Abstract: Objectives. The aim of this review is to discuss different methods using the transradial approach (TRA) of accessing the native coronary arteries and bypass grafts to optimize the quality of angiographic results and support for interventional procedures. Background. Successful coronary cannulation provides the basis for optimal angiography and interventional success. There is limited literature describing successful transradial techniques of coronary and bypass graft cannulation. In this review, a variety of different challenges and their solutions are provided. Methods. Successful TRA methods for routine cannulation and modified methods for challenging cannulation of both native coronaries and bypass grafts are described based on the experience of several high-volume radial operators. Results. Differences in catheter/vascular lumen interactions endow different operating characteristics to catheters depending on whether the femoral or either radial approach is used. Understanding these differences contributes to success in TRA. In addition, techniques for cannulation of anomalous coronary origin, use of special catheter curves, small and large lumen guide catheters, sheathless guide catheters, universal catheters, and a special technique to cannulate the internal mammary artery from the contralateral radial artery are reviewed, with supporting figures. Conclusions. Despite lower bleeding and vascular complication rates as compared with transfemoral approach (TFA), the adoption of TRA has been relatively slow, particularly with cases of complex anatomy such as bypass graft cannulation. Anatomical challenges at various levels of the catheter course play an important role in TRA coronary and bypass graft cannulation failure. A logical approach and understanding of these challenges can augment procedural success and enhance quality.
J INVASIVE CARDIOL 2015;27(9):E182-E189
Key words: transradial approach, coronary cannulation, bypass graft cannulation
Transradial approach (TRA) for coronary artery intervention offers several advantages over the more traditionally used transfemoral approach (TFA).1-6 A reduction in bleeding and access-site related complications resulting in decreased morbidity and hospitalization has been consistently demonstrated in patients treated by TRA.1-8 The growth of TRA for coronary angiography and interventions has been relatively slow despite these advantages. There is a learning curve to the technique and operators may be hesitant in changing approaches due to perceived technical and anatomical issues associated with it.7-17 Operators without a skill set to reach the coronary tree and successfully cannulate vessels may experience a reduced overall success rate and poor study quality with inadequate images or poor support in the case of an intervention that could potential affect patient outcome or ability to achieve success.
Successful native coronary and bypass graft cannulation is a critical foundation skill to derive high-quality angiography and successful interventions. Fundamental angiographic skills derived from femoral procedures are applicable to a point, but transradial procedures carry unique challenges including issues with puncture site, radial, subclavian and aortic arch region.7-17 The device industry has worked for many decades to design hardware for cannulation of coronary ostia and bypass grafts while working from the femoral artery. TRA techniques are relatively young and less mature in comparison. Differences in cannulation routes between TFA and both right and left TRA add nuances in catheter characteristics between procedural approaches, along with techniques to transmit torque.9 Several experienced radial operators have designed diagnostic and guide catheters with different curves of particular utility and techniques to deliver larger-bore catheters for complex procedures through the relatively limited diameter of the radial artery.7,9,11 Ultimately, learning from the experiences of others can accelerate the learning curve and provide skills to ensure quality angiography and successful interventions.
Understanding the Catheter’s Course: TRA vs TFA
Approaching the heart from the femoral artery, it does not matter whether right or left femoral artery is used for coronary cannulation. Similarly, from the arm, the approach from the radial or ulnar arteries is quite analogous. But with TRA, there are subtle differences between the right and left approaches that are shown in the schematic diagrams of Figure 1.9 These figures depict the idealized catheter course via the TFA, right TRA, and left TRA. The sites of resistance in the passage of catheters and guidewires are different for each of these three approaches and provide some explanation as to the different maneuvers needed to cannulate the coronary arteries. For the TFA and the left TRA, there is one level of resistance affecting the torque of the catheter. While both approaches share a single level of resistance, forces applied at this single point will be different between the two approaches and alter catheter performance. From the right TRA, there are two levels of resistance. This adds a secondary interaction of the catheter with the vessel wall that needs to be overcome or accounted for in manipulating the coronary catheters.
Concept of hand-eye coordination. The maneuvers to allow the operator to torque and steer different catheters through the various angles of the vasculature are different between femoral and radial procedures. In routine cases with no significant tortuosities of the subclavian artery and no dilation and/or distortion of the arch, torque may not be a major issue, and the operator can cannulate the coronary ostia without much effort using techniques carried over from routine femoral angiography. Many femoral operators have found a fixed sequence of clockwise or counterclockwise torqueing maneuvers that have been handed down over generations of cardiology trainees. These rote maneuvers are less helpful for transradial procedures.
