The highlights of the last decade in interventional cardiology have been the introduction of drug-eluting stents and an overall simplification of percutaneous coronary interventional procedures from a technological standpoint. Indeed, most interventions currently consist of either direct stenting or pre-dilatation followed by stent implantation; the use of rotational atherectomy and other niche techniques has become less common.
On the other hand, tremendous advances have been made in antithrombotic strategies for interventional procedures. High-dose heparin has largely been replaced by activated-clotting-time-guided heparin therapy or direct thrombin inhibition with short-acting bivalirudin. Furthermore, there is now a strong emphasis on platelet aggregation inhibition with drugs other than platelet glycoprotein IIb/IIIa receptor inhibitors (GPIs). Several new antiplatelet agents have been shown to result in a significant reduction in ischemic complications and will likely play an important role in the future.1,2
These new antithrombotic strategies have resulted in a significant reduction in the incidence of femoral bleeding complications that accompany percutaneous interventional procedures.3 However, even with the associated use of femoral closure devices, they have not been eliminated. Furthermore, the recent recognition that post-percutaneous coronary intervention bleeding complications confer a definite mortality risk has resulted in interventional cardiologists refocusing on transradial access.4
Reviewing the evidence, there is little doubt about the superiority of the radial approach compared with the femoral approach regarding the reduction of bleeding and access-site complications. Jolly et al. recently reported a meta-analysis including all comparative studies from the 1980s to 2008.5 Overall, they reported a 73% relative reduction with the transradial approach compared with the standard femoral approach (0.0 versus 2.3%; p<0.001). Surprisingly, they also observed a trend in the reduction of major adverse cardiac events (MACE) (death, myocardial infarction [MI], stroke) with the transradial approach (2.5 versus 3.8%; p=0.058). This observation led to the design of the large ongoing International Randomized Trial of Transradial Versus Trans-femoral PCI Access Site Approach in Patients With Unstable Angina or MI Managed With an Invasive Strategy (RIVAL), which has already included more than 4,000 patients (final target: 8,000) and will evaluate whether the transradial approach is capable of reducing the ischemic risk beyond the bleeding risk compared with femoral approach.
The transradial approach was first described more than 20 years ago, yet its practice varies widely around the globe. Although interventional cardiologists use a transradial approach in approximately 50% of cases in many countries, the practice has remained vigorously promoted by only a few centers in the US and largely ignored by the majority until recently.6 As reported by Rao et al. in 2008, transradial percutaneous coronary intervention (PCI) was used in <1.5% of cases until 2007, but since then that figure has already doubled. Before discussing the use of the transradial approach for high-risk patients, we will review a few issues regularly used to argue against the transradial approach.
The Learning Curve
Radial artery access is now much easier, with smaller 21-gauge needles and 0.18-inch guidewires. Data suggest that the failure rate is usually less than 5%, which means that the success rate is greater than 95%. Over the years, pioneers of the transradial approach have described several tricks to navigate beyond radial artery tortuosity and other anatomical variations in order to successfully cannulate coronary arteries.8 The success rate, of course, depends on operator patience and experience. If the initial attempt fails or appears complex, good judgment is required. In a recent international survey, 30% of operators answered that they would try the contralateral radial artery in case of initial failure and more than 50% responded that they would revert to the femoral approach.
Once catheters have reached the ascending aorta, the transradial approach for angiography and intervention is basically a similar technique to the femoral approach. The length of the learning curve is variable but does require commitment. In our academic center, where the radial approach is the default strategy, cardiology residents quickly learn the procedure and are regularly astonished when they learn that not every cardiologist practices it. There is little question that femoral and radial approaches will continue to co-exist in catheterization laboratories and both techniques should be mastered. Fortunately, several educational programs have become available and provide excellent opportunities to review technical aspects in a limited period of time.
Dedicated Catheters
Soon after the introduction of the transradial approach, several pioneers developed new catheter curves aiming to image the left and right coronary arteries with a single catheter or to increase support in case of intervention. In fact, there is no need to learn new curves to practice the transradial approach.9 For those practicing the standard femoral approach, they should stick with their routine. If you begin your training with the transradial approach, the easiest way is to use a 3.5 left Judkins for the left coronary artery and a 4.0 right Judkins for the right coronary artery. For interventions, guiding catheters are basically similar to those used with the femoral approach and everyone should develop their own preference.
Radiation Exposure
This is an important topic traditionally neglected by interventional cardiologists but that is now very fashionable. By definition, the use of X-rays for diagnostic angiography and intervention requires delivery of a certain amount of ionizing radiation to the patient and the staff.10 The overall principle is summarized by the ALARA acronym, which stands for ‘as low as reasonably achievable.’ The biohazard due to radiation can be separated into stochastic and non-stochastic risks. The non-stochastic risk is related to a dose threshold: if a certain dose level is reached, a biological effect can be seen. This might be a cutaneous burn for the patient or cataract formation for the operator. The stochastic risk is purely probabilistic and as such often minimized, but is feared as it is linked to cancer induction. Nobody cares really until one learns that a colleague has developed a neoplasm. It is obvious that the stochastic and non-stochastic risks for the patient are minimal and not influenced by the type of access site. More stringent radiation protection rules have also considerably reduced exposure to interventional cardiologists and attending staff. Whereas a few studies have adopted an alarming tone regarding the possibility of increased radiation exposure with the transradial compared with the femoral approach, they had severe limitations that invalidate their conclusion.11 Nevertheless, they should oblige each catheterization laboratory to verify its radiation protection measures.12 Knowing that a significant part of the radiation received by operators is reflected by the patient, the use of a leaded screen above the table, lead protective shields below the table, the use of adjusted lead aprons and glasses, and frequent reminders that radiation exposure is inversely correlated with the square of the distance should be regularly emphasized.
