Decisions regarding coronary interventions should be combined with objective evidence of myocardial ischemia. The most common physiologic approach utilizes hospital facilities outside the catheterization laboratory, requiring additional time and cost. With the introduction of sensor-tipped angioplasty guide wires, distal coronary flow velocity and pressure can be obtained in the cardiac catheterization laboratory, facilitating physiologically based decisions regarding the need for intervention. In the catheterization laboratory, physiologically significant stenoses can be characterized as having impaired post-stenotic coronary flow reserve