The investigators aim to assess safety and efficiency of Tiger II (5Fr; Terumo Interventional Systems, Somerset, New Jersey) vs Judkins (5Fr; 3.5L/4R, Medtronic Co) catheters, in coronary angiography via the right transradial route. This is a prospective, randomized, two-centre, study of parallel design. Consecutive patients with acute coronary syndrome (ACS), eligible for non-urgent coronary angiography, are randomized after successful cannulation of right radial artery and informed consent to either Tigger II or Judkins 3.5L/4R catheters.

From the entrance of the first diagnostic catheter into the sheath and until the completion of the diagnostic coronary angiography will be the measurement of the endpoints of the study.

In case of failure to complete the coronary angiogram with the catheter study a crossover to the other catheter of the study will take place except in cases of severe spasm, where catheter choice will be at the discretion of the operator. In case of failure of the other study's catheter, next catheter's selection will be at operator's discretion. Patients included in the study, who do not process to adhoc PCI, will be monitored with baseline creatinine and creatinine value at day 2 or 3 after coronary angiography.

In all angiography films will be conducted offline analysis by two experienced operators for scoring opacification grade and coronary ostium contact with the catheters used.

DEFINITIONS Mild spasm Spasm causing well tolerated local pain Moderate spasm Spasm which causes severe pain but the handling of catheters remains satisfactory Severe spasm Spasm that leads to change diagnostic catheter or access site Duration of coronary angiogram Is defined as the time from the insertion of the first diagnostic coronary catheter in the sheath to the exit of the last diagnostic catheter from the sheath Radiation time Radiation time from the insertion of the first diagnostic coronary catheter in the right radial sheath to the exit of the last diagnostic catheter from the sheath Dose area product (DAP) DAP from the insertion of the first diagnostic coronary catheter in the sheath to the exit of the last diagnostic catheter from the sheath Contrast volume Contrast volume (ml) used from the insertion of the first diagnostic coronary catheter in the sheath to the exit of the last diagnostic catheter from the sheath Contrast induced nephropathy (CIN) Relative increase ≥25% from baseline or absolute increase ≥ 0.5mg/dl of serum creatinine within 48-72 hours of intravenous contrast administration Opacification grade 0=poor/non-diagnostic

1. moderate opacification only in systole or diastole
2. moderate opacification throughout cardiac cycle
3. complete opacification but not throughout cardiac cycle
4. complete opacification throughout cardiac cycle Catheter contact with coronary ostium

0=none and non-diagnostic study

1=none but diagnostic study 2=non-coaxial contact 3=coaxial contact Catheter stability within the coronary ostium 0=no catheter's steady engagement of the ostium throughout the angiographic view

1=catheter's steady engagement of the ostium throughout the angiographic view Catheter failure Completion of coronary angiogram after study catheter crossover with or without right radial access site crossover Based on pilot data and previously published data we hypothesized that Tiger catheter use will lead to an absolute decrease of at least 5 ml in contrast volume compared with Judkins catheters (48 and 53 ml for Tiger και Judkins catheters respectively, with estimated standard deviation of 17 for both). With a 2-sided alpha of 0.05, group sample sizes of 316 and 316 will achieve 95% power to detect this difference.

Inclusion Criteria:

1. Written informed consent
2. Indication for non-urgent coronary angiography
3. Successful cannulation of right radial artery
4. Availability of both Tiger and JL3.5/JR4 catheters

Exclusion Criteria

1. Indication for urgent coronary angiography (ST-elevation myocardial infarction or non ST-elevation myocardial infarction with indication for coronary angiogram within 2 hours)
2. Hemodynamic instability
3. Non palpable right coronary artery
4. Abnormal Allen test
5. Prior coronary artery bypass grafting
6. Chronic kidney disease or dialysis