Cardiac Catheterization in Congenital Heart Disease: Pediatric and Adult - Part 6 ppt

CHAPTER 18 Coarctation dilation 464 completely. The sheath is withdrawn and pressure applied over the vessel manually. As soon as all the sheaths are out, the drapes over the patient are removed completely so that the lower abdomen and upper thigh areas adjacent to the entire inguinal area are visible. While holding pressure over the arterial puncture site with the fingers of one hand, a pulse distal to the puncture site (dorsalis pedis or posterior tibial) is palpated with the fingers of the other hand. The amount of pressure applied over the arterial puncture site is varied or “titrated” so that just enough pressure is applied to prevent bleeding (or a subcutaneous hematoma formation) while at the same time allowing the palpation of a peripheral pulse continually. In larger or heavier patients, it is better to apply pressure over the arterial site with a firm “roll” of “4 × 4s”, since the exact site of arterial puncture deep within thick subcutaneous tissues does not correspond at all to the site of the skin puncture and subsequent pres- sure. The pressure from the “roll” of bandage covers a wider area deep within the tissues and is more likely to control deep bleeding from the artery. The same tech- nique for monitoring the peripheral pulse is used while pressure is applied with the “roll” of bandage. In addition to the care of the local puncture sites, these patients are monitored systemically very closely in a recovery area for at least six hours. During this observa- tion period, they should have a secure intravenous line and receive a high maintenance infusion of 1/4 normal saline or Ringer’s lactate. The intravenous fluids are con- tinued for twelve hours. A patient following dilation of a coarctation of the aorta usually has diuresed during the procedure from both the contrast agents used and from the increased renal blood flow as a consequence of the relief of the coarctation. Often these patients start out “dry” from being NPO for a prolonged period of time before the procedure begins. The combination of these factors results in a very significant volume depletion, which, in turn, aggravates vagal or other vascular responses caused by the changes in the distribution of arterial blood flow. Surprisingly, post-dilation patients rarely suffer from the “post-coarctectomy” syndrome that is seen commonly following surgery. Dilation patients rarely have any aggravation of their upper extremity blood pressure, although the systemic pressures may not drop to normal immediately 13 . Post-dilation patients essentially never have abdominal discomfort and usually resume oral intake within 6–12 hours after dilation. There have been reports of serious post-procedure complications following the dilation of coarctations, so no matter how smoothly the procedure went, these patients are observed overnight. Although they may exhibit pain during the actual balloon inflation in the coarctation site, once the balloon is deflated, the pain subsides. Any persistent or recurrent pain should be taken seriously and investigated thoroughly. Dilation of coarctation neonates and young infants Coarctation of the aorta in the neonatal patient presents some unique features. These infants frequently present to the cardiologist catastrophically ill with heart failure, in acidosis and in shock. They frequently have additional defects, some of which complicate the catheter manage- ment and some of which actually help the catheter man- agement. The identification of any additional defects is made from the clinical examination and the echocardio- gram. The echo cannot consistently provide the details about the coarctation size, anatomy and severity, and fre- quently underestimates the size of the adjacent aortic seg- ments. Decisions about therapeutic intervention for the neonatal coarctation of the aorta should not be made entirely on the basis of the echo. A vigorous, but brief attempt is made at stabilizing infants who are less than three to four weeks old with vent- ilation, inotropics, volume support and prostaglandin. Stabilization attempts are continued only as long as the infant improves. If there is going to be any improvement in the clinical condition, it is noticeable within one to two hours. With, or without, the stabilization after that dura- tion of time, the infant is taken to the catheterization lab- oratory. If the infant is not responding noticeably to the resuscitative efforts, more time only allows further deteri- oration. If the infant is responding, the improvement will continue on the way to, and in, the catheterization labor- atory. The exact procedure performed depends upon the presence or absence of associated lesions and, when pres- ent, which associated lesions are present. Besides their general hemodynamic instability, the very small femoral arteries with the associated very weak or absent femoral pulses represent the greatest challenge for balloon dilation of coarctation of the aorta in the very small infant. In each individual case, the most expeditious technique possible is utilized to approach and treat the coarctation. Once the coarctation area has been reached with a catheter, the gradient is measured, the selective aortogram(s) performed and accurate measurements of the coarctation and adjacent vessels are made in order to choose the proper balloon. When the infant responds to the administration of prostaglandins with opening of the ductus arteriosus, the stabilization of the infant is usually rapid and very effect- ive. The presence of the patent ductus indirectly facili- tates access to the coarctation by improving perfusion to the lower extremities significantly, and increases the amplitude of the femoral pulses, which facilitates percuta- neous arterial access. The presence of a patent ductus, however, compromises the results of balloon dilation of a neonatal coarctation. Without the patent ductus, the CHAPTER 18 Coarctation dilation 465 balloon is constrained within the aorta and the “path of least resistance” is to crush the abnormal ridge of tissue within the aortic lumen. A wide open ductus arteriosus, on the other hand, allows the dilation balloon to move away from the coarctation “ridge” into the “ampulla” of the ductus rather than crushing or compressing the ridge. In addition, when the ductus does constrict during its nor- mal closure, it probably also constricts some of the adjac- ent aorta, recreating the coarctation. Most of the newborns and small infants with coarcta- tion do have at least a potential interatrial communication. In all of these infants, venous access is obtained and an angiographic catheter is introduced into at least the left ventricle from the venous approach. At the same time, in a small sick infant, no prolonged effort should be made at advancing this catheter from the left ventricle into the aorta, as is utilized in coarctation dilation in the older patient. The chambers and vessels are very small and the tissues “softer” and prone to puncture. The catheter in the left ventricle provides continual systemic pressure mon- itoring before, during and