Selection of Hardware and Cathlab preparation for Transradial Approach
Urmil Shah
The Heart Care Clinic, Bodakdev, Ahmedabad Gujarat

Introduction
Although the transfemoral approach (TFA) for cardiac catheterization and intervention has gained widespread acceptance, the transradial approach (TRA) for coronary procedures has gained progressive acceptance since its first introduction by Campeau in 1989 for diagnostic coronary angiography and its improvement by Kiemeneij and Laarman for percutaneous transluminal coronary angioplasty (PTCA) and stenting1,2. Evidences suggest that lower access site complications, improved patient comfort, and reduced costs, in addition to almost nil vascular site complications, are the major advantages contributing considerably for increasing popularity of TRA for coronary angiography and angioplasty, including primary percutaneous coronary interventions (PCI)3,4. Moreover, recently published reports support that apart from reducing complications, such as major bleeding, TRA selection may also result in a better clinical outcome compared to femoral access5.
Conversely, there are some valid concerns regarding the use of TRA for coronary access which may limit its widespread adoption. A range of reasons underlying a procedural failure by TRA have been identified: inability to successfully puncture the radial artery, failed cannulation of coronary ostia due to difficulty in rotating and/or manipulating the catheters, inadequate catheter support or an inability to track the device in the correct place6. Achieving access to the radial artery is technically more challenging and time-consuming than gaining femoral access, but when the right skills are grasped, the technique is much easier and reliable7. Hence, selection of pertinent hardwares is elementary but an issue of extreme importance in performance of PCI.

Diagnostic Catheterization via Transradial approach
Sizing and Selection of Catheter
            Since the radial artery is smaller compared to the brachial and femoral arteries, naturally the operator should use small-caliber needles, wires, and catheter in order to ensure optimal safety.  It is advisable to use a micropuncture needle (21 gauge, 4 cm long) that would allow placement of a 0.018 inch-guide wire (MicroPuncture Set, Cook Incorporated, Bloomington, IN). The guide wire should be advanced with great care. Resistance to passage or radial artery tortuosity and further advancement can lead to dissection or perforation. Faced with resistance to wire advancement, placement of a short small-bore plastic introducer over the wire can be used for angiography of the distal portion of the radial artery. Once fully advanced, this guide wire allows for the placement of a long 5F hydrophilic sheath (23 cm) with a tapered introducer. Anticoagulation (typically 2,500 to 5,000 U heparin IV) is administered immediately after sheath insertion, and many operators also administer a cocktail of vasodilators (nitroglycerine 100 or 200 µg and/ or Nicorandil 2-4 mg (+) verapamil 1.25 to 2.5 mg or Diltiazem 5-10 mg) via the sheath to reduce radial artery spasm. The use of hydrophilic sheaths, however, has resulted in a dramatic reduction in radial artery spasm that can, in turn, lead to significant discomfort during catheter manipulation or sheath removal.

correspondence:  Dr urmil.shahThe Heart Care Clinic, 201, Balleshwar Avenue, Opp Rajpath Club, Sarkhej - Gandhinagar Road,Bodakdev, Ahmedabad – 380015
E-mail:urmil.shah@heartcareclinic.org

curve (JR, MP) catheter near the tip of a 0.025” hydrophilic wire. After successful passage of the 4F catheter, the initial wire is exchanged for a regular 0.035” one. In rare cases, in which the diagnostic catheter cannot pass through, a mictovascular catheter (Transit) may resolve the difficulty. The floppy wire can then be exchanged for a stiff PCI wire (even 0.018”), which will hopefully straighten the loop and allow the catheter to pass through successfully.
Following options can also be tried to facilitate the challenging manipulations when guide wire movement is difficult:

Rotate the needle to change the angle of the bevel
Do a radial angiogram
Use a hydrophilic-coated wire
Trya.018PTCAwire
PTCA wire
Give vasodilators through the needle and then try to advance wire

Diagnostic angiography via the radial artery approach requires some modifications from routine transfemoral angiography. Diagnostic catheters (usually 5F) are advanced into the aortic root over a 0.035-inch 1-mm J wire. If passage of the J wire into the ascending aorta is difficult owing to subclavian artery tortuosity, having the patient take a deep inspiration helps avoid the descending aorta, as does counterclockwise catheter rotation.

