Best practices for transradial angiography and intervention: A consensus statement from the society for cardiovascular angiography and intervention's transradial working group

The radial approach to angiography and intervention has emerged internationally as the preferred alternative to the traditional femoral approach 1. Multiple observational and randomized trials performed to date have shown an association between radial access and reduced risk for bleeding and vascular complications 2. Other studies have shown an association between radial approach and reduced costs 3, increased patient satisfaction 4, 5, and reduced mortality in high-risk patient subgroups like those with ST-segment elevation myocardial infarction (STEMI) 6. Disadvantages include increased radiation exposure to the operator during the learning curve, limitation of guide catheter size in some patients, and radial artery occlusion. The increased understanding of the potentially favorable risk:benefit ratio of transradial procedures has led to a near 10-fold increase in the adoption of radial access in the United States between 2007 and 2011 7. Concomitant with this surge in radial approach has been a proliferation of studies that have examined various technical aspects and outcomes from transradial procedures. Transradial angiography and intervention was once largely guided by anecdote and case series reports, but now there is a solid evidence base to guide some aspects of radial practice. The purpose of this document is to provide consensus opinion on what is considered "best practice" for facets of radial procedures where there is supportive evidence in order to maximize the benefits, standardize certain practices to minimize complications, and summarize areas that need further study. The Society for Cardiovascular Angiography and Intervention (SCAI) has formed a committee of members to focus specifically on radial procedures. Membership is open to any member of SCAI. The committee is tasked with planning and executing radial training programs and generating SCAI-approved statements that relate to transradial practice. The SCAI Radial Committee decided upon topics selected for the present "best practices" statement by consensus. The decision was guided by patient-level and operator-level outcomes as well as the amount and quality of evidence to guide a specific practice. Randomized clinical trial data was considered to be the highest level of evidence followed by observational studies that reported adjusted outcomes. No formal grading of evidence was undertaken. The topics for inclusion were then selected from candidate topics by committee consensus. Three topics emerged as the focus of the statement: (1) monitoring for and reducing the risk of radial artery occlusion, (2) reducing patient and operator radiation exposure during radial procedures, and (3) transitioning to transradial for primary PCI. Three other topics, felt to be important, but in need of further study, are also discussed: (1) the role of preprocedure testing for dual circulation, (2) the optimal antithrombotic strategy for transradial PCI, and (3) the elements of a successful transradial training program. The Radial Committee discussed the evidence supporting practices for each topic and final recommendations were formulated through consensus. If randomized trials or observational studies were not available, recommendations were formulated through consensus of the committee members. An important limitation of transradial catheterization and intervention is radial artery occlusion (RAO). A recent international survey of transradial practice showed that only half of physicians performing transradial catheterization routinely check for radial artery patency before discharge 8. Although most radial occlusions may be asymptomatic, there are several reasons to preserve radial patency. First, not all RAO is asymptomatic and cases of hand ischemia have been reported 9. Second, RAO that persists makes repeat procedures through the ipsilateral radial artery either impossible or more complex requiring angioplasty of the occluded radial artery. Finally, maintaining radial artery patency is also important in case the artery is needed as a conduit for intra-arterial pressure monitoring, coronary artery bypass surgery, or hemodialysis access. Based on these considerations, it is recommended that all patients who undergo transradial procedures be monitored for RAO before discharge as well as during the initial post-procedure follow-up visit. This can be either be done using ultrasound or by using the "reverse" Barbeau test (Table 2). In addition, it is recommended that strategies to minimize RAO be used by operators in all patients undergoing transradial procedures. Table 1 lists the evidence-based practices that are either proven to reduce RAO risk or are likely to reduce RAO risk. The most important practice that reduces the risk of RAO is nonocclusive or "patent" hemostasis (Table 2). A consistent finding across studies comparing radial and femoral approaches is the increased radiation exposure for the patient and operator with radial procedures 10. In one of the largest studies on this topic that studied diagnostic catheterization procedures from multiple operators, radial access was associated with a 23% increase in radiation exposure over transfemoral procedures, a difference that was similar across operators with varying radial experience 11. Limiting radiation exposure during transradial procedures is an important safety