immediately after the dilation procedure. The pressure in the left ventricle reflects the severity of the coarctation unless there is associated aortic stenosis or the infant is in terrible heart failure. A left ven- tricular angiocardiogram is performed which provides some, and possibly, very good information about the coarctation and the overall anatomy. Infants who do not respond to prostaglandins and who have no associated lesions, and those who have associated aortic stenosis, are the most difficult for coarctation dilation. The echocardiogram should diagnose associated aortic stenosis and give an estimate of its severity, although either one of the two lesions can mask the significance of the other. The prograde left ventricular catheter is useful in these patients for monitoring pressures and for the administration of fluid and medication, and is possibly helpful in determining the relative severity of com- bined lesions. Percutaneous entry into the artery is accomplished with meticulous attention to detail, a very delicate single wall vessel puncture technique, and patience (as described in Chapter 4). The area around the expected arterial punc- ture site is infiltrated with local anesthesia, being as care- ful as possible not to puncture the artery with the needle during the infiltration. If the artery is punctured inadvert- ently, pressure is held over the site for at least 2–4 minutes before beginning the purposeful puncture of the artery. Special 21-gauge percutaneous needles and extra-floppy tipped 0.018″ or 0.014″ wires are essential for the percuta- neous entry into the artery in these patients. Once the artery has been entered with the guide wire, the area sur- rounding the puncture site is re-infiltrated liberally with local anesthesia. A 3- or 4-French “fine tipped” sheath/dila- tor is introduced into the artery. The preliminary diagnostic information about the coarctation is obtained with the re- trograde catheter. If the infant is still very unstable, an end and side hole multipurpose catheter is used. This type of catheter allows pressure measurements and quality aor- togram(s), and at the same time can be used to position the guide wire for the dilation without the necessity of even one catheter exchange. The second catheter previously positioned in the left ventricle helps to confirm the pres- ence of associated aortic stenosis. However, with poor left ventricular function and an associated coarctation of the aorta, even very severe aortic stenosis can be masked. Once the coarctation has been identified as the only significant lesion, it is measured accurately and the dilation of the coarctation is carried out as expediently as possible using the single-catheter, retrograde technique. It is preferable to stabilize the distal end of the guide wire in one of the subclavian arteries, although an excessively long time or effort should not be taken to achieve this loca- tion. The balloon for the coarctation dilation is chosen to equal the size of the smallest segment of the aorta adjacent to the coarctation. Once the dilation has been completed and the balloon removed over the wire, the end-hole catheter is re-advanced over the wire and very gently past the coarctation to the aorta proximal to the coarctation. The wire is removed and pressures are recorded simulta- neously through the catheter from the ascending aorta and through the side arm of the sheath from the femoral artery. A repeat aortogram is recorded, injecting through the end-hole catheter proximal to the coarctation site. The catheter should not be withdrawn across the coarc- tation site until all post-dilation studies or any re-dilation has been accomplished. If the dilation was unsatisfactory and a re-dilation is necessary, the wire is replaced through the catheter which is already across and well beyond the lesion in order that no catheter manipulation back across the freshly dilated area is necessary. When the catheter has been withdrawn across the area, it should not be manipulated back across the area 3 . Co-existent critical aortic stenosis and coarctation in infants When there is significant aortic stenosis in association with the neonatal coarctation, it is preferable to address the aortic stenosis first. In the presence of the combined lesions, perfusion of the coronary and cerebral circula- tions is dependent, at least partially, on the increased afterload in the ascending aortic pressure provided by the coarctation. Removing this afterload before opening the aortic valve could compromise the coronary and cerebral circulations even further. In addition, if the coarctation is dilated first, all of the manipulations (sometimes extens- ive) required for crossing the aortic valve, and the aortic valve dilation, will have to be through the freshly dilated CHAPTER 18 Coarctation dilation 466 coarctation site with the potential for traumatizing the already damaged aortic intima in the coarctation site even further. With combined aortic stenosis and coarctation, the diameters of the aortic valve annulus and the coarctation with the appropriate adjacent aortic diameters are meas- ured from a left ventricular angiocardiogram or an aortic root injection before an attempt is made to pass a catheter across the stenotic valve. A left ventricular angiocardio- gram is obtained with injection through a prograde left ventricular catheter, while the aortic root injection is obtained with the retrograde multipurpose or angio- graphic catheter that has been manipulated past the coarc- tation and around the arch to the aortic root. Once the valve and coarctation measurements are obtained, the appropriate dilation balloon for the aortic valve dilation is prepared using the “minimal prep” technique but with a prolonged attempt at removing all air. No attempt is made to cross the aortic valve until the balloon for the dila- tion is prepared and “poised” for introduction. These infants are often so precarious that even a tiny 4-French catheter crossing the stenotic orifice is enough to cause a rapid decompensation in their hemodynamics. To cross these valves, a 0.018″ or 0.014″, very floppy tipped, exchange length, torque-controlled, coronary artery, guide wire is advanced through a multipurpose or selective right coronary catheter which is already posi- tioned in the aortic root. The wire is advanced out of the catheter and multiple, rapidly repeated, short probes are made toward the aortic valve area with the very soft wire tip. Because even a very soft tipped wire exiting the tip of the catheter can be very stiff for the first few millimeters out of the tip, the tip of the catheter is kept a centimeter away from the valve annulus during the probes with the tip of the wire. The tip of the wire is redirected within the aortic root by simultaneously rotating the catheter (to change the anterior to posterior direction) and moving the catheter to and fro (to change the right to left side angle). Unless another wire or catheter is already passing through the valve, the exact location of the orifice really is not known. The more “probes” that are made with the wire along with multiple changes in the angle of the