All patients with CKD scheduled for CAG will be eligible, assuming their ability to understand the character and individual consequences of participation as well as giving written informed consent. CKD is defined as estimated glomerular filtration rate (eGFR) \<60 mL/min per 1.73 m2 using modification of diet in renal disease (MDRD) formula or serum creatinine (Cr) \> 1.5 mg/dL.
The MDRD formula was defined in the following way. Where the Cr concentration is in mg/dL:
eGFR = 186 × serum Cr-1.154 × Age-0.203 × (0.742 if female) Exclusion criteria are age less than 20 years or more than 85 years, liver cirrhosis greater than or equal to Child class B, decreased serum platelet level (\< 100,000/uL), patients who received or are schedule to receive percutaneous renal intervention, currently are taking anticoagulation drugs, unable to give informed consent. Patients in shock, maintaining hemodialysis, hemofiltration, peritoneal dialysis will be excluded.
