Medical devices for mapping cardiac tissue

Abstract

Medical devices and methods for making and using medical devices are disclosed. A method for removing an artifact of a biological reference signal present in a biological source signal may comprise sensing a biological reference signal with one or more electrodes and sensing a biological source signal, wherein the biological source signal comprises an artifact of the biological reference signal. The method may further comprise determining, based on the biological reference signal, the artifact of the biological reference signal and subtracting the artifact of the biological reference signal from the sensed biological source signal.

What is claimed is: 
     
         1 . A system comprising:
 a plurality of electrodes configured to sense a biological source signal and a biological reference signal of a patient; and   a processor configured to:
 receive the biological source signal, wherein the biological source signal comprises an artifact of the biological reference signal; 
 determine morphological differences between the biological reference signal and the artifact of the biological reference signal; 
 determine the artifact of the biological reference signal based on the determined morphological differences; and 
 subtract the determined artifact from the sensed biological source signal. 
   
     
     
         2 . The system of  claim 1 , wherein to determine morphological differences between the biological reference signal and the artifact of the biological reference signal, the processor is configured to: generate one or more shifted copies of the biological reference signal. 
     
     
         3 . The system of  claim 2 , wherein to determine the artifact of the biological reference signal based on the determined morphological differences, the processor is configured to: generate, based at least in part on the generated one or more shifted copies of the biological reference signal, an estimated artifact of the biological reference signal. 
     
     
         4 . The system of  claim 3 , wherein to generate, based at least in part on the generated one or more shifted copies of the biological reference signal, an estimated artifact of the biological reference signal, the processor is configured to:
 form a projection matrix comprising the biological reference signal and one or more shifted copies of the biological reference signal;   determine a set of linear combination coefficients using a projection technique; and   form the estimated artifact of the biological reference signal from the projection matrix and the set of linear combination coefficients.   
     
     
         5 . The system of  claim 4 , wherein the projection technique comprises at least one of: a least-squares regression, a constrained least-squares regression, a maximum likelihood estimation, non-linear programming, and linear programming. 
     
     
         6 . The system of  claim 3 , wherein to generate, based at least in part on the generated one or more shifted copies of the biological reference signal, an estimated artifact of the biological reference signal, the processor is configured to:
 generate a convolution matrix comprising the biological reference signal and one or more shifted copies of the biological reference signal; and   determine an optimal multiplication vector x, such that a product of the convolution matrix and the optimal multiplication vector x produce a solution vector b′, where the solution vector b′ is a solution that is most closely correlated to the biological source signal.   
     
     
         7 . The system of  claim 1 , wherein to determine morphological differences between the biological reference signal and the artifact of the biological reference signal, the processor is configured to: model the patient's tissue as an R-C network. 
     
     
         8 . The system of  claim 1 , wherein the processor is further configured to perform principal component analysis on the biological reference signal to reduce redundancy in the biological reference signal. 
     
     
         9 . The system of  claim 1 , wherein the processor is further configured to:
 identify beat windows around the identified beat timings in the biological reference signal and the biological source signal; and   concatenate the beat windows to produce a concatenated biological reference signal and a concatenated biological source signal.   
     
     
         10 . The system of  claim 1 , wherein to determine morphological differences between the biological reference signal and the artifact of the biological reference signal, the processor is configured to determine morphological differences between the concatenated biological reference signal and the artifact of the concatenated biological source signal; wherein to determine the artifact of the biological reference signal based on the determined morphological differences, the processor is configured to determine the artifact of the concatenated biological reference signal based on the determined morphological differences; and wherein to subtract the determined artifact from the sensed biological source signal, the processor is configured to subtract the determined artifact from the concatenated sensed biological source signal. 
     
     
         11 . A method comprising:
 receiving a biological reference signal of a patient; and   receiving a sensed biological source signal of the patient, wherein the received biological source signal comprises an artifact of the received biological reference signal;   determining a distortion of the received biological reference signal based on a location in which the received biological source signal was sensed;   determining the artifact of the biological reference signal based on the determined distortion; and   subtracting the determined artifact from the received biological source signal.   
     
     
         12 . The method of  claim 11 , wherein determining a distortion of the received biological reference signal based on a location in which the received biological source signal was sensed comprises: generating one or more shifted copies of the received biological reference signal. 
     
     
         13 . The method of  claim 12 , wherein generating one or more shifted copies of the received biological reference signal comprises estimating, based at least in part on the generated one or more shifted copies of the biological reference signal, an artifact of the biological reference signal. 
     
     
         14 . The method of  claim 13 , wherein estimating, based at least in part on the generated one or more shifted copies of the biological reference signal, an artifact of the biological reference signal comprises:
 forming a projection matrix comprising the biological reference signal and one or more shifted copies of the biological reference signal;   determining a set of linear combination coefficients using a projection technique; and   forming the estimated artifact of the biological reference signal from the projection matrix and the set of linear combination coefficients.   
     
     
         15 . The method of  claim 14 , wherein the projection technique comprises at least one of: a least-squares regression, a constrained least-squares regression, a maximum likelihood estimation, non-linear programming, and linear programming. 
     
     
         16 . The method of  claim 13 , wherein estimating, based at least in part on the generated one or more shifted copies of the biological reference signal, an artifact of the biological reference signal comprises:
 generating a convolution matrix comprising the biological reference signal and one or more shifted copies of the biological reference signal; and   determining an optimal multiplication vector x, such that a product of the convolution matrix and the optimal multiplication vector x produce a solution vector b′, where the solution vector b′ is a solution that is most closely correlated to the biological source signal.   
     
     
         17 . The method of  claim 11 , determining a distortion of the received biological reference signal based on a location in which the received biological source signal was sensed comprises modelling the patient's tissue as an R-C network. 
     
     
         18 . The method of  claim 11 , further comprising performing principal component analysis on the biological reference signal to reduce redundancy in the biological reference signal. 
     
     
         19 . The method of  claim 18 , further comprising:
 identifying beat windows around the identified beat timings in the biological reference signal and the biological source signal; and   concatenating the beat windows to produce a concatenated biological reference signal and a concatenated biological source signal.   
     
     
         20 . The method of  claim 19 , wherein determining a distortion of the received biological reference signal comprises determining a distortion of the concatenated biological reference signal; wherein determining the artifact of the biological reference signal based on the determined distortion comprises determining the artifact of the concatenated biological reference signal based on the determined distortion; and wherein subtracting the determined artifact from the received biological source signal comprises subtracting the determined artifact from the concatenated biological source signal.