goal. There are few randomized trials comparing strategies to reduce radiation exposure; however, given the increasing number of operators who are adopting the radial approach (and the increasing number of patients undergoing radial procedures), the recommendations of the committee reflect a consensus and include strategies that apply to transfemoral procedures as well. Radiation shielding for invasive cardiac procedures is covered in detail elsewhere and readers are referred to the SCAI document on radiation safety 12; however, there are issues regarding radiation protection specific to radial procedures (Table 3). Specific devices designed to reduce radiation exposure during RRA have recently been reported. Use of an extension tube between the proximal part of the coronary catheter and the manifold showed a nonsignificant trend toward lower left-arm operator exposure (28.7 ± 31.0 µSv vs. 38.4 ± 44.2 µSv, P = 0.0739) 14. A transradial radiation protection board has been specifically designed to rest in a plane tangential to the cath table, between the patient's arm and side, which is associated with a significant reduction in operator radiation exposure compared with control (19.5 10.5–35 µSV versus 28 18-65 µSV, P = 0.003) 15. Finally, a small study examining the use of a lead-free radiation shield over the right radial sheath insertion site showed a 13–34% reduction in operator radiation exposure 16. Another issue to consider is the routine use of the left radial artery, which is associated with shorter procedure times, particularly among patients over the age of 75 years and those with short stature 17. The most important predictor of both patient and operator radiation exposure with radial approach may be operator proficiency. Two recent studies, including a substudy from the RIVAL trial 18, have shown that increasing operator experience with radial approach is associated with decreasing patient and operator radiation exposure such that very proficient radial operators have been able to largely minimize the differences between radial and femoral access 19. The use of radial access for primary PCI in STEMI potentially affords the greatest opportunity to improve outcomes compared to femoral access. Patients presenting with STEMI are frequently placed on aggressive anticoagulant and anti-platelet therapies that increase their risk of vascular access site complications. The prespecified STEMI subgroup from the randomized RIVAL (RadIal V. femorAL for coronary intervention) study showed an association between radial access and reduced mortality compared with femoral access 5. These data, along with the RIFLE-STEACS trial 20 provide evidence supporting a mortality benefit of transradial primary PCI when performed by experienced operators. An important issue to consider in the context of transradial primary PCI is the door-to-balloon time (D2B). Transradial PCI cases may prolong this important quality metric due to difficulty in obtaining arterial access, variations in arm or chest arterial vasculature making access to the coronary arteries difficult, or variations in aortic root architecture complicating guide catheter engagement of the coronary arteries. While this concern may be well founded and fluoroscopy times are longer with the radial approach 21, a relationship between radial approach and prolonged time to reperfusion is not consistently borne out in the literature 21, 22. Based on these data, if transradial primary PCI prolongs time to reperfusion, it does not appear to be a clinically significant difference provided that the operator and center are experienced with radial approach. Indeed, the trials analyzed in both meta-analyses included very experienced radial operators and centers. The committee considered the evidence for transradial primary PCI against the backdrop of longer times to reperfusion. Given that delayed reperfusion adversely affects patient outcomes and negatively impacts quality metrics, recommendations for transradial PCI must take into account two main factors: (1) strategies to minimize procedure times and (2) defining appropriate benchmarks for when "bailout" to the femoral approach is necessary. Further, the patients included in the RIVAL and RIFLE-STEACS trials included selected patients with STEMI and some high risk subsets like those with shock may not be suited for radial approach by operators who are not experienced with transradial primary PCI. Table 4 lists access site crossover rates and procedure times from observational and randomized studies comparing radial with femoral access for primary PCI. It is challenging to determine when an operator has "sufficient" transradial experience for performing transradial primary PCI. The committee's recommendations reflect consideration of the relationship between radial experience and decreased procedure failure and procedure time 39, and relying solely on a specific volume cutoff. Importantly, the committee felt that it was mandatory to measure door-to-balloon metrics once a transradial primary PCI program is established so that any upward "creep" in D2B beyond the recommended benchmarks can be identified. Once identified, corrective action may include a requirement for more elective transradial PCI experience before continuing to perform transradial primary PCI. An area of controversy is the need for testing collateral circulation in the hand before performing transradial procedures. Although the clinical Allen's test relies on visual assessment of the hand, an