wire, the more likely is the chance of the wire passing through the orifice of the “invisible” valve. If the wire does not cross the valve after trying for several minutes using the original multipurpose catheter, the multipurpose catheter is replaced with a preformed, either right or left coronary catheter and the “probing” at the valve repeated with similar changes in direction of the catheter tip. The tighter, preformed curves at the tips of coronary catheters allow a greater ability to change the angle of approach toward the small valve orifice. Once the wire crosses the valve, it is advanced as far as possible into the ventricle, hopefully even looping the soft tip within the left ventricle apex. With the wire passed as far as possible into the ventricle, the catheter is advanced over the wire into the ventricle. If the infant’s hemody- namics do not remain stable with the catheter across the valve, the wire is fixed in the ventricle and the catheter is immediately removed and replaced rapidly over the wire with the previously prepared balloon dilation catheter. The dilation of the valve is carried out with as rapid an inflation and deflation as possible and while recording angiographically or on “stored fluoroscopy”. After the inflation/deflation, the balloon is immediately with- drawn out of the valve over the wire into at least the ascending aorta. If the infant remains stable with the end-hole catheter passed through the valve, the wire is removed. A “pig- tail” is formed on the tip of the long floppy tipped, stiffer, exchange guide wire and a 180° curve is formed on the transition zone between the long floppy tip and the stiff shaft of the wire. This individually formed wire is re- advanced through the catheter into the left ventricle. The preformed “pig-tail” on the wire keeps the wire from digging into the myocardium as it is manipulated in the ventricle. The 180° curve at the transition area of the wire directs the tip of the wire back toward the left ventricular outflow tract and allows the stiff portion of the shaft of the wire to be positioned further across the valve. With the wire maintained in position, the catheter is removed and replaced with the already prepared balloon catheter. The balloon is positioned across the valve and the inflation performed while recording the inflation angiographically or on “stored fluoroscopy”. The inflation/deflation is per- formed as rapidly as possible. During the inflation the left ventricular pressure increases and the infant develops bradycardia. As soon as the deflation of the balloon is complete, the balloon is withdrawn over the wire and out of the aortic annulus. The infant’s heart rate should return and the left ventricular pressure will drop to normal levels. The return of a good heart rate and a good, but lower, left ventricular pressure are immediate indications of the success of the dilation. Ideally, there will be a lower left ventricular pressure, but in the presence of the associated coarctation, the gradient may be “moved downstream” to the coarctation site with little lowering of the left ventricu- lar pressure. The radiographic recording of the inflation/ deflation is reviewed. If a “waist” appeared on the balloon and then disappeared during the inflation, some true dilation of the valve orifice is assumed. The balloon is withdrawn back to the area of the coarctation. If the dia- meter of this balloon is smaller, or, at least, no more than a millimeter larger, than the measurement of the smallest diameter of the aorta adjacent to the coarctation, the coarctation site is dilated with the same balloon. If the bal- loon is two or more millimeters larger than the adjacent aorta in the area of the coarctation, the balloon is replaced CHAPTER 18 Coarctation dilation 467 with an appropriate diameter balloon and the coarcta- tion dilated. After both the aortic valve and the coarctation have been dilated the balloon is removed and replaced with a catheter to re-evaluate the hemodynamics. If there is a left ventricular catheter in place, the “net” results of the com- bined dilation are determined by measuring the left vent- ricular and femoral artery pressures simultaneously using the side arm of the sheath for the femoral artery. If the net left ventricular to femoral artery gradient is low, it is assumed that both procedures were successful and the procedure can be concluded. A left ventricular angiocar- diogram through the prograde catheter provides visual- ization of both the aortic valve and the coarctation area. An end-hole catheter is passed over the wire to the left ventricle and the retrograde wire removed. Pressures are recorded on withdrawal of the retrograde catheter from the left ventricle, to the aorta and across the coarctation site to quantitate the residual gradients at each area. If the net gradient is still significant, the culprit lesion(s) is/are identified from the pressures and angiograms. If there is no prograde catheter in the left ventricle, the results of the dilations must still be determined. A Multi- Track™ catheter provides the most “secure” way of iden- tifying the major residual problem without having to remove the wire from the left ventricle. Pressures are recorded and angiograms are performed through the Multi-Track™ catheter anywhere along the course from the left ventricle to the descending aorta and all without having to remove the wire, which can be maintained posi- tioned in the left ventricle. A small, stiff wire is placed in the true catheter lumen of the Multi-Track™ catheter to stiffen and support the catheter shaft as Multi-Track™ is being advanced over the exchange wire. Once the Multi- Track™ catheter is in the left ventricle, the wire within the true lumen is removed. Angiograms are performed where appropriate and pressures are recorded as the Multi- Track™ is withdrawn over the exchange wire. When a significant area of residual obstruction is identified, the decision is made whether this should or can be treated from the pressures, the review of the balloon dilations and the current angiograms performed through the Multi- Track™ catheter. If a lesion is to be re-dilated, the Multi- Track™ is removed over the wire and the appropriate balloon dilation catheter reintroduced to the culprit lesion. If a Multi-Track™ catheter is not available or cannot be used with the particular system, then an end-hole, multi- purpose catheter is advanced over the wire to the left ventricle and the exchange wire removed. Pressures are recorded and sequential angiograms are obtained through this catheter as it is withdrawn from the left vent- ricle to the ascending aorta and from the ascending aorta to the descending aorta. This, of course, removes the pre- viously secure wire access back into the ventricle! If the significant or predominant gradient is at the aortic valve, the catheter withdrawal is stopped in the aortic root and a decision is made as to whether further catheter therapy is possible. If the aortic valve is to be re-dilated, the soft floppy tipped wire is reintroduced through the catheter and manipulated across the aortic valve into the left ven- tricle. The dilation