Impedance devices and methods of using the same in connection with a mammalian vasculature

Abstract

Impedance devices and methods of using the same in connection with a mammalian vasculature. In an embodiment of a method for determining vessel compliance, the method comprises the steps of introducing at least part of an impedance device into a site within a vessel, the impedance device comprising an elongated body having a distal body end, and a first electrode located along the elongated body at or near the distal body end, providing electrical current to the first electrode and a first external electrode not coupled to the elongated body to generate the electric field, the first external electrode positioned upon or within a mammalian body having the vessel therein, operating the impedance device to obtain two or more conductance values within the electric field, and calculating vessel compliance based upon the relationship between a change in vessel parameter and a change in pressure during a cardiac cycle.

1 . A method for determining vessel compliance, the method comprising the steps of:
 introducing at least part of an impedance device into a site within a vessel, the impedance device comprising:
 an elongated body having a distal body end, and 
 a first electrode located along the elongated body at or near the distal body end, the first electrode configured to obtain conductance values within the vessel within an electric field; 
   providing electrical current to the first electrode and a first external electrode not coupled to the elongated body to generate the electric field, the first external electrode positioned upon or within a mammalian body having the vessel therein;   operating the impedance device in connection with two or more fluid injections in the vessel at or near the site to obtain two or more conductance values within the electric field, each of the two or more fluid injections having a known conductivity;   calculating a first vessel parameter of the site based on at least two of the two or more conductance values and the conductivities of at least two of the two or more fluid injections;   calculating a second vessel parameter of the site based on at least two of the two or more conductance values and the conductivities of at least two of the two or more fluid injections;   calculating a change in vessel parameter based upon the first vessel parameter and the second vessel parameter;   calculating vessel compliance based upon the relationship between the change in vessel parameter and a change in pressure during a cardiac cycle.   
     
     
         2 . The method of  claim 1 , further comprising the step of:
 determining the extent of vessel disease based upon the calculated vessel compliance.   
     
     
         3 . The method of  claim 2 , wherein the extent of vessel disease is determined to be relatively low if the calculated vessel compliance is relatively high, and wherein the extent of vessel disease is determined to be relatively high if the calculated vessel compliance is relatively low. 
     
     
         4 . The method of  claim 2 , wherein the extent of vessel disease includes a vessel disease selected from the group consisting of atherosclerosis, vessel calcification, degenerative calcific disease, congenital heart disease, rheumatic disease, and coronary artery disease. 
     
     
         5 . The method of  claim 1 , wherein the first vessel parameter and the second vessel parameter each comprise a vessel cross-sectional area, and wherein the change in vessel parameter comprises a change in vessel cross-sectional area. 
     
     
         6 . The method of  claim 1 , wherein the impedance device further comprises a second electrode positioned along the elongated body, wherein the step of operating the impedance device is performed using first electrode and the second electrode, and wherein the step of calculating a first vessel parameter is further based upon a known distance between the first electrode and the second electrode. 
     
     
         7 . The method of  claim 1 , further comprising the step of:
 calculating an index of compliance based in part upon a difference between the first vessel parameter and the second vessel parameter divided by the first vessel parameter.   
     
     
         8 . A method for determining vessel compliance, the method comprising the steps of:
 introducing at least part of an impedance device into a site within a vessel, the impedance device comprising:
 an elongated body having a distal body end, and 
 a first electrode located along the elongated body at or near the distal body end, the first electrode configured to obtain conductance values within the vessel within an electric field; 
   providing electrical current to the first electrode and a first external electrode not coupled to the elongated body to generate the electric field, the first external electrode positioned upon or within a mammalian body having the vessel therein;   operating the impedance device to obtain two or more conductance values;   calculating a change in cross-sectional area based in part upon the two or more conductance values;   calculating vessel compliance based upon the relationship between the change in cross-sectional area and a change in pressure during a cardiac cycle; and   calculating an index of compliance based in part upon a difference between the first vessel parameter and the second vessel parameter divided by the first vessel parameter.   
     
     
         9 . An impedance device for determining vessel compliance, the impedance device comprising:
 an elongated body having a distal body end, and   a first electrode located along the elongated body at or near the distal body end, the first electrode configured to obtain conductance values within a mammalian luminal organ within an electric field;   wherein when electrical current is provided to the first electrode and a first external electrode not coupled to the elongated body to generate the electric field, the first external electrode positioned upon or within a mammalian body having the vessel therein, the first electrode is operable, in connection with two or more fluid injections in the vessel at or near the site, to obtain two or more conductance values within the electric field;   wherein a first vessel parameter of the site and a second vessel parameter of the cite can be calculated based upon at least two of the two or more conductance values and known conductivities of at least two of the two or more fluid injections, wherein a change in vessel parameter can be calculated based upon the calculated first vessel parameter and the calculated second vessel parameter, and wherein a vessel compliance can be calculated based upon a relationship between the change in vessel parameter and a change in pressure during a cardiac cycle.   
     
     
         10 . The impedance device of  claim 9 , forming part of a system, the system further comprising:
 the first external electrode;   an injection source for injecting one or more solutions through the impedance device to a target site;   a current source for providing current to the impedance device; and   a data acquisition and processing system that receives conductance data from the impedance device.   
     
     
         11 . The impedance device of  claim 9 , wherein the first electrode is configured to operate as an excitation electrode and a detection electrode. 
     
     
         12 . The impedance device of  claim 11 , wherein the first electrode is configured to generate the electric field with an external electrode within a mammalian body when the external electrode that is not coupled to the elongated body is positioned upon or within the mammalian body and when the first electrode and the external electrode are activated. 
     
     
         13 . The impedance device of  claim 12 , wherein the first electrode is configured to detect the electric field generated by the first electrode and the external electrode. 
     
     
         14 . The impedance device of  claim 12 , further comprising:
 a second electrode positioned along the elongated body, wherein the second electrode is configured to detect the electric field generated by the first electrode and the external electrode.   
     
     
         15 . The impedance device of  claim 14 , wherein the first electrode is configured to generate the electric field with a first external electrode within a mammalian body when the first external electrode that is not coupled to the elongated body is positioned upon or within the mammalian body and when the first electrode and the external electrode are activated. 
     
     
         16 . The impedance device of  claim 15 , wherein the second electrode is configured to detect the electric field with a second external electrode within the mammalian body when the second external electrode that is not coupled to the elongated body is positioned upon or within the mammalian body. 
     
     
         17 . The impedance device of  claim 14 , wherein a known distance between the first electrode and the second electrode is between 0.5 mm and 1 mm, inclusive. 
     
     
         18 . The impedance device of  claim 14 , wherein the calculated vessel compliance is also based upon a known distance between the first electrode and the second electrode. 
     
     
         19 . The impedance device of  claim 9 , wherein the first electrode is configured to generate the electric field with an external electrode within a mammalian body when the external electrode that is not coupled to the elongated body is positioned upon or within the mammalian body and when the first electrode and the external electrode are activated. 
     
     
         20 . The impedance device of  claim 9 , further comprising:
 a second electrode and a third electrode each positioned along the elongated body, the second electrode and the third electrode configured to detect the electric field generated by the first electrode and the external electrode.