Cardiac Catheterization in Congenital Heart Disease: Pediatric and Adult - Part 2 ppsx

CHAPTER 3 Cardiac catheterization equipment 84 Oxygen consumption apparatus In order to determine cardiac output accurately using the Fick principal, in addition to the very accurate and timely blood samples, an accurately measured oxygen (O 2 ) con- sumption determination is necessary. The measured O 2 consumption is not necessary for the calculation of relative amount of shunting, since all values for the O 2 consumption cancel each other out in the calculations of shunts, which are based on differences in oxygen saturation in the blood. However, for the accurate determination of the absolute value of the cardiac output, actual pulmonary blood flow, any vascular resistance or valve areas, the actual O 2 con- sumption must be measured. There are tables of “normal values” which are proportionate to body surface area; however, these do not take into account the variable metabolic states of the patients. In most pediatric labor- atories, oxygen consumption is measured by means of a constant flow-through hood in conjunction with a gas analyzer for measuring oxygen content of the air, such as the MRM-2 Oxygen Consumption Monitor (Waters Instruments Inc., Rochester, MN). O 2 consumption is discussed in more detail in Chapter 10. A source of carbon dioxide Balloon flow directed catheters are often used in pedi- atric/congenital cardiac catheterization laboratories, even in those laboratories which utilize torque-controlled catheters predominately. Even when the operator is not concerned about a very small amount of air in the venous system, in the pediatric/congenital population of patients, it is always assumed that any air which enters the blood anywhere can, and will, reach the systemic circula- tion, where even a small amount of air can be catastrophic. In the pediatric/congenital laboratory, carbon dioxide (CO 2 ) is always used in the balloons of “floating” balloon catheters. Each catheterization laboratory has a source of CO 2 gas and a means of transferring the CO 2 to the catheterization table and into the balloon catheter. A disposable tank of CO 2 gas, which has a gas control valve and is secured to a mount on a wall or cabinet, serves very nicely as a reservoir of CO 2 . For use in a bal- loon catheter, the CO 2 from the tank is allowed to flow into a sterile 3 ml syringe through a stopcock, which is closed immediately and tightly once the syringe is filled. CO 2 is extremely diffusable and escapes instantaneously into air through any opening, including the tiny opening in the tip of a syringe. If the tip of a syringe full of CO 2 remains open, even while transferring the syringe the short distance from the side of the catheterization room to the catheterization table, the CO 2 diffuses out of the syringe and the syringe fills with room air before it can be attached to the balloon catheter. The balloon catheter on the catheterization table is attached to the stopcock of the syringe, the stopcock is opened so that the syringe and the balloon lumen are in communication, the balloon is filled from the syringe and the stopcock on the syringe is turned off immediately. CO 2 is very diffusable through the Latex™ of the bal- loon itself and, as a consequence, empties (diffuses) out of the balloon fairly rapidly. To compensate for this dif- fusibility, a second 10 ml “reservoir” syringe is attached to the 3 mml syringe through the side port of a three-way stopcock (Figure 3.1). The 10 ml syringe is filled from the CO 2 tank and the stopcock is turned off to the distal open- ing in the three-way stopcock. This leaves the 10 ml and the 3 ml syringes in communication with each other through the stopcock and, at the same time, closed off to the outside air. Thereafter, once the distal port of the stop- cock is attached to the lumen of the balloon, the 3 ml syringe can be refilled from the 10 ml syringe while the balloon is refilled from the 3 ml syringeaall through a completely closed system. The smaller, 3 ml syringe pro- vides a means of filling the balloon more accurately, but 3 ml only fills the balloon twice at the most. The small syringe is refilled repeatedly from the 10 ml syringe with- out having to return to the CO 2 canister for each refill of the balloon or 3 ml syringe. Radio-frequency (RF) generator With refinements in radio-frequency generators and FDA approval of controlled perforations using radio-frequency energy, a radio-frequency (RF) generator specifically for perforation is now a standard piece of equipment in the pediatric/congenital interventional catheterization lab- oratory. A small perforating generator (Baylis Medical Company, Montreal, Canada) is designed and approved for perforation of the interatrial septum. An even more important (but “off label”) use for the RF energy is the Figure 3.1 Syringes and three-way stopcock arrangement used as a “portable reservoir” for the use of CO 2 on the catheterization table. CHAPTER 3 Cardiac catheterization equipment 85 perforation of atretic valves or occluded vessels in con- genital defects. With the heat from the RF wire tip, very dense natural tissues can be perforated without the use of significant force. The perforating RF generator uses a specific fine RF wire and tiny catheter (Baylis Medical Co. Inc., Montreal, Canada), which pass through a preformed, torque con- trolled, end hole guiding catheter to the desired position to be perforated. When the RF wire/generator is used, a relatively large “grounding pad” is fixed on the surface of the patient’s skin to complete the “circuit” during the energy generation. The RF generator for perforating does not have a maxi- mum temperature limit for the catheter tip like the RF gen- erator used for the ablation of intracardiac electrical pathways. Without some significant internal engineering adjustments within the generator for each case, the perfo- rating RF generator cannot be used interchangeably with the ablation RF generator and, as a consequence, requires a separate RF generator from the ablation RF generator. The perforating generators and equipment are discussed in detail in Chapter 31. Capital equipment which is desirable but not routinely or necessarily available in pediatric/congenital catheterization laboratories and which also require associated consumable items A variety of different equipment which requires fairly expensive consumable accessories initially was used prim- arily in investigational studies in pediatric/congenital catheterization laboratories. At the present time, this type of equipment is being used more regularly in a few pediatric/congenital interventional catheterization lab- oratories. This equipment includes intravascular ultra- sound (IVUS), intracardiac echocardiography (ICE) and the Doppler needles. Intravascular ultrasound (IVUS) Intravascular ultrasound (IVUS) has had considerable, but sporadic, use in the pediatric/congenital therapeutic catheterization laboratory. Most of the IVUS is used in studying the walls of vessel before, immediately after and in the long-term follow-up after various balloon dilations or intravascular stent implants. At the same time that pathologic lesions are being studied, the operators are still determining the normal appearance for these vessels by IVUS imaging. The findings have been striking, very interesting, and at times even frightening, however, the IVUS findings seldom significantly influence decisions about the particular pediatric/congenital lesion or patients. The same situation occurs with the study of the coronary arteries in the pediatric cardiac transplant patientsa interesting findings