Transradial Basics: A practical approach to coronary catheterization and intervention via the radial artery.
Matthew L. Bilodeau, MD, PHD, and Daniel I. Simon, MD, FACC, FAHA, FSCAI.
The use of a percutaneous transradial artery approach for diagnostic coronary angiography was first described by Dr. Lucein Campeau.1 Dr. Ferdinand Kiemeneij adapted equipment and advanced the use of the radial artery for percutaneous coronary intervention (PCI).2,3 Randomized studies comparing radial and femoral artery access for coronary angiography and PCI have consistently found that a radial approach reduces access site complications, decreases length of hospital stay, and yields better outcomes at lower costs.4-8. The radial approach is generally preferred by patients because of reduced periprocedural discomfort, decreased time to ambulation, and improved post procedural quality of life.6 The radial artery is superficial and easily compressible with no major nerves or veins in its vicinity, thereby reducing the risk of neuropathies or arteriovenous fistulas. Importantly, major vascular complications involving radial artery access are rare (this is addressed in more detail on page 46). Significant atherosclerosis of the radial and brachial artery is rare, so in this regard, transradial catheterization is particularly advantageous for patients with peripheral vascular disease or morbid obesity. In appropriately selected patients, repeat radial artery access can be performed safely and successfully.9
There is a significant operator learning curve associated with the radial approach, which incurs higher procedure failure rates, increased radiation exposure, and longer procedure durations.8,10 Despite being more challenging than routine femoral artery access, success rates for experienced operators in achieving radial artery access are more than 95%.11 The smaller artery size rarely restricts interventional device options given the availability of hydrophilic-coated sheaths for 6- and 7-F guiding catheters, thereby providing device flexibility for complex procedures involving, for example, bifurcation treatment, embolic protection, thrombectomy, or even rotational atherectomy (burr < 1.75 mm). In the modern era of PCI, experienced operators enjoy procedural success rates with the radial approach that are similar to the femoral approach11,14 but require new techniques for appropriate guide support. With operator experience and careful patient selection, success rates for coronary angiography and intervention in patients with coronary artery bypass grafting (CABG) are similar between radial and femoral approaches.15-17
RADIAL ARTERY ACCESS
Radial artery occlusion is the most common complication of radial artery access, with a varied incidence of 3% to 9%.18 Radial artery occlusion is a thrombotic process that can be reduced by using a sheath size with an outer diameter that is less than the inner diameter of the radial artery,19,20 administering periprocedural heparin,21 and achieving patent hemostasis.22 Although occlusion of the radial artery may preclude future transradial catheterization, it is seldom of any clinical significance because of the anatomy of the deep and superficial palmar arches, which allow the ulnar artery to deliver a collateral vascular supply to the hand. Most operators use the validated, modified Allen’s test to evaluate patency of the palmar arches.12,13 This test relies on pulse oximetry of the thumb to detect arterial blood flow with compression of the radial artery. The presence of an arterial waveform (even if delayed or with reduced amplitude) and a hemoglobin oxygen saturation > 90% (Figure 1, Barbeau grades A, B, and C) confirm the adequacy of a collateral vascular supply to the hand.
In general, the right arm is favored for routine transradial catheterization, because access via the left arm requires marked adduction of the arm to retain a routine laboratory setup with positioning of the operator on the patient’s right side. Additionally, cardiac surgeons prefer to harvest radial artery conduit for CABG from the arm of a patient’s nondominant hand (most commonly the left arm), and conduit arteries for CABG should be avoided because catheterization is associated with intimal thickening and endothelial dysfunction.23-25 Additionally, the following special considerations may dictate arm selection: (1) the arm with an arteriovenous fistula for hemodialysis should not be used for transradial catheterization; (2) selective angiography of the left internal mammary artery is most easily accomplished via the left radial artery; and (3) an arm with an abnormal modified Allen’s test result (Figure 1, Barbeau grade D) should be avoided.
