Ventricular fibrillation detection

Abstract

Systems and techniques are disclosed for determining the onset and offset of a ventricular fibrillation event and for distinguishing ventricular fibrillation from noise. In some examples, an electrocardiogram (ECG) signal is obtained; a transform is applied to the ECG signal to obtain an analytical pair, the analytical pair including the ECG signal and the transformed ECG signal; a speed-amplitude is determined from the analytical pair; and an onset of a ventricular fibrillation event is identified based at least one of a value of a cost function of the speed-amplitude over a window and a quantity of occurrences the speed-amplitude crosses a threshold over the window.

1 . A method for detecting a ventricular fibrillation event in an electrocardiogram (ECG) signal, the method comprising:
 applying a transform to the an ECG signal to obtain an analytical pair, the analytical pair including the ECG signal and the transformed ECG signal;   determining a speed-amplitude from the analytical pair; and   identifying an onset or offset of a ventricular fibrillation event based on a value of a cost function of the speed-amplitude over a window.   
     
     
         2 . The method of  claim 1 , wherein the transformation comprises a Hilbert transformation. 
     
     
         3 . The method of  claim 1 ,
 wherein the threshold comprises a first threshold; and   wherein identifying the onset or offset of the ventricular fibrillation event comprises identifying the onset or offset of the ventricular fibrillation based on:   the value of the cost function of the speed-amplitude over the window,   the quantity of occurrences that the speed-amplitude crosses the first threshold over the window, and   a quantity of occurrences that the speed amplitude crosses a second, different threshold over the window.   
     
     
         4 . The method of  claim 3 , wherein identifying the onset or offset of the ventricular fibrillation event comprises determining for the window that:
 the value of the cost function meets a first parameter,   the quantity of occurrences that the speed-amplitude crosses the first threshold over the window meets a second parameter, and   the quantity of occurrences that the speed amplitude crosses the second threshold meets a third parameter.   
     
