Systems and methods for detecting tissue contact during ablation

Abstract

Systems and methods for assessing tissue contact, including positioning an electrode adjacent a tissue region; delivering radiofrequency energy to the electrode, wherein the delivered radiofrequency energy is sufficient to ablate at least a portion of the tissue region; obtaining a plurality of impedance measurements from the electrode during the delivery of the radiofrequency energy; calculating a change in the impedance measurements over a pre-determined time period; and generating an alert if the calculated change is less than a pre-defined value.

What is claimed is: 
     
         1 . A method of operating a medical device having an electrode, comprising:
 positioning the electrode adjacent a tissue region;   delivering radiofrequency energy to the electrode, wherein the delivered radiofrequency energy is sufficient to ablate at least a portion of the tissue region;   obtaining a plurality of impedance measurements from the electrode during the delivery of the radiofrequency energy;   calculating a change in the impedance measurements over a pre-determined time period; and   generating an alert if the calculated change is less than a pre-defined value.   
     
     
         2 . The method of  claim 1 , wherein the pre-determined time period is between approximately 5 seconds and approximately 20 seconds. 
     
     
         3 . The method of  claim 1 , further comprising terminating delivery of radiofrequency energy to the electrode. 
     
     
         4 . The method of  claim 1 , wherein the generated alert includes visually displaying at least one of 1) a measured impedance value, 2) a calculated difference between a measured impedance value and a predetermined impedance value, and 3) a calculated difference between at least two measured impedance values. 
     
     
         5 . The method of  claim 1 , further comprising attributing the calculated change in the impedance measurements to a tissue contact condition, wherein the generated alert signals the tissue contact condition. 
     
     
         6 . A method of operating a medical device having a plurality of electrodes, comprising:
 positioning the plurality of electrodes adjacent a tissue region;   delivering radiofrequency energy to each electrode, wherein the delivered radiofrequency energy is sufficient to ablate at least a portion of the tissue region;   obtaining a plurality of impedance measurements from each of the plurality of electrodes during the delivery of the radiofrequency energy;   calculating a change in the impedance measurements for each of the plurality of electrodes over a pre-determined time period;   comparing the calculated change for at least one of the plurality of electrodes to the calculated change in at least one of the other plurality of electrodes; and   generating an alert based at least in part on the comparison.   
     
     
         7 . The method of  claim 6 , wherein the pre-determined time period is between approximately 5 seconds and approximately 20 seconds. 
     
     
         8 . The method of  claim 6 , further comprising terminating delivery of radiofrequency energy to at least one of the plurality of electrodes. 
     
     
         9 . The method of  claim 6 , wherein the generated alert includes visually displaying at least one of 1) a measured impedance value, 2) a calculated difference between a measured impedance value and a predetermined impedance value, and 3) a calculated difference between at least two measured impedance values. 
     
     
         10 . The method of  claim 5 , further comprising attributing the calculated change in the impedance measurements to a tissue contact condition, wherein the generated alert signals the tissue contact condition. 
     
     
         11 . A medical system, comprising:
 a medical device having a plurality of electrodes; and   a control unit in communication with the plurality of electrodes, the control unit programmed to:
 deliver radiofrequency energy to the plurality of electrodes, wherein the delivered radiofrequency energy is sufficient to ablate tissue; 
 obtain a plurality of impedance measurements from the plurality of electrodes during the delivery of the radiofrequency energy; 
 calculate a change in the impedance measurements over a pre-determined time period; and 
 generate an alert if the calculated change is less than a pre-defined value. 
   
     
     
         12 . The system of  claim 11 , wherein the pre-determined time period is between approximately 5 seconds and approximately 20 seconds. 
     
     
         13 . The system of  claim 11 , wherein the control unit is programmed to terminate delivery of radiofrequency energy to the electrode. 
     
     
         14 . The system of  claim 11 , wherein the generated alert includes visually displaying at least one of 1) a measured impedance value, 2) a calculated difference between a measured impedance value and a predetermined impedance value, and 3) a calculated difference between at least two measured impedance values. 
     
     
         15 . The system of  claim 11 , wherein the control unit is programmed to attribute the calculated change in the impedance measurements to a tissue contact condition, and wherein the generated alert signals the tissue contact condition.