Figure 2: Brachial Artery Loop (a) Before wiring (b) During wiring (c) Artery unlooped by a hydrophilic coated guidewire

left main via the right radial artery requires smaller catheters (e.g. JL 3.5 compared with JL4, XB3 compared with XB3.5) compared with those used for femoral or left radial procedures.
Engagement of the coronary ostia may be facilitated by leaving the guide wire within the catheter to enhance torquability. Use of a smaller injection syringe (i.e. 8 ml rather than 12 ml) or a power injection may optimize angiography with 4F and 5F catheters.
To limit exchanges, some operators prefer using a single catheter (e.g. AL1, AL2, Kimny, Barbeau) for both left and right coronary angiography. Catheter exchanges should always be performed with a guide wire remaining in the ascending aorta.
            The Kimineij catheter and other catheter shapes have accomplished this and could serve as a universal catheter with the ability to perform left and right coronary arteriography and left ventriculography using the same catheter. The catheter requires specific manipulations to use it safely and hence involves a learning curve.
            The latest in the series of universal catheters is the Optitorque™ Catheter with a Tiger tip (“Tiger catheter,” Terumo Interventional Systems, Somerset, New Jersey) developed with a Judkins left catheter shape with an “opened up” primary curve, allowing bilateral coronary arteriography.

There is a paucity of data comparing standard Judkins catheters and Tiger catheters for performing right radial access coronary angiography and left ventriculography. However, a multicentre study, which compared the efficacy and safety of the Amplatz Left (AL) versus the radial –dedicated Tiger catheter for right transradial approach (RRA) coronary angiography, showed, the use of Tiger was associated with a significantly higher success rate than that of the AL (95% Vs 75%)9.
            In case of normal anatomy, where innominate-arch junction is not distorted (Fig.1 (1)), the turn to enter into the ascending aorta is smooth and does not pose challenges in performing diagnostic or interventional procedures. On the other hand, the procedure requires special attention and unusual curves, whenever necessary, along with judicious use of catheter to accomplish the procedure in case of abnormal anatomy due to dilation and/or distortion of the aorta (Fig.1 (2)–(4)) at innominate-arch junction. The slippery Terumo wire facilitates relatively ease entry into the ascending aorta in challenging situations. A 0.032-inch or a 0.025-inch hydrophilic Terumo Gliderwire can be used successfully when problems may be encountered while entering aorta or use of standard guide may be challenging due to its tendency to slip into the descending aorta.
            Arterial Lusoria, a rare situation (prevalence rate around 0.1% among 20,000 transradial cases), needs special attention and unusual curves, whenever necessary, along with judicious use of catheter to accomplish the procedure. For diagnostic procedure to cannulate the left coronary ostium, a Judkins left, Optitorque TIG, or an Amplatz left catheter; where as to cannulate right coronary ostium a Judkins right or an Amplatz right catheter can be utilized. 
            Suitable catheters include those designed for the femoral approach and dedicated radial catheters. The catheters conventionally designed for transfemoral angiography, usually requires more technical skill when employed for coronary engagement from the radial artery.Unlike the transfemoral approach, the anatomic and geometric characteristics of accessing the ascending aorta from the right or left radial artery are very different. The left radial approach is similar to the femoral approach in view of the fact that it involves entering the ascending aorta from the aortic arch. The right radial approach, on the other hand, is different from the femoral approach in view of the fact that it involves a vertically downward approach to the ascending aorta, completely excluding the aortic arch (in majority of the patients, except those with arteria lusoria). Femoral catheter shapes perform adequately from the left radial approach and hence allow the femoral operator to avoid major changes in catheter selection or manipulation. The right radial approach involves some alteration in selection of catheter shapes and major modification of catheter manipulation techniques, forming the bulk of the “learning curve.” The learning curve for transradial catheterization is variable and ranges between 20–200 procedures.
             While doing angiography on post Coronary Artery Bypass Graft (CABG) patient, one can prefer to go from left radial artery as it becomes easy to engage Left Internal Mammary arteries (LIMA) otherwise, angiography of right radial artery; it is difficult to negotiate the diagnostic catheter from aorta to left sub-clavian artery occassionally. Side winder catheter or SIMS catheter (Portex Limited, Hythe, Kent, UK) may be helpful to pass the wire into sub-clavian artery and one can exchange diagnostic JR-4 catheter afterwards and one observe LIMA. 