but not correlated with management decisions. Although many feel that the information from IVUS in these lesions is invaluable, the high cost of the dedicated IVUS machine itself, the additional significant cost of each of the disposable IVUS catheters and, finally, the lack of definitive decisions which can be made from the IVUS findings at present has led to the very slow acceptance of the technique. Almost certainly, as experience with IVUS increases, there will be greater correlation of the findings from IVUS with the clinical outcomes and, in turn, the use of IVUS will increase until it becomes an inte- gral part of every pediatric/congenital cardiac catheter- ization laboratory. Intracardiac echo (ICE) apparatus The use of intravascular echo (ICE) for the placement of occlusion devices for atrial septal defects (ASD) has generated significant interest in the use of ICE in the pedi- atric/congenital catheterization laboratory in the past few years. Intracardiac echo provides dramatic, clear and easily understandable views of intracardiac structures. Intracardiac echo does require a reorientation of thinking about intracardiac images and requires the use of an additional 11-French venous access site. Like the IVUS machine, the basic ICE console is very expensive, but often the console used for the transesophageal echo (TEE) is the same console as for the ICE catheters, which makes the console more available. On the other hand the cost of the ICE catheters is even worse than that of the IVUS catheters, with each disposable ICE catheter being very expensive. At present, ICE images are equivalent to TEE images in most cases although there are situations where the images are very discrepant. The cost of using single- use ICE catheters is calculated to be less than the com- bined cost of the TEE and associated cost of general anesthesia for ASD implants. There is now the capability of having ICE catheters resterilized commercially and each catheter can be reused three times, reducing the per use cost significantly. Most pediatric institutions at the present time, however, find it hard to justify switching to the use of ICE instead of TEE while still utilizing general anesthesia for the interventional catheterization proced- ure. If and when ICE probes come down in both size and price, ICE could replace TEE for the placement of ASD occlusion devices. Doppler needles To help locate vessels for percutaneous puncture, there is a tiny, disposable Doppler probe, which functions through CHAPTER 3 Cardiac catheterization equipment 86 a special needle and comes as a setathe Smart Needle™. The needle/probe is attached to a disposable sterile cable, which attaches to a small, portable, reusable, Doppler machine. The special needle is filled with saline or flush solution and introduced just barely into the superficial cutaneous tissues and the fluid level in the needle checked and refilled. The needle must remain full of fluid in order to transmit a Doppler signal. The Doppler probe is intro- duced into the intact fluid column within the special needle while the needle full of fluid is positioned in the very superficial subcutaneous tissues. The angle and depth of the needle/probe are directed toward the desired vessel according to the intensity of the Doppler signal generated from the probe within the needle. The quality of the signal from these Doppler needles distinguishes between arte- rial and venous flow and can determine the side-to-side location of the particular vessel by the changing intensity of the particular signal. The intensity of the signal does not help to determine depth per se, however, as the tip of the needle/probe touches and compresses the wall of the vessel, the signal does change significantly. The Doppler apparatus itself is a capital item, but is used with the special disposable needles and probes, which represent a significant, ongoing expense. There are only two sizes of the needle/Doppler probe combination available, the smaller of which is a 20-gauge, which is not particularly useful for small infants where this technology theoretically could be very useful. The Doppler needles are much more effective for larger vessels where it usually is not as necessary to have a Doppler signal to find the vessel. Entirely disposable consumable equipment Each separate piece of expendable equipment in the cathe- terization laboratory is chosen carefully and specifically for the utility and safety of its use while, at the same time, considering the cost of the item. Because of the complexity of the procedures performed in the modern pediatric/ congenital cardiac catheterization laboratory, each proce- dure has its own requirements for specialized catheters and other pieces of consumable equipment. The require- ment for a specialized piece of equipment is frequently unpredictable or changes during any one procedure. As a consequence, a modern pediatric/congenital cardiac cathe- terization laboratory is obligated to carry a very large inventory of a huge variety of consumable items. The size of this inventory is magnified in the pediatric/congenital laboratory by the large variation in the size of the patients (from a few kilograms to a few hundred kilograms) and the infinite varieties of defects and procedures encountered. In spite of the huge variety of equipment which is avail- able and used for congenital heart patients, very little of this equipment is designed (or intended) for use in pedi- atric or congenital cardiac catheterization procedures. The consumable equipment which is developed specifically for the pediatric/congenital heart procedures is often manufactured in very small volumes and then requires even more precision (often hand) manufacturing. This in turn, often results in very high costs for the individual items. In spite of their high costs, almost all of the consum- able equipment for use in the catheterization laboratory is for one-off use only and is disposable. These combined factors necessitate a very expensive as well as large invent- ory for each laboratory performing catheterizations on pediatric/congenital heart patients. The alternative, which is a common practice outside of the United States, is to have each piece of consumable equipment supplied and delivered individually for each separate case by the equipment vendors. This, of course is dependent upon a demonstrated, reliable and rapid source of direct vendor supply to the individual catheterization laboratory and very precise pre-planning of each case. Even with the best of planning, this policy does not take into account unexpected findings which occur every day in catheterization laboratories which are studying and treating congenital heart lesions. Also, with the vendor system, each individual piece of equipment is far more costly to the hospital or the patient. The vendors are reim- bursed for maintaining the large inventory of equipment (instead of the hospital) and, in addition, are reimbursed for their time and availability. All of these expenses of the vendors are included in the cost of the equipment to the consumer. The total inventory of consumable equipment in each laboratory varies with the individual physicians working in the laboratory and with the types of procedures per- formed in the particular laboratory. There are often many similar items which can be used to accomplish the same result, so the particular piece of equipment which is used varies with the preference and experience of the oper- ators, the economics and the “customs” of the particular laboratory. This technical manual obviously emphasizes those preferred by the author. Because of continual im- provements