alternative has been described using the pulse oximetry probe and plethysmography ("Barbeau" test) 40. While the latter modification suggests a measure of objectivity, the fundamental question is whether the results of the test are predictive of hand ischemia when RAO occurs. The bulk of the literature examining this issue is in the critical care setting among patients with indwelling radial artery pressure monitoring catheters. There are several case series of patients with indwelling radial arterial lines who developed ischemic complications, but these complications had no correlation to the results of tests assessing the presence of collateral circulation before cannulation 41, 42. Case series of patients with abnormal collateral flow who have had radial artery harvesting for use as bypass grafts have reported no postoperative hand ischemia 43. With a lack of outcome data that demonstrates the predictive value of testing for dual circulation, some radial operators have moved away from routine use of such tests 8. Even in the setting of litigation risk, claims related to femoral artery complications overshadow claims related to radial artery complications 44. Arguments for and against testing are shown in Table 5. Antithrombotic therapy is essential during PCI to reduce thrombotic complications but increases the risk for access-site and nonaccess site bleeding 45. Both types of bleeding are associated with an increased risk for long-term mortality, but the risk appears higher with nonaccess site bleeding 46. Several pharmacological bleeding avoidance strategies have been studied in the setting of PCI. These include appropriate dosing of antithrombin and antiplatelet agents 47, intravenous enoxaparin 48, and bivalirudin 49. Although both observational and randomized studies have shown that these therapies reduce the risk of bleeding compared with heparin with or without glycoprotein IIb/IIIa inhibitors, the majority of the patients in these studies underwent transfemoral PCI. Since radial access virtually eliminates the risk of access-site bleeding compared with femoral access, it is tempting to assume that more potent antithrombotic therapies can be used during transradial PCI. Whether this maximizes both safety and efficacy is unclear due to the absence of large-scale studies involving both radial access and different anticoagulant strategies. Moreover, there are no randomized studies specifically comparing different antithrombotic combinations and different vascular access strategies. Such trials are currently ongoing (clinicaltrials.gov identifiers NCT 01398254, NCT 01433627, NCT 01084993) and will inform the optimal antithrombotic strategy for transradial PCI. As practicing invasive/interventional cardiologists in the United States increasingly take interest in performing transradial procedures, there is a growing need for efficient, high-quality, and personalized transradial training programs that educate the entire catheterization laboratory team. Although there is an association between the volume of radial procedures performed and reductions in procedure time 39, the shape and slope of the radial "learning curve" is less clear. A study performed among Canadian operators indicated that a case volume of 50 transradial PCIs was sufficient to demonstrate a plateau in procedure metrics such as procedure time, fluoroscopy time, and procedure success 50. Whether these data are applicable to other countries where total PCI volumes may be less or more, or to all operators across whom technical proficiency may vary is unknown. It is likely that the learning curve may be higher (100–150 procedures) for some operators. Given the association between volume and outcomes, it is likely that the relationship between radial volume and proficiency is a continuum. There are no formal guidelines for the number of radial cases a trainee should complete during general or interventional cardiology fellowship training, nor are there guidelines on a minimum number of transradial PCIs that operators should perform to maintain proficiency. The COCATS guidelines for training in diagnostic and interventional catheterization currently state that "exposure" to radial, femoral, and brachial access is necessary 51. Table 6 lists proposed curriculum content of structured basic and advanced transradial training courses. The effectiveness of existing training programs at encouraging and sustaining an attendee's radial practice is unknown. It is likely also important to have specific training for nurses and technicians. The role of simulators in radial training remains to be elucidated, as does the role of proctoring programs where a radial expert spends 1–2 days at a center to facilitate radial cases. Future research should focus on which formats are most effective at not only imparting knowledge regarding radial procedures but also practical clinical skills that focus on diagnostic angiography, PCI, and recognition and management of complications. As the adoption of radial approach continues to increase worldwide, it is important to develop and expand the evidence base that underlies its use. The present document outlines evidence-based best practices as they relate to three important aspects of transradial procedures and summarizes areas needing further study. Although the recommendations made in this document are based on the highest level of evidence available, they are ultimately a result of expert consensus. As such, they should be revised as the literature continues to evolve.