Pressure sensing guidewire and methods for calculating fractional flow reserve

A method for calculating fractional flow reserve, the method comprising:

• advancing a pressure sensing guidewire through a body lumen of a patient to a first position proximal of an intravascular occlusion;
• determining a first proximal pressure within the body lumen with the pressure sensing guidewire;
• measuring an aortic pressure within the patient;
• equalizing the first proximal pressure with the aortic pressure;
• advancing the pressure sensing guidewire to a distal position that is distal of the intravascular occlusion;
• determining a distal pressure within the body lumen with the pressure sensing guidewire;
• proximally shifting the pressure sensing guidewire to the first position;
• determining a second proximal pressure within the body lumen with the pressure sensing guidewire;
• calculating a pressure drift, wherein the pressure drift is the difference between the second proximal pressure and the aortic pressure;
• and
• calculating drift-compensated fractional flow reserve, wherein the drift-compensated fraction flow reserve corresponds to (the distal pressure+the pressure drift) divided by the aortic pressure.