in the consumable equipment and the avail- ability of certain items, the specialty items and even the equipment routinely used in any laboratory change frequently. Most of the specialized equipment (needles, wires, sheaths, dilators, catheter, etc.) mentioned in this section is discussed in detail in later sections dealing with specific techniques or procedures using it. General consumable items There is some consumable equipment that is required in every cardiac catheterization procedure and is pro- vided for every case, regardless of what additional, more CHAPTER 3 Cardiac catheterization equipment 87 specific items are necessary for a particular procedure. These include flush solutions, connecting and flush/pres- sure tubing, “manifolds” (which include stopcocks and pressure transducers), and the catheterization “trays” or “packs” for the catheterization table. Flush solutions Each procedure requires a quantity of sterile, physiologic fluid for flushing transducers, connecting tubing and catheters. It is also necessary to have some additional fluid solution on the table, usually in a bowl, for rinsing/flush- ing pieces of equipment which are not connected to the flush/pressure system. The safest and most satisfactory sources of fluids for the catheterization laboratories are the 500 or 1,000 ml, collapsable plastic bags of physiologic fluids. The bags are far superior and safer than the older bottles of these fluids. The collapsible bags are emptied completely of any air initially and then safely pressurized by an external pressure bag. Once the bags have been prepared properly and meticulously, there is absolutely no danger of ever pumping air into the system and/or the patient, regard- less of the amount of fluid remaining in the bag or the position of the bag. The safety of the collapsible bags of fluid is in stark con- trast to the constant potential danger of the older bottles of flush solution. The bottles were frequently pressurized by pumping air under pressure into the bottle of fluid! If a bottle emptied or got tilted while in use so that the outlet to the tubing was placed toward the top of the bottle, the air under pressure above the fluid level preferentially and very forcefully entered the flush system (and the patient if the tubing was connected to the catheter!). With fluid bags, a special intravenous tubing set con- taining a sharp hollow spike is introduced or “spiked” through a tubular port in the bottom of the bag. After the bag has being spiked, it is turned upside down so that the port is situated at the top of the bag. Once the tubing is con- nected into the bag, the bag is squeezed until all the air rises out of it and is forced out of the connecting tubing to be followed by an intact column of the fluid in the tubing. When the bag is completely empty of air, 3 units of hep- arin are added to each ml of flush solution through the second, adjacent port on the bag. Once the bag and the connecting tubing are emptied completely of air and the heparin has been added, the bag is turned over to the upright position so the ports (or openings) are oriented at the bottom of the bag. Once the bag and tubing are cleared completely of air with the tubing now coming out of the bottom of the bag, there is no way for air to enter the sys- tem passively, even if the bag while still under pressure is placed on its side or even with the ports positioned at the top as the bag empties completely! In order to generate pressure in the bags for flushing, pressure is applied to the outside of the bags of fluid with a pressure cuff. The fluid bags with their tubing are supplied from the manufacturers in sterile packaging and can be maintained sterile if they are to be used directly on the sterile catheter- ization field. Connecting and flush/pressure tubing Each catheterization procedure requires a variety of tubing for fluid delivery to the patient and for the trans- mission of pressure from the catheter to the pressure transducers. The tubing extending from the fluid bags to the manifold is discussed above. If desired, this tubing is maintained sterile when it is opened and when it is con- nected to the fluid bags or transducers. The tubing carries the fluid under pressure from bags of flush solution to a system of stopcocks, or “manifold”, where the fluid is dis- tributed to the pressure transducers and to the separate pressure tubing, which attaches to indwelling lines and catheters which, in turn, are in the patient. All tubing that is to transmit pressure for recording must be non-compliant tubing in order to transmit the pres- sure accurately and reproducibly. This requires tubing which is thick walled and non-elastic, but at the same time transparent and flexible. These fluid/pressure lines con- necting to the patient’s catheters/lines should have small lumens in order to minimize the amount of fluid delivered to the patient when the tubing/catheters are flushed. This becomes particularly important when the entire length of tubing must be flushed thoroughly after a medication is administered through the length of the tubing. Ideally, each separate length of tubing between separate catheters/ lines in the patient and each separate transducer is color- coded to correspond to the color of the specific pressure tracing from the transducer as it is displayed on the mon- itor. This is extremely convenient, or even essential, when more than two pressure lines are being used. The color- coding of each separate tubing facilitates communication between the catheterizing physician, the manifold nurse/ technician and the recording nurse/technician and, in turn, increases the accuracy and efficiency of recording, flushing and changing gains on specific lines/transduc- ers. The length of tubing on the field which extends from the catheter in the patient to the manifold, is maintained sterile except for the end which is connected to the mani- fold of stopcocks, which usually is off the field. Manifold system The “manifold” is a system of three-way stopcocks in series. The series of stopcocks allows the connection of the line(s) from the fluid bags to all of the transducers and, in turn, the transducers to the separate pressure lines and CHAPTER 3 Cardiac catheterization equipment 88 allows the lines from the fluid source to be diverted directly to the pressure/flush lines. The manifold can be built individually for each case with a series of three-way stopcocks clamped together in line, however, there are now a variety of commercially available manifolds that are manufactured (Merit Medical Systems, Salt Lake City, UT, and Argon Medical, Athens, TX) to suit almost any desired set-up or number of transducers. The manufac- tured manifolds not only are more convenient, but are cheaper and more secure than creating one’s own with separate stopcocks and separate transducers. Preferably, the manifold is mounted “remotely” and out of the sterile catheterization field on a stand, which, however, is attached to the side or end of the catheteriza- tion table. The manifold stand is adjustable in height. The height of the manifold (and transducers) positioned on the catheterization table is adjusted at the beginning of each case according to the anterior–posterior diameter (thickness) of the chest of different patients. This allows the series of transducers to be positioned at the mid posi- tion (mid-cardiac level) in the posterior–anterior diameter of any particular patient’s chest. Once fixed on the edge of the table, the manifold, and in turn the transducer remain at a fixed height relative to the patient’s heart/ chest, regardless of the up or down movements of the table