Transradial access (TRA) has been widely adopted for coronary angiography and percutaneous coronary intervention, as it has been shown to significantly reduce bleeding complications, vascular complications, and mortality compared with transfemoral access (TFA). Based on this evidence, recent international guidelines recommend TRA as the preferred access strategy.

Radial artery occlusion (RAO), a potential complication following TRA, is often clinically silent and therefore underestimated. However, RAO has important clinical implications, particularly in patients who may require repeated coronary procedures, those in whom the radial artery may be used as a conduit for coronary artery bypass grafting, or patients with chronic kidney disease requiring arteriovenous fistula formation. Therefore, maintaining radial artery patency after the procedure is of considerable clinical importance.

Distal radial access (DRA), which utilizes the radial artery at the anatomical snuffbox, is a relatively recent approach. Multiple studies and meta-analyses have demonstrated that DRA provides comparable procedural success rates to TRA while significantly reducing bleeding complications and the incidence of RAO. Notably, despite the generally accepted association between smaller vessel diameter and higher risk of occlusion, DRA paradoxically shows a lower incidence of RAO. The underlying mechanism for this observation remains incompletely understood.

Sgueglia et al. evaluated peak systolic velocity using Doppler ultrasonography under conditions of arterial compression and reported that antegrade blood flow was better preserved during distal radial artery compression compared with proximal radial artery compression. This finding suggests a potential mechanistic explanation for the lower incidence of RAO observed with DRA.

However, there is a paucity of studies that systematically evaluate hemodynamic changes under simulated real-world hemostatic conditions at both proximal and distal radial arteries.

Therefore, the aim of this study is to quantitatively assess hemodynamic changes induced by simulated occlusive hemostasis at the proximal and distal radial arteries using Doppler ultrasonography, and to elucidate the mechanisms underlying the lower incidence of RAO observed with DRA.

Inclusion Criteria:

A. Adults aged ≥19 years B. Patients scheduled for coronary angiography due to atypical chest pain, stable angina, or acute coronary syndrome C. Patients undergoing transthoracic echocardiography for assessment of cardiac function prior to coronary angiography D. Palpable proximal and distal radial arteries

Exclusion Criteria:

A. Cardiogenic shock B. Patients who have undergone coronary angiography via distal radial access prior to echocardiographic evaluation C. Refusal or inability to provide informed consent D. Presence of an ipsilateral arteriovenous fistula E. Pregnant or breastfeeding women

Adults (≥19 years) scheduled for coronary angiography for atypical chest pain, stable angina, or acute coronary syndrome, undergoing pre-procedural transthoracic echocardiography, with palpable proximal and distal radial arteries; excluding those with cardiogenic shock, prior distal radial coronary angiography before echocardiography, inability/refusal to consent, ipsilateral arteriovenous fistula, or pregnancy/breastfeeding.