Is Distal Transradial Access a Step Forward for Coronary Angiography and Intervention?

Percutaneous transradial access (TRA) for coronary angiography (CAG) was published by Campeau in 1989,¹ while TRA for percutaneous coronary intervention (PCI) was published by Kiemeneij in 1993.² Compared with the classic transfemoral access, TRA has been shown to be cost effective, with fewer access-site related complications, earlier patient ambulation, and greater postprocedural comfort.³ In patients with acute coronary syndromes, TRA diminishes net adverse clinical events through a reduction in major bleeding and all-cause mortality⁴ and has been recommended as the standard approach for CAG and PCI (class I, level A) by recent 2018 European guidelines on myocardial revascularization.⁵

Although infrequent, vascular complications still remain, and include radial artery spasm, perforation, thrombotic occlusion, hematoma, pseudoaneurysm, arteriovenous fistulas, and compartment syndrome.³

In 2017, Kiemeneij published a technical report on distal TRA (dTRA),⁶ which has recently gained popularity worldwide. As a refinement of the traditional proximal TRA (pTRA) technique, this relatively new technique has advantages in terms of patient and operator comfort, faster hemostasis, and risk of proximal radial artery occlusion (RAO).³ Since the arterial puncture is performed after the point of emergence of the radial superficial palmar branch with the dTRA technique, blood flow through the palmar arch would not be compromised in cases of RAO, and the risk of ischemic injury would be minimal.⁷ Yet, by avoiding the conventional puncture site and subsequent related complications seen on imaging studies, the radial artery would be preserved for future use (particularly for repeat TRA procedures).^3,7 

Coomes et al⁸ recently published a systematic scoping review of 19 publications comprising 4212 participants undergoing cardiac catheterization via dTRA. Ovid Medline and Embase databases were searched from inception up to September 2018. Reports assessing dTRA for cardiac intervention in adults with any outcomes were eligible. Descriptive summary statistics were calculated from pooled data. Mean patient age was 63.8 years and most patients (77%) were men. Distal TRA was primarily undertaken for stable coronary artery disease (87.6%), with 41.7% for diagnostic procedures and 46.9% for PCI. The overall success rate with dTRA was 95.4% (range, 69%-100%). Complications occurred in 2.4% of cases, and consisted mostly of bleeding/hematoma (18.2%). Overall, complication rates did not significantly differ between dTRA and pTRA. Proximal RAO in patients undergoing dTRA was very low (1.7%).⁸

Our initial experience detailing observational data with dTRA as the default for any routine CAG and/or PCI has been recently published.^9-11 Mean patient age was 62.4 years and most (65.9%) were men. The majority of patients (49.4%) had acute coronary syndromes. Overall, 15.1% had ST-segment elevation myocardial infarction (STEMI). The distal radial artery was successfully punctured in all 435 consecutive patients, always without ultrasound guidance. We had only 3% access-site crossovers (successful arterial puncture, but failed wire advancement and sheath insertion), mainly performed via contralateral dTRA (53.8%). Successful dTRA sheath insertion was then achieved in 98.6% of all patients. Redo ipsilateral dTRA was performed in 2.5% of patients. No major adverse cardiac/cerebrovascular or major ischemic local events were recorded. According to EASY hematoma classification,¹² no significant access-site related hematoma type ≥2 was recorded. There was no documentation of hand/thumb dysfunction after any procedure. Although not very reliable due to lack of Doppler ultrasound evaluation in our cohort, distal and proximal radial artery pulses were palpable in all patients at hospital discharge.⁹ Notwithstanding this limitation, performing dTRA without ultrasound guidance might facilitate the widespread use of the technique. 

In the first randomized comparison of dTRA versus pTRA for CAG in 200 patients, Koutouzis et al¹³ described a 30% rate of access-site crossover (the primary endpoint of the trial) in the dTRA group versus only 2% in the traditional arm (P<.001). Currently, there are two ongoing randomized trials comparing dTRA with pTRA. The DISCO Radial Trial (ClinicalTrials.gov identifier NCT04171570) will evaluate 1300 individuals with the objective of demonstrating superiority of dTRA over pTRA in terms of RAO by Doppler ultrasound.¹⁴ The Comparison of Success Rate Between Distal Radial Approach and Radial Approach in STEMI (ClinicalTrials.gov Identifier: NCT03611725) will compare the success rate of arterial puncture between dTRA and pTRA groups in patients presenting with STEMI.¹⁵ 

In cases utilizing left dTRA, since the left arm is positioned over the patient’s belly toward the operating physician with the sheath inserted on the dorsal side of the hand, catheters can be more easily handled without the need to lean over the patient, resulting in greater operator and patient comfort.⁹ Whether the right or left arm should be the preferred approach for dTRA is still to be determined. 

The short length of standard radial catheters may be an important drawback of dTRA. Given that the distal radial artery is up to 5 cm below the pTRA entry site, these catheters may therefore be too short, especially in taller patients, and procedures may have to be performed “on the tip” of the catheter.⁹ Another potential limitation of dTRA is the need to use 7 Fr or larger catheters for complex PCI (eg, bifurcation, trifurcation, rotational atherectomy with larger burrs, chronic total occlusion, etc) when the 7 Fr Glidesheath Slender (Terumo) is unavailable.¹⁶ 

In conclusion, dTRA is a novel access site in the interventional cardiology field, with current data demonstrating high success and infrequent complication rates — global procedural metrics that are comparable with historical pTRA.⁸ Although a higher number of arterial puncture attempts may be required to obtain distal radial artery access, due to smaller arterial lumen diameter or to operator inexperience, dTRA may conversely provide important advantages over pTRA, including patient comfort, shorter hemostasis time, and lower RAO rates.³ Despite preliminary findings, the updated observational data indicate that dTRA appears to be feasible, safe, and generalizable for the majority of patients undergoing CAG and PCI. Further randomized and larger trials are needed and expected in order to assure the observational clinical benefits and safety of this relatively new and potential disruptive technique.

Excerpted from J INVASIVE CARDIOL 2020;32(9):E238-E239. 

Key words: editorial, radial artery technique