and patient. Pressure transducers Pressure transducers are very accurate electromechanical devices for measuring pressure. External transducers are connected to catheters and indwelling lines in the patient through the pressure/flush lines and the manifold. Each transducer, in turn, is connected electrically to the physiologic recorder, where it is calibrated and balanced electronically. Most modern catheterization laboratories utilize relatively inexpensive, but very accurate, dispos- able transducers designed for one-off use (Merit Medical Systems, Salt Lake City, UT and Argon Medical, Athens, TX). In spite of their disposable labeling, these transducers remain very stable even through multiple uses and fre- quently are used for several cases before being discarded. When transducers are connected through a manifold, they are isolated from the sterile field (and any blood/ fluid from the patient) by the length of the indwelling catheters or monitoring lines plus the length of the flush/pressure tubing and, in turn, are not contaminated by blood during any one case, unless fluid backs up through the entire length (100–150 cm) of catheter/flush/ pressure tubing. As a consequence each transducer, when attached through a remote manifold system, is used several times before being discarded. When reused, the transducers are reattached to new sterile tubing, flushed with sterile flush solution and recalibrated and balanced. The transducers are re-balanced to “air zero”, occasionally during each case as well as between cases. When there is any question about the accuracy of a disposable trans- ducer, it is discarded and replaced quickly and easily. Each transducer has its own calibration factor, which usually must be entered into the electronic recording equipment. When a pressure from a single location is transmitted through two separate lines to two different trans- ducers, a single pressure tracing (line) should be produced on the monitor (see Figure 10.1). This provides a rapid, very easy check of the accuracy of a new transducer which is introduced into the system. Catheterization “packs” Every catheterization procedure requires one or more sterile drapes over the patient on the catheterization table, operating gowns for all of the scrubbed personnel, towels, sterile wipes (“4 × 4s”), bowls for flush solution and waste fluids, multiple syringes, several needles, a knife blade, tubing/towel clamps, containers for medications or con- trast solution, sterile drapes for the adjacent side-tables, sterile covers for the equipment that is immediately adja- cent to the sterile field (X-ray tubes, image intensifiers, radiation screens, etc.) and occasional other items which are unique to a particular catheterization laboratory. In modern cardiac catheterization laboratories, all of these items are disposable and are set up as a tray on a table adjacent to the catheterization table to suit the pref- erences and needs of each individual case and operator. Most of these items can be available, packaged together commercially, as a single, sterile “pack” or “set”, which is prepared to suit the needs of a particular catheterization laboratory. When the specifically manufactured commer- cial packs are used, once the pack is opened and arranged on the adjacent (sterile) worktable, for the most part, the case is ready to begin. Usually a few individual, extra dis- posable items like special introductory needles and wires for the particular case, the color-coded connecting/flush tubing which is used between the catheters and the trans- ducers, gloves and extra gowns for each scrubbed physi- cian/nurse, and any special drapes are added to the materials in the standard pack. Most catheterization laboratories utilize a few reusable/sterilizable metal items like scissors, needle holders and instrument clamps, which are added to the tray during the set-up. In addition to their convenience, the table set-ups using all disposable items have several other major advantages. The most significant advantage of the disposable “tray and set-up” is the safety factor at the end of the case. Once the very few reusable items and sharps are removed from the catheterization table, the entire table drape containing all of the contaminated consumable equipment and mater- ials is rolled up as one, contained mass of contaminated CHAPTER 3 Cardiac catheterization equipment 89 (bloodied) materials without any of these individual items having to be touched by any individual. The single contained mass is disposed of in a “bio-hazard” trash container with only the one, single handling and that from the outside of the mass of contaminated material! As a consequence, the individual contaminated items from the catheterization are not handled by any of the person- nel in the laboratory. In addition, none of the materials are handled subsequently by any hospital personnel for the purpose of separating and cleaning, as is necessary with reusable items. An additional advantage in most industrialized soci- eties who utilize accurate cost accounting is that the dis- posable packs are cheaper than the combined initial cost of all of the comparable reusable items plus the additional costs of the labor for the cleaning, repackaging, sterilizing, stocking and redistributing of all of these items. Unique consumable items for each particular case In addition to the “general” consumable items used dur- ing every case, each separate catheterization procedure requires some special individualized items depending upon the patient’s size, the procedure being performed and the preferences of the individual catheterizing physi- cian(s). These items are requested specifically before or during each particular case. Needles for percutaneous puncture The ideal needles are chosen for the single wall puncture technique, which is preferred for the percutaneous entry into all vessels and is discussed in detail subsequently in Chapter 4 2 . The entry technique into the vessels is very similar to the introduction of a needle into a peripheral vein, except that in the catheterization laboratory the ves- sel usually is not visible, and often not even palpable. The needles which are used for the percutaneous technique using a single wall puncture are small in diameter, thin- walled, short beveled and, at the same time, very sharp needles. When a needle with a long bevel at the tip is intro- duced at any angle to the vessel, the tip and bevel of the needle incise through both the front and back walls of a small vessel while the lumen of the needle is still not within or does not align with the lumen of the vessel. A short-beveled needle, on the other hand, allows the lumen of the needle to fit within and align better within the lumen of the vessel once the vessel is punctured. The longer, sharp, cutting edge on the tip of the long-beveled needle lacerates multiple structures, including the vessel, as it enters the tissues. The shorter bevel, on the other hand, tends to dissect through the tissues as opposed to lacerating them. At the other extreme, a needle which has a bevel that is too short or is dull, loses all of its cutting ability in penetrating the tissues and/or the vessel and tends to dissect past and push the vessels aside as it is introduced into the subcutaneous tissues. There must be an absolutely smooth taper from the in- side of the hub of the needle into the lumen of the needle. There can be no inner ridges, flanges or edges which would interfere with the absolutely smooth passage of a wire from the hub of the needle into the attached shaft/lumen of the needle. It is preferable that the hub of the needle is clear in order to have an