Instead of regimented catheter maneuvers, the use of hand-eye coordination becomes a valuable skill in transradial catheterization. When there is significant dilation, distortion, and/or tortuosity at the subclavian level, or aberrancy such as arteria lusoria or loops at the arch level, a deliberate approach to catheter manipulation is required. Rather than being concerned about whether to perform a clockwise or counterclockwise rotation, the operator needs to simply look at the screen and direct the catheter’s tip toward the coronary ostia.9 The eyes and hands of the operator should work and act in unison in a goal-oriented fashion. Small movements in an integrative approach that maximizes movement that is goal seeking while reversing counterproductive motion is the key for success.
Choosing Catheter Shapes for Native Coronary Cannulation During TRA
General considerations. There are different catheters available for TRA available in a variety of sizes and diameters. The choice of diagnostic or guide catheter is influenced by the site of radial access (right TRA vs left TRA), operator preference, and coronary origins (normal or anomalous). A list of catheters available for TRA is shown in Table 1. For TR diagnostic catheterization, a 5 Fr Optitorque Tig catheter (Terumo Corporation) is a good choice because it cannulates both left and right coronary arteries, and a left ventriculogram is also possible because it has an additional side hole. Moreover, this catheter has an advantage over JL and JR curves because multiple catheter exchanges can be eliminated if both coronary arteries can be completed with the same catheter. The major limitation of the Optitorque Tig curve is lack of back-up support; for this reason, it is not a good catheter shape for interventions.
JL and JR curves are also used for diagnostic studies with a high success rate by experienced operators. However, two catheters are required and multiple exchanges may increase the chance of radial artery spasm. Use of a JL curve a half size smaller, such as a JL3.5 instead of JL4, that might be commonly used first from the femoral artery; likewise, a JR4.5 rather than a JR4 may improve catheter/ostium fit on a routine basis via TRA, depending on the specific catheter brand. While Judkin’s curves between manufacturers may appear similar in dry packages, their characteristics in vivo can result in slightly different operating characteristics.
For diagnostic cannulation of anomalous origins of coronary ostia, AL, AR, or Multipurpose (MP) curves can be used. Whether arriving to the ostium from the leg or the arm, one needs a catheter that will extend close to the anterior surface of the aorta along the sino-tubular junction, where these origins are most likely to exist. Some trial and error may be necessary, but looping catheters such as a larger curved Amplatz or a looped MP can often provide the reach across the aorta when the ascending aorta projects the catheter initially posterior, while smaller curved Amplatz designs such as AR1 or direct cannulation with an MP may be efficient when the ascending aorta delivers the catheter anteriorly directly toward the anomalous origin.
Although various guide catheters are used by operators for percutaneous coronary intervention (PCI), the EBU (Medtronic, Inc), XB (Cordis Corporation), or Voda (Boston Scientific) are most commonly used for left coronary cannulation. JL curve is a common second choice for left coronary cannulation. For right coronary cannulation, JR curve should be preferred during PCI. In selected situations, AR, AL, MP, and Pa-Pa (Medtronic, Inc) curves can be used. While Judkin’s curves are not particularly thought to be good supporting guides from the femoral artery, they do provide better support when delivered from the radial arteries. More force is coaxially directed down the ascending aorta, in contrast to the loss of force experienced around the arch of the aorta during passage from the femoral artery.
Technical considerations. For left coronary cannulation, most operators start with an extra back-up curve (EBU, Voda, or XB), particularly for long or medium length left main coronary artery (LMCA). For short LMCA, a strategy to start with a JL curve is also reasonable. For right coronary cannulation, JR is a good curve to start with. For a downward take-off of right coronary artery (RCA), an MP-1 curve is more suitable. For shepherd’s hook origin, or a more superiorly directed origin of the RCA, an internal mammary artery (IMA) or an AL curve guide catheter can be a good choice.