Inability to access the radial artery is the most common cause of failure for the transradial catheterization procedure.26 Although experienced operators often cannulate the radial artery with the arm in an adducted position; we recommend that operators in the learning phase place the arm in an abducted position with hyperextension of the wrist. After successful cannulation, the arm is adducted to the patient’s side to permit operator positioning and laboratory setup similar to the femoral approach. The radial artery tapers to a smaller caliber near the radial styloid, where it gives origin to the palmar carpal and superficial palmar branches. The preferred site to access the radial artery is 2 cm proximal to the radial styloid. The radial artery should not be accessed over the flexor retinaculum. Local anesthesia with 1% lidocaine is used sparingly (0.51 mL with skin infiltration only) to minimize radial artery manipulation and spasm.
Specialized kits for percutaneous transradial cannulation are available from several vendors (Table 1) and typically include a micro puncture needle (21 gauge, 4-5 cm in length), a 0.018-inch guidewire, and a 5- or 6-F hydrophilic-coated sheath (23-25 cm in length) with a tapered tissue dilator. The pulse is palpated at the intended puncture site to create a mental map for the course of the radial artery. The needle is inserted at an angle of approximately 30° to the skin. When pulsatile blood flow is achieved, the direction of the needle is adjusted slightly to make it more coaxial with the artery. The guidewire is then inserted carefully through the needle and advanced with a gentle twirling motion. Encountering any resistance indicates likely subintimal wire path. The wire should be withdrawn and the needle repositioned. Fluoroscopy can be helpful to visualize passage of the guidewire, especially in the early learning phase. Once the guidewire is fully advanced, a small skin nick is made with a scalpel at the point of needle entry to accommodate sheath insertion. Great care is needed to avoid incision of the artery. A hydrophilic-coated sheath with the tapered tissue dilator should then pass smoothly over the guidewire into the radial artery. The sheath may be secured in place with a single suture to prevent withdrawal during catheter manipulations and exchanges.
A major source of difficulty with the radial approach is vasospasm and subsequent patient discomfort that can occur with sheath placement and removal and with catheter manipulations. The use of hydrophilic-coated sheaths reduces radial artery spasm and improves patient comfort.27-31 The radial artery has a prominent medial layer that is dominated by alpha-1 adrenoreceptor function. 32 Adequate sedation to relieve anxiety is also an important preventative measure to minimize the contribution of circulating catecholamines to radial artery spasm. A cocktail of vasodilators (eg, 100µg of nitroglycerin and/or 1.25-2.5 mg of verapamil) administered via the radial sheath may prevent and relieve radial artery spasm,33 although vasodilators are used less frequently today by many operators due to the excellent performance of hydrophilic sheaths. To prevent radial artery occlusion, unfractionated heparin (UFH) is administered immediately upon establishing access with a single bolus dose of 50 units/kg to a maximum dose of 5,000 units. Intravenously administered UFH causes less patient discomfort and is as effective in preventing radial artery occlusion compared with UFH administered via the radial sheath.34 Some operators prefer to use bivalirudin instead of UFH because of its shorter half-life, as well as its clinical advantages in patients undergoing ad hoc PCI.35 If right heart catheterization is planned in conjunction with a transradial left heart catheterization, both venous (ie, internal jugular, femoral, or antecubital/ brachial) and radial artery access are achieved before administering anticoagulation. If endomyocardial biopsy is necessary, left heart catheterization should be performed using the femoral approach to eliminate the indication for concurrent anticoagulation. In the rare case that circumstances dictate a radial approach, performing the left and right heart procedures on separate visits to the cardiac catheterization laboratory is preferred, because radial artery occlusion occurs in up to 70% of patients in whom UFH has been withheld.19
TRANSRADIAL CORONARY ANGIOGRAPHY AND INTERVENTION