procedure is repeated with a more appropriate diameter balloon. If there is a significant net left ventricle to femoral artery gradient, but little or no gradient at the aortic valve, the coarctation is still the culprit. The previous coarcta- tion dilation is reviewed. If a larger balloon can be used, the wire is reinserted into the catheter and positioned in the aortic root before the catheter is withdrawn across the coarctation. The end-hole catheter is removed over the wire, the appropriate diameter balloon is passed over the wire and the coarctation re-dilated. Reassessment of the result depends upon which catheters are available, as described above. Whenever an infant is found to have coarctation of the aorta with aortic stenosis, associated mitral stenosis of some type and degree should be suspected. The Shone’s complex of multiple left heart obstructive lesions includes various types of mitral valve stenosis along with the coarctation and aortic stenosis, and frequently results in an even sicker infant. Any one, or all, of the levels of obstructive lesions can be severe and require intervention, however usually the coarctation and aortic lesions are the most pressing and are the only ones that can be addressed reasonably in the newborn period. Congenital mitral stenosis can be treated by balloon dilation in the slightly older child, and is addressed separately in Chapter 20. The most favorable associated lesions in an infant with coarctation that need dilation are a ventricular septal defect (VSD) and transposition of the great arteries. A VSD provides access to the aorta from the right heart and in turn from the venous access. Although access to the coarctation through the VSD is anticipated, these infants should have an indwelling arterial line for systemic pres- sure monitoring. In these patients, a curved tipped, end- hole or multipurpose catheter introduced through a short sheath from a percutaneous venous introduction is used for the “right heart” procedure. In infants, when manipu- lating a venous catheter from the right ventricle toward the outflow tract, as the catheter is torqued clockwise, it frequently and, even preferentially, passes dorsally through the ventricular defect and, from there, into the ascending aorta. Otherwise, with purposeful manipula- tion of the catheter dorsally and cephalad from the right ventricle, entering the aorta almost always is accom- plished in infants with a significant VSD. From there, approaching the coarctation around the arch is a straight- forward procedure with a wire and curved tip catheter. A selective aortogram is performed and the lesion and CHAPTER 18 Coarctation dilation 468 adjacent vessels measured accurately. The coarctation is crossed with a prograde end-hole catheter and the catheter is exchanged for the exchange length, stiff, guide wire. The balloon is introduced from the vein and advanced through the right ventricle, through the VSD and to the coarctation. The dilation is accomplished all prograde from the venous entry site without the need for even a 3-French sheath in a femoral artery. The post- procedure measurements are carried out with an end-hole catheter replacing the balloon catheter in the aorta before the “prograde” guide wire is removed. The same ability to perform a dilation of a coarctation from a venous access holds true for infants with coarcta- tion of the aorta in association with transposition of the great arteries (with or without a ventricular septal defect or aortic or pulmonary override). This is a particularly common association in patients with the so-called Taussig– Bing complex of transposition of the great arteries, ven- tricular septal defect and pulmonary artery override. A standard end-hole or a balloon “wedge” catheter passes easily from the right ventricle and out into the aorta. With minimal manipulation the catheter is maneuvered into the descending aorta to the coarctation. The diagnosis and dilation are performed similarly to that in the infant with an associated VSD. Intravascular stents in coarctation of the aorta The use of intravascular stents for the treatment of coarc- tation of the aorta has become the primary approach for coarctation in the larger adolescent and adult. The use and advantages of intravascular stents in both native and re/residual coarctation are covered in detail in Chapter 25. Their use in conjunction with dilation of coarctation of the aorta has changed the approach to these lesions dra- matically. Intravascular stents not only support the ves- sels at the maximal dilated diameter of the balloon, but also, in doing so, eliminate the need for any over-dilation of the vessel. However, the basic rules for the implant of intravascu- lar stents in pediatric and congenital lesions apply even more stringently to their use in coarctations. In particular, no stent should be implanted in the aorta if it cannot be dilated up to the ultimate adult diameter of the aorta in that particular patient. This “rule” so far has precluded the rea- sonable and/or sensible use of stents in coarctation of the aorta in infants and small children. The implant of a stent that cannot be dilated to the diameter of the adult aorta, creates a new, very fixed diameter coarctation as the patient grows. A coarctation with a stent in place, which is too small for the aorta and which cannot be dilated fur- ther, must be managed surgically. There is a much higher risk for surgery on a coarctation with a stent in place than for the surgical repair of native coarctation, even in an infant. The narrow segment of aorta that contains the stent, at the very least, must be “filleted” open and then patched, if not totally resected or bypassed with a pros- thetic graft. At the same time, this same patient who requires such extensive surgery on the aorta, no longer has the extensive collaterals to protect the spinal cord and the lower half of his body. Hopefully, the further develop- ment of “open ring” stents or some type of resorbable stent, will eventually make it possible to use stents in the initial treatment of coarctation in infants and children. In the interim, balloon dilation of coarctation is very effective in infants and children. Even if the obstruction of the coarctation is not eliminated totally with an initial dilation, or even with several balloon dilations, if the aorta is not over-dilated and torn or ruptured, a successful bal- loon dilation with a stent implant can be accomplished when the patient reaches adolescence or adulthood. For the infant and child, a “conservative” dilation of both native and re/residual coarctation should be the primary approach to these lesions. Complications specific to coarctation dilation The majority of the early dilations reported in the Valvuloplasty and Angioplasty of Congenital Anomalies (VACA) registry were for re-coarctation of the aorta and, as a consequence, the majority of the acute complications were in these re-coarctation dilations. In the VACA series of re-coarctation dilations there were five deaths (two vagal, one aortic rupture, one CNS death and one death due to shock) 1 . A better understanding of the effect of the post-dilation