Therapeutic Cardiac Catheterization



Therapeutic Cardiac Catheterization


Charles E. Mullins



Although very few procedures and/or specific devices are “approved” for use in pediatric and congenital heart lesions in the United States by the Food and Drug Administration (FDA), therapeutic catheterization procedures now not only are accepted worldwide by knowledgeable physicians but also represent the primary indication for performing cardiac catheterizations in congenital heart patients. For more than five decades, cardiac catheterizations have been the definitive diagnostic tool for all cardiac diseases. The diagnostic cardiac catheterization allows establishment of the hemodynamic quantification of normal and abnormal physiologies of the heart. With the addition of selective biplane angiography to the diagnostic catheterization, the anatomic defects can be defined very precisely. Catheterization has been particularly important in establishing the diagnosis of and managing complex congenital cardiac defects. As more complex techniques for the surgical correction of congenital heart defects have been developed, a detailed catheterization with accurate angiography has become a prerequisite to performing surgery. In the last two decades, a proliferation of “noninvasive” diagnostic techniques have been developed and have enabled many patients now to be sent to surgery without having to undergo catheterization. Despite the many noninvasive diagnostic technologies, cardiac catheterization still remains the gold standard and is absolutely essential for many of the fine details of the complex anatomy and the hemodynamics in congenital heart lesions.

Techniques for treating intracardiac and intravascular defects definitively in the cardiac catheterization laboratory were introduced more than four decades ago. From the very first introduction of a diagnostic cardiac catheter, cardiologists envisioned the concept of correcting cardiac defects using the cardiac catheterization laboratory. Use of therapeutic procedures in the pediatric cardiac catheterization laboratory first became a reality with the innovative and courageous development of the balloon atrial septostomy catheter and procedure by Dr. William Rashkind in 1966. This procedure was a lifesaving palliation for critically ill infants and, equally as important, it demonstrated the feasibility of performing therapeutic procedures for congenital heart disease in the catheterization laboratory. The balloon atrial septostomy procedure paved the way for all subsequent catheterization procedures aimed at therapy. This particular procedure has served the test of time and still is an essential procedure in the care of infants with complex congenital heart disease. Porstmann (1967) reported the closure of the patent ductus using a large and complex delivery system requiring a combined venous and arterial approach. The Porstmann procedure was the first “corrective” procedure performed in the catheterization laboratory, but it now rarely is used.

Additional therapeutic catheterization procedures of major importance for congenital heart lesions, particularly in pediatric patients, were slow in developing. Although the procedures that were developed were unique for the congenital heart patients, most of the equipment used was (and is!) developed for, and in turn represents “hand me downs” from, adult therapeutic catheterization procedures. During the last two decades, development of new procedures proliferated, and several specific new devices were developed, until the therapeutic
procedures for congenital heart lesions now represent the most revolutionary developments in the management of congenital heart disease since the introduction of surgery for these patients.

The numerous therapeutic catheterization procedures available for the pediatric cardiac patients are divided arbitrarily into seven main categories: septostomies, catheter removal of intravascular foreign bodies, valve dilations, vessel dilations, vessel dilation with intravascular stent implant, valve and vessel perforations/recanalizations, and occlusion/closure procedures. Each of these categories contains well-established procedures as well as many procedures that remain investigational. All of the therapeutic catheterization procedures require special equipment and special skills. The success and safety of the procedures correlate with the skill and experience of the operators and the centers performing the procedures. For these reasons, not every pediatric cardiologist or every pediatric cardiac center should attempt every therapeutic catheterization procedure.


ATRIAL SEPTOSTOMIES

The oldest, one of the most established, and still used therapeutic catheterization procedures is the balloon atrial septostomy. The balloon septostomy is most effective in infants younger than 1 month of age. It is the one therapeutic catheterization procedure that should be available in all centers caring for infants with congenital heart disease. The balloon septostomy is lifesaving in newborn infants with transposition of the great arteries in whom no other intracardiac communication exists and in infants with hypoplastic left heart syndrome with a restrictive atrial communication. It provides some immediate mixing of the totally separated systemic and pulmonary venous blood and/or “venting” of the left atrium. This mixing is required urgently to correct hypoxemia and acidosis and to stabilize these infants, even if performing an arterial switch or a “Norwood”-type surgical procedure is anticipated within hours or days.