Catheters used for diagnostic coronary angiography (usually 5 F) (Table 1) are advanced into the aortic root over a 0.035-inch, 1-mm, J-tipped guidewire. Catheter exchanges should be performed with a guidewire remaining in the ascending aorta. A steerable guidewire is sometimes necessary to pass though a tortuous subclavian artery. Deep inspiration by the patient and counterclockwise catheter rotation can be helpful in redirecting the guidewire into the aortic root from the descending aorta. Standard diagnostic catheters used in the femoral approach (ie, JL and JR) may be used for coronary angiography from the radial approach. In general, left coronary engagement from the right radial approach requires a catheter that is 0.5 catheter size smaller than what would be used with the femoral or left radial approach. For example, a JL 3.5 to 4 and a JR 4 are generally appropriate for the femoral and left radial approaches, and a JL 3 to 3.5 and a JR 4 are typically used from the right radial approach to perform left and right coronary angiography, respectively. To limit catheter exchanges, some operators use AL 1 or AL 2 and alternatively shaped universal catheters (Kimny, Barbeau, Jacky, etc.) to perform both left and right coronary angiography. Engagement of the coronary ostia may be facilitated by leaving the guidewire within the catheter to enhance torqueability, especially in patients with a tortuous aorta. In these patients, it may also be necessary for the operator to hold torque on the catheter during angiography to maintain engagement with the coronary ostium. A smaller injecting syringe (8 mL rather than 12 mL) or a power injector may improve angiography with 4- and 5-F catheters. A standard pigtail catheter or a universal catheter with side holes (Barbeau or Jacky) can be used for left heart catheterization and ventriculography.
Coronary intervention via the radial artery requires only minor modifications relative to the femoral approach, but guiding catheter selection and lack of support are frequent sources of frustration during the learning phase. Many standard and alternatively shaped catheters are available for transradial PCI (Table 1). We perform more than 90% of transradial PCI using either XB/EBU 3 or 3.5, JR 4, or hockey stick guide catheters. Intervention with 5- or 6-F guiding catheters requires periodic deep catheter engagement for stent deployment. Upsizing the radial sheath should be performed with meticulous attention to hemostasis, because compartment syndrome is a known and serious complication of even brief forearm bleeding.36 Antithrombotic therapy for transradial PCI should be administered in accordance with protocols for transfemoral PCI. The administration of bivalirudin after UFH in patients undergoing ad hoc transradial PCI appears to be safe.37 We routinely administer bivalirudin after UFH as long as the activated clotting time is < 200 to 220 seconds.
POSTPROCEDURE RADIAL ARTERIOTOMY MANAGEMENT
The sheath is removed in the cardiac catheterization laboratory immediately after radial artery procedures. The activated clotting time is not routinely used to guide sheath removal because the radial artery is superficial and easily compressible. Several radial artery compression devices have been developed for use after percutaneous transradial catheterization (Table 1). Venous engorgement and paresthesias are not uncommon during radial compression with these devices. Care must be taken in the application of these devices to avoid compression of the ulnar artery. Capillary refill and pulse oximetry of the thumb are used to monitor perfusion in the hand (Table 2). Despite increased cost over simple strap-like devices, we have elected to use the TR Band because it is easy to use, allows direct visualization of the puncture site, and provides effective and comfortable hemostasis. Institutional use of a single hemostasis device has facilitated the development of a nurse-managed, postprocedure transradial artery access protocol (Table 2).
A patient may recover from an uncomplicated transradial catheterization in an armchair rather than a bed. Moreover, immediate ambulation is permissible once the patient has recovered from sedation. Before discharge, patients should be informed of common problems that occur after transradial catheterization, to limit use of the catheterized arm for 24 hours, and to keep the puncture site clean, dry, and covered with an adhesive bandage until it is completely healed (Table 2).
Radial artery catheterization provides the safest access approach, but requires a significant case commitment (75 -100 diagnostic and 25 PCI procedures) during the learning phase. It is also helpful to engage the wider cardiac catheterization and recovery room staff in the implementation of a successful radial artery program. As reimbursement shifts to the outpatient setting, the radial artery approach will become even more attractive.
BMCToday.Net, February 2010.