Radial access is recommended as the standard approach for coronary angiography (CAG) and percutaneous coronary intervention (PCI) based on the evidence in which RA reduced mortality and bleeding events compared with femoral access. Recently, the use of distal radial artery (DRA) is rapidly increasing in accordance with the publication of several studies that have shown easy hemostasis, reduced bleeding complications and low arterial occlusion rate via distal radial approach. However, the diameter of DRA is relatively smaller than radial artery (RA) which can limit the widespread use of this access route. Regarding the size discrepancy, there is a lack of evidence to guide which patients are acceptable or not for CAG and PCI. Therefore, the main purpose of this study was to provide the reference diameter of DRA using ultrasonography in Korean patients. The clinical predictors for small DRA also were evaluated.

Radial access is recommended as the standard approach for coronary angiography (CAG) and percutaneous coronary intervention (PCI) based on the evidence in which RA reduced mortality and bleeding events compared with femoral access. Recently, the use of distal radial artery (DRA) is rapidly increasing in accordance with the publication of several studies that have shown easy hemostasis, reduced bleeding complications and low arterial occlusion rate via distal radial approach. However, the diameter of DRA is relatively smaller than radial artery (RA) which can limit the widespread use of this access route. Regarding the size discrepancy, there is a lack of evidence to guide which patients are acceptable or not for CAG and PCI. Therefore, the main purpose of this study was to provide the reference diameter of DRA using ultrasonography in Korean patients. The clinical predictors for small DRA also were evaluated.

Assessment of arterial diameter by ultasonography Patients were lying on the bed with relaxation in an quiet room. The outer diameters of both DRA and RA were assessed by a perpendicular angle using a linear ultrasound probe (3-4-10.8 MHz) and the average values were recorded. The diameter of RA was measured from 2-3 cm above wrist crease. Anatomical landmark for the measurement of DRA was the bony surface area just distal space from extensor pollicis longus tendon in which the DRA was best palpable then runs down between the first metacarpal and second metacarpal bone (just out of anatomical snuffbox area)

Inclusion Criteria:

• Patients planned to perform transthoracic echocardiography with arterial ultrasonography

Exclusion Criteria:

• Age under 20-year
• Poor image quality
• repeated measurement

Patients planned to perform transthoracic echocardiography with arterial ultrasonography were consecutively enrolled in a single center.