Indeed, if the practice of right radial approach does not modify working habits, it should be recognized that the left radial approach can lead to a relative over-exposure compared with the standard femoral approach. In most institutions, the left radial approach is reserved for patients with previous coronary bypass grafts, as the left mammary artery is more easily cannulated from the left side. Collaboration with industrial vendors is still required to further minimize radiation exposure of patients and operators since the treatment of complex lesions (such as chronic total occlusion) may lead to a significant increase in fluoroscopy time.
Radial Artery Occlusion
Given the dual circulation of the hand, radial artery occlusion has long been considered as collateral damage and a minor problem of the transradial approach. Indeed, clinical sequelae in cases of postprocedural radial occlusion are usually absent, but the artery is lost for future procedures.13 Hand ischemia following a transradial procedure has been described, and at present a pre-procedure Allen test using plethysmography/oximetry is still recommended. Patients without a patent ulnar artery and dual blood supply to the hand should not undergo transradial procedures.
Several factors have been shown to increase the incidence of radial occlusion. Arterial damage from oversized catheters should be avoided. Virtually all interventional cases should now be performed through 6-French guide catheters and many through 5-French catheters. Most operators currently use 5-French catheters for diagnostic procedures. Prolonged and forceful post-procedure radial artery compression is perhaps the most common cause of radial occlusion.14 Recent experimental work has demonstrated that patent artery hemostasis documented with plethysmography significantly reduced radial artery occlusion.15 The incidence of permanent radial occlusion should be less than 5%. Since we are witnessing a significant reduction in the strength of antithrombotic regimens, each program will be required to monitor its own incidence of radial occlusion. It is important to emphasize that the only way to objectively evaluate radial occlusion is to perform a reverse Allen test using plethysmography/oximetry or echo Doppler of the radial artery if there is suspicion of occlusion prior to discharge. Many patients with radial occlusion will have a palpable radial pulse from the dual hand circulation.
Antithrombotic Therapies and Bleeding
Regardless of the strength of antithrombotic and/or antiplatelet therapies, the transradial approach has been associated with very limited risk of bleeding.16 In fact, the transradial approach virtually eliminates access-site-related bleeding. Although bivalirudin has been associated with a significant reduction in major bleeding and large hematoma formation compared with heparin + platelet GPIs after the femoral approach, few data regarding the potential benefit of bivalirudin and the transradial approach have been reported.17 In a sub-analysis of the Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial, Hamon et al. compared the effects of bivalirudin alone versus heparin or bivalirudin + GPI in patients treated by femoral and transradial approach.18 Interestingly, whereas non-access-site bleeding was significantly reduced with bivalirudin alone compared with the two other groups with GPI (2.7 versus 4.5 versus 3.8%; p<0.0001) with the femoral approach, no significant differences were noted among the three groups with the transradial approach (3.0 versus 1.8 versus 2.3%; p=0.36). Even the incidence of hematoma >5cm, which was significantly reduced after bivalirudin alone in the femoral subgroup (0.7 versus 2.3 versus 2.3%; p<0.0001), was in fact similar in the three groups after the transradial approach (0.8 versus 0.4 versus 0.4%; p=0.54). Since bivalirudin has the potential to reduce the incidence of organ bleeding, more research is required in patients at high risk of organ bleeding and treated by the transradial approach.
Myocardial Infarction and Primary/Rescue Percutaneous Coronary Intervention
These patients are the most intensely anticoagulated and many will have received thrombolytic therapy prior to arrival at the PCI center. Thus, the potential for access complications is highest in this group and the potential benefit from transradial access greatest. We have reviewed the experience from 2003 to 2009 in studies comparing the femoral and transradial approach for PCI in acute ST-elevation MI (STEMI). Overall, clinical experience included more than 4,400 patients. Importantly, no significant delay to treatment was observed after the transradial approach, and procedural success was similar after the transradial and femoral approaches. Most importantly, the MACE rate, as well as the incidence of bleeding and vascular complications, was lower after the transradial compared with the femoral approach (see Tables 1 and 2). Hospital stay was also shorter after the transradial approach.
Outpatient Percutaneous Coronary Intervention, Quality of Life, and Cost Savings
Given the better acute results associated with coronary stenting and modern antithrombotic therapy, several studies of same-day discharge after uncomplicated PCI have been reported over the last decade.32 With the use of a few clinical and angiographic criteria and an observation period of four to six hours after PCI, a number of patients can be safely discharged on the same day as their procedure.33 Given the immediate ambulation post-PCI and the reduction of access-site bleeding and complications, the transradial approach offers a particularly appealing strategy in the current environment of significant cost constraints. This accelerated turnover has been shown to be associated with significant cost reduction and is also appreciated by most patients. It should be emphasized that same-day discharge to non-PCI referring centers is relatively easy to implement, whereas home-discharge programs induce a significant change of practice and require specific resource allocation to provide a safety net, as well as promoting drug compliance and risk factor management.
Conclusion and Perspectives
For more than a decade, the transradial approach has been promoted by dedicated aficionados and largely ignored by the large majority of interventional cardiologists. Some countries have now adopted the transradial approach, and there are signs that it is becoming more popular in the US. In a recent international survey conducted on more than 1,000 interventional cardiologists in 75 countries, approximately 50% of respondents answered that their transradial practice will increase in the future. The transradial approach is definitely ready for prime time and has the potential to rapidly become the default technique for invasive cardiology and replace the femoral approach in the majority of patients.