Tools for Transradial Intervention
The benefits of TRI are clearly greatest in the group of patients transferred to an interventional centre for the management of acute coronary syndromes (ACS) following radial angiography10. Recent data suggest that transradial-access PCI can be performed successfully as a follow-on procedure in complex patients and complex lesions, such as in acute-MI patients and those older than 80 years of age11.
As far as equipments are concerned, variety of equipments are available for radial artery access. Since radial artery is smaller than the femoral one, selection and manipulation of TRI is somewhat different than in TFI.
Majority of coronary interventions today are performed via 6F guides and almost all recently designed stents can be delivered through 6F guiding catheters12. Though, catheters or sheaths of up to the size of 8F can be accommodated through the radial approach13,14, at present guiding catheters larger than 6F are rarely required for the purpose of PCI15,16. The most difficult part of any approach is to have strong guide support, sufficient for stent advancement across the target lesion. Coaxial alignment and adequate backup support from the contralateral aortic wall is a prerequisite for safe stenting17.

Guiding Catheter Back-up for Transradial Approach
There are two types of back-up for a guide catheter; “passive” and “active back-up”. Passive back-up is obtained when a catheter is inserted into the coronary artery and left where it is. Active back-up entails the operator manipulating the catheter in some way. When a JR catheter is inserted into the right coronary artery, it is deeply engaged to the end of segment 3, and a stronger back-up is obtained.
Depending on their shape, some catheters are mainly suitable for passive back-up although active back-up may still be obtained (depending on the situation), and others are better suited to passive back-up with active back-up almost impossible. There are still others that are better for active back-up than for passive back-up. The decisive factors are not only the catheter’s shape, but also the size and characteristics of the shaft, whether the right or left radial artery is to be approached, or the shape of the aorta or the site of the coronary artery ostium of each individual patient.
The concern arises as to the extent one should try to obtain passive back-up in transradial coronary intervention. Initially, when rigid inflexible Palmaz-Schatz stents were being implanted using bare mounts, it was strong passive back-up that made the procedure easier. However, when the stent is unable to reach the lesion, it becomes extremely difficult to get the bared Palmaz-Schatz stent back into the guide catheter. This procedure demands sureness of touch and allows no room for failure. With the recent improvements in the performance of stents, it is suggested that passive back-up is rarely required once the catheter is fixed in the coronary artery. With the engagement of the stent assured, and even if the stent cannot pass through the stenosis, it can be retracted. However, it remains essential that the wire and balloon cross the lesion in the first place to ensure complete distal engagement and then rely on active back-up.Both passive and active back-up can be acquired with the 6F guide catheter. When it is required to use “kissing” balloons or doing rotablation with a 6F guide-catheter, it provides a strong passive back-up and devices can be easily inserted. It is possible to obtain stronger passive back-up with the 7F or larger than with the 6F, as long as the shape of the catheter remains the same.  This size, however, is not suitable for deep engagement and active back-up is unlikely to be obtained. Contrary to this, a 5F catheter

can offer a very weak passive back-up as the catheter is merely “hung” onto the coronary artery. However, this soft catheter is suitable for deep engagement and active back-up is easier to obtain. A long-tip catheter offers the benefit of strong passive back-up and makes easy the extremely difficult maneuvers such as crossing the wire and balloon through a chronic total occlusion or wiring with Shepherd’s crook.
Difficult Guide Placement and Guide Wire Movement
Although diagnostic and guiding catheters are now increasingly suited for radial intervention, the placement is still somewhat different than that used via femoral access. Radial intervention requires knowledge of appropriate catheters and sizes, as detailed earlier. After successful access is achieved, it is sometimes difficult to advance the guide wire with conventional equipment and methodology under certain conditions. These rare conditions include unusual coronary anatomy, chronic total occlusion, heavy vessel calcification, tortuosity and angulation, or ostial disease which prohibits deep engagement of the guiding catheter. Methods to enhance stent delivery in challenging coronary anatomy include adequate “lesion or vessel preparation” by balloon such as with the AngioSculpt® (AngioScore, Inc., Fremont, California), or the Cutting Balloon (Boston Scientific Corp., Natick, Massachusetts), and by ablation methods. The choice of supportive guide catheter, “5-in-6” guide catheter method, the use of “extra-support”, single or multiple “buddy wires”, and greater support can be obtained by positioning an additional wire or an inflated balloon in a side branch or even dissection plane.
Alternatively when optimal guide catheter support is lacking and distal stent delivery is challenging, stenting can be facilitated from proximal to distal segments by burying a guide wire under the struts of the proximal stent (“buried wire” method).
Several other maneuvers facilitate guide placement:

1. Start the guide below the ostium (especially when approaching the left coronary), by pushing down on the catheter, the tip will bend up towards the left main. Pulling the catheter back then, will allow the tip to cannulate the ostium. This is different from conventional placement via a femoral approach, which usually engages the ostium from a superior position.
2. Always use an exchange length wire when changing catheters to avoid the need to recross the great vessels.
3. Although rarely needed the patient can be asked to inspire and/or change the angle of the arm to facilitate catheter movement.

Stabilizing a guide with the Extra-support wire during TRI
Different types of Extra-support wires like Stabilizer Platz (Cordis) and Zinger Support (Medtronic) are available nowadays. While using Extra-support wires, one has to be aware of coronary artery spasm proximal to lesion, especially in tortuous artery (Concentrine effect).
Stabilizing a guide with the “Buddy” wire technique during TRI
In this technique, a second angioplasty wire can be advanced parallel to the first one. It straightens the tortuous proximal segment and provides better support for device tracking. A second wire in a side branch can be very useful in “anchoring” the guide (e.g., second wire in LCX when dilating LAD lesion). This provides for better “backup” and allows retraction of the guide without loss of position when necessary. It also prevents the guide from being “sucked in” beyond the LM when pulling back high profile, poorly rewrapped balloon catheters following stent deployments or post-stent dilations. However, a second wire in a non-diseased branch would cause unnecessary denudation of endothelium in that vessel. If one wire does not help, a third or fourth wire may help to advance the interventional devices.

TRI of Tortuous Arteries
Tortuous coronary arteries often provide a challenge to the interventional cardiologist. PCI of these lesions is associated with a lower success rate (70-85%) and higher acute complications (upto 15%)18-21. Tortuousity may be defined as at least 2 or more than 75º bend proximal to the target lesion or at least one proximal bend 90º. Proper selection of hardware, guide catheters, guide wire and balloon catheter is critical for success and safety of these procedures. The pre-requisites for guide catheter is better support, perfect co-axiality, kink resistance and ability to fix the tip of catheter in ostium of intubated artery contributing to a stable position. For LAD interventions XB, or XB LAD is chosen, whereas a Voda or EBU catheter may be appropriate for the LCX interventions.
Interventions for Left Coronary Artery
For left coronary angioplasty, especially Left Anterior Descending Artery (LAD), the extra-backup curves are advised. Extra backup catheters, EBU (Medtronic, Minneapolis, MN, USA) or XB (Cordis, Cordis Corporation, Johnson & Johnson, USA) or Voda (Boston Scientific/Scimed, Maple Grove, MN, USA) are suitable to provide adequate backup during PCI for the left coronary system. The first-choice guide for the left coronary artery (LCA) is the 6F 3.5 extra back-up, which provides greater support than the Judkins due to larger contact area and  the fact that it nearly makes a right angle with the contralateral aortic wall. An inherent drawback of extra backup guides is the tendency for deep intubation of the LAD or the left circumflex artery (LCX) in the presence of a short left main (LM). The Judkins guide is useful in the setting of noncomplex lesions or in LM stenosis, in which good support is not a critical factor. Judkins left catheters are also preferred for the left main coronary artery (LMCA) interventions and in rare cases, in which extra backup catheters are not suitable. When the target artery is the LCX, a 0.5 larger size is preferred for better coaxial alignment. If active support is deemed necessary, deep seating in the LAD can be achieved with a 5F short-tip Judkins (JL). An Amplatz left (AL1.5 or 2.0) is suitable for complex lesions of the LCX and provides greater passive support. Cannulation of the LCA ostium and obtaining optimal back-up support might be fairly difficult in patients with a dilated and unfolded aorta. In cases where the innominate artery has a distal origin, the guide approaches the LCA primarily from the left and this hinders manipulation. Deep inspiration and leaving the wire in the guide may help in this setting.

