stent in any other ductus, the goal is to “line” the entire lumen of the ductus, including covering both ends of the ductus with the stent. Similarly to the patients with pure ductus-dependent pulmonary circulations, a 4 mm diameter stent is used in these patients. Once the through-and-through wire is established and the appropriate balloon/stent for the particular ductus is chosen and prepared for delivery, the prostaglandin infusion is discontinued. Assuming no acute or sudden deterioration in the infant’s saturation/ hemodynamics, the infant is observed for at least 30 minutes while off the prostaglandin infusion and the aortogram repeated. Often the combination of the irritation of the through-and-through wire/catheter, the pre- ceding manipulations during the balloon dilations of the valve, and the discontinued prostaglandin infusion distorts the ductal anatomy significantly. The ductus anatomy is re-examined carefully and the measurements repeated. If the ductus acutely goes into spasm or the infant dete- riorates significantly when the prostaglandin infusion is stopped, the prostaglandin infusion is restarted and the stent is delivered to the ductus before re-stopping the prostaglandin as described previously. The pre-mounted stent on a 4 mm balloon dilation catheter is introduced over the venous end of the through- and-through wire and advanced over the wire, through the right ventricle, pulmonary valve and into the ductus arteriosus. Although small stents notoriously are poorly visible, or even invisible in large adult patients, in small infants they are seen clearly in both the collapsed and the expanded states. Once the balloon/stent combination is in position in the ductus, and before the stent is expanded in the ductus, the anatomy of the whole ductus and, in particular, the exact location and diameter of the areas of minimal ductal diameter are re-imaged angiographically. If there is not a second catheter in the aorta, the aortogram is accomplished by advancing a 4- or, preferably, a 5-French, end and side-hole catheter retrograde over the arterial end of the through-and-through wire. The catheter is advanced just to the aortic end of the ductus and a pressure, Tuohy™ “Y” adaptor is attached over the wire at the proximal end of the retrograde catheter. An angiogram is performed over the wire through this retrograde catheter, the tip of which should be adjacent to the ductus and the stent/balloon catheter coming from the other end of the wire. With the anatomy precisely identified and recorded, the retrograde catheter is withdrawn back into the descending aorta as the stent/balloon catheter is positioned exactly in the ductus. The stent should cover both ends of the ductus completely including, in particular, the area of the narrowest portion of the ductus, which usually is at the pulmonary end of a long tortuous ductus. When satisfied with the stent length and location, the stent is expanded by inflation of the balloon to its full diameter or to the recom- mended maximum pressure of the balloonawhichever comes firstafollowed by a rapid deflation. A repeat angiogram is recorded with injection through the aortic catheter before the deflated balloon is withdrawn from the stent positioned in the ductus. When satisfied that the stent is fully inflated and fixed in the ductus, the deflated balloon is withdrawn cautiously out of the stent, over the wire and out of the body. The retrograde catheter is re- advanced to the aortic end of the stent and a final repeat CHAPTER 25 Coarctation and systemic arterial stents 656 angiocardiogram is recorded through this catheter before the wire is withdrawn. Similarly to the other stents in the neonatal ductus, if there is an area of the ductus which is not covered completely, a second, overlapping stent should be implanted at that time. When satisfied with the position, the adequacy of expansion of the stent and the “lining” of the entire ductus by the stent(s), an end-hole catheter is introduced over the venous end of the wire and advanced into the pulmonary artery. The wire is carefully withdrawn out of the stent through the venous catheter. The hemodynamics and anatomy are carefully re- assessed and a decision is made whether an atrial sept- ostomy is to be performed. Hemodynamically, an atrial communication in the presence of some elevation of the right atrial pressure enhances left ventricular filling and systemic output, albeit with some systemic desaturation and at the expense of some forward flow through the right ventricle/pulmonary arteries. On the other hand, with at least a moderate sized right ventricle, the right ventricular pressure near normal, and even in the presence of significant tricuspid valve regurgitation, a restrictive atrial communication and the associated elevated right atrial pressure should enhance right ventricular filling and, in turn, encourage forward blood flow through the right ventricle, pulmonary artery, and lungs. Until more definitive data are available on which ventricles will grow with adequate flow, and with what type of stimulus, this remains an on the spot judgment decision, which must be made in the catheterization laboratory, during each indi- vidual case. Stenting of the ductus in the hypoplastic left heart syndrome The patent ductus is essential for the systemic output in the infant with severe left heart obstructive lesions and, particularly, an associated “hypoplastic left heart” syndrome. In most cases, the open ductus is maintained with prostaglandins until the infant undergoes the first stage “Norwood” surgical palliation. In that surgery, the entire ductal tissue is excised purposefully and widely when the distal pulmonary artery is anastomosed to the aorta and no catheter intervention on the patent ductus should be considered when a “Norwood” surgical palliation is considered. An alternative approach to the “Norwood” and “single ventricle” approach to the patient with a hypoplastic left heart is an orthotopic cardiac transplant. However, when the infant is “listed” and