Coronary artery disease (CAD) remains one of the leading causes of mortality, as reported by the World Health Organization (1). Coronary angiography (CAG) and percutaneous coronary intervention (PCI) are essential procedures for the diagnosis and treatment of CAD. These procedures can be performed using transradial, transbrachial, or transfemoral access. Just 12 years later, in 1989, Campeau reported the first 100 diagnostic CAGs using the radial approach, following the first successful femoral artery PCI in 1977 (2). The RIVAL study later verified the safety and high success rate of this approach, establishing it as the preferred referral technique for catheterization in compliance with the guidelines of the European Society of Cardiology (3).

Unfortunately, this procedure carries certain risks, including bleeding, hematoma, and pseudoaneurysm. In addition, prolonged bed relaxation following the procedure raises the risk of lower limb thrombosis and pulmonary embolism (4). Transradial artery access (TRA) is associated with fewer bleeding and vascular complications and significant safety advantages over transfemoral artery access (5). In 1993, Kiemeneij and Laarman, respectively, showed that TRA performed better than transfemoral access in a variety of areas, such as a lower risk of bleeding, a shorter length of hospital stay, early mobilization, reduced costs, and higher patient satisfaction; as a result, TRA has become the preferred approach for CAG (6–9). Despite its benefits, TRA also has certain drawbacks. These drawbacks include mild bleeding at the access site and radial artery occlusion (RAO) after the procedure. RAO, both early and late, which varies in frequency from 5% to 30% in various studies, is the most common complication (5, 10–12).

Babunashvili and Dundua recently developed dTRA, a retrograde method to unblock obstructed ipsilateral radial arteries (13). Its superiority over cTRA lies in providing enhanced comfort for both the patient and the operator throughout the process, and it can be performed without a palpable radial artery in an anatomical snuffbox (14). Moreover, it preserves antegrade blood flow via the superficial palmar arch in instances of RAO. Additional benefits include fewer complications at the puncture site, a shorter hospital stay, and the preservation of the radial artery for revascularization procedures such as coronary artery bypass grafts or the creation of AV-fistulas in patients with chronic kidney disease (15, 16) because these patients often exhibit more complex coronary artery disease and an elevated risk of periprocedural and postprocedural complications, including hemorrhage, thrombotic incidents, and contrast-induced acute kidney damage (17). Having said that, this method is not without its share of disadvantages, some of which include greater difficulty in needling, an increased risk of nerve irritation, and an inability to pass through bigger sheaths (16). Thus, the application of dTRA in interventional surgery for coronary heart disease remains debatable, necessitating more evidence of its safety and efficacy.

Thus, we conducted a meta-analysis to compare the efficacy and safety of dTRA compared to cTRA for coronary angiography and percutaneous coronary intervention.

As TRA has a lower risk of consequences than transfemoral access, including death in patients presenting with acute coronary syndromes, it is presently the preferred access method for coronary operations (50, 51). However, TRA is not a panacea—RAO remains the “Achilles’ heel” of this method. In addition, because the hand has two sets of blood vessels coming from the palmar arch, RAO rarely shows up in the real world. However, RAO prevents the radial artery form being used for future invasive treatments or coronary artery bypass grafting. Estimates of how often it happens remain uncertain because the rates depend a lot on patient characteristics, procedural factors, anticoagulation protocols, and hemostasis techniques (52). DTRA through the anatomic snuffbox has emerged as a new method for CAG and PCI in the last few years (10). Meanwhile, several investigations have shown that recanalizing radial artery stenosis or occlusion via dTRA is both safe and practical (53–55). Moreover, no studies have reported that dTRA is associated with a higher radiation dose (56). The reduced size of the distal radial artery heightens the difficulty of puncture (55). Therefore, we conducted this meta-analysis to compare the efficacy and safety of dTRA vs. cTRA for coronary diagnostic or interventional catheterization.

Our results indicated that dTRA substantially decreases the incidence of RAO compared to cTRA. Thrombosis is a significant contributor to the development of RAO, with its pathogenesis and etiology involving abnormalities in blood flow (stasis), vascular endothelial damage, and hypercoagulability (57). The smaller diameter of the radial artery, the lower amount of nitric oxide released during puncture, endothelial damage, and reduced blood flow due to sheaths and catheters, along with the increase in intimal hyperplasia and intima-media thickness due to constant intubation, contribute to the higher likelihood of RAO with cTRA (58, 59). Among these factors, endothelial damage is the most significant cause of RAO. The repeated introduction and withdrawal of catheters can easily damage the arterial intima, leading to RAO (60). While most RAO cases are asymptomatic, the condition makes it harder to use for catheterizations and as a conduit in people who need coronary artery bypass grafting or radial arteriovenous fistula formation in people with kidney dysfunction. As a result, RAO prevention and management are critical. Preinterventional visualization of the radial artery in both limbs with Doppler ultrasonography is recommended to evaluate the characteristics of the radial artery. It is particularly beneficial for selecting an artery with a larger diameter and determining the size and depth of the artery. Consequently, arterial cannulation is facilitated, diminishing the need for multiple puncture attempts. This imaging modality can assist in determining the suitable sheath size to decrease the sheath-to-artery mismatch, reducing the incidence of RAO (61). In addition, anticoagulants can also effectively prevent and treat thrombosis, thus averting the beginning of RAO (62), including novel oral anticoagulants (63). Furthermore, the lack of blood flow during hemostasis dramatically also increases the probability of RAO, as flow interruption at this stage is a key predictor of such occlusion (64). Studies have shown that interventions like patent hemostasis (65), nitroglycerin administration through the sheath before its removal (66), and ipsilateral ulnar artery compression during radial artery hemostasis (67) can reduce the incidence of postcatheterization RAO (68). In this context, dTRA may help preserve the potency of forearm radial artery during hemostatic compression or obstruction at the puncture site. Maintaining blood flow in the distal radial access is crucial to preventing proximal thrombus formation and keeping the forearm radial artery open after TRA (21). This is made easier by the collateralization of blood vessels. In the context of forearm radial artery obstruction, dTRA is preferable to cTRA.