vasodilation and the exaggerated physiologic vasovagal response to the pressure drop associated with dilations has helped to eliminate the extreme vasovagal response to the procedure. The patients are maintained on a high maintenance volume of intravenous fluids during the dilation and this fluid infusion is maintained for six to twelve hours after the dilation. The intravenous access is left in place until after the patient is ambulated. With these precautions, the vasovagal type reactions have been eliminated. Significant central nervous system (CNS) injuries and at least one death attributed to CNS injury have been reported following dilation of coarctation of the aorta. The exact etiology of all of the CNS injuries has never been determined unequivocally. Fortunately, with more atten- tion to the position of the distal end of the guide wire for support of the dilation balloon and extremely stringent precautions concerning emboli from the materials and/or the procedure, the central nervous system complica- tions essentially have been eliminated. It is critical that the CHAPTER 18 Coarctation dilation 469 distal end of the support wire is not positioned in a carotid or vertebral artery or possibly even in the ascending aorta. Catheters passed over wires are maintained on a contin- ual flush in order to eliminate any accumulation of blood and clot around the wire within the catheter or at the wire–catheter interface. Flushing over the wire is accom- plished by introducing the wire through a wire back- bleed valve with a flush side port, which is attached to the hub of the catheter. The side port of the wire back-bleed valve is maintained on continual flush from the pres- sure/flush system. In spite of the theoretical potential for an aortic tear, patients undergoing coarctation dilation are heparinized fully with the hope of eliminating clot forma- tion on the wires or catheters. Although possible, acute, through and through tears in the aortic wall from the dilation of coarctations have been exceedingly rare. One report early in the history of dila- tion of coarctation of the aorta was in a patient with re-coarctation of the aorta who had remarkably little or no reaction or scar formation from the prior surgery and apparently little or no reaction to the acute local injury. The patient had a through and through tear in the aortic wall and eventually succumbed to the lesion. Possibly, aortic tears cannot be avoided unequivocally, however it appears likely that aortic tears can be prevented by less aggressive initial dilation of aortic coarctations and not over-dilating any segment of the aorta adjacent to the area of the coarctation by measuring that area of the aorta and using that measured diameter to determine the diameter of the balloon for the dilation. Dilation of a typical “native” coarctation presumably tears a “membrane” that lies across the lumen of the aorta and does not extend the tear significantly into the wall of the aorta. Dilation of an equally tight “re or residual” coarctation probably involves dilation of the actual wall of the aorta which has con- stricted down in the area of the previous therapy and, as a consequence, these should be dilated more conservatively. Most patients exhibit pain acutely during the process of inflating a balloon in the aorta, however the pain subsides when the balloon is deflated. If a patient has persistent pain after acute dilation of the coarctation, the area of the coarc- tation should be investigated carefully with selective aortography or intravascular ultrasound in the area of the dilation. Even without identifying a tear, the patient should be observed in the catheterization laboratory until the pain subsides or for one or more hours if the pain persists. If a through and through tear with progressive extravasation is detected, the balloon is reinflated at a low pressure in the area of the tear. The inflation is just enough to “tamponade” the vessel and allow the patient to be taken to the operating room for a repair. Such a surgical aortic repair certainly will require relatively prolonged cross clamping of the aorta and in turn, may require femoral vein to femoral artery bypass. There has been one report of paraplegia following a balloon dilation of a re/residual coarctation of the aorta in a small infant with associated complex congenital heart disease 14 . The prior surgery on the aorta had involved an uncomplicated end-to-end anastomosis. There was no pro- longed ischemia, no evidence of aortic tear nor any evid- ence for embolic phenomena to explain the paraplegia. In the early reported series of coarctation dilation, there was an 8.5% incidence of significant enough injury to the arterial introductory site to require intervention or have permanent sequelae at the entrance site into the vessel. In those early years of balloon dilation, the balloon dilation catheters were very large and the balloons themselves were large and grotesque by today’s standards. All of the balloons greater than 6 mm in diameter were on 9-French catheter shafts, the balloons were relatively thick walled and they did not fold well around the catheter so that the balloon “mass” had a very large profile. In order to be introduced through a sheath these balloons required an 11- or 12-French sheath! As a consequence to “reduce the size” of the entry hole into the vessel most of these early balloons were introduced into the vessels directly over a wire without a sheath in the vessel. This in fact probably did not reduce the diameter of the “hole” in the vessel wall and certainly contributed to significantly more local trauma to the vessel walls. Considering the balloon catheters used at that time, the incidence of arterial injury actually was remarkably low! Many refinements in the balloons with marked reduc- tion in the size of the catheter shafts and decrease in the balloon profiles have not only allowed a smaller “hole” for introduction into the vessel, but have also allowed dilation balloons routinely to be introduced through indwelling sheaths. With the combination of smaller balloon profiles, routine use of indwelling sheaths, very meticulous care of the introductory sites into the arteries, liberal, repeated use of local anesthesia, heparinization (perhaps?), and personal attention to the site during hemostasis after the balloon/sheath is removed, local vessel injury is now very rare. When an acute arterial injury does occur, it is treated aggressively at the time of the catheterization. With an absent pulse, the patient is continued on heparin therapy for one or two hours or until the pulse returns. If there is no return of a pulse within 1–2 hours the patient is either begun on thrombolytic therapy with continued heparin or is taken back to the catheterization laboratory for a mechanical recanalization of the vessel, as described in Chapter 34 on purposeful perforations. With only a 20-year history of balloon dilation of coarcta- tion of the aorta, any long-term adverse sequelae from the procedure are as yet unknown. The “longer-term” adverse sequelae that have occurred so far, seem to occur more with the dilation of “native” coarctation