An intracoronary catheter measures pressure distal to a lesion (Pd) and has a fluid lumen for administers adenosine to a patient's vasculature. A controller is configured to provide an injection of adenosine, wait for a period of time, measure Pd, and compare Pd to the Pd measured before the injection of the adenosine. If the difference between the pressures is small or below a threshold, the controller will stop further injections of adenosine because Pd has been determined to be at a relatively constant value. If the pressure difference is large or above a threshold, the controller will provide another adenosine injection, wait for a time period and again measure Pd and compare it to the previous Pd. This process will continue until the measured Pd reaches a relatively constant value.