awaiting the transplant, the ductal patentcy must be maintained until the transplant is performedaoften for weeks or months. To maintain the patency of the ductus medically requires a continuous, precisely controlled, intravenous (IV) infusion of prostaglandin. The maintenance of the IV and the precise control of the rate of the prostaglandin in a neonate require a 24/7 neonatal intensive care environment. Even in this environment the infant is in a very pre- carious situation. An alternative technique is to maintain the ductal patency with an intravascular stent 20,21 . Once the decision is made to “list” the patient for a transplant, then the implant of a stent in the ductus should be considered immediately. The longer the patient waits, the lower the pulmonary resistance becomes and the sicker the infant becomes. The longer the patient remains on prostaglandin, the greater the likelihood of systemic infection and the more friable the ductal tissues become. The infant with a “hypoplastic left heart” who is to undergo the implant of a stent in the ductus is taken to the catheterization laboratory with the ductus patency maintained with the prostaglandin infusion. The infant is intub- ated and ventilated on 17–18% oxygen. If the patient does not have an indwelling arterial line, a femoral artery is cannulated with a 20-gauge Quick-Cath™, and a multi- purpose, end and side-hole catheter is introduced through a sheath in the femoral vein. This catheter is manipulated through the right ventricle to the pulmonary artery and to the ductus arteriosus. A biplane angiogram is recorded in the PA and lateral views with the injection directly into the ductus. This angiogram is to visualize the exact diameter, length and configuration of the ductus. If necessary, the X-ray tubes are re-angled to “cut the ductus on edge” more precisely and the angiogram repeated. Precise measurements are made of the length and diameter of the ductus from the views that elongate the ductus optimally. Freeze-frame images of the desired views are stored for use as “road maps” during the implant of a stent into the ductus. The end and side-hole catheter is advanced through the ductus into the distal descending aorta. A 0.018″ or 0.035″ exchange length guide wire (depending upon which stent and which balloon catheter is to be used), is advanced far into the distal aorta, the tip of the wire is fixed in the ilio- femoral artery, and the catheter is removed over the wire. If there appears to be any distortion of the pulmonary artery–ductus–descending aorta anatomy by the wire, a repeat angiogram is recorded over the wire and through the catheter in the ductus before the catheter is removed. This angiogram performed with the catheter over the wire is accomplished by injecting the contrast through a Tuohy™ high-pressure “Y” adaptor attached to the hub of the catheter while the catheter is still positioned over the wire. A stent is chosen that is as large in diameter as the ductus/descending aorta can accommodate and long enough to extend completely through the ductus. The expanded stent must extend from well within the pulmonary artery, through the ductus, to well into the descending aorta. CHAPTER 25 Coarctation and systemic arterial stents 657 Unlike the stents in the ductus for pulmonary atresia patients, where a very controlled flow using a small stent (3– 4 mm) is desired, in patients with hypoplastic left heart, the stent must be large enough to accommodate all of the cardiac output and not create any resistance to this flow because of restriction from a limited diameter of the stent. Depending upon the patient’s size, this usually requires an 8–12 mm diameter stent. The pre-mounted standard “Large” Genesis™ stents (Johnson & Johnson– Cordis Corp., Miami Lakes, FL) are satisfactory for this use up to 10 mm in diameter. The Genesis™ stents are available pre-mounted in diameters up to 9 mm and in lengths of 19, 29 and 39 mm. These stents can be introduced through a short, 6-French sheath and advanced over a 0.035″ guide wire without the necessity of pre- positioning a long sheath across the lesion. “Large” Genesis™ stents are very flexible and conform to the cur- vature of the ductus. None of the coronary artery stents are suitable for this use because of the maximum diameter of 4 to 5 mm. The Express™ Biliary LD stents (Medi-Tech, Boston Scientific, Natick, MA) are available pre-mounted in similar sizes, but have larger side “cells” as a consequence of their open-cell design, which may be a problem for any use in the ductus because of the propensity for rapid ingrowth of the ductal tissues through any space. Once the wire is in place and the stent is ready for delivery, the prostaglandin infusion is stopped. The stent is advanced over the wire and positioned across the ductus. The balloon/stent is maintained in this position while monitoring the patient’s distal arterial pressure and systemic saturation for 30 minutes or until the patient’s hemodynamics begin to deteriorate. The idea is to allow the large diameter, often patulous, ductus to constrict enough after the prostaglandin is stopped to hold the stent in place. The blood pressure and systemic saturation decrease as the prostaglandin wears off and the ductus begins to close. Unless a second venous catheter has been introduced into the pulmonary artery or the stent/balloon was delivered to the ductus through a long sheath, an angiogram in the pulmonary artery to verify the status of the ductus and the stent position is not possible at this time. After the 30 minutes or with any deterioration of the patient, the stent’s position is compared to the freeze- frame “road map” images of the ductus, and when in the appropriate position, the balloon is inflated slowly to deploy the stent precisely in the ductus. Once fully inflated, the balloon is deflated rapidly. The large diameter stent should fix very securely in place in the ductus. The inflation/deflation is repeated one, or more, times and then the balloon is removed from the body over the wire. An