Intravascular pressure and flow data diagnostic systems, devices, and methods
In part, the disclosure relates to computer-based methods, devices, and systems suitable for performing intravascular data analysis and measurement of various types of data such as pressure and flow data. The disclosure relates to probes and methods suitable for determining an event in a cardiac cycle such as flow threshold such as a peak flow, a fraction thereof, other intravascular parameters or a point in time during which peak flow or a change in one of the parameters occurs. An exemplary probe includes one or more of a pressure sensor, a resistor, a flow sensor and can be used to generate diagnostic data based upon measured intravascular and other parameters. In part, the disclosure relates to methods and systems suitable for determining a coronary flow reserve value in response to one or more of intravascular pressure and flow data or data otherwise correlated therewith.
1. An intravascular pressure and flow monitoring system comprising:
a display;
an intravascular guide wire-based probe comprising one or more sensors disposed on a distal end a guide wire, the one or more sensors comprising:
an active resistor that is sensitive to temperature and pressure, and
a passive resistor that is sensitive to temperature but is not sensitive to pressure;
one or more memory devices; and
a processor in communication with the one or more memories
wherein the one or more memory devices comprise instructions executable by the processor to cause the processor to:
process a first electrical signal associated with the active resistor and the passive resistor;
process a second electrical signal associated with the passive resistor;
determine intravascular pressure values based on the first electrical signal using a measurement circuit formed from the guide wire-based probe and an interface device;
determine intravascular flow values using a transfer function based on the second electrical signal using the measurement circuit formed from the guide wire-based probe and the interface device; and
generate, based on the intravascular pressure values and the intravascular flow values, a pressure versus flow curve that changes over time, and cause the display to display said pressure versus flow curve that changes over time.
2. The intravascular pressure and flow monitoring system of claim 1 , wherein the pressure versus flow curve is displayed on a substantial real time basis.
3. The intravascular pressure and flow monitoring system of claim 1 , wherein the transfer function T(x) is of the form T(x)=a+b*ln(x), wherein T is temperature, x is flow, and a and b are constants, or wherein the transfer function T(x) is of the form T(x)=a+b*x c , wherein T is temperature, x is flow, and a, b and c are constants.
4. The intravascular pressure and flow monitoring system of claim 1 , wherein the one or more memory devices further comprise instructions which, when executed by the processor, cause the display of one or more cardiovascular related values on the display obtained during one or more points in time.
5. The intravascular pressure and flow monitoring system of claim 4 , wherein the one or more cardiovascular related values are selected from the group consisting of a flow velocity, a pressure value, a maximum flow, a minimum flow, a relative extremum of flow, one or more fractional flow reserve (FFR) values, coronary flow reserve (CFR) values, coronary flow velocity reserve (CFVR) values, instantaneous flow reserve (IFR) values, and one or more index of myocardial resistance (IMR) values.
6. The intravascular pressure and flow monitoring system of claim 4 , wherein the one or more memory devices further comprise instructions which, when executed by the processor, cause the display of one or more trajectories or signatures generated in response to intravascular probe data with respect to one or more positions in an artery.
7. The intravascular pressure and flow monitoring system of claim 4 , wherein the one or more memory devices further comprise instructions to determine one or more temperature values using a linear or other function in response to the second electrical signal from the measurement circuit formed from the intravascular guide wire-based probe and the interface device.
8. The intravascular pressure and flow monitoring system of claim 4 , wherein the one or more memory devices further comprise instructions to calibrate the intravascular guide wire-based probe by the following calibration method steps:
selecting an excitation voltage for a pressure sensor such that a temperature of the sensor and a temperature of blood in which the pressure sensor is disposed substantially match;
determining an absolute temperature of blood in a blood vessel of interest; and
measuring a flow value in the blood vessel using the pressure sensor; and
wherein determining an absolute temperature of blood in a blood vessel of interest comprises obtaining measurements during changes to a switch configuration in an interface system.