1.1.1

Is it really necessary to do a modified Allen’s or Barbeau test prior to RAC if there is a palpable radial artery pulse?

According to recent prospective data there is little additional safety introduced in radial catheterizations by performing preprocedural Allens’ or Barbeau test. In an elaborate mechanistic trial, the ipsilateral thumb capillary lactate was used as the primary physiological surrogate for distal ischemia after radial artery catheterization immediately after catheterization, at 30 days, and at 1 year. Valgimigli M et al. prospectively looked at 83 patients with normal and 120 patients with abnormal Allen’s test (and Barbeau test) before the cannulation and found no difference in the incidence of the primary endpoint in the “normal” as well as the “abnormal” Allen’s groups immediately after catheterization and at 30 days and 1 year. Only 5 patients out of 203 had a (asymptomatic) loss of radial pulse (day 1) and only one of whom had had an abnormal Allen test (radial pulsation returned in two of these patients at the scheduled 30 day follow up). Contemporary labs are adopting an inclusive strategy of doing radial catheterizations without Allen’s or Barbeau’s . There have been surgical reports of radial artery harvest for coronary bypass in those with abnormal Allen’s with no deleterious after-effects most likely due to extensive routes of collaterization throughout the ulnar and radial systems in the forearm . Currently, there are weak clinical evidence of the utility of these testing for collateral hand circulation and no proof that a normal Allen’s test is warranted for safety reasons. Radial artery access should not be denied just based on an abnormal Allen’s test; this is especially imperative in those with lower extremity peripheral artery disease in whom femoral artery access could be difficult, dangerous or impossible . Many experienced radial operators worldwide have performed hundreds of thousands of radial catheterizations based solely on a palpable radial artery in those with abnormal Allen’s test without any increase in the rate of hand ischemia — the hand has a tremendous collateral circulation. However, overt concerns about medico-legal implications and public reporting have continued to plague many US operators in accessing the palpable RA with abnormal Allen’s test despite modern data to the contrary.

1.1.2

What about the additional radiation exposure when we trade in radial for femoral approach?

There are some published data which show that radial access procedure increases the average radiation exposure – may be up to double – but this varies enormously by operator experience and center experience. Standard radiation protection protocols are adequate for most TRCs with the exception of the left radial approach (in coronary artery bypass graft cases, for example). Commercially available radiation protection drapes over the patient can dramatically reduce scatter radiation by up to 12-fold for the eyes and 29-fold for the hands . Unfortunately, in spite of being relatively cheap, their acceptance has considerably lagged behind in most hospitals in the US. Most disposable commercially available radiation protection drapes (RADPAD; Worldwide Innovations & Technologies, Overland Park, KS; X-Drape®, AADCO Medical Inc., Randolph, VT) range from approximately $20 to $30 per drape, adding little to the cost of the procedure but potentially contributing a great deal to the safety of the operator(s). Other specific, but often underutilized ways to decrease scatter radiation during TRC include (1) Placing the arm close to the body, and not extending it out (2) using lower frames (7 fps) with diluted (50%) contrast, navigating in “fluoroscopy-save” (FS) versus cinematography mode to traverse a difficult radial anatomy — applying lessons learned from peripheral angiography. In pilot randomized trials, FS mode during elective TRC exposed the operator to a third of the radiation dose (240 μR versus 605 μR, p = 0.046) and the patient received less than half of the radiation (151 ± 69 vs. 260 ± 125 mGy, p = 0.001) when compared to routine cine mode angiography . Ultimately, as operators and centers get more experienced at TRC, they get more efficient in reducing radiation exposure and eventually this difference will likely be eliminated when the transradial and transfemoral approaches are used with at least equal frequency . The estimated annual effective radiation dose received by catheterization lab operators is comparable to the natural background exposure of about 2.4 mSv/year . Even with a (potential) doubling of radiation exposure by virtue of TRC, the cumulative annual exposure of an average operator is likely to be less than the World Health Organization recommended 0.5 mSv/month limit. In the global context however, the lifetime radiation risk is probably better measured against the National Council on Radiation Protection and Measurements (NCRP, United States) limit of whole body effective dose of 10 mSv × age/lifetime.

