Device and procedure for visual three-dimensional presentation of ecg data

Abstract

The analysis of ECG (electrocardiogram) data by exploiting computerized three-dimensional spatial presentation of the measured data using the vector concept. A three-dimensional presentation of the human heart may be correlated with waveforms specific for standard ECG or derived ECG signals based on the dipole approximation of the heart electrical activity. The three-dimensional heart model may be rotated, and the ECG signals are interactively linked to the model. Cardiac ischemia (inadequate blood supply) is detected by calculating an ECG ST-segment vector magnitude or an ST-T spatial angle change of a heart vector from the heart model and comparing these to respective predetermined ischemia criteria, using actual or virtual ECG lead sites.

1 - 4 . (canceled) 
     
     
         5 . A method of detecting ischemia comprising:
 computing from patient ECG data at a plurality of lead sites on the patient's body a time variable heart vector;   normalizing the time variable heart vector;   calculating a value of (a) a normalized ST-segment vector magnitude, or (b) an ST-T spatial angle change from the normalized time variable heart vector; and   determining presence of ischemia by comparing the calculated value to a respective predetermined ischemia criterion.   
     
     
         6 . The method of  claim 5 , wherein the plurality of lead sites are each actual lead sites. 
     
     
         7 . The method of  claim 5 , wherein the plurality of lead sites are each virtual lead sites. 
     
     
         8 . The method of  claim 5 , wherein normalizing the time variable heart vector comprises normalizing the heart vector to a normalization surface having a selected attenuation value. 
     
     
         9 . The method of  claim 5 , further comprising computing a normalization factor,
 wherein computing a normalization factor comprises computing a lead normalization factor, ρ i  for one of the lead sites according to:   
       
         
           
             
               
                 ρ 
                 i 
               
               = 
               
                 
                   
                     ∫ 
                     0 
                     T 
                   
                    
                   
                     
                       
                         
                           V 
                           i 
                         
                          
                         
                           ( 
                           t 
                           ) 
                         
                       
                       · 
                       
                         [ 
                         
                           
                             
                               H 
                               → 
                             
                              
                             
                               ( 
                               t 
                               ) 
                             
                           
                           · 
                           
                             
                               L 
                               → 
                             
                             i 
                           
                         
                         ] 
                       
                     
                      
                     
                         
                     
                      
                     
                        
                       t 
                     
                   
                 
                 
                   
                     ∫ 
                     0 
                     T 
                   
                    
                   
                     
                       
                         [ 
                         
                           
                             
                               H 
                               → 
                             
                              
                             
                               ( 
                               t 
                               ) 
                             
                           
                           · 
                           
                             
                               L 
                               → 
                             
                             i 
                           
                         
                         ] 
                       
                       2 
                     
                      
                     
                         
                     
                      
                     
                        
                       t 
                     
                   
                 
               
             
           
         
         wherein V i (t) is the measured voltage over time from the lead site, {right arrow over (H)}(t) is the time variable heart vector, {right arrow over (L)} is a lead vector corresponding to the lead site, and T is a time period. 
       
     
     
         10 . The method of  claim 9 ,
 wherein computing a normalization factor comprises:   computing lead normalization factors from a plurality of the lead sites; and   selecting a normalization factor from within the range defined by the maximum and the minimum lead normalization factors computed for the plurality of lead sites.   
     
     
         11 . The method of  claim 10 , wherein selecting a normalization factor from within the range defined by the maximum and the minimum lead normalization factors computed for the plurality of lead sites includes selecting the average value of the plurality of lead normalization factors. 
     
     
         12 . An article of manufacture encoded with computer readable information produced by the method of  claim 5 . 
     
     
         13 . The method of  claim 5 , further comprising:
 producing information about the normalized ST-segment vector magnitude by calculating sqrt (X 2 +Y 2 +Z 2 ), where X, Y, and Z are components of the normalized heart vector at the selected time point.   
     
     
         14 . The method of  claim 5 , wherein the respective ST-segment vector magnitude ischemia criterion is greater than about 0.1 mV. 
     
     
         15 . The method of  claim 5 , wherein the respective ST-T spatial angle change criterion is more than about a 10° change. 
     
     
         16 . The method of  claim 5 , wherein the respective S-T spatial angle change criterion is less than about a 60° change. 
     
     
         17 . The method of  claim 5 , wherein the normalized time variable heart vector corresponds to ECG data from virtual lead sites having a different distance from the patient's heart than any of a plurality of actual lead sites on the patient's body. 
     
     
         18 . A system for detecting ischemia, comprising:
 a processor adapted to receive patient ECG data at a plurality of lead sites on the patient's body and to compute there from a time variable heart vector;   a memory coupled to the processor and which stores the patient ECG data and the time variable heart vector;   wherein the processor normalizes the computed time variable heart vector and calculates there from a value of (a) a normalized ST-segment vector magnitude, or (b) an ST-T spatial angle change and determines presence of ischemia by comparing the calculated value to a respective predetermined ischemia criterion.   
     
     
         19 . The system of  claim 18 , wherein the plurality of lead sites are each actual lead sites. 
     
     
         20 . The system of  claim 18 , wherein the plurality of lead sites are each virtual lead sites. 
     
     
         21 . The system of  claim 18 , wherein the respective ST-segment vector magnitude ischemia criterion is greater than about 0.1 mV. 
     
     
         22 . The system of  claim 18 , wherein the respective ST-T spatial angle change criterion is more than about a 10° change. 
     
     
         23 . The system of  claim 18 , wherein the respective S-T spatial angle change criterion is less than about a 60° change. 
     
     
         24 . The system of  claim 18 , wherein the normalized time variable heart vector corresponds to ECG data from virtual lead sites having a different distance from the patient's heart than any of a plurality of actual lead sites on the patient's body.