Determining onsets and offsets of cardiac depolarization and repolarization waves

Abstract

An exemplary computer-implemented method is disclosed for detection of onset of depolarization on far-field electrograms (EGMs) or electrocardiogram (ECG)-or ECG-like signals. The method includes determining a baseline rhythm using a plurality of body-surface electrodes. The baseline rhythm includes an atrial marker and a ventricular marker. A pre-specified window is defined as being between the atrial marker and the ventricular marker. A low pass filter is applied to a signal within the window. A rectified slope of the signal within the window is determined. A determination is made as to whether a time point (t 1 ) is present such that the rectified slope exceeds 10% of a maximum value of the rectified slope. A point of onset of a depolarization complex in the signal is determined. The point of onset occurs at a largest curvature in the signal within the window.

1 . A method of cardiac pacing comprising:
 a) determining a baseline rhythm using a plurality of body-surface electrodes, the baseline rhythm includes an atrial marker and a ventricular marker (Vs);   b) defining a pre-specified window between the atrial marker and the ventricular marker;   c) applying a low pass filter to a signal within the window;   d) determining a rectified slope of the signal;   e) determining a time point (t 1 ) in which the rectified slope exceeds 10% of a maximum value of the rectified slope;   f) determining a point of onset of a depolarization complex in the signal;   g) determine an electromechanical delay for each of a plurality of candidate cardiac pacing lead sites using the determined point of onset of the depolarization complex; and   h) select an implant site for a pacing lead for delivering cardiac pacing based upon the determined electromechanical delays.   
     
     
         2 . The method of  claim 1  wherein automated determination of the point of onset of the depolarization complex is performed without detection of a threshold. 
     
     
         3 . The method of  claim 1  wherein the largest curvature in the signal is determined from a curvature of the signal defined as r=|y″|/(1+|y′| 2 ) (3/2)  in which y″ and y′ are the double and single derivatives of y=f(t), respectively. 
     
     
         4 . The method of  claim 1  wherein a simplified version of a curvature equation, r≈|y″|/(1+|y′|2), may be used to compute an index that tracks the curvature of the signal, eliminating computation of square roots. 
     
     
         5 . The method of  claim 2  wherein determining the point of onset of the depolarization complex comprises searching for the largest curvature of the signal or an index tracking a curvature of the signal at a sharp deflection in the curvature of the signal, the sharp deflection being indicative of the onset of the depolarization complex. 
     
     
         6 . The method of  claim 1  further comprising: searching for the largest curvature within the pre-specified window and ending on a maximum peak or a minimum valley. 
     
     
         7 . The method of  claim 1  further comprising: removing high-frequency artifacts in the signal through the low pass filter. 
     
     
         8 . The method of  claim 1  further comprising:
 receiving an ECG signal by a cardiac resynchronization therapy (CRT) device, 
 wherein determining the point of onset of the depolarization complex comprises determining a point of onset of a QRS complex in the ECG signal received by the CRT device. 
 
     
     
         9 . The method of  claim 18  wherein receiving the ECG signal by the CRT device includes receiving one of a leadless ECG signal and a far-field ECG signal. 
     
     
         10 . The method of  claim 8  further comprising:
 automating measurements of cardiac electrical activation times with respect to the determined point of onset of the QRS complex. 
 
     
     
         11 . A system of cardiac pacing comprising:
 a) processing means for determining a baseline rhythm using a plurality of body-surface electrodes, the baseline rhythm includes an atrial marker and a ventricular marker (Vs);   b) processing means for defining a pre-specified window between the atrial marker and the ventricular marker;   c) processing means for applying a low pass filter to a signal within the window;   d) processing means for determining a rectified slope of the signal;   e) processing means for determining a time point (t 1 ) in which the rectified slope exceeds 10% of a maximum value of the rectified slope;   f) processing means for determining a point of onset of a depolarization complex in the signal, wherein the point of onset occurs at a largest curvature in the signal;   g) processing means for determining an electromechanical delay for each of a plurality of candidate cardiac pacing lead sites using the determined point of onset of the depolarization complex; and   h) processing means for selecting an implant site for a pacing lead for delivering cardiac pacing based upon the determined electromechanical delays.   
     
     
         12 . The system of  claim 11  wherein automated determination of the point of onset of the depolarization is performed without detection of a threshold. 
     
     
         13 . The system of  claim 11  wherein the largest curvature in the signal is determined from a curvature in the signal defined as r=|y″|/(1+|y′| 2 ) (3/2)  in which y″ and y′ are the double and single derivatives of y=f(t), respectively. 
     
     
         14 . The system of  claim 11  wherein a simplified version of a curvature equation r≈|y″|/(1+|y′|2), may be used to compute an index that tracks the curvature of the signal thereby eliminating computation of square roots. 
     
     
         15 . The system of  claim 12  wherein determining the point of onset of the depolarization complex comprises searching for the largest curvature in the signal or an index tracking a curvature of the signal at a sharp deflection in the curvature of the signal, the sharp deflection being indicative of the onset of the depolarization complex. 
     
     
         16 . The system of  claim 11  further comprising: processing means for searching for the largest curvature within the pre-specified window and ending on a maximum peak or a minimum valley. 
     
     
         17 . The system of  claim 11  further comprising: removing high-frequency artifacts in the signal through the low pass filter. 
     
     
         18 . The system of  claim 11  further comprising:
 receiving means for receiving an ECG signal by a cardiac resynchronization therapy (CRT) device 
 wherein determining the point of onset of the depolarization complex comprises determining a point of onset of a QRS complex in the ECG signal received by the CRT device. 
 
     
     
         19 . The system of  claim 18  wherein the receiving means for receiving the ECG signal by the CRT device includes means for receiving one of a leadless ECG signal and a far-field ECG signal. 
     
     
         20 . The system of  claim 18  further comprising: processing means for automating measurements of cardiac electrical activation times with respect to the determined point of onset of the QRS complex. 
     
     
         21 - 27 . (canceled)