If there is significant tortuosity in the subclavian region, or loop due to dilatation and/or distortion of aorta, or arteria lusoria, normal torque of catheter is not preserved. Hence, hand-eye coordination plays an important role for cannulation of coronary ostia. Rather than using the wrist movements for the torque of the catheter (regularly practiced while working through TFA), use the finger movements to cannulate coronary ostia while working through the TRA.9
At times, torque transmission may be difficult using just hand-eye coordination. Rather than allowing the catheter to kink under increased resistance to turning, placing a wire within the lumen of the catheter can add body to the equipment and enhance the ability to deliver torque to the end of the catheter. In such cases, using a wired catheter to steer grossly to the origin of the coronary, and then hand-eye movement to fine-tune the placement will usually succeed. If the catheter does kink, it needs to be replaced, as this will markedly reduce its performance and result in a nidus for spasm or knot formation.
Dealing with special situations. Special situations often are easily handled if the anatomy is understood and the general characteristics of the vascular origin are known. Blindly exploring the aorta without some degree of understanding of the anatomy is a recipe for a long case and inadequate angiography. While performing an intervention in an anomalous RCA arising high and anteriorly from the ascending aorta, a 6 Fr MP-1 catheter can usually provide coaxial alignment and good back-up support (Figure 2). During an intervention in an anomalous RCA arising from the left coronary cusp, a JL 3 guide catheter usually sits coaxially in the RCA ostium and offers good back-up support (Figure 3). Rarely, an AL guide catheter may be chosen for extra back-up purpose during RCA intervention. Unfortunately, it holds a greater chance of damaging or dissecting the RCA ostium; hence, it should be used with caution and respect for its potential hazards, especially by inexperienced operators (Figure 4).
JL guide catheters also provide an excellent extra back-up support for RCA cannulation (comparable to the support of EBU guide catheter for LCA).9 For cannulating the RCA using a JL curve, it should be carefully rotated in the same fashion. In case of difficulty, take a 0.032˝ standard guidewire and introduce the stiff end through the catheter lumen. Under no circumstances should the wire end be allowed to exit the catheter, as it has the potential to perforate the arterial wall. Bring the back end of the wire up to the primary curve of the catheter, again not letting it protrude outside the tip. Try to engage the RCA ostium in the regular fashion. It should engage successfully in most instances (Figure 5). At times, while engaging the RCA ostium working through right or left TRA, a 5 Fr or 6 Fr JR guide catheter has a tendency to selectively cannulate the conal artery (although this is more of a problem with a 5 Fr Tig Optitorque catheter). This situation is identified by a damping of the aortic pressure tracing. In this situation, the catheter should be disengaged immediately and a second attempt to engage the RCA ostium should be undertaken. If this problem persists, the use of the stiff end of a 0.032˝ or 0.035˝ guidewire (as described for cannulation of RCA using JL guide curve) should successfully engage the catheter in the RCA ostium (Figure 6). Alternatively, up-sizing to a JR4.5, which tends to have a slightly more inferior orientation than the JR4, might fit better. It is possible to use a deep-intubation technique via TRA to effectively tackle difficult distal lesions and to perform thrombosuction (Figure 7). This technique should be used very sparingly and only by very experienced radial operators.
Choosing Catheter Shapes for Bypass Graft Cannulation During TRA
General and technical considerations. After the introduction of the TRA, cannulation of bypass grafts was considered a relative contraindication. In contemporary interventional practice, both right and left TRA can be effectively utilized for bypass graft cannulation as well as PCI. Most bypass graft interventions in prior coronary artery bypass graft patients (93%) are performed in saphenous vein grafts (SVGs), with much fewer (7%) performed in arterial bypass grafts.21 This is consistent with the lower failure rates of arterial grafts, and especially LIMA bypass grafts.21
A 5 Fr Optitorque Tig catheter can be used with a high success rate for diagnostic cannulation of SVGs and radial artery (RA) bypass grafts through both right and left TRA (Figure 8). JR and AR catheters are also effective for cannulation and intervention of SVGs and RA grafts to the LCA and RCA (Figure 9). The MP-1 catheter is useful for cannulation and maintenance of coaxiality with the ostium during SVG to RCA intervention (Figure 10). If the aortic root is significantly dilated and/or distorted, an AL curve can be carefully used to cannulate the SVG to LCA or RCA (Figure 11). There is no difference in technique for cannulating SVGs and RA grafts working through the right or left TRA. For graft interventions through the TRA, 6 Fr guide catheters are usually preferred because it is possible to use most distal protection devices through them.