end- and side-hole catheter is advanced over the wire and into the stent. An angiogram is recorded within the ductus (stent), injecting over the wire with the use of a Tuohy™ “Y” connector on the catheter. If the stent is not fully expanded, if it is at all unstable, or if there are areas of ductal tissue that are “exposed” or “uncovered” by the stent, a further dilation of the stent or the implant of an additional stent will be necessary to cover the ductal tissue completely. If a second stent is necessary and the wire still is in place, the additional stent can be implanted during this same procedure without any significant further or repeated manipulations through the freshly implanted stent. Once satisfied with the location and expansion of the stent(s), the wire is removed from the catheter and the catheter withdrawn. The infant is maintained off the prostaglandin infusion. Depending upon the status of the pulmonary vascular resistance, the infant usually can be discharged and observed as an outpatient until a donor heart becomes available. Even with a very satisfactory stent in the ductus, the infant still needs very close follow-up. As the pulmonary vascular resistance falls significantly, the infant’s lungs can become flooded, with a proportionate decrease in the effective systemic cardiac output through the ductus. The presence of the stent in the ductus does not interfere with a cardiac transplant procedure since the stented ductus and the adjacent tissues are removed at the time of the transplant. The main disadvantage to stenting the ductus in an infant with hypoplastic left heart syndrome is when a donor heart does not become available of for some other reason, the decision for the course of treatment is reversed and a “Norwood” procedure is required. A large stent in the ductus arteriosus complicates, or even possibly ren- ders impossible, the usual “Norwood” surgery. Complications of arterial stents Complications of systemic arterial stents include exagger- ation or extension of any of the complications of balloon dilation of any vessel including, particularly, coarctation of the aorta or dilation of other arterial lesions. At the same time, since the implant of a stent requires no over- dilation of the artery, complications related to dilation with the balloons are very rare. Iatrogenic obstructions caused by the implant of stents that have a maximum diameter that will be too small for the eventual size of the adult aorta, should be a totally avoidable “complication” of stents used in the treatment of coarctation of the aorta and other arteries. There now are stents available that can be dilated to 25+ mm, which makes these stents large enough in diameter for any adult proximal descending aorta. These potentially larger diameter stents should be used in any growing patient with even the potential of having the aorta in the area of coarctation grow to larger than 16–18 mm in diameter. A stent CHAPTER 25 Coarctation and systemic arterial stents 658 with a limited diameter, which creates an obstruction because it is too small for the aorta, creates an obstruction that is much more difficult to repair than the usual native or “residual” post-operative obstruction. When the patient is too small to implant a stent that can be dilated to the anticipated diameter of the adult aorta, it is preferable to treat the patient with balloon dilation without a stent or with surgical repair initially. A stent can be implanted later to “finalize” the correction of any residual lesion following prior dilation or surgery. A very serious complication of the catheter treatment of coarctation of the aorta using balloon dilation with or without stent implant is injury to the central nervous system (CNS) during the catheterization procedure. CNS injury most likely occurs from air and/or clot embolization coming from catheters, sheaths or wires that are present in the systemic circulation proximal to the carotid and vertebral vessels. Meticulous attention to clearing fluid lines, catheters and sheaths of any air and/or clot, keeping guide wires in the circulation “covered” with a catheter that is maintained on a continual flush for as long as possible, the continual flushing of all catheters and sheaths that are positioned in the heart, and the routine use of systemic heparin, particularly during “left heart” procedures, should reduce or eliminate CNS problems. Direct injury from the tip of a wire positioned in a cranial artery has been implicated in central nervous system injury. Never positioning a wire tip in either a carotid or a vertebral artery eliminates this particular possibility. Probably the most common complication of the use of stents in the arteries is injury to the local artery at the site of catheter/stent introduction with subsequent compromise of arterial blood flow in the involved extremity. These injuries occasionally are unavoidable because of the necessarily very large sized balloon catheters/sheaths that are used to deliver stents to the aorta. Meticulous care of the arteries, which was discussed earlier in this chapter and in Chapter 4, is the best prevention and, in turn, best treatment of this problem. Local anesthesia is used liber- ally and repeatedly around the artery and surrounding tissues before, during, and at the end of the procedure. Local anesthesia is administered even if the patient is receiving general anesthesia. A precise, single-wall puncture is utilized for the entrance into the artery. Although an indwelling sheath often is as much as 2–3 French sizes larger than the dilation balloon or balloon catheter that is used for the stent delivery, an indwelling sheath, which is relatively fixed in the artery, is always less traumatic to the artery than a constantly moving catheter or a bare, rough, “folded” balloon/stent being introduced into and withdrawn out of the artery. When the sheath is removed from the artery, the puncture site is compressed manually and personally while continually monitoring the puncture site for bleeding and, at the same