immediate, clear view of the fluid/blood returning into the needle. The AMC needles (Argon Medical, Athens, TX) have these ideal characteristics and are available in various sizes (diameters) and lengths. The smallest diameter needle is used, which will accommodate the spring guide wire which is being used for the percutaneous introduction. The shaft of the needle only needs to be long enough to reach the vessel through the subcutaneous tissues. The needle should be significantly smaller in diameter than the vessel which is being punctured and entered. With a smaller diameter needle, the entire tip, not just an edge or part of the tip of the needle, enters the vessel cleanly. For infants and small children, a 21-gauge needle approxi- mately 3 cm in length is used. For larger children and young adults of normal body stature, a 19-gauge needle approximately 5 cm in length is used, and for very large or obese patients, an 18-gauge 7–8 cm long needle is used. The correct technique for the use of these needles is described in more detail in Chapter 4 (Needle, Wire, Catheter Introduction). The true “Seldinger™ technique” is not used for per- cutaneous puncture into vessels. With the Seldinger™ technique, the needle purposefully passes through both the front and back walls of the vessel. A true Seldinger™ puncture technique requires a special, two-component, Seldinger™ needle, which has a solid, sharp trocar within the lumen of a hollow blunt cannula 3 . The special Seldinger™ needle is a thin-walled, absolutely blunt tipped, hollow metal cannula with a squared-off tip and a Luer-lock proximal hub. A sharp, solid, metal stylet or trocar fits snugly within the hollow cannula and extends just beyond the tip of the cannula. The blunt tip of this outer metal cannula tapers smoothly onto the surface of the inner stylet/trocar. The combined inner stylet and outer cannula make up the Seldinger™ needle. The solid inner stylet/trocar has a sharp, beveled tip which extends beyond the blunt tip of the hollow cannula. The sharp- ened bevel of the stylet provides the tip for puncturing the tissues and vessel. The stylet is fixed within the outer squared-off or blunt cannula during the Seldinger puncture. The combined blunt cannula with the contained, beveled stylet is intro- duced into the tissues and toward the suspected location CHAPTER 3 Cardiac catheterization equipment 90 of the vessel. The tip of the combination trocar/cannula is introduced into the tissues and advanced deep into the subcutaneous tissues, purposefully and completely through the front and back walls of the vessel. Once the com- bination stylet/cannula has been introduced well into the tissues and the vessel presumably has been transected, the inner, solid, sharp stylet/trocar is withdrawn from the cannula. Obviously, with the Seldinger™ technique, the needle set is purposefully passed completely through both the front and back walls of the vessel. With the stylet completely out of the blunt cannula, the hub and proximal end of the blunt cannula are pressed against and more parallel to the skin surface while the cannula is withdrawn very slowly from within the tissues and (hopefully) back into the lumen of vessel. The Seldinger™ technique and its modifications are described in detail in Chapter 4. The Chiba™ needle is another very special needle used when the transhepatic technique is used for per- cutaneous vessel entry. The Chiba™ needle is similar to a Seldinger™ needle but with a very long blunt outer plastic cannula and a long sharp inner metal stylet. The Chiba™ needle is described in more detail in the discussion of ves- sel introduction by the transhepatic puncture technique in Chapter 4. Guide wires for cardiac catheterization There is an infinite variety of guide wires available from multiple manufacturers for use in the cardiac catheter- ization laboratory. Most guide wires used in the cardiac catheterization laboratory are of spring steel wire con- struction and consist of a very smooth, hollow winding of a very fine stainless steel wire. The central lumen with- in this outer winding of very fine wire contains a central, relatively stiff straight “core” wire and a soft and very flexible fine, ribbon-like, safety wire. Variations in these three components and how they are used together create the specific characteristics of each individual guide wire. The safety wire extends the entire length of the outer winding and is fixed (“welded”) at both ends of the outer wire winding. The core wire is between 1 and 15 cm shorter than the safety wire and the outer winding wire at the distal end. The absence of core wire at the distal end creates the softer more flexible tip of the spring guide wire. Some guide wires have a core wire which tapers to a very fine distal tip and is attached at both ends of the outer wire windings and replaces the separate safety wire. All spring guide wires should be treated very gently during use. They should never be forced into any location nor should dilators and catheters be forced over them. The operator must constantly be aware of the entire length of wire in order to prevent perforation through vascular structures by the tip of the wire, and the formation of kinks or knots in a portion of the wire that happens to be out of the field of view. Sharp kinks or acute bends in wires are to be avoided in all circumstances, as they pre- vent the wire from moving freely within the catheter or the catheter from passing over the wire, and eliminate any torque characteristics of the wire. When a kink or sharp bend is created in a wire, it is abandoned. Wires specifically for vessel entry The most essential criterion for a guide wire which is used for percutaneous vessel entry is that it has a very soft, flex- ible (or even floppy), but straight, tip. Even a relatively soft-tipped wire, in actuality, is very stiff and straight as the first 1 to 2 mm of the tip of the wire protrudes beyond the tip of the needle. A very floppy tip on the wire is imperative when the needle is not exactly aligned or par- allel within the long axis of the lumen of the vessel as the wire is advanced out of the needle. The extra soft tip of the wire allows the very distal tip of the wire to bend or be deflected into the lumen of the vessel when the needle is aligned or angled more perpendicularly off the long axis of the vessel. Special “extra” or “very” floppy tipped wires are available for percutaneous entry into very small vessels (Argon Medical, Athens, TX). The wires from Argon are specially designed for this purpose, while there are other wires available with very soft tips which were designed for other uses, such as very small (0.014″) floppy-tipped, coronary guide wires. The “extra” floppy tips are created at the expense of thickness and strength of the core and safety wire components. As a consequence, the “extra” floppy-tipped wires are even more fragile and require even gentler handling. The size (diameter) of the spring guide wire used for any percutaneous introduction should be of a size significantly smaller in diameter than the internal diameter of the needle being used, and never the same size and/or an “exact fit” within the needle. For example, a 0.018″ wire is used within a 21-gauge needle or a 0.021″ wire is used in a 19-gauge needle. The smaller diameter of the wire within the larger lumen of the needle allows for slight, additional, side-to-side play of the wire within the needle lumen, which in turn, allows for freer angulation of the tip of the wire as it is advanced past the tip of the needle and enters into the vessel (see Chapter 4 for details of this). “J”-tipped wires are popular for