1.1.3

Acute radial artery injury after instrumentation: are instrumented radial artery conduits ideal for coronary artery bypass grafting (CABG)?

TRC leads to local puncture damage at the minimum but potentially can cause more extensive trauma to the radial artery including acute intimal tears (67.1% and more frequent in the distal rather than in the proximal RA), medial dissections (35.6%) and eventually chronic intimal thickening after repeated TRC procedures . However, there are only scant objective data on the impact of these effects on long-term radial artery graft patency and on clinical outcomes after bypass surgery. It is such fear of a theoretical risk of (radial artery) graft compromise which had initially caused much hesitancy among US cardiac surgeons in harvesting an instrumented radial artery and pushed back early US interventionalists from adopting a radial approach. Although, cumulative clinical experience has proven otherwise, it might be prudent to avoid TRC in elective cases going for possible CABG until this issue is definitively settled. When TRC is performed in such cases, routinely using smaller bore (4F) catheters and meticulously exchanging catheters over a wire should help to minimize trauma. Long-term randomized data are needed to looks for signals of earlier graft failure and adverse clinical outcomes after CABG in patients with instrumented radial artery grafts compared to “fresh” arterial grafts. However, proven strategies for preventing radial artery occlusion like use of standard hydrophilic sheath, routine intra-arterial anticoagulation (unfractionated heparin 70 U/kg up to 5000 U and bivalirudin 0.75 mg/kg bolus followed by 1.75 mg/kg/h intra-procedure infusion), patent (nonocclusive) hemostasis and avoiding repeated access of the same radial artery will reduce long-term radial artery occlusion [ Fig. 2 ].

Strategies for successful transradial catheterization and transitioning to a radial program. The three key components of transitioning to a radial program involve investing in a meticulous and systematic approach to reducing long-term radial artery occlusion (see section 3), protocols to reduce operator and patient total radiation exposure, especially in the initial period of operator training (see section 2) and finally, understanding the limitations of the radial access and knowing when to quit and look for a bail out strategy (see section 5).

1.1.4

Issue of using arm for arteriovenous fistulas (AVF) for hemodialysis

The argument of not using the radial artery of the contralateral arm without the AVF or AV graft stems from the concern about preserving the forearm arteries of the other arm as a potential future dialysis access site. There is no formal rule on this from the national Kidney Disease Outcomes and Quality Initiative guidelines; however, common sense practice would support such a practice . The use of extreme caution, smaller bore catheters (4F), routine preprocedure intra-radial vasodilator-anticoagulation “cocktail” and avoidance of repeated same artery cannulation would make it unlikely that dialysis access will be compromised in the future, especially given the fact that up to 80% of radial artery occlusions spontaneously canalize. A “vascular-team” approach liaising with vascular surgery is recommended in such cases.

1.1.5

Radial access in ST elevation myocardial infarction (STEMI)

There has been a steady acceptance of radial approach by operators even in cases of acute emergency such as STEMI intervention. Several studies and meta-analyses have demonstrated that radial approach doesn’t extend procedure duration or the time to reperfusion. There were a 73% reduction in major bleeding events in patients for radial access and a significant reduction in death, myocardial infarction, need for urgent revascularization or stroke when STEMI interventions were performed via a TRC versus the standard femoral approach in two large contemporary meta-analyses. Even though there is a 3.6% crossover rate (from radial to femoral) in STEMI interventions, multicenter, randomized (STEMI-RADIAL) clinical trials have independently verified that the major benefit of the radial approach during ST-segment elevation myocardial infarction (STEMI) is due to a 80% reduction in access site complications as compared to the traditional femoral approach. This major puncture site benefit is also extended to the non-STEMI ACS populations where radial access has also shown a significant reduction in major vascular complications (1.4% vs. 3.6% in favor of radial, p < 0.001 in the RIVAL study) although there is no demonstrable survival benefit in this population as compared to the distinct trend towards a survival benefit in the STEMI cohort in the STEMI-RADIAL Trial. The benefits of radial approach are seen across both genders and have persisted even in the elderly (age > 75 years) . The additional benefit of the radial approach in emergent cases and in shock is that it frees up the femoral arteries for swift (large bore) mechanical circulatory support, should it be needed.

