TRA is the standard and most common approach for coronary angiography today. However, an evidence-based radial compression protocol is still lacking. In this relatively large cohort study, we demonstrated that our new protocol was significantly and strongly associated with (1) a lower incidence of RAO (the primary endpoint) and (2) a shorter hemostasis time (the co-primary endpoint) compared with the traditional commercially recommended radial compression protocol. The effect size of this new protocol was large, suggesting a potentially large clinical benefit for patients.
In the past three decades, studies have shown the advantage of TRA over the traditional trans-femoral approach, mainly in terms of the incidence of complications (11). TRA causes fewer puncture site complications and requires less restriction of body movement after the procedure (21). However, the traditional radial compression protocol still takes 2 – 3 hours and sometimes causes RAO, which remains the most frequent complication of TRA (12). Since it restricts the use of the artery for future procedures, not only catheter angiography but also as a conduit for coronary artery bypass grafting or arteriovenous fistula for hemodialysis, it is important to prevent RAO regardless of whether it is symptomatic or asymptomatic.
One reported mechanism of RAO is acute arterial thrombosis caused by arterial wall injury, some of which resolves later, while others remain occluded (22). Another mechanism is intimal-medial thickening resulting from vascular injury (23, 24). Since excessive pressure during hemostasis can damage the arterial wall, compression for hemostasis should be performed with appropriate pressure for as short a time as possible. The RAO International Group published a consensus paper in 2019, focusing on the incidence, risk factors, and prevention of RAO (12). In the paper, the group recommends ‘non-occlusive’ or ‘patent’ hemostasis, as well as short compression, since complete occlusion of the artery is a risk for RAO (25). As stated in the paper, the suggested method using an oximetry-plethysmography device requires a significant work burden. In contrast, our new protocol does not require a special device, although the amount of air is always just before bleeding occurs, and thus the artery is likely to be kept patent. As a result, the incidence of RAO in the new protocol was low (0.9%).
Another important clinical implication of our new protocol is a significant reduction in hemostasis time. Invasive catheter angiography is the gold standard for evaluating anatomical stenosis of the coronary artery and is often performed in an outpatient setting. However, the long resting time after the procedure sometimes prevents patients from returning home on the same day. Outpatient invasive catheter procedures are easier and more accessible if the resting time after the procedure can be shortened. Since the new protocol requires air removal every 30 min, the number of visits to patients may increase in the new protocol. However, a nurse generally has to stay in the patient recovery room until the hemostasis is completed to watch them. Therefore, a short resting time will reduce nurses’ workload and lead to more cost-effective hospital management.
Recently, the distal radial artery approach has been reported as a new puncture method for coronary angiography (26,27,28). This technique may also enable a short-time hemostasis and lower rates of RAO (27). However, this technique is relatively difficult and cannot be applied to all patients. Besides, a couple of unique complications, such as scaphoid fracture due to injury of the feeding arteries, have been reported (28). Thus, further evaluation is necessary before the distal radial artery becomes the standard method.
Our study results are best understood in the context of several limitations. First, this is an observational study in which we evaluated the clinical work performed in our hospital. Although we employed statistical analysis to mitigate the risk of confounding and the observed effect size was large, our findings need to be validated in randomized control studies. Second, there were a significant number of patients for whom the 6-month radial artery patency data were unavailable, even though over 1,300 patients were finally evaluated. Third, we did not routinely perform ultrasound examinations to check for RAO. There may have been some patients whose radial arteries were actually patent. However, even with ultrasound-visible blood flow, an artery without detectable palpitation may still not be feasible for TRA. Fourth, we did not routinely assess the radial artery diameter using ultrasound. Next, the incidence of minor hematoma that does not require surgical treatment, blood transfusion, or hospital stay was not recorded. Finally, the entire study population were Asian adults, whose body size and body mass index are substantially smaller than those in North America and Europe. Hence, the results may need to be validated in non-Asian countries.