The present invention relates to methods for determining whether blood flow is restricted in a blood vessel of an individual suspected of compromised blood flow in the vessel, the method comprising the steps of delivering UTP, a derivative thereof, or a salt thereof to the vessel, assessing blood flow quantitatively in the vessel by obtaining a value that correlates to blood flow in said vessel, comparing the obtained value with a reference value, and determining whether the individual has compromised blood flow based on the results of the comparison. The invention also provides for methods of diagnosing atherosclerotic and ischemic heart diseases using UTP, a derivative thereof, or a salt thereof, as well as methods for inducing maximal hyperemia for diagnostic purposes. The invention further relates to UTP, a derivative thereof or a salt thereof for use as a diagnostic agent. More specifically, the invention relates to the use of UTP, its derivatives and salt in any of the above mentioned diagnostic methods.