Dealing with special situations. A LIMA graft is easy to cannulate through the left TRA using an IMA catheter. The same IMA catheter can be effectively used for cannulation of the right internal mammary artery (RIMA) using right TRA. However, in many post-CABG patients, left radial arteries may have already been harvested for use as bypass graft conduit. In these patients, left TRA is not possible and LIMA cannulation can be done either through TFA or right TRA. Due to the extensive cross-collaterals found in the forearm, the absence of the radial artery may not necessarily preclude the successful use of the ulnar artery to cannulate an ipsilateral mammary artery graft.
One technique to cannulate LIMA using right TRA has been published.20 Working from the right radial artery, cross-over to the left subclavian artery can be challenging. Partial cannulation of the left subclavian artery using either an Optitorque Tig catheter or a Simon-1 catheter can be done and a 0.032˝ hydrophilic guidewire (Glidewire; Terumo Corporation) can be negotiated carefully through left subclavian and down the brachial artery deep into the ulnar artery (Figure 12A). The patient’s left elbow joint is flexed to trap the guidewire in the left cubital fossa (Figure 12B) and prevent prolapse back into the central aorta when exchanging catheters. Subsequently, either Optitorque Tig or IMA catheters can be easily negotiated in the left subclavian artery and the LIMA can be effectively cannulated (Figure 12C).
Role of 5 Fr Guide Catheters
Although 5 Fr guide catheters are presently used less frequently for interventions than large-diameter guides, it is important to understand their behavior during native coronary and bypass graft cannulation.
Advantages. A 5 Fr guide catheter allows interventions through a 5 Fr introducer sheath. There is an increase in comfort level and high success rate while working through very small and tortuous radial arteries or anomalous variants in the forearm.9 During deep intubation maneuvers, 5 Fr guide catheters are much less traumatic than larger guides and can provide significant back-up support or act in a fashion similar to a Guideliner-type catheter.
Disadvantages. During PTCA catheter removal, negative pressure can develop within the guide because of its small lumen; this allows the introduction of air and potentially risks air embolism in the coronaries. Five Fr guides also provide relatively poor visualization of the coronary system compared with 6 Fr and 7 Fr guide catheters, although this can be overcome with power injectors. They also limit the use of rotational atherectomy, distal protection devices, kissing-balloon, and kissing-stent techniques. Despite the potential limitations, some experienced operators report broad success with 5 Fr guides.
Role of Sheathless Guide Catheters
The outer diameter of a standard hydrophilic sheath is approximately 2 Fr sizes larger than the outer diameter of its corresponding guide catheter.9,18,19 Therefore, sheathless guide catheter insertion allows a larger internal lumen without increasing outer diameter size and a 8 Fr sheathless guide has the same outer diameter as a 6 Fr introducer sheath. Hence, it enables an operator to perform complex transradial interventions in most radial arteries. A similar strategy allows 5 Fr and 6 Fr sheathless interventions, equivalent to the use of 3 Fr and 4 Fr sheaths, in patients with very small radial artery lumens or for whom maintenance of radial artery patency is paramount. Minimizing trauma upon insertion of the sheathless guide catheter into the radial artery is the key to success with such an approach.
A sheathless guide catheter with hydrophilic coating and a long tapered central dilator is ideal for a seamless transition between wire, dilator, and guide catheter, leading to atraumatic entry and passage through the radial artery. These innovative catheters do work and provide an opportunity to deliver relatively large working lumens with minimal artery trauma. They are unfortunately only available in a limited fashion around the world, including the United States, and are also relatively expensive.
Role of 7 Fr Guide Catheters
In very complex interventions, such as LMCA bifurcation or complex CTO, the use of a 7 Fr guide catheter is warranted to accommodate multiple bulky devices. On the other hand, only 30% of radial arteries have a diameter sufficient to accommodate a 7 Fr introducer sheath and a 7 Fr guide catheter easily.9 Moreover, a sheathless guide catheter system is not available in many cath labs. Operator should be well versed with modified sheathless guide catheter techniques and balloon-assisted tracking techniques to increase the success rate using regular 7 Fr guide catheters without damaging the radial artery.9,12,19
Use of modified sheathless guide catheter technique. If a large-lumen catheter is required, one of the commercially available sheathless guides is the best option, but unfortunately this is not available in many markets. In such cases when a 7 Fr guide catheter is still needed, the technique that uses a modified sheathless guide catheter approach may work. This technique combines several catheter sizes commonly found in catheterization laboratory inventories in combination to construct a de facto sheathless system. After local anesthesia, radial artery puncture is done using a standard puncture technique. Once a 0.025˝ straight-tip hydrophilic guidewire is inserted into the radial artery through the plastic cannula, the cannula is pushed in the radial artery over the guidewire. Then, the guidewire is removed and diluted contrast is injected through the hub of the plastic cannula to record the passage of the radial artery. This limited angiogram provides information about radial artery diameter, tortuosity, and any anatomical abnormalities. A 7 Fr introducer sheath is very carefully negotiated over the wire just to keep a maximum of two centimeters of its tip inside the radial artery. The dilator of the sheath is removed and spasmolytic cocktail (200 µg of nitroglycerin and 5 mg of diltiazem) is given through the side port.