Compared to cTRA, dTRA decreases the incidence of hematoma, as shown in this current meta-analysis. Hematoma formation is likely caused by poor compression positioning, dual antiplatelet therapy, heparin use, advanced age, delicate skin, and multiple puncture attempts. A standardized technique for compression duration and a specialized compression device may help reduce the incidence of possible bleeding issues (69, 70). Our findings indicate that dTRA can reduce hemostasis time compared to cTRA; this may suggest a decreased occurrence of hematoma in dTRA, attributable to the anatomical structure of the distal radial artery, which has a smaller diameter and is situated over a bony basis formed by the scaphoid and trapezium carpal bones (26).

Our results indicated that dTRA has a lower procedural success rate and effective catheter puncture rate compared to cTRA, which necessitates a longer puncture time. Multiple variables may contribute to their occurrence: (1) the radial artery in the AS is narrower than that at the wrist (71), complicating puncture or sheath insertion following a successful puncture; (2) the distal radial artery frequently displays tortuosity, which can readily result in the unsuccessful insertion of the guidewire and sheath into the radial artery; and (3) dTRA is a novel approach for CAG and PCI, and many operators lack expertise in puncture management and must surmount the learning curve (29). The standard ultrasound-guided approach and enhanced proficiency in the puncture technique may elevate the success rate over time and reduce the risk of puncture-induced vasospasm (44). Lee et al. (69) discovered that the puncture duration progressively stabilized after roughly 150 distal radial artery punctures. A multicenter study indicated that after treating 150 patients, the learning curve achieved an optimal average of two puncture attempts, each lasting under 30 s (72). Deora et al. indicated that, after a specific learning curve (minimum of 50 successful punctures), operational time could be further reduced with further expertise, particularly in assessing the arterial entry via the distal radial artery (73). Therefore, the learning curve varies among different operators, depending on their skills in radial artery access puncture. Mori et al. found that ultrasound-guided dTRA for CAG or PCI exhibited a reduced failure rate compared to traditional dTRA (74). Two meta-analyses (75, 76) compared ultrasound-guided puncture with a palpation-based blind puncture for traditional radial artery access, indicating that ultrasound-guided puncture yields a greater first-pass success rate, reduced puncture time, and decreased hematoma development. Furthermore, although the success rate of catheter puncture for dTRA is lower than that for cTRA (2.89% lower), the success rate remains notably high (91.93% vs. 94.82%). Based on the lower complication rate of dTRA, predominantly with a lower incidence of RAO, we preferentially recommend dTRA for interventional surgeries in coronary heart disease. The cTRA procedure may serve as an alternative in cases where dTRA is unsuccessful.

A subgroup analysis focusing on patients with ACS was performed in our study. Compared with cTRA, dTRA significantly reduced the incidence of RAO, puncture site bleeding, hematoma, and radical artery spasms but had a significantly longer puncture time (WMD = 1.16 min). Notably, there was no significant difference between the two groups in the total procedural time. In the acute environment, every minute is critical, particularly for patients with ST-segment elevation myocardial infarction, and dTRA necessitates additional time for effective arterial access. Apostolos et al. have discussed the use of dTRA in patients with acute coronary syndrome (77). dTRA has been linked to expedited hemostasis, quicker patient mobilization, and a reduction in local sequelae, including substantial hematomas or compartment syndrome. Considering these factors, the prior delays from dTRA should not impede its initial application in patients with acute coronary syndrome. In addition, Desora et al. indicated that, after a specific learning curve, operational time can be further minimized with further expertise, particularly in assessing the arterial entry via the distal radial artery (73).

Although previous meta-analyses (50, 78–80) have compared dTRA and cTRA, the number of articles included in these meta-analyses was relatively low due to insufficient search strategies or shorter study durations. To our knowledge, this updated meta-analysis includes the largest number of studies comparing the outcomes of dTRA vs. cTRA for cardiovascular interventional diagnosis and/or treatment. To manage confounding variables, we performed subgroup analyses focusing on patients with ACS or RCTs. This may result in a more trustworthy judgment. The findings of our meta-analysis provided valuable perspectives on the clinical selection of interventional surgical techniques, which enhance clinical practice and research in the area of cardiovascular interventional diagnosis and/or treatment. However, we acknowledge the possible shortcomings of our study. First, a large number of the studies were not randomized controlled trials, which resulted in a relatively poor quality of evidence and credibility. Second, we could not manage confounding variables, including varying inclusion criteria, population disparities, and the level of experience of surgeons, which may lead to heterogeneity among the trials and introduce bias. Consequently, more clinical outcomes reported by prospective randomized controlled studies are essential to further validate the benefits of dTRA.

In conclusion, our results demonstrated that dTRA is a feasible and safe approach for coronary angiography and percutaneous coronary intervention. Compared with cTRA, dTRA significantly reduces postoperative complications, particularly the occurrence of RAO, and expedites the period to hemostasis.