At present, coronary angiogram is usually performed either through an artery in your groin or wrist. An important limitation of the wrist approach is an increase rate of blockage of the wrist artery. It is possible that the dose of blood thinner (i.e. heparin) may decrease the risk of blockage. Early studies seem to suggest that higher dose is required to reduce the risk of this important complication. However, to date there has not been a definitive study to determine the most appropriate heparin dose for the prevention of this complication. The main goal of this study is to determine the appropriate heparin dose to prevent wrist artery blockage and to determine risk factors for developing such a complication.

Inclusion Criteria:

• Patients older than 18 years of age who were referred for either urgent or elective cardiac catheterization were eligible for the study if a normal Allen's test was demonstrated

Exclusion Criteria:

• myocardial infarction with shock,
• ST-elevation myocardial infarction,
• patients undergoing planned percutaneous coronary intervention, and
• patients in whom transradial approach is contraindicated such as hemodialysis patients