A 125 cm-long, 5 Fr MP-1 diagnostic catheter is then placed inside a 7 Fr guide catheter lumen and its tip is protruded beyond the lumen of the 7 Fr guide catheter. This 5 Fr within a 7 Fr system now becomes a “modified mother-and-child system” (Figure 13). It is introduced carefully through the 7 Fr introducer sheath over a 0.032˝ or 0.035˝ J-tip standard or hydrophilic guidewire under fluoroscopic guidance. The protruded part of a 5 Fr MP-1 catheter helps provide a seamless transition for the smooth passage of a 7 Fr guide catheter through the arterial tree. It allows atraumatic passage of a 7 Fr guide catheter through a small-diameter radial artery. Moreover, it also minimizes the “razor effect” on the intima of the artery. When the guide catheter over a 5 Fr MP-1 diagnostic catheter enters the brachial artery, the tip of the introducer sheath can be pulled back over the shaft of the 7 Fr guide catheter (Figure 14). Once the 7 Fr guide catheter over a 5 Fr MP-1 catheter enters the ascending aorta, the coronary ostium is cannulated using standard technique.
Use of balloon-assisted tracking technique (BAT). BAT is an easy-to-use alternative technique that helps increase the success rate of diagnostic procedures and PCI during TRA without damaging the vasculature.12 In case of resistance to catheter movement or significant local pain, BAT can be performed with a predictably high success rate. A 2.5 x 15 or 20 mm PTCA catheter should be used, and depending on the type of anatomical complexity, a low or medium inflation balloon pressure should be used for successful tracking of a 7 Fr guide catheter. About 7-10 mm protrusion of inflated balloon segment is adequate to negotiate most vasculature complexities. Because a PTCA balloon catheter is used, the entire assembly is tracked over a 0.014˝ soft-tip PTCA guidewire. BAT helps easily track a 7 Fr guide catheter through complex RA anatomy, small diameter radial artery, and radial artery spasm by eliminating the “razor effect” (Figure 15).
Delivery of optimal interventional care demands excellent angiographic technique and subsequent support for interventional procedures. While radial procedures can obviate several of the disadvantages of transfemoral access related to access-site complications, this could be negated by technical difficulties while performing transradial procedures. Understanding the anatomy and dynamics of catheter performance from the radial artery can rationalize successful catheter choice and technique for transradial diagnostic and interventional procedures. Knowledge of the behavior of different catheters during special situations is important, along with which catheters are most likely to work from others’ prior experience. Although the 5 Fr and 6 Fr guide catheters are the typical workhorse catheters, operators should also know the intricacies of using smaller-size and larger-size diagnostic and guide catheters. An operator should be well versed with different catheter shapes for bypass graft cannulation during left and right TRA and techniques to overcome complex arterial graft origins, such as when ipsilateral radial access is not available. Despite the many diagnostic and guide catheter shapes available, an ideal “radial Judkins curve” has not yet been developed, but then neither has a perfect femoral catheter.
Acknowledgment. The authors are grateful to Mr Yash Soni and Mr Chidambaram Iyer for their extremely valuable support during preparation of this manuscript.
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From the 1Apex Heart Institute, Ahmedabad, India; 2Department of Cardiology, Sheth V.S. General Hospital and Smt. N.H.L. Municipal Medical College, Ahmedabad, India; 3Department of Cardiology, Mercy Hospital and Community Medical Center, Scranton, Pennsylvania; 4Beth Israel Medical Center, New York, New York; and 5Penn State Hershey Medical Center, Hershey, Pennsylvania.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.
Manuscript submitted September 4, 2014 and accepted September 8, 2014.
Address for correspondence: Tejas Patel, MD, FACC, FSCAI, FESC, Chairman, Apex Heart Institute, Ahmedabad-380 054, India. Email: firstname.lastname@example.org