time, the artery distal to the puncture for a pulse. This hemostasis can take 30, 60, or more minutes, but should be accomplished before the patient leaves the observation and care of the catheterizing physician! Stent displacement is relatively common during the implant of stents in coarctation of the aorta. There often is a large discrepancy in diameter between the aorta proximal to the coarctation and the aorta distal to the coarctation. A stent that is expanded to a diameter that is calculated to fix the stent in the aorta proximal to the coarctation, can easily become free-floating in the much larger distal aorta. At the same time, expanding the stent to a diameter satisfactory for the diameter of the aorta distal to the coarctation would split the smaller-diameter aorta that is proximal to the obstruction. In order to avoid displacement, the stent is implanted with the majority of the stent positioned in the aorta proximal to the narrowing and no attempt is made at “approximating” the distal end of the stent to the larger distal aorta during the initial implant procedure. If a stent dislodges and moves further distally in the aorta, the stent is purposefully repositioned in the distal aorta so that it does not compromise vital side branches, and then it is expanded and fixed in the more distal location. Tears in the arterial wall or flaps off the intima/media are less common, or at least, less recognized, during stent implants in systemic arteries, including congenital coarctation of the aorta, than with balloon dilation alone of these same lesions. When the proper sized stents are used after the artery is measured properly and very accurately, the adjacent aorta should not be “over-dilated” at all and, at the same time, any slight disruption of the intima/ medial tissue within the area of the stent is compressed back against the wall of the aorta by the stent. As the endothelium and neointima develop over and around the stent, the combination of the wall “thickening” by the “new endothelial tissues”, the scarring as a consequence of any tears that did occur, and the “metal scaffolding” of the stent within the area, all together create a very solid arterial wall. The artery in the precise area of the stent is very non-compliant, but no more so than a surgical scar involving the same area! Aneurysms have occurred acutely during the implant of stents in coarctations of the aorta. These occurred more commonly with the use of the larger Palmaz™ stents ( Johnson & Johnson, Warren, NJ) and occurred predomin- antly (only?) when the stents were dilated acutely to their final large diameters with a single inflation of a large diameter balloon. Acute aneurysms are not reported with the sequential dilation of stents to their precise, eventual large diameters, or with the use of stents that do not develop sharp tips at their ends as they expand. Aneurysms following the implant of stents in coarctation of the aorta are still being studied, and should be looked CHAPTER 25 Coarctation and systemic arterial stents 659 for in every patient who undergoes a stent implant in the aorta. Tears or ruptures of the aorta occur with dilation of native coarctation, re-coarctation of the aorta, and middle aortic syndrome, but should not occur with the conservative implant of the correct size stent in coarctations. Meticulous, accurate measurements of the lesion itself and the adjacent vessels, and avoiding oversized dilations/stents compared to the size of the lesion itself and the adjacent vessel, presumably should prevent this complication during stent implant. In cases of very severe stenosis of classic coarctation or middle aortic stenosis, a staged dilation/implant during several sequential catheterizations is utilized to avoid splitting very narrowed vessels by a single dilation to a very large diameter. A stent that is still narrowed within a vessel can always be dilated further at a later date. Once the artery/aorta is split or torn, there is little or no “turning back”, although several operators have reported on the successful use of a covered stent as an emergency “bail-out” therapy in the catheterization laboratory 22,23 . Stents implanted in coarctation of the aorta have been reported to fracture or kink 24 . This probably is a result of the type of stent used in the area. There have been no adverse events from these findings and a recurrent narrowing as a result of a fracture or kink can be treated with the implant of an additional stent within the original stent. The implant of stents into the patent ductus of newborn infants has its own specific complications. These complications are in addition to the inherent complications of extensive catheter manipulations in very sick newborn or small infants. As with all complications, the best treatment is prevention by paying meticulous attention to the details of the procedure and the use of known, established techniques until newer/better techniques are proven. Irritation and spasm of the ductus is a potential problem with any manipulation around or through the ductus. This spasm is not always responsive to prostaglandin infusion or re-infusion. Should intractable ductal spasm occur, having the equipment ready for immediate deployment of a stent is the best treatment. This, however, is not a guarantee of successful recovery since the “mass” of even the “tiny” stent/balloon occasionally cannot be advanced through the ductus once it begins to spasm. Disruption/tears of the ductal tissues is another potential with stent implant into the patent ductus, particularly when the stent delivery is rushed. The tissue is inherently very friable and cannot tolerate rough handling. When disruption of the ductus does occur, it usually is catastrophic. Stent displacement during implant into the “patulous” ductal tissue in an infant is a real problem. Prevention, by the use of a slow meticulous positioning and by waiting for the prostaglandin to wear off before deploying the stent, is the best treatment. When a stent displaces from the ductus, an attempt