Implantable device and method for monitoring venous diameter

Abstract

An implantable medical device system and associated method receive a signal from an implantable sensor operatively positioned relative to a vein, the signal being responsive to changes in a diameter of the vein. A diameter of the vein is determined in response to the sensor signal and used in estimating central venous pressure (CVP).

1 . A method for use in an implantable medical device, comprising:
 receiving a signal from an implantable sensor operatively positioned relative to a vein, the signal being responsive to changes in a diameter of the vein;   determining a diameter of the vein in response to the sensor signal; and   estimating a central venous pressure (CVP) based upon the vein diameter.   
     
     
         2 . The method of  claim 1  wherein the implantable sensor comprising at least a pair of measurement electrodes. 
     
     
         3 . The method of  claim 1  wherein the sensor comprises an electrode and the sensor signal comprises an impedance signal. 
     
     
         4 . The method of  claim 1  wherein the sensor comprises an ultrasound transducer and the signal comprises an ultrasound signal. 
     
     
         5 . The method of  claim 1  wherein the sensor comprises a first electrode, a second electrode and a third electrode positioned along a preformed portion of a medical lead body, wherein the sensor signal comprises a voltage signal, and wherein determining the vein diameter comprises:
 applying an electrical pulse between the first electrode and the second electrode in a driver electrode pair; 
 measuring the voltage signal between the second electrode and the third electrode in a measurement electrode pair; 
 computing the vein diameter in response to the measured voltage signal; and 
 the preformed portion changing shape with a change in vein diameter and causing a distance between one of the driver electrode pair and the measuring electrode pair to change in response to the shape change of the preformed portion. 
 
     
     
         6 . The method of  claim 5  wherein the first, second and third electrodes being triangulated. 
     
     
         7 . The method of  claim 1  wherein determining the vein diameter comprises determining a change in vein diameter corresponding to a respiratory cycle. 
     
     
         8 . The method of  claim 7  further comprising sensing a signal responsive to respiration for detecting the respiratory cycle. 
     
     
         9 . The method of  claim 7  further comprising detecting congestive heart failure in response to a change in vein diameter corresponding to the respiratory cycle being absent. 
     
     
         10 . The method of  claim 7  wherein estimating the central venous pressure comprises determining a trend in the change in vein diameter corresponding to a respiratory cycle. 
     
     
         11 . The method of  claim 10  further comprising determining a respiration rate and wherein the trend in the change in vein diameter corresponding to a respiratory cycle compares the respiration rate to the change in vein diameter. 
     
     
         12 . The method of  claim 1  further comprising determining a trend in the estimated CVP. 
     
     
         13 . The method of  claim 12  further comprising detecting a worsening heart failure condition in response to the estimated central venous pressure and the trend in the estimated CVP. 
     
     
         14 . An implantable medical device, comprising:
 processing means for receiving a signal from an implantable sensor operatively positioned relative to a vein, the signal being responsive to changes in a diameter of the vein;   processing means for determining a diameter of the vein in response to the sensor signal; and   processing means for estimating a central venous pressure (CVP) based upon the vein diameter, wherein the implantable sensor comprising at least a pair of measurement electrodes.   
     
     
         15 . A method for use in an implantable medical device, comprising:
 receiving a signal from an implantable sensor operatively positioned relative to a vein, the signal being responsive to changes in a diameter of the vein;   determining a diameter of the vein in response to the sensor signal;   estimating a central venous pressure (CVP) based upon the vein diameter;   wherein the sensor comprises a first electrode, a second electrode and a third electrode positioned along a preformed portion of a medical lead body, wherein the sensor signal comprises a voltage signal, and wherein determining the vein diameter comprises:   applying an electrical pulse between the first electrode and the second electrode in a driver electrode pair;   measuring the voltage signal between the second electrode and the third electrode in a measurement electrode pair;   computing the vein diameter in response to the measured voltage signal; and   the preformed portion changing shape with a change in vein diameter and causing a distance between one of the driver electrode pair and the measuring electrode pair to change in response to the shape change of the preformed portion.