Given the time dependency in STEMI, a consensus statement put forth by the Society for Cardiovascular Angiography and Intervention’s expert committee (Transradial Working Group) recommends a bail out [ Fig. 2 ] strategy to either contralateral radial or femoral access if it takes more than 3 min to gain radial access or the time from introducer sheath placement in the radial artery to engaging the infarct-related artery with the guide catheter is >10 min (including the time to inject the non-infarct artery), or the total time from radial artery introducer sheath placement to dilating the infarct lesion is >20 min .

1.1.6

Making radial access safer: ultrasound guided access

In the last two years multiple meta-analyses of randomized controlled trials (RCTs) have demonstrated that this approach is also viable for radial arterial access. Gu W-J et al. analyzed 7 RCTs (546 patients) and demonstrated that direct visualization by ultrasound significantly reduced attempts and time for successful arterial cannulation, while reducing rates of hematoma when compared to the usual method of radial artery catheterization by pulse palpation . However, there are significant heterogeneity in trial design and significant selection bias evident in all 7 trials diluting the possible beneficial effects of additional ultrasound guidance. Whether this has the potential to further reduce overall cost of cardiac catheterization is debatable at this time. One area of confusion in the trials is the lack of transparency in the details of ultrasound use to cannulate the radial artery. For example, it is unclear if ultrasound use in these trials was just related to locating the radial artery or was it actually used throughout the procedure from initial localization to puncture and cannulation. As a general interventional rule, operator experience is an obligate variable in all such trials and has been shown to be important in a more recent meta-analysis as well. There is a learning-curve for ultrasound-guided radial access. It is unknown how subtle technical differences in radial artery puncture such as an “anterior wall stick”, rather than a “though-and-through” counter-puncture technique followed by wire cannulation through a soft and flexible catheter might play a role, if any, in subsequent incidence of radial artery occlusion in the short term.

1.1.7

Reduced costs

In the contemporary climate of aggressive cost curtailment in the delivery of quality healthcare, it has become apparent that TRC is safer, and performs better in patient-care quality metrics like pain and discomfort and it leads to earlier ambulation when compared to the traditional femoral approach. As early as 2007, Roussanov et al. demonstrated that TRC saved $300 to $400 per case ; contemporary practices could save more than $800 per patient relative to transfemoral interventions . This can’t be over emphasized. The adoption of bundled payments and the mandate on quality metrics in the Medicare Access and CHIP Reauthorization Act of 2015 (MACRA) demands that hospitals in the United States consider same day discharge after cardiac interventions as the norm rather than the exception — TRC is the logical solution if we consider this from a purely economic viewpoint. However, a more accurate way to analyze this would be to do a “Time-Driven Activity-Based Costing” to reflect changes in operating conditions . For example, there is an inherent risk of complications that is directly proportional to the time spent in the laboratory; TRC takes longer, in general, and there has to be a weighted risk adjustment for that. Other issues like the fact that TRC often utilizes more resources (at least in the beginning) like catheters and involves more personnel activity and radiation dose to employees and loss of potential time for additional cases (TRC might take longer on an average, which might add up at the end of the month) should also be analyzed systematically for real “time” saving versus virtual “cost” saving when comparing femoral versus radial approaches.

1.1.8

Future directions: skills learned from TRC can be applied to others areas of intervention

Balloon-assisted tracking (BAT) of a catheter through the radial artery is innovative and it is an acceptable (atraumatic) technique that is now being used to negotiate radial artery loops, kinks and spasm . The additional wire support offered by the conical inflated balloon tip helps the operator to negotiate difficult loops and tortuosity without increasing the risk of vessel perforation and/or plaque dissection . Other pioneers are beginning to access non-coronary vascular beds using the radial approach, e.g., the feasibility of carotid artery stenting through both the ipsilateral and contralateral transradial approach has been described as an alternative to the femoral approach in patients with severe peripheral arterial disease .