is made to capture the stent on a balloon and reposition it back into the ductus. A new balloon which is at least 1 mm larger than the maximum diameter of the stent is more effective for “capturing” an errant coronary stent. When a coronary stent becomes displaced from the ductus and is positioned or implanted in any other artery (even very peripherally), the coronary stent, unequivocally, eventually will produce a very significant stenosis in that vessel because of its very small maximum diameter. If a displaced stent cannot be cap- tured and reimplanted successfully in the ductus or removed from the patient with a catheter, the stent should be removed surgically from the errant vessel within a few days after the attempted implant procedure, unless the errant vessel is considered “expendable”. The majority of the complications of stent implants in arterial locations are eliminated by the use of extremely accurate measurements, a conservative diameter at the initial implant, and by paying meticulous attention to the details of every step of the procedure. The morbidity and complications of dilation with intravascular stent implant for systemic arteries appear to be comparable to or even less than surgical therapy of these same lesions. Dilation with stent implants in coarctation and other congenital systemic arterial lesions still represents a “new” treatment, which requires decades of follow-up to determine its real efficacy and safety. References 1. Dotter CT et al. 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Chest pain during stenting of a native aortic coarctation: a case for acute intercostal muscle ischemia and rhabdomyolysis. Catheter Cardiovasc Interv 2002; 57(2): 217–220. 14. Thanopoulos BV et al. Long segment coarctation of the thor- acic aorta: treatment with multiple balloon-expandable stent implantation. Am Heart J 1997; 133(4): 470–473. 15. Tyagi S et al. Percutaneous transluminal angioplasty for stenosis of the aorta due to aortic arteritis in children. Pediatr Cardiol 1999; 20(6): 404–410. 16. Redington AN and Somerville J. Stenting of aortopulmonary collaterals in complex pulmonary atresia. Circulation 1996; 94(10): 2479–2484. 17. El-Said HG et al. Stenting of stenosed aortopulmonary collaterals and shunts for palliation of pulmonary atresia/ ventricular septal defect. Catheter Cardiovasc Interv 2000; 49(4): 430–436. 18. Gibbs JL et al. Stenting of the arterial duct: a new approach to palliation for pulmonary atresia. Br Heart J 1992; 67(3): 240–245. 19. Michel-Behnke I et al. Stent implantation in the ductus arteriosus for pulmonary blood supply in congenital heart disease. Catheter Cardiovasc Interv 2004; 61(2): 242–252. 20. Ruiz CE et al. Brief report: stenting of the ductus arteriosus as a bridge to cardiac transplantation in infants with the hypoplastic left-heart syndrome. N Engl J Med 1993; 328(22): 1605–1608. 21. Slack MC et al. Stenting of the ductus arteriosus in hypoplastic left heart syndrome as an ambulatory bridge to cardiac transplantation. Am J Cardiol 1994; 74(6): 636–637. 22. Khan MS and Moore JW. Treatment of abdominal aortic pseudoaneurysm with covered stents in a pediatric patient. Catheter Cardiovasc Interv 2000; 50(4): 445–448. 23. Tyagi S, Rangesetty UC, and Kaul UA. Endovascular treatment of aortic rupture during angioplasty for aortic in-stent restenosis in aortoarteritis. Catheter Cardiovasc Interv 2003; 58(1): 103–106. 24. Ledesma M et al. Stent fracture after stent therapy for aortic coarctation. J Invasive Cardiol 2003; 15(12): 719–721. 661 Introduction Occlusion of abnormal or persistent arterial or arteriovenous structures or vessels feeding vascular leaks or tumors by catheter embolization techniques has been utilized for over thirty years 1 . The embolization techniques were developed and perfected primarily by the vascular radi- ologists working in the abdominal viscera, gastrointestinal areas and the central nervous system, particularly in “end artery” vessels. Many materials and devices, including the patient’s own clotted blood, Gelfoam™, colloidal plugs, “glues”, detachable balloons and coil occlusion devices have been used for these peripheral occlusions 1– 6 . In the pediatric and congenital heart population there are numerous abnormal congenital and acquired vascular communications and intravascular “leaks” which require or, at least, can be benefited by transcatheter occlusion. The occlusion of these vascular lesions in pediatric and congenital heart patients has been performed in the catheterization laboratory for over two decades. The abnormal flow through these communications usually results in significant abnormalities of the underlying hemodynamics and compromises the patient’s symptomatic and hemodynamic status. The abnormal vascular communications which are encountered in pediatric and congenital heart patients include traumatic fistulae, systemic to pulmonary artery collaterals, systemic arteriovenous fistulae, pulmonary arteriovenous fistulae, coronary arterial-cameral fistulae, perivalvular leaks and a variety of residual, surgically created systemic to pulmonary artery communications including Blalock–Taussig, modified Blalock–Taussig, Potts, and Waterston/Cooley shunts. There are numerous different catheter-delivered devices and techniques available for the occlusion of these abnormal vascular structures. There is no single device applic- able for every lesion and multiple devices may be suitable, and used, for any one lesion. These devices/materials are used either by themselves or (frequently) in combination with one or more of the other devices. The specific occlusion device used depends upon the type, size and location of the communication/leak as well as the availability of a particular device either locally or as approved, in the particular country. Some of these devices are designed specifically for a particular lesion and are discussed in detail in other chapters in the description of the occlusion of the specific intracardiac defect. These same descriptions are not repeated in this