An atrial septostomy is indicated in many other infants with a variety of other cyanotic lesions in whom an adequate, preexisting, interatrial septal communication is not present, but, at the same time, the continuity of the circulation depends on such a lesion. For example, a septostomy is performed in infants with hypoplastic right heart syndromes, such as pulmonary or tricuspid atresia, in which all of the systemic venous blood must pass from the right atrium through the atrial septum to return to the effective systemic circulation. In patients with total anomalous pulmonary venous return, the only access of both the systemic and pulmonary venous returns back to the systemic circulation is through the atrial septal defect. If the atrial septal defect is at all restrictive in any of these lesions, a septostomy is indicated.

Although improvements have been made in the balloon catheters available for the balloon septostomy, the balloon atrial septostomy procedure is essentially the same as originally described by Rashkind and Miller (1966). An inflatable, spherical balloon attached at the distal end of a catheter is used to tear an opening in the interatrial septum. The deflated balloon is advanced from the right atrium into the left atrium, and the balloon is inflated in the left atrium and then rapidly and forcefully pulled (i.e., jerked) through the atrial septum into the right atrium, which, in turn, tears an opening in the interatrial septum. The hole created allows free mixing or passage of blood across the atrial septum.

Some patients with these cyanotic defects and/or even more complex lesions live for months or years before requiring enlargement of an atrial septal defect or further surgery. When one of these patients older than 1 month of age does require a further opening of the atrial septum, the balloon septostomy procedure alone merely stretches the atrial septal tissues and does not create a permanent opening because of the thickened, tougher septa. Dr. Sang Park extended the use of the septostomy procedure for these older patients with the introduction of the blade septostomy catheter in 1975.

The blade septostomy procedure is accomplished using a catheter with a small retractable blade at its distal end. The catheter, with the blade retracted, is advanced through a long sheath into the left atrium. The blade is opened carefully in the left atrium, and the blade catheter is withdrawn forcefully, but slowly and with careful control, through the atrial septum, which, in turn, incises an opening in the septum. This procedure is repeated, changing the side-to-side angle of the blade with each withdrawal. After the multiple incisions with the blade are completed, a balloon septostomy is performed to further increase the septal opening.

In much older patients with septae, which are extremely resistant to further tearing by the septostomy balloon, a dilation balloon is used after the blade incision to open the atrial septum further. A deflated “angioplasty” balloon catheter is advanced over a wire until the balloon is centered across the atrial septum. The dilation balloon is inflated, further extending the previous blade cuts. As with other dilation procedures, two smaller dilation balloons used simultaneously are as effective as or more effective than is one balloon, but they cause less trauma to the venous system.

As an alternative to the blade atrial septostomy, particularly in patients with a very small left atrium, intravascular stents now are placed across the septal opening to maintain the patency of the atrial septal defect. A balloon expandable intravascular stent is expanded in a small interatrial communication on a dilation balloon. The expanded stent remains at the final diameter of the balloon, fixing the opening in the septum at the expanded diameter, preventing “recoil” or late closure of the atrial defects.

The balloon, blade, and balloon and/or stented septostomies are palliative procedures, but often they are the only procedures available or required for many of the extremely complex congenital heart lesions. Although the patients often are extremely ill, the catheter septostomies, when performed cautiously and with meticulous attention to the technical details of the procedures, are effective and safe procedures.


CATHETER REMOVAL OF INTRAVASCULAR FOREIGN BODIES

Since they were first introduced purposefully into the vascular system, pieces of indwelling intravenous lines, cardiac catheters, or implantable intravascular devices occasionally have broken off, come loose, or otherwise gone astray in the circulation. The most common of these foreign bodies are pieces of indwelling “catheters” from hyperalimentation or chronic chemotherapy lines, which have been sheared off during attempted removal. Most of these loose pieces and devices are in the systemic venous side of the circulation and end up migrating to the right heart and/or, more often, to the pulmonary arteries. These foreign bodies originally required surgical removal and occasionally even an open heart procedure.

Early in the development of cardiac catheterization, devices were modified from urologic devices and/or fabricated by cardiologists for the purpose of catching and retrieving the errant objects. Multiple, commercially manufactured catheter devices, which are miniaturized in order to pass through small catheters or sheaths, now are available specifically for the removal of foreign bodies in the cardiac catheterization laboratory. These devices include a variety of wire loop snares, collapsible wire
baskets, and small grasping forceps. With the use of these tools and biplane fluoroscopy to localize the errant object, physicians can grasp essentially any item within the heart or pulmonary artery and withdraw it from the circulation through a sheath without requiring even a cutdown over the exit vessel. Removal of intravascular foreign bodies performed in the catheterization laboratory is the accepted therapy for most intravascular foreign bodies, although some very large, dislodged, intravascular devices still must be removed surgically.


BALLOON DILATIONS

The development, manufacture, and use in the 1970s of tiny, cylindrical, fixed-diameter, high-pressure balloons for dilating renal and coronary arteries began a revolution in the treatment of cardiovascular disease. These balloons inflate to a predetermined, fixed diameter when inflated to a specified pressure, and, at that diameter, the surface becomes very hard and rigid. The extension of this technology to similar but larger balloons in the early 1980s opened the way to the dilation of stenotic valves and larger vessels in patients with congenital heart disease. Techniques using the larger balloons initially were described for the dilation of pulmonary veins, pulmonary valves, recoarctations of the aorta, pulmonary branch stenoses, and aortic valves. The very long-term results of the balloon dilation procedures still are being determined, however, in a large initial collaborative study, and now, after 20 years of use, the dilation procedures have been demonstrated to be immediately effective, to be safe for the patient, to produce much less morbidity, and also to have sustained results equal to comparable surgical procedures. The balloon dilation procedures are accepted as the standard therapy for most obstructive congenital heart lesions.


VALVULOPLASTY (VALVE DILATIONS)

A double balloon technique is recommended for virtually all valve dilations. The advantages of the double balloon technique are multiple. The greatest advantage is that two smaller balloons with a much lower profile of each deflated balloon are easier and less traumatic to introduce into the peripheral vessels than is a single, larger deflated balloon that would be required for the same annulus size. Additionally, because two “lumens” always persist between and adjacent to the two inflated balloons within a “circular” orifice, blood flow through the lesion being dilated never is obstructed totally as it is with a single balloon. In turn, systemic cardiac output is not reduced as drastically while the balloons are being inflated. The two balloons make the dilation of much larger valves possible when single balloons of adequate size are not available and/or are too massive in their deflated profile.

The pulmonary valve was the first valve to be dilated successfully and is the valve with which the most extensive and valid experience has been accumulated. Shortly after the introduction of the technique in 1982, a voluntary collaborative registry from 27 pediatric cardiology centers was established. By the end of 1986, data on the experience with more than 800 patients who had pulmonary valve dilation established the procedure as safe and effective. Longer-term data just now are becoming available. The 20-year or longer follow-up data continue to demonstrate the acute success of dilation of valvular pulmonary stenosis, with no recurrence of the stenosis after an initial successful dilation. Pulmonary valve regurgitation is created, but it appears to be tolerated very well for at least the two decades of follow-up.

Before a dilation of the pulmonary valve is performed, the hemodynamics and exact anatomy are established by cardiac catheterization and selective angiography. From previous echocardiograms and/or the angiocardiograms, an accurate measurement is made of the diameter of the valve annulus. Two long exchange guidewires are passed through two separate catheters previously introduced and maneuvered from the right and left femoral veins into distal pulmonary arteries. The catheters are removed, leaving the two wires in place. The appropriate balloons are passed over the separate wires, positioned side by side in the valve, with the balloon centers located exactly within the stenotic orifice. The combined diameter of the two balloons that are used is 1.5 to 1.8 times the diameter of the annulus of the pulmonary valve. The balloons are inflated simultaneously and rapidly to the maximal recommended pressure of the balloons and/or until the circumferential indentation in the balloons created by the stenotic valve disappears; then they are deflated rapidly. To ensure that the balloons were in the optimal position, the positioning of the balloons is changed slightly and the inflation and deflation process is repeated several times. After dilation, the hemodynamics and angiograms are repeated. Pulmonary valve dilation using these techniques is safe, effective, and probably curative. It is the accepted standard therapy for pulmonary valve stenosis.

Valvular aortic stenosis was the next congenital valvular lesion to be treated with balloon dilation. Enthusiasm for aortic valve dilation initially was limited because of the expected difficulties and dangers of performing extensive manipulations in the arteries and in the systemic circulation and the fear that significant aortic regurgitation would be created. Eventually, several major centers began dilating valvular aortic stenosis on carefully controlled protocols. With success and complication rates, which were comparable to surgical results, reported from the investigating centers, the procedure gained a wider acceptance. In many centers, it is now the treatment of choice. Like the surgery for valvular aortic stenosis, dilation of the aortic valve still is a palliative procedure.

Balloon dilation of aortic valve stenosis is indicated for patients with pure aortic valvular stenosis that is severe enough to indicate treatment using the same criteria used for surgical intervention. The goal in the dilation of the aortic valve is not to “cure” the patient but to reduce the obstruction from a critical level to a mild degree without producing significant aortic regurgitation. After hemodynamic parameters have been recorded and accurate measurements of the aortic annulus diameter have been obtained, end-hole catheters are introduced from both femoral arteries. Each catheter is passed retrograde across the stenotic aortic valve into the left ventricle. Exchange length guidewires are passed through the catheters and positioned securely in the left ventricle. The catheters are removed, leaving the wires in place. Two balloon dilation catheters with long balloons are advanced over the wires until the balloons are centered in the stenotic valve orifice. The combined diameters of the two balloons are equal to or no more than 10% larger than the diameter of the aortic annulus. The balloons simultaneously and rapidly are inflated and deflated, splitting the stenotic valve. If a single balloon is used for aortic valve dilation, an even longer balloon is used, and the diameter of the single balloon should be no larger than the diameter of the valve annulus.

The double balloon technique, the use of much longer dilation balloons, and the very accurate measurement of the annulus with strict attention to the precise balloon-to-annulus ratio have rendered aortic valve dilation safer and more successful. However, even these techniques and precautions have not eliminated all the risks nor improved the predictability of the procedure. Although aortic valve dilation is used widely and no longer is considered an investigational procedure, its
use should be limited to centers with adequate equipment and expertise and centers where long-term data on the technique and results of the procedure are being accumulated.

In the Middle East, Far East, and in less developed Western countries, rheumatic fever with resultant rheumatic mitral stenosis remains rampant. In those areas of the world where rheumatic heart disease exists, experience with the dilation of rheumatic mitral valve stenosis has been extensive and successful. Because of the control of rheumatic fever, rheumatic mitral valve stenosis is a rare problem in children and adults in the developed nations of the world, and congenital mitral stenosis is the major form of mitral disease encountered in developed countries. Congenital mitral stenosis usually results in a grossly deformed mitral valve and valve apparatus. The congenital stenotic mitral valves are poor candidates for any type of intervention except valve replacement, and little enthusiasm exists for, and there is even less experience with, dilation of the congenitally stenotic mitral valve. The techniques for dilation of the stenotic rheumatic mitral valves have been applied with satisfactory results to some of the more severe congenital mitral stenoses. These patients otherwise require surgical mitral valve replacement.

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Jul 24, 2016 | Posted by in ORTHOPEDIC | Comments Off on Therapeutic Cardiac Catheterization
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