Learning curve of distal transradial access for coronary intervention: a single-center retrospective study.

Background: The vascular access site for coronary intervention has evolved from the femoral artery to the conventional radial artery; more recently, the distal transradial access (dTRA) approach has been established. Although dTRA is preferred owing to its association with improved patient comfort and reduced complications, it is associated with a steep learning curve. We aimed to analyze the learning curve of the dTRA approach and explore the factors associated with procedural success to gain insights shortening the learning curve and enhancing safety and efficiency. Methods: This was a single-center, retrospective observational study of 150 consecutive coronary procedures attempted via the dTRA by an experienced radial operator between April 23, 2025, and August 23, 2025. To delineate the learning curve, we analyzed the operator's success rate, number of puncture attempts, and procedure time across case intervals. The least absolute shrinkage and selection operator (LASSO) logistic regression model was used to identify the predictors of access failure. Results: The overall success rate was 87.3% (131 of 150 procedures). The spline-based learning curve analysis demonstrated a two-phase maturation process: the operator's predicted probability of success plateaued after approximately 75 cases, while measures of procedural efficiency (puncture attempts and time) continued to optimize and stabilized at approximately 100 cases. LASSO regression analysis revealed the anterior-wall puncture technique as a significant technical factor associated with success. Conversely, high baseline brain natriuretic peptide (BNP) and systolic blood pressure (SBP) levels were identified as patient-related clinical risk markers predicting procedural failure. Notably, 100 pg/mL and 10 mmHg increases in BNP and SBP levels were associated with 1.9% and 0.8% decreases in the odds of success, respectively (odds ratio = 0.98 per 100 pg/mL and 0.992 per 10 mmHg, respectively). Conclusion: For an experienced operator in radial access, proficiency in the dTRA technique was achieved after approximately 75 procedures. From a technical standpoint, promoting the anterior-wall puncture technique may effectively increase success rates. Considering the patient's perspective, high pre-operative BNP and SBP levels serve as potential risk markers predicting puncture difficulty and demand substantial attention during pre-procedural assessment. However, the validity of these findings warrants further investigation.