chapter. Since most of the devices can be utilized for the occlusion of multiple different structures and many of the abnormal vascular communications can be occluded with several different devices, each of these miscellaneous vascular lesions and the separate vascular occlusion devices that are used for that lesion are included in the discussion of the particular lesions in this chapter. The multiple devices themselves that are available for these occlusions are discussed initially in this chapter, before the details of their use in the various lesions for which they can be used. Devices/equipment for vascular occlusions Occlusion coils Stainless steel occlusion coils are the most widely used of the catheter-delivered occlusion devices and have had the longest continued use in pediatric and congenital heart lesions. They are particularly useful for small or tortuous vessels and have gained enormous popularity and use for the catheter occlusion of the patent ductus arteriosus (PDA). The specific coils used for PDA occlusion and the modifications of the delivery system/techniques specifically for the PDA are discussed separately and in detail in Chapter 27 (“PDA Occlusion”). Many of these modifications, which were developed specifically for PDA occlusions, are useful for the occlusion of general vascular structures. 26 Occlusion of abnormal small vessels, persistent shunts, vascular fistulae including perivalvular leaks CHAPTER 26 Vascular occlusions—miscellaneous vessels, fistulae 662 Occlusion coils are available as specific lengths of various sizes (gauges) of stainless steel, spring guide wire. The “guide” wires are pre-formed during manufacturing so that they will coil into a cylindrical tube of a specific diameter of the wire in their “resting” state. The number of loops of coil and the length of the “tube” of coils depends upon the original length of the straightened wire. Most of the “occlusion coils” have multiple tiny threads or fila- ments of nylon fabric intertwined within the windings of the spring wires to promote better thrombosis within a vessel. Occlusion coils are best suited for the occlusion of long and/or tortuous vessels with irregular internal diameters, and especially those which have a significant narrowing somewhere along the course of the vessel. Since a successful occlusion is expected to cut off all blood flow through the vessel, the vessels being occluded should not be the sole blood supply to a particular area of tissue unless necrosis of the tissues that are supplied by the vessel is desired. Gianturco™ coils and 0.052 ″ stainless steel coils The coil occluder with the most extensive use in pediatric and congenital heart patients is the standard Gianturco™ coil. The Gianturco™ coil is a length of special stainless steel spring guide wire in which the stiffening “core” wire is pre-formed to curl into a “coil” or “wire cylinder” of a specific diameter in its “free” or “resting” state. These coils are available in multiple sizes of the spring wire, multiple diameters of the coil (“cylinder”) and multiple lengths of the coil wire. The Gianturco™ coil has multiple fine nylon fiber segments embedded within the windings of the spring wire in order to increase the thrombogenicity of the implanted coil. Gianturco™ coils are available in spring wire diameters of 0.025″, 0.035″, 0.038″ and now, an additional coil of 0.052″ wire diameter, in lengths between 1.2 and 15 cm and in coil diameters from as small as 2 mm to as large as 20 mm in diameter. The very smallest diameter, short coils are available only in the 0.025″ diameter wires while very large diameter coils are available only in the more recently available 0.052″ wires. The total length of the straightened segment of coil wire in conjunction with the particular diameter of the preformed loops of the coils, determine the number of loops which are formed by any particular length of coil. Each Gianturco™ coil comes from the manufacturer in a straight metal introducer tube. The internal lumen and the length of the introducer tube are specific for the diameter of each wire and the straightened length of the wire. The mass of the wire of the coil itself creates a mechan- ical occlusion and the embedded nylon fibers add to the thromboses in the area where the coil is deposited and, in turn, occlude the vessel or communication. The coils are best suited for deposit into tubular vessels that have some length and vessels that have an area of narrowing somewhere within the channel of the vessel or the abnormal communication. A stenosis distally in the channel of the vessel prevents even coils that are undersized from migrating out of the target vessel and embolizing to an area or vital organ distally beyond the vessel. The coils are delivered through polyethylene, end-hole only, catheters, which have an internal diameter which is just slightly greater than the diameter of the wire of the spring coil. Other end-hole only catheters manufactured from materials that impart a smooth or slick inner surface and that are slightly larger in their internal diameters than the wire of the coil can be used for coil delivery. The catheter for coil delivery must not have side holes. Side holes allow the potentially curved tip of the coil to catch in, or pass into, a side hole of the catheter as the tip of the coil crosses the side hole. The tip of a coil catching in a side hole of the catheter will prevent the coil from being delivered through the tip of the catheter. Since the standard Gianturco™ coils have no attachment to the delivery wire, the coil catching in a side hole also prevents any retrieval of the coil without totally removing the delivery catheter. Both the material of the catheter and the internal diameter of the catheter are critically important in order to prevent the coil from “binding” within the lumen of the catheter during the delivery through the catheter. A catheter that is smaller in internal diameter than the coil wire obviously does not allow the coil with its imbed- ded fibers to be introduced