catheter, the choice of the percutaneous transluminal coronary angioplasty (PTCA) guidewire depends upon the characteristics of the lesion. For most lesions, a balanced middle-weight (BMW, Guidant, Abbott Vascular, US) guidewire is used. While tackling chronic total occlusions, a Pilot 50/150 (Guidant, Abbott Vascular, US), a Cross-It 100/200 (Guidant, Abbott Vascular, US), a  Conquest (Asahi Intech, Japan) wire, or a Miracle wire (Asahi Intech, Japan) series is used, depending upon the character and severity of the occlusion.
Primary angioplasty and TRI: Addition of Suction Device
For primary angioplasty, the 6F guiding catheter is preferred as most of the thrombus extraction catheters that are available are 6F-compatible. For thrombus extraction from the left anterior descending (LAD) and the right coronary artery (RCA), a deep intubation of the guiding catheter is advocated if the patient’s anatomy permits. The greatest advantage of transradial PCI in acute myocardial infarction is that patients can be taken for PCI immediately after thrombolysis without much concern about local vascular complications, which are a major concern when using the transfemoral route after thrombolysis22,23,24. As stated earlier, once the coronary artery is cannulated, the steps of PCI are essentially similar to those involved in PCI performed through the transfemoral approach. Stenting via the radial route is considered technically more challenging.
The Thrombuster II device has been approved for the removal of thrombus and debris in the coronary or peripheral artery by percutaneous suction25. It is a single-user, easy to handle design based on rapid exchange short monorail system (10mm) using standard guidewire techniques and is available in two sizes for use in 6Fr and 7Fr standard guiding catheters. It has a radiopaque marker at distal guidewire lumen and a proximal luer-lock port. The proximal luer lock connector connects extension tube and the lock type aspiration syringe (30cc) that allows for easy and effective aspiration. The catheter is 140cm long, and its distal portion (30cm) is hydrophilically coated. The inner diameter of aspiration lumen is 1.10mm at proximal part and 1.00mm at distal part as for 6Fr type and 1.32mm at proximal part and 1.20mm at distal part as for 7Fr type. This feature, together with the better flow kinetics of a circular lumen and the hydrophilic coating, is thought to improve its performance. In addition, the proximal cross sectional area of 0.95mm2 and 1.37mm2 (in the 6Fr and 7Fr systems respectively) are the largest currently commercially available thrombectomy devices.
Conclusions  
The transradial approach for coronary procedures is a safe technique and virtually abolishes vascular entry site complications and permits a wide range of diagnostic and therapeutic interventions. Although there is a steep initial learning curve with transradial catheterization, once cardiologists are comfortable with this procedure in elective settings, they can begin to use the technique in many percutaneous coronary interventional procedures, including acute myocardial infarction7. Given the potential benefits associated with transradial cardiac catheterization, it is a technique with which current and future interventional cardiologists should gain increased familiarity and comfort. Nonetheless, technical challenges may impose crossover to another approach, with a rate of about 1 in 14. On the whole, the radial approach is an interesting choice in a broad range of patients, provided that experienced operators, state-of-the-art materials, and willingness to crossover to the femoral approach are available.

References:

1.Campeau L. Percutaneous radial artery approach for coronary angiography. Cathet Cardiovasc Diagn. 1989;16:3–7
2.Kiemeneij F, Laarman GJ. Percutaneous transradial artery approach for coronary stent implantation. Cathet Cardiovasc Diagn. 1993;30:173–178
3.Cooper CJ, El-Shiekh RA, Cohen DJ, et. al. Effect of transradial access on quality of life and cost of cardiac catheterization: a randomized comparison. Am Heart J. 1999;138:430–436
4.Mann JT, Cubeddu G, Schneider JE, Arrowood M. Right radial access for PTCA: a prospective study demonstrates reduced complications and hospital charges. J Invas Cardiol. 1996;8:40
5.Sciahbasi A, Pristipino C, Ambrosio G, et.al. Arterial Access-Site–Related Outcomes of Patients Undergoing Invasive Coronary Procedures for Acute Coronary Syndromes (from the ComPaRison of Early Invasive and Conservative Treatment in Patients With Non–ST-ElevatiOn Acute Coronary Syndromes [PRESTO-ACS] Vascular Substudy). Am J Card 2009; 103 (6):796-800

