Devices, systems, and methods for assessment of vessels

A system for evaluating a blood vessel of a patient, comprising:

• a first instrument sized and shaped for introduction into the blood vessel of the patient;
• and
• a processing system configured for communication with the first instrument and a second instrument, wherein the processing system configured to:
• obtain a plurality of pressure measurements from the first and second instruments while the first instrument is moved longitudinally through a length of the blood vessel from a first position to a second position and the second instrument remains stationary;
• determine, using the plurality of pressure measurements, a plurality of pressure ratios along the length of the blood vessel;
• output, on a display in communication with the processing system, a map representative of the length of the blood vessel such a portion of the map is representative at least one pressure ratio of the plurality of pressure ratios, wherein the portion of the map comprises:
• a first visual characteristic when the at least one pressure ratio is above a threshold pressure ratio;
• or
• a second visual characteristic when the at least one pressure ratio is below the threshold pressure ratio.