into, or advanced through, the catheter. A catheter with an internal diameter significantly larger than the diameter of the wire of the coil allows the coil to bend and partially “coil” within the catheter or allows the pusher wire to push past the coil instead of actually “pushing” the coil through the catheter. Either occurrence will cause the coil to bind within the catheter. The delivery catheters are available with many pre- formed tip configurations in order to facilitate entry into specific areas. Straight delivery catheters, which the operator can pre-shape to suit his particular needs, are also used to deliver coils. End-hole, only, floating balloon catheters can be used to deliver the coils to certain locations or in particular circumstances. The inflated balloon helps to fix the tip of the catheter in place and/or prevents portions of the coil from extending back into a more proximal main vascular channel. The catheter lumen of the floating balloon catheter obviously must be of a slightly larger internal diameter than the diameter of the coil wire that is being delivered through the balloon catheter. The coil is introduced into the proximal hub of the delivery catheter through the straight metal “loader” as a straight length of wire. The straightened coil is pushed out of the loader, into the delivery catheter and through the CHAPTER 26 Vascular occlusions—miscellaneous vessels, fistulae 663 delivery catheter with a teflon-coated, spring guide wire of the same or similar wire size as the coil wire. The coil is delivered by pushing it completely through and out of the distal end of the delivery catheter. As the coil is extruded out of the delivery catheter, it immediately begins to form the small loop of its predetermined “coil” diameter as it opens into its coiled configuration. Once the extrusion from the catheter starts with the standard Gianturco™ or the 0.052″ coils, there is no way of withdrawing the coil back into the catheter or stopping or reversing the delivery. Even if the coil is noted to be in an unsatisfactory position as it starts to extrude from the catheter, it can only be extruded completely and then retrieved with a separate retrieval catheter and system. When choosing the appropriate occlusion coil, the diameter, the length and the general configuration of the vessel to be occluded are imaged angiographically. The length and diameters of the vessel are measured very accurately on the angiograms. The Gianturco™ coil occludes the vessel by the creation of an irregular mass of the coil wire and the nylon fiber strands that are incorpor- ated within the wire in which a thrombus forms. The coil used should be 1–2 mm larger in diameter than the vessel that is to be occluded. The slightly larger diameter results in the coil unraveling in an irregular configuration within and across the vessel lumen rather than into a neat “donut” like cylinder or smoothly coiled configuration. If the diameter of the coil is far larger than the diameter of the vessel, the coil does not “coil” at all, but rather tends to align straight within the vessel lumen and, in turn, does not form an effective occlusive mass in the vessel. When the coil is extruded from the catheter, it not only must have the appropriate diameter and length to fix to the walls of the vessel, but also must not be excessively long. When the coil is too long, it can extend proximally out of the target vessel and into the more central feeder vessel, which potentially can be back into the normal circulation and interfere with vital structures. If, at the other extreme, the diameter of the formed coil is too small for the vessel, the coil rolls up into a tight “donut”, does not occlude the entire vessel, and is likely to tumble distally or even out of the desired vessel. Once one coil is secured within a vessel, additional coils of different sizes and/or diameters can, and frequently are, intertwined within or deposited proximal to the original coil to complete the occlusion. Even when used in tandem, but without a distal narrowing or some other type of device for fixation, the standard Gianturco™ coil generally is only usable in tubular structures of no more than 7–8 mm in their distended diameter. For larger vessels and vessels without an area of discrete stenosis, either the standard Gianturco™ coils are used in conjunction with other intravascular occlusion devices or the 0.052″ coils are used initially to begin the occlusion of the vessel. Occlusion coils can be deposited into long vessels that have a discrete distal narrowing, where the coil then lodges in place at the narrowing, although it is not “fixed” against the wall. In that circumstance, coils can be “floated” into the vessel, one after another to create a mass of coils, proximal to the stenosis in the vessel. When this technique is used, the final coil in the vessel should be of a slightly larger diameter then the diameter of the vessel in order to wedge the last coil against the walls of the vessel. The one “fixed” coil assures that the “loose” coils packed within the vessel do not “float” back out of the vessel into the vital circulation. Currently, by far the most common use of the Gianturco™ coil in congenital heart lesions is for the clo- sure of the patent ductus arteriosus. This is an entirely separate subject and is discussed in detail in Chapter 27 and is not covered in this chapter at all. There are many abnormal vessels, collaterals and persistent surgically created systemic to pulmonary artery shunts, which frequently are associated with more complex lesions. These vessels require occlusion when the additional systemic flow competes with normal pulmonary flow, particularly when the abnormal communication persists after the major intracardiac defect has been corrected. These communications traditionally required surgical division during the corrective procedure or as a separate, later, surgical procedure. When the occlusion of these defects is performed surgically during the intracardiac repair, it significantly prolongs or