Methods for assessing fractional flow reserve

Abstract

Systems for determining fractional flow reserve are disclosed. An example system may include a pressure sensing guidewire for measuring a first pressure, a second pressure sensing medical device for measuring a second pressure, and a processor coupled to the pressure sensing guidewire and coupled to the second pressure sensing medical device. The processor may be designed to generate a plot of the magnitude of the second pressure over time, identify one or more time intervals of the plot that have a slope less than zero, determine a mean of the second pressure, and calculate the ratio of the first pressure to the second pressure when (a) the second pressure is less than or equal to the mean of the second pressure and (b) during the one or more time intervals when the slope of the plot is less than zero.

What is claimed is: 
     
         1 . A system for determining fractional flow reserve, the system comprising:
 a processor configured to be coupled to a first medical device and to a second medical device, the first medical device being configured to measure a first pressure and the second medical device being configured to measure a second pressure; and   wherein the processor is configured to:
 generate a plot of the magnitude of the second pressure over time, 
 identify one or more time intervals of the plot that have a slope less than zero, 
 determine a mean of the second pressure, and 
 calculate the ratio of the first pressure to the second pressure when (a) the second pressure is less than or equal to the mean of the second pressure and (b) during the one or more time intervals when the slope of the plot is less than zero. 
   
     
     
         2 . The system of  claim 1 , wherein the first medical device includes an optical pressure sensor. 
     
     
         3 . The system of  claim 1 , wherein the first medical device includes a tubular member having a proximal region with a first inner diameter and a distal region with a second inner diameter different from the first inner diameter. 
     
     
         4 . The system of  claim 1 , wherein the second medical device includes a catheter with a pressure sensor. 
     
     
         5 . The system of  claim 1 , wherein the first pressure, the second pressure, or both are wirelessly transmitted to the processor. 
     
     
         6 . The system of  claim 1 , wherein the processor is configured to calculate the ratio of the first pressure to the second pressure in the absence of a hyperemic agent. 
     
     
         7 . The system of  claim 1 , wherein the processor is coupled to a display. 
     
     
         8 . The system of  claim 7 , wherein the display is designed to display the plot. 
     
     
         9 . A system for determining fractional flow reserve, the system comprising:
 a processor configured to be coupled to a first medical device and to a second medical device;   wherein the first medical device is configured to measure a distal pressure at a location distal of a lesion;   wherein the second medical device is configured to measure an aortic pressure; and   wherein the processor is configured to:
 generate a plot of the magnitude of the aortic pressure over time, 
 identify one or more time intervals of the plot that have a slope less than zero, 
 determine a mean of the aortic pressure, and 
 calculate the ratio of the distal pressure to the aortic pressure when (a) the aortic pressure is less than or equal to the mean of the aortic pressure and (b) during the one or more time intervals when the slope of the plot is less than zero. 
   
     
     
         10 . The system of  claim 9 , wherein the first medical device includes an optical pressure sensor. 
     
     
         11 . The system of  claim 9 , wherein the second medical device includes a catheter with a pressure sensor. 
     
     
         12 . The system of  claim 9 , wherein the first medical device includes a tubular member having a proximal region with a first inner diameter and a distal region with a second inner diameter different from the first inner diameter. 
     
     
         13 . The system of  claim 9 , wherein the processor is configured to calculate the ratio of the distal pressure to the aortic pressure in the absence of a hyperemic agent. 
     
     
         14 . The system of  claim 9 , wherein the processor is coupled to a display. 
     
     
         15 . The system of  claim 14 , wherein the display is designed to display the plot. 
     
     
         16 . The system of  claim 9 , wherein the processor is designed to scale the mean of the aortic pressure by a scaling factor in the range of 0.75 to 1.25. 
     
     
         17 . The system of  claim 9 , wherein the processor is designed to reject time intervals when the aortic pressure is less than a pressure lower bound. 
     
     
         18 . The system of  claim 9 , wherein the distal pressure, the aortic pressure, or both are wirelessly transmitted to the processor. 
     
     
         19 . A system for determining intravascular pressure ratios, the system comprising:
 a processor configured to be coupled to a distal pressure sensing medical device and to an aortic pressure sensing medical device;   wherein the processor is configured to:
 generate a plot of the magnitude of an aortic pressure measured by the aortic pressure sensing medical device over time, 
 identify one or more time intervals of the plot that have a slope less than zero, 
 determine a mean of the aortic pressure, and 
 calculate the ratio of a distal pressure measured by the distal pressure sensing medical device to the aortic pressure when (a) the aortic pressure is less than or equal to the mean of the aortic pressure and (b) during the one or more time intervals when the slope of the plot is less than zero. 
   
     
     
         20 . The system of  claim 19 , wherein the distal pressure sensing medical device includes a pressure sensing guidewire and wherein the aortic pressure sensing medical device includes a pressure sensing catheter.