6.Louvard Y, Pezzano M, Scheers L, et. al. Coronary angiography by a radial artery approach: feasibility, learning curve: one operator's experience. Arch Mal Coeur Vaiss. 1998;91:209–215
7.Goldberg SL, Renslo R, Sinow R, French WJ. Learning curve in the use of the radial artery as vascular access in the performance of percutaneous transluminal coronary angioplasty. Cathet Cardiovasc Diagn. 1998;44:147–152
8.Louvard Y, Dumas P, Louberye C, Lefevre T, Morice MC. Predictive factors of failure in transradial coronary angiography and angioplasty. Arch Mal Coeur 2002; 95 (Suppl 3): 514
9.Doganov A, Benamer h, Garot P, et.al. Transradial approach for coronary angiography; looking for the ideal multipurpose catheter? Amplatz Left versus Tiger shapes randomized comparison. Am J Cardiol 2005; 96: 120
10.Sciahbasi A, Pristipino C, Ambrosio G, et.al. Arterial access-site-related outcomes of patients undergoing invasive coronary procedures for acute coronary syndromes (from the PRESTO-ACS vascular substudy). Am J Cardiol 2009; 103: 796-800.
11.T S N Lo, I R Hall, R Jaumdally, et.al. Transradial rescue angioplasty for failed thrombolysis in acute myocardial infarction: reperfusion with reduced vascular risk. Heart. 2006 August; 92(8): 1153–1154.
12.Brito JC, Júnior AA, Oliveira A, Von Sohsten R, Filho AS. Transradial Approach for Coronary Interventions. Arq Bras Cardiol 2001; 76: 374-378
13.Hinds KL, Kauffman DM, Drinkwater VL. Transradial catheterization reduces nursing time and intensity in patients undergoing cardiac catheterization. Circulation 1996; 94: 2091.
14.Guidelines for percutaneous transluminal coronary angioplasty. A report of the American College of Cardiology/American Heart Association Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures (Subcommittee on Percutaneous Transluminal Coronary Angioplasty). J Am Coll Cardiol 1988; 12: 529-545.
15.Rao SV, Ou FS, Wang TY, et. al. Trends in the prevalence and outcomes of radial and femoral approaches to percutaneous coronary intervention. J Am Coll Cardiol Intv 2008; 1:1379-1386.
16.Metz D, Meyer P, Touati C et. al. Comparison of 6F with 7F and 8F guiding catheters for elective coronary angioplasty: results of a prospective, multicenter, randomized trial. Am Heart J 1997; 134: 131–137.
17.Ochiai M, Isshiki T, Toyoizumi H, et. al. Efficacy of transradial primary stenting in patients with acute myocardial infarction. Am J Cardiol 1999; 83 (6): 966-968
18.Tan K, Sulke N, Taub N, et. al. Clinical and lesion morphologic determinants of coronary angioplasty successvand complictions: Current experience. J Am Coll Cardiol 1995; 25: 855-865.
19.Ellis SG, Nandormael MG, Cowley MJ, et. al. Coronarybmorphologic and clinical determinants of procedural outcome with angioplasty for multivessel disease. Implications for patient selection. Circulation 1990; 82: 1193-1202.
20.Flood RD, Popma JJ, Chuang YC, et. al. Incidence, angiographic predictors, and clinical significance of coronary perforation occurring after new device angioplasty. J Am Coll Cardiol 1994; 23: 301A.
21.Holmes DR, Berden L, Simpson SG, et. al. Abrupt closure: CAVEAT experience. J Am Coll Cardiol 1994; 23: 1585A.
22.Thompson CA. Transradial Approach for Percutaneous Intervention in Acute Myocardial Infarction. J Inv Cardiol 2009; 8 (Suppl A): 25-27
23.Saito S, Tanaka S, Hiroe Y, et. al. Comparative study on transradial approach vs. transfemoral approach in primary stent implantation for patients with acute myocardial infarction: Results of the test for myocardial infarction by prospective unicenter randomization for access sites (TEMPURA) trial. Catheter Cardiovasc Interv 2003;59: 26–33.
24.Cantor WJ, Puley G, Natarajan MK, et.al. Radial versus femoral access for emergent percutaneous coronary intervention with adjunct glycoprotein IIb/IIIa inhibition in acute myocardial infarction--the RADIAL-AMI pilot randomized trial. Am Heart J 2005;150:543–549.
25.Ramcharitar S, Sianos G, Van der Giessen WJ. Use of a thrombus extraction catheter (Thrombuster II®) in an acute myocardial infarction. EuroInterv.2007; 3: 529-531