complicates the surgery. Most of these abnormal communications now are occluded with Gianturco™ coils either before or shortly after the major surgery 7 . With the use of coils, further extensive extra surgery or repeat surgery is unnecessary for the elimina- tion of persistent systemic to pulmonary artery collaterals or for any surgically created systemic to pulmonary artery shunts that are present at the time of, or following, the “total” correction. Other lesions in which the coils are useful are arteriovenous fistulae, including systemic coronary-cameral, peripheral arteriovenous fistulae as well as pulmonary arteriovenous fistulae. These lesions can produce either left to right or right to left shunts. In these lesions it is critical to identify a stenotic or “end” vessel into which the device can be fixed very securely in order to reduce the dangers of embolization to an essential more distal vessel or vital structure in the systemic circulation. The 0.052 inch stainless steel coil In order to provide a more robust coil, a more occlusive coil and a coil particularly for use in the patent ductus arteriosus, the 0.052″ stainless steel coil was developed. The 0.052″ coil is a larger, stiffer version of the standard Gianturco™ coil with the wire of the coil being the heavier [...]... surrounding circulating blood and/ or the Bucrylate™ must be injected very specifically into the area Bucrylate™ was very difficult to handle and to control during delivery both during animal testing and during several clinical uses If injected too fast it embolized distally and/ or backward into proximal branches and, in doing so, occluded all areas that it entered If injected too slowly, it occluded the injecting... fibers intertwined in the spaces between the wire coils of the spring wire There, the similarity ends Target™ coil wires are made of very small diameter 0.014″ and 0.0 18 platinum wires In spite of their very small diameters, and because of the platinum material, these coils are very radio-opaque and easily visible under fluoroscopy in the catheterization laboratory Because of the material and tiny size... wire The mandril passing within the delivery/pusher wire and the coil acts as a stiffening “core” wire The mandril has a short segment of “spring” wire attached at its proximal end to serve to identify the proximal end and as a “hub” for moving and torquing the mandril Detachable™ coils commercially come stretched out as a straight spring wire positioned within a thin, clear, straight loading tube of... through a torque-controlled, 5- or 6-French guiding catheter The nylon 3-French infusion catheter (Cook Inc., Bloomington, IN) with a radio-opaque tip is less flexible than the SlipCath™ but also makes a good delivery catheter for delivery to more proximal areas in small, but less tortuous vessels The technique for loading and delivering the Tornado™ coil is similar to the delivery of a “free-release” Gianturco™... The mandril wire is advanced through the delivery/pusher wire and 8 10 mm beyond the distal tip of the “screw” mechanism of the delivery/ pusher Very carefully and without pushing the coil forward in the loader, the mandril is introduced into the proximal end of the coil by gentle trial and error probing and then advanced 8 10 mm into the hollow coil The delivery/pusher wire is advanced over the mandril... thrombosis and vascular occlusion, the wire should be capable of being wadded into a fairly compact mass Flexibility of the wire is accomplished by removing the straight, stiffening safety core wire(s) from inside of a standard stainless steel spring guide wire Once the safety core is removed from a spring guide wire, the remaining spring wire becomes very soft and can be compacted easily into a tight... available around the world and even in the United States in the past Although still available in some locations around the world, none of the detachable occlusion balloons are available any longer in the US market B-D Mini-Balloon™ The B-D Mini-Balloon™ occlusion device (Becton Dickson Co.) probably had the widest use in congenital heart defects when it was available12 These were very tiny occlusion devices... dislodging the original device/coil This is accomplished using a Terumo Glide™ (Boston Scientific, Natick, MA) wire and a tiny, end-hole-only catheter similar to crossing a freshly implanted coil in a PDA As the coil is being extruded from the catheter, which has passed through/past the original device/coil, the catheter is withdrawn into, or adjacent to, the original device/coil in order to catch or entwine... radio-opacity for injection into the circulation The particles mixed with dilute contrast are drawn out of their sterile container into a syringe and injected with the same syringe into the 673 CHAPTER 26 Vascular occlusions—miscellaneous vessels, fistulae desired site through a pre-positioned catheter Similar to the autologous clots and Gelfoam™, there is little control over the location where the particles... back into the delivery catheter As the coil is withdrawn into the catheter, the mandril remains positioned proximal to and outside of the coil If the same coil is to be repositioned using the same catheter, the mandril is re-advanced into the coil (which now is straightened within the catheter) before the coil is re-extruded into the vessel This retrievability during delivery adds total control and . minutes while off the prostaglandin infusion and the aortogram repeated. Often the combination of the irritation of the through -and- through wire/catheter, the pre- ceding manipulations during. the catheterization laboratory with the ductus patency maintained with the prostaglandin infusion. The infant is intub- ated and ventilated on 17– 18% oxygen. If the patient does not have an indwelling. creating a “through -and- through” route from a femoral vein, through the right heart and ductus, down the descending aorta and out through a femoral artery sheath/catheter. If the through -and- through

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