of the aorta CHAPTER 18 Coarctation dilation 470 where the aorta is not “protected” by a surrounding area of scar tissue, as is found around the re-coarctations. The most bothersome finding after coarctation dilation is the creation of an “aneurysm” at the site of the coarctation dilation. The incidence of these aneurysms has varied markedly in different series, but in general they are rare. The “aneurysms” are usually a small out-pouching in the aortic wall in the area of the balloon dilation. This out-pouching is usually apparent immediately after the dilation. In most cases the out-pouching does not enlarge and in fact seems to remodel into the aortic wall along with the overall remodeling of the aorta. The out-pouching of the aorta is considered an aneurysm when the area “remodels” into a persistent, discrete out-pouching. There are no reported long-term adverse consequences of the aneurysms, however, in at least one series, several of the patients with an aneurysm did undergo surgery for it. The indication for the surgery was not because of any clinical problem due to the aneurysm, but because of the fear of what might happen to the aneurysm over time. The pathology of those aneurysms that were operated upon showed tears through the intima and media of the vessel wall. Some aneurysms have been followed for as long as 18 years with no increase in their size and no sequelae. Aneurysms of the aorta following surgical repair are not uncommon. These aneurysms are more frequent when there is a persistent narrowing of the aorta proximal to the coarctation repair site or when the surgical repair was carried out with a patch angioplasty. These post-surgical aneurysms are large saccular dilations of the entire area of the coarctation/aorta distal to the more proximal “obstruction”. Most of these aneurysms continue to grow with time and most have been referred for surgical revision. The total incidence of aneurysms following coarcta- tion dilation initially was small and actually seems to be decreasing and, possibly, not occurring at all in more recent series. In the earlier days of coarctation dilation, the measurements of the coarctation and the adjacent vessels were less accurate, and less attention was paid to the narrow adjacent structures. Often, marked over-dilation of these areas was carried out with balloons significantly larger in diameter than the adjacent vessel, either because of the inaccuracies in measurement or purposefully in an attempt to achieve a more lasting result. Perhaps the more conservative dilations done with the knowledge that the aorta can be dilated further later or can be held open with an intravascular stent without the need for any over- dilation will totally eliminate the aneurysms associated with coarctation dilations. When a discrete aneurysm does occur, it should be followed closely, probably at least every one or two years with repeated CT, MRI, or angiographic imaging. A discrete aneurysm can be excluded by a stent graft (large covered stent) or covered with a standard intra- vascular stent to support the aortic wall in the area and then to have coils packed into the aneurysm behind the intravascular stent. Conclusion Balloon dilation is an accepted standard treatment for both native and re/residual coarctation of the aorta in patients of all ages in many major cardiovascular centers dealing with congenital heart disease. The safety of the acute procedure now appears to be very good, perhaps because of a better understanding of the lesions and a more conservative approach to the dilation procedure. A patient who undergoes a conservative dilation of coarc- tation of the aorta and who has a less than optimal result, but at the same time has no complications, can always have the dilation of the coarctation repeated with, or without, the implant of an intravascular stent to “complete” the procedure. The success of dilation of coarctation of the aorta over the years and the reduction in the complications and the difficulties with repeat surgery on patients with re/residual coarctation have made dilation of native and re/residual coarctation the procedure of choice in most centers. Most centers stipulate that all patients who have dilation of any type of coarctation of the aorta should be followed indefinitely. In patients who are, or are at least near to, full-grown many centers now regularly perform primary intravascular stent implants along with dilation of coarctation of the aorta. The use of stents in coarctation of the aorta is covered in detail in Chapter 25. References 1. Hellenbrand WE et al. Balloon angioplasty for aortic re- coarctation: Results of the Valvuloplasty and Angioplasty of Congenital Anomalies Registry. Am J Cardiol 1990; 65: 793–797. 2. Tynan M et al. Balloon angioplasty for the treatment of native coarctation: Results of the Valvuloplasty and Angioplasty of Congenital Anomalies Registry. Am J Cardiol 1990; 65: 790–792. 3. Finley JP et al. Balloon catheter dilatation of coarctation of the aorta in young infants. Br Heart J 1983; 50: 411–415. 4. Lock JE et al. Balloon dilation angioplasty of aortic coarcta- tions in infants and children. Circulation 1983; 68(1): 109–116. 5. Kappetein AP et al. More than thirty-five years of coarctation repair. An unexpected high relapse rate. J Thorac Cardiovasc Surg 1994; 107(1): 87–95. 6. Wada T et al. Prevention and detection of spinal cord injury during thoracic and thoracoabdominal aortic repairs. Ann Thorac Surg 2001; 72(1): 80–84; discussion 85. CHAPTER 18 Coarctation dilation 471 7. Kalita J et al. Evoked potential changes in ischaemic myelo- pathy. Electromyogr Clin Neurophysiol 2003; 43(4): 211–215. 8. John CN et al. Report of four cases of aneurysm complicating patch aortoplasty for repair of coarctation of the aorta. Aust NZ J Surg 1989; 59(9): 748–750. 9. Fletcher SE et al. Balloon angioplasty of native coarctation of the aorta: midterm follow-up and prognostic factors. J Am Coll Cardiol 1995; 25(3): 730–734. 10. Anjos R et al. Determinants of hemodynamic results of bal- loon dilation of aortic recoarctation. Am J Cardiol 1992; 69(6): 665–671. 11. Bonhoeffer P et al. The multi-track angiography catheter: a new tool for complex catheterisation in congenital heart dis- ease. Heart 1996; 76(2): 173–177. 12. Joseph G, Mandalay A, and Rajendiran G. Percutaneous recanalization and balloon angioplasty of congenital isolated local atresia of the aortic isthmus in adults. Catheter Cardiovasc Interv 2001; 53(4): 535–541. 13. Choy M et al. Paradoxical hypertension after repair of coarc- tation of the aorta in children: balloon angioplasty versus surgical repair. Circulation 1987; 75(6): 1186–1191. 14. Ussia GP, Marasini M, and Pongiglione G. Paraplegia follow- ing percutaneous balloon angioplasty of aortic coarctation: a case report. Catheter Cardiovasc Interv 2001; 54(4): 510–513. 472 Introduction In most major pediatric centers balloon dilation of the aor- tic valve in the cardiac catheterization laboratory is the accepted standard for the primary treatment of aortic valve stenosis. Balloon dilation of aortic valve stenosis to treat valvar aortic stenosis was first published in 1984 1 . Balloon dilation of the aortic valve provides palliation that is comparable to the palliation for similar aortic valve stenosis achieved by a surgical aortic valvotomy, but without the risks and morbidity of surgery 2,3 . Significant improvements in the dilation balloons, guide wires and techniques over the past 15 years have improved the suc- cess rate and decreased, but not eliminated, the morbidity and mortality of the aortic dilation procedure for infants, children and adolescents. The indications for dilation of the aortic valve are similar to the indications for surgical aortic valvotomy and, as with the indications for surgery, the indications for balloon dilation vary with the age of the patient. In the newborn the diagnosis of aortic valve stenosis comprises a very heterogeneous spectrum of anatomy, including everything from a nearly atretic aortic valve with a small aortic annulus and/or an associated very small, hypoplastic left ventricle, to an equally stenotic valve, but with a large, dilated poorly functioning left ventricle. The exact anatomy and the resultant left ventric- ular function determine the indications for balloon dila- tion in this group. The echocardiographic demonstration of aortic valve stenosis with associated poor left ventricu- lar function or low cardiac output, particularly with an otherwise “normal” sized left ventricle, is a major indi- cation for intervention in a newborn regardless of the measured gradient by either echo or catheterization 4 . After the clinical evaluation along with a quality echocar- diogram, the definitive diagnosis of valvular aortic steno- sis is established by the hemodynamics obtained in the catheterization laboratory. In the older infant and young child with clinical findings of aortic valve stenosis, the indication for valvotomy is determined from the peak to peak hemodynamic gradient measured across the valve in the catheterization laboratory. In the absence of any signs of “poor ventricular function”, aortic valve dilation is per- formed arbitrarily in very young children for a peak to peak gradient greater than 65 mmHg across the valve. Very young children do not participate in organized, severely strenuous, or sustained physical activities and do not create much additional gradient with their level of activ- ity. In adolescent and adult patients, who are more likely to participate in severely strenuous or sustained physical activity, symptoms referable to the heart or a measured peak to peak gradient across the valve of over 50 mmHg is the arbitrary indication for valve dilation. These criteria were established for a surgical aortic valvotomy on the basis of “natural history” studies, and probably are too conservative for balloon dilation of the aortic valve. TechniqueCgeneral General anesthesia with intubation and controlled venti- lation is used in newborns, in critically ill patients with aortic stenosis, and in any patient in whom the carotid artery approach is being used. The same general proced- ure is used for the “diagnostic” cardiac catheterization of the patient who is not critically ill but who is undergoing aortic dilation, as is used for the catheterization of any other patient. The catheterization is performed under deep sedation and local xylocaine anesthesia with supple- mental sedation given intravenously periodically through- out the procedure. A secure peripheral intravenous and an arterial line are established and an indwelling “Foley” catheter placed in the bladder in all patients past infancy who are undergoing a balloon dilation of the aortic valve. There are several different approaches and techniques utilized to accomplish balloon dilation of a stenotic aortic valve. The specific technique used depends upon the 19 Aortic valve dilation CHAPTER 19 Aortic valve dilation 473 particular circumstances of each individual patient and also on the individual preferences of the operator and/or the catheterization laboratory. The aortic valve can be approached retrograde from the femoral, brachial, um- bilical, or carotid arteries. The aortic valve can also be approached prograde from the right heart after passing into the left heart through either a patent foramen ovale or by crossing through the intact atrial septum with a transseptal puncture. The atrial transseptal approach to the left atrium is the preferred technique to acquire the left heart hemodynamics and angiography when the atrial septum is intact, while the retrograde approach through the femoral arteries is the most commonly used approach for the actual balloon dilation of the aortic valve. A double- balloon dilation of the valve using a retrograde approach from both femoral arteries is preferred for most aortic valve dilations 5 . Technique For the combined prograde and retrograde approach to the aortic valve dilation procedure, a short venous sheath is introduced into one femoral vein and two very small indwelling arterial cannulae are introduced into both the right and left femoral arteries. The right heart catheteriza- tion is performed using an angiographic “marker” catheter introduced through the short venous sheath. When a transseptal procedure is to be performed and there are any concerns about or a peculiarity of any part of the anatomy of the left heart, an angiocardiogram is per- formed with injection into the pulmonary artery before the transseptal puncture. The recirculation of the contrast through the left atrium and left ventricle clearly demon- strates the exact positions and any peculiarities of the left heart anatomy. The left heart hemodynamics are obtained by means of a prograde left heart catheterization either through a pre- existing interatrial communication or through a trans- septal atrial puncture. Using the prograde approach to the left heart, all of the hemodynamics, as well as quality, select- ive left ventricular or aortic angiograms, are obtained before any “time” is incurred in the arteries with the larger indwelling arterial sheaths. When the necessary right heart information has been obtained, the prograde venous catheter is advanced into the left atrium and from there into the left ventricle. Pressures are recorded from the left ventricle and the femoral arteries, and the left ventricular angiography is obtained to determine the severity and type of the aortic stenosis. In the absence of a pre-existing atrial communication, the right heart catheter and short venous sheath are replaced with a transseptal set of the largest French size the patient can accommodate comfortably and safely. The long sheath of the transseptal set should have an attached back-bleed valve with a side arm/flush port. A trans- septal left atrial puncture is performed using the long sheath/dilator transseptal set as described in detail in Chapter 8. Once the long sheath is positioned in the left atrium and the sheath and its back-bleed valve apparatus are cleared meticulously of all air and clots, the side port of the sheath is attached to the pressure/flush system. At this time in the procedure, the patient is given 100 mg/kg of heparin through the long sheath. An angiographic catheter one French size smaller than the sheath is advanced through the sheath and manipulated from the left atrium into the left ventricle. Simultaneous pressures are re- corded from the left atrium, left ventricle and a femoral artery. With the knowledge that the femoral artery pres- sure can be as much as 20 millimeters higher than the aor- tic root pressure as a result of the elastic recoil of the systemic vasculature, this measured difference in pres- sures between the left ventricle and femoral artery gives an estimate, but does not give an accurate measurement of the true transvalvular aortic gradient. Following the transseptal puncture and when the initial pressures have been recorded, a selective biplane angio- cardiogram is performed with an injection into the left ventricle. The angiocardiogram defines the precise anatomy of the aortic root and the aortic valve stenosis, and demonstrates any associated left ventricular outflow track abnormalities. At least one view of the angiocardio- grams should be as close to perpendicular to the valve annulus as possible. The lateral (LAT) X-ray tube is placed in a 60° left anterior oblique position with between 30° and 60° cranial angulation. The amount of cranial angulation is determined by how horizontally the heart is situated in the chestathe more horizontally the heart lies in the thorax, the greater the cranial angulation. The posterior– anterior (PA) X-ray tube is placed in a 30°, right anterior oblique position with 30+° of caudal angulation. The PA tube should be almost perpendicular to the LAT tube in both planes. If the valve is not cut precisely on edge with the initial picture, the X-ray tubes are rotated appropri- ately and the angiocardiogram repeated. Very accurate angiographic measurements are made of the diameter of the valve annulus at the base of the aortic sinuses where the valve leaflets attach or “hinge” in the annulus. The meas- urements are obtained from a systolic frame where the leaflets are open and the annulus is at its largest diameter during the cardiac cycle. The measurements must be cali- brated against a valid reference measurement system. Depending upon the measurement system in the particu- lar laboratory, an exact determination of the actual dia- meter of the valve annulus is made or calculated utilizing an accurate reference system for calibration of the measure- ments. As discussed earlier in Chapter 11, the use of the diameter of a catheter as the reference measurement is not [...]... placed on a slow continuous flush The transseptal sheath remains in the left ventricle and the catheter in the descending aorta before, during and after the dilation procedure This allows simultaneous aortic and left ventricular pressure monitoring and recording during and immediately after the dilation procedure In addition, both the catheter in the aorta and the transseptal sheath in the left ventricle... while maintaining the wire in its position well into the descending aorta and through the long sheath and, at the same time, the tip of the sheath is maintained near the left ventricular apex Each balloon dilation catheter is introduced over the wire into the long sheath in the femoral vein and advanced to the aortic valve, all of the time maintaining the sheath and the catheter lumen on a continuous flush... endotracheal intubation for control of their respiration and to keep the head and face out of the “operating” field in the neck The carotid approach for the dilation is usually used in conjunction with a prograde catheter from a systemic vein and a separate indwelling femoral arterial monitoring line The majority of the hemodynamic and anatomic information is obtained through these lines before the carotid cut-down... sheath, is “pulled” or softened in heat and then formed into at least a 180° curve at the distal end The balloon angiographic catheter is introduced into the long sheath and advanced through the sheath and into the left ventricle During the introduction and the entire time the balloon catheter is being advanced within the sheath, both the sheath and the catheter are maintained on a constant flush Once... time to the procedure The prograde catheter and indwelling arterial line actually simplify and add to the safety of the procedure The venous prograde catheter in the left ventricle and the separate indwelling femoral arterial line provide continuous left ventricular and systemic arterial pressure monitoring before, during and after the dilation without having to cross the aortic valve repeatedly with... the wires are observed continuously and maintained precisely and securely in their positions during the introduction of the balloons through the sheath and during the process of advancing the balloon catheters retrograde around the arch The portions of the wires that are outside of the body are maintained straight and are fixed against a firm structure on the table (or against the patient’s leg) 477... stenosis Catheter Cardiovasc Interv 2002; 56( 4): 5 16 –520; discussion 521 491 20 Mitral valvuloplasty Introduction In the more developed countries of the world, mitral stenosis in children is predominately congenital in origin and, fortunately, is a relatively rare abnormality1 The stenosis in the congenitally malformed mitral valve has multiple variations and involves all parts of the mitral valve apparatus... prepared using a “minimal prep” technique The stenotic aortic valve is crossed only after the balloon has been prepared and is ready to be introduced These infants are so precarious that the 3- or 4-French catheter alone crossing the stenotic orifice is enough to occlude the orifice and cause the infants to decompensate acutely and occasionally irreversibly A 3- or 4-French, pre-curved right or left Judkins™... dilation sheath/dilator/wire passes into the descending aorta from the right carotid artery cut-down and has to be withdrawn and maneuvered specifically back into the aortic root Alternatively, the wire may pass directly into the left ventricle during its initial introduction When the sheath is in the proper position in the ascending aorta, the dilator and wire are removed and the sheath is cleared meticulously... curves (passing from the umbilical to the iliac artery and from the descending to the ascending aorta) As a consequence, torque control and to -and- fro control over the catheter are restricted markedly In addition, the “push” on the proximal shaft of the catheter entering the umbilical artery must be toward the groin and, counter-intuitively, “away” from the direction of the aortic root Finally, there . 69 (6) : 66 5 67 1. 11. Bonhoeffer P et al. The multi-track angiography catheter: a new tool for complex catheterisation in congenital heart dis- ease. Heart 19 96; 76( 2): 173–177. 12. Joseph G, Mandalay. are observed continuously and maintained pre- cisely and securely in their positions during the introduc- tion of the balloons through the sheath and during the process of advancing the balloon. systemic vein and a separate indwelling femoral arterial monitoring line. The majority of the hemodynamic and anatomic information is obtained through these lines before the carotid cut-down is initiated.