percutaneous vessel entry, particularly for introduction into the larger vessels. They have the advantage that once the J tips of the wires are well within the vessel, they advance more easily through the vessel without catching on or deflecting into, side branches or tributaries off the central vessel. On the other hand, they have the disadvantage that the tip of the wire forms a sharp angle away from, and essentially CHAPTER 3 Cardiac catheterization equipment 91 perpendicular to, the long axis of the needle as soon as the tip of the wire extends initially beyond the tip of the nee- dle. When the J tip of the wire is extruded, the vessel must be large enough for the distal end of the wire and its tip to enter the vessel “sideways” or the angle of the bevel of the needle must be at an exact angle to be in line with the lumen, which requires that the needle is almost perpen- dicular to the long axis of the vessel. J-tipped wires are not recommended for initial vessel entry through the needle in infants and small children with small vessels or in debilitated patients where the venous pressure is very low. J-tipped wires are recommended only for percuta- neous entry into very large vessels which are well distended (e.g. in patients with known higher venous pressure and large veins or in larger arteries). Once the initial wire and a plastic cannula or dilator are well within the vessel, then a J-tipped wire is very useful for advanc- ing the wire tip through the central channel of the vessel. General usage guide wires Spring guide wires have many other uses in the catheter- ization laboratory besides percutaneous entry into vessels. When used in the body within or extending out of catheters, all guide wires should be introduced through a wire back- bleed/flush port and maintained on a slow continuous flush. The continuous flush facilitates the movement of a wire that is within a catheter and reduces (eliminates) the possibility of thrombus formation around the wire. Wires made of different materials, in many sizes (dia- meters), many lengths and configurations and for many dif- ferent uses are available. The use of soft straight tipped wires and J-tipped wires for vessel entry has been men- tioned. An infinite variation in the degree of softness and the length of the distal soft tip is available in all sizes and configurations of the wires. Wires with long, soft tips are used when they are advanced beyond the tips of catheters, for example to enter into more distal vessels or even to pass carefully through valves in either the prograde or ret- rograde directions. Some of the floppy tips are manufac- tured from or coated with special materials like platinum to make them more easily visible. Wires of larger diameter or heavier construction are available to support both small and large catheters during various catheter manipula- tions, particularly when catheters are advanced over wires which have previously been positioned in specific locations. In order for a guide wire that is positioned within the body to allow a relatively long catheter to be introduced over the wire outside of the body, the wire must be very long. Special “exchange length” (260–300 cm) wires allow even very long catheters to be removed en- tirely out of the body over the wire with the distal end of the wire still fixed in a particular distal location within the heart or vasculature. Whenever an exchange of a catheter over the wire may be a possibility during a catheterization, an exchange length wire is used for the initial positioning. Many of the spring guide wires are available with spe- cial coatings (heparin or teflon), supposedly to make them less thrombogenic and to allow them to slide more easily through catheters. The use of these coated wires is helpful or is imperative to keep the wire and catheter from bind- ing together when using a spring guide wire within any of the extruded plastic catheters. The coatings on the wire, however, do seem to make the coated wires slightly stiffer than the comparable size and type of non-coated wire. As a consequence, coated wires are not recommended for the initial percutaneous introduction into vessels. The coatings presumably make the wires less thrombogenic, however this is not proven and certainly does not remove the necessity of keeping the wire on a continuous flush when it is positioned within a catheter in order to prevent clotting. The exchange length wires and the coated wires are special, and usually more expensive, variations of the more standard spring guide wires; however, they are in such common usage that they usually are not considered special or unique. There are, however, some wires of very special design for unique uses. Extra stiff, or Super Stiff™ wires (Medi-Tech, Boston Scientific, Natick, MA) are available in the standard and exchange lengths. The shafts of the stiffest of these extra-stiff wires are actually very rigid. All of these stiff wires do have a segment of various lengths of a soft or “floppy” distal end. When used pro- perly and in spite of their rigidity, these wires actually make the delivery of stiffer catheters and sheaths much safer, and they provide a much better support for balloon catheters during dilation procedures. They are indispens- able for some of the more specialized therapeutic catheter- ization procedures and their use in these procedures is discussed in more detail in the chapters dealing with those techniques. Special, stiffer wires such as the 0.014″ Iron Man,™ the 0.018″ V-18 Control,™ and the 0.021″ Platinum Plus™ wires are available in these smaller sizes and are very useful for supporting small balloon dilation catheters. These wires were developed primarily for use in coronary arteries, but are invaluable in the cardiac catheterizations of infants and small children. When the core wire is attached to the outer “winding” wire throughout the length of a spring guide wire, it allows the entire length of wire to be rotated (torqued) in a specific direction. If the combined wire and core wire are stiff and rigid enough, the wire can be torqued with a 1:1 ratio of the degree of rotation from end to end. With a curved, soft distal end on these wires, a torque wire can then be directed into very specific locations, into particu- lar vessels, branches or orifices by applying purposeful torque on the proximal wire. The rotation or torquing of the wire is facilitated by a small handle or “torque vise” CHAPTER 3 Cardiac catheterization equipment 92 attached on the proximal shaft of the torque wire. Again, this capability is absolutely essential in the performance of some of the more specialized therapeutic techniques, and is described in detail in Chapter 6. Another wire which is probably the most unique of the special designs and is very effective for entering dif- ficult locations is the Glide™ or Terumo™ wire (Terumo Medical Corp., Somerset, NJ). This is not a stainless spring guide wire but a long, fine, shaft of uniform diameter, Nitinol™ metal with a hydrophilic coating. The Nitinol™ material of the Terumo™ wire makes it very flexible and at the same time, virtually kink resistant. The hydrophilic coating, when very wet, makes the wire extremely slippery, however it becomes sticky and resistant to movement as the coating begins to dry. The combination of the springy shaft material, the slippery characteristics and a soft tip allows the wire to follow even small tortuous channels and to make acute turns when extended out of the tip of the catheter. Although these characteristics make a freely moving, non-constrained, tip less likely to perforate struc- tures, these same characteristics, however, also allow the wire to penetrate through myocardium and vascular walls more easily than standard spring guide wires. When the tip of the Terumo™ wire is exiting a catheter or the shaft of the wire is otherwise constrained because the shaft cannot bow or bend freely away and, at the same time, the tip is forced against intravascular or intracardiac structures, it readily perforates tissues. Standard, straight spring guide wires can be curved or formed to particular shapes for special uses. A J or even “pig-tail” curve can be formed on the soft tip of a standard straight spring guide wire. The soft or floppy distal end of the wire is pulled gently between a finger and a sharp straight edge of an opened scissors or clamp similar to curling the end of a piece of ribbon. Enough pressure between the finger and the straight edge is applied to curl the wire, yet not so much pressure is applied that the wire is stripped, pulled apart or the safety wire within the outer winding wire is broken. This curving of a soft wire tip is a learned procedure. Once a slight angled curve is formed on the soft tip of a torque controlled wire, the wire can be directed purposefully from side to side. Curves formed on the stiff ends of wires are very useful for deflecting the tips of catheters, particularly in deflect- ing the tip in two or more directions (three-dimensionally) simultaneously. The stiff end of a wire is always, and only, used completely within a catheter and never extended beyond the tip of the catheter. Curves are formed on the stiff ends of standard spring guide wires by manually bending a smooth curve with the fingers or wrapping the stiff end of the wire smoothly around a finger or a small syringe. The stiff end cannot be curved by pulling it between the finger and a sharp edge like the curving of the soft end. In forming any curve on a wire, special care is taken not to create any sharp bends or kinks in the wire. A sharp bend or kink creates resistance or even prohibits the passage of the wire through a needle, dilator, or catheter. A bend or kink along the shaft of a wire also prevents any rotation or torquing of the wire within a catheter. The details for forming these curves and the special uses of these wires are discussed in Chapter 6. In addition to the use of spring guide wires for adding extra support to catheters and for forming compound curves within catheters, there are special, smooth, fine stainless steel wires which are manufactured especially for the purpose of providing extra support for very floppy catheters and for forming specific curves on catheters. The Mullins’ Deflector Wires™ (Argon Medical, Athens, TX) are fine, polished stainless steel wires with a very tiny welded bead or micro ball at each tip. The tiny “bead” at each end keeps these wires from digging into the inner walls of the catheters. These wires are available in 0.015″, 0.017″ and 0.20″ diameters. The details of their use are described in Chapter 6. There are also special active “deflecting” wires with control handles used for actively deflecting or bending the tip of the wire and, in turn, the tip of catheters (Cook, Inc., Bloomington, IN). These are discussed in more detail in Chapter 6, dealing specifically with deflector wires. The standard guide wires and special wires are available from a variety of manufacturers including Boston Scientific, Cook, Argon, Medtronic and Guidant. Sheath /dilator sets for catheter introduction Percutaneous introduction and then the use of an indwelling vascular sheath in vessels is the standard tech- nique used for vascular access in the catheterization of pediatric and congenital heart patients. The advantages and the exact technique of this approach as well as the rea- sons for particular preferences for certain types of sheath and dilators are covered in detail in Chapter 4, “Catheter Introduction”. The specifications of the sheaths and dila- tors and their specific uses are discussed here. As with the needles and wires, the sheaths and dilators are available in many sizes and varieties and from many different manufacturers, including Argon, Cook, Cordis, Medtronic, Daig, Terumo and Boston Scientific. The French size of the dilator, like the French size of a catheter, designates the outer diameter of the dilator. At the same time, the French size of the sheath designates the inner diameter of the sheath and/or the diameter of the dilator/catheter that the sheath will accommodate. Usually the outer diameter of the sheath is approximately one French size larger than its advertised (inner) dia- meter, but depending upon the thickness and the materials from which the sheath is manufactured and the tightness of the fit of the sheath over the dilator, the outer diameter CHAPTER 3 Cardiac catheterization equipment 93 of the sheath can be as much as 2–3 French sizes larger than the stated sheath diameter/size. The Association for the Advancement of Medical Instrumentation (AAMI) established the standards for catheters, sheaths and dilators over three decades ago. The manufacturers agreed that sheaths must have precise manufacturing tolerances for the minimum diameter of their inner lumens while dilators and catheters must have equally strict tolerances for their maximum outer diameters. A catheter of a stated French size must pass smoothly through a sheath of the same advertised French size. A catheter should never be adver- tised as being a particular French size if it is even 0.01 mm larger in diameter than the advertised French size, and sheaths should never be advertised as a particular French size if the lumen is 0.01 mm narrower than the advertised French size. At the same time, when the catheter is passing through a sheath of the same French size, there should be no significant slack or extra space around the catheter within the lumen of the sheath and, in turn, no bleeding around the catheter even when there is no back-bleed valve in place on the sheath! There are some specific requirements for the ideal sheath/dilator sets used in cardiac catheterizations, par- ticularly in pediatric and congenital patients. The distal end of the dilator should have a long, fine and smoothly tapered tip. The inner lumen of the dilator tip should fit tightly over the guide wire designated for use with the dilator, and the tip of the dilator should have a smooth, fine transitional taper onto the surface of the wire. For example, the tip opening of a 4-, 5-, or 6-French dilator fits snugly over a 0.021″ wire, while a 7-French, or larger, di- lator fits snugly over a 0.025″ wire. In order to facilitate manipulation as a single unit during their introduction into a vessel, the dilator should lock securely into the sheath when the two are attached together. When the sheath and dilator are locked together, the taper of the dilator should begin at least one cm beyond the tip of the sheath; e.g. if the dilator has a 2 cm long taper, the tip of the dilator should extend 3 cm beyond the tip of the sheath when the hubs are together. Sheaths should be very thin walled, but their walls should be stiff and firm enough that they do not crumple, kink, or “accordion” on themselves when reasonable for- ward pressure or torque is applied to the sheaths. Most sheaths are now manufactured from thin teflon tubing. The tip of the sheath should fit very tightly over the di- lator, so that there is no gap or “interface space” between the outside of the dilator and the inner diameter of the tip of the sheath. The very tip of the sheath actually often tapers slightly to accomplish this tight fit over the dilator. The sheath should have a female Lure™ lock connecting hub at the proximal end and should have an available, but detachable back-bleed valve/flush port that is not permanently attached to it. When introduced from the inguinal area, the sheath should be long enough to extend into the common femoral vein and, when in position there, to have the tip aligned parallel with the iliac vein. In small infants, it is preferable for a sheath that is introduced into the femoral vein to extend proximal to the bifurcation of the inferior vena cava. When the tip of a short sheath only reaches and is positioned in an iliac vein in an infant, the tip tends to orient perpendicularly to the opposite iliac vein. This posi- tion traumatizes the vein wall unnecessarily, particularly as various catheter tips are advanced beyond the tip of the sheath. Twelve cm seems to be an optimal compromise in the length of the intravascular portion of the sheath (not including the length of the connection to the hub, the hub and the back-bleed valve) for both infants and larger sized patients. Sheath/dilator sets for special uses In addition to sheaths of the usual lengths for peripheral percutaneous introduction, there is now a variety of extra long sheath/dilator sets available from several manufac- turers including Cook, Daig, Arrow and Medtronic. These are used to circumvent unusual or difficult vessel intro- duction sites as well as for special diagnostic and many therapeutic catheterization procedures. Most (all?) of the currently available long sheaths come with attached back- bleed valves/flush ports. When a vein or an artery somewhere beyond the intro- ductory site has sharp bends or is very tortuous, an extra long sheath which extends through or past the bends and through all of the areas of tortuosity is positioned in the vessel at the onset of the procedure to bypass the bend or tortuosity. With the longer sheath in place, the manipula- tion around a sharp bend or through the tortuosity is per- formed only the one time during the introduction of the long sheath/dilator. Thereafter, the indwelling, longer sheath directs wires, catheters and devices through and past the sharp angles or tortuosity with no additional manipulations being necessary. Extra long sheaths are used to guide catheters directly and repeatedly to an area within the heart itself (biopsies, blade catheters), for transseptal procedures, to deliver special devices to particular areas within the heart or great vessels (stents, occlusion devices), and for the withdrawal of foreign bod- ies from the vascular system. There are large, long, special sheaths from Cook and Arrow which have a metal “braid” or winding in their walls to reinforce the sheaths against kinking. All of these special sheaths are discussed in sub- sequent chapters dealing with the specialized techniques for which they are used. All of the sheath/dilator sets which are necessary to accommodate the introduction of all sizes and varieties of catheters and devices which are utilized for all sizes of [...]... landmark Only a very superficial skin wheal is created initially with the 25 gauge needle If a vessel is entered inadvertently and blood withdrawn into the syringe during the in ltration of xylocaine with the small 25 -gauge needle, this needle is withdrawn from the skin and pressure is applied for at least several minutes before either continuing the xylocaine in ltration or starting the purposeful vessel puncture... for distinguishing between arterial and venous flow and are fairly accurate for determining the side to side location Vascular access of both arteries and veins in the deep subcutaneous tissues beneath the skin The type of vessel beneath the probe is distinguished by the difference in the timing and frequency of the audible flow signals, arteries and veins having distinctly different timing and frequencies... site and along the course of the wire beneath the skin between the skin puncture and the puncture into the vein This supports the wire beneath the skin and prevents the wire from bending or kinking in addition to preventing subcutaneous bleeding as the sheath/dilator set is advanced over the wire through the skin and subcutaneous tissue into the vessel A high-speed “drilling” motion of the combined... laboratories in the twenty-first century utilize a percutaneous puncture with a needle and guide wire to enter the vessels and then an indwelling sheath within the vessel during catheter manipulations This certainly is the accepted standard approach in the majority of centers in the United States However, the time-tested technique of performing a “cut-down” with an incision in the skin extending through... tissues and the wall of the vessel is necessary, using the plastic cannula of a MediCut™ The Medi-Cut™ is introduced over the wire and advanced deeply enough into the skin to enter into the vein By advancing the Medi-Cut™ as deeply into the tissues as possible (to the hub of the Medi-Cut™), the funnel shaped proximal taper on the Medi-Cut™ cannula enters the skin and subcutaneous tissues and, in turn,... procedure more difficult and less sterile Needle, wire and dilator/sheath introduction Needle introductioncinitial vessel entry In infants and small children, the needles and wires that are used are designed specifically for the purpose of percutaneous introductions (Argon Medical Inc., Athens, TX; Cook Inc., Bloomington, IN) The needle is thin walled and as small in diameter as possible in order to enter... to be used on the hubs of indwelling intravenous lines as a port for repeated injections The valve was punctured with a needle each time medications or fluids needed to be introduced into the indwelling line The ports are less than one cm in length and have a distal male slip lock attachment, which fits into the hub of Cardiac catheterization equipment a standard female Luer-lock hub/connector of a catheter... major vessels CHAPTER 4 are surprisingly close to the skin surface (as little as 3 mm in an infant and less than 1–1.5 cm even in most larger children and adults) In the precise area under the inguinal ligament, both vessels run parallel to the skin surface and parallel to the long axis of the leg The single-wall puncture technique for the introduction of the needle into the vessel is identical to the... cannula is within the vein and that the vein actually is patent If the vein is patent and the Medi-Cut™ is well within the vein, the soft J curved wire is reintroduced through the Medi-Cut™ and advanced carefully while the course of the wire is observed under fluoroscopy In rare circumstances, when the vein is widely patent but there is an unusual branch or turn in the course of the vein, a torque-controlled... introduced into both the artery and the vein through a direct needle puncture and the sheath/dilator is introduced over a wire into the vessel without a separate incision in the vessel Percutaneous technique The percutaneous technique is applicable for the introduction of catheters into both veins and arteries The percutaneous, indwelling sheath technique performed correctly and carefully results in . filled. CO 2 is extremely diffusable and escapes instantaneously into air through any opening, including the tiny opening in the tip of a syringe. If the tip of a syringe full of CO 2 remains open,. nurse/technician and, in turn, increases the accuracy and efficiency of recording, flushing and changing gains on specific lines/transduc- ers. The length of tubing on the field which extends from the catheter in. imaging. The findings have been striking, very interesting, and at times even frightening, however, the IVUS findings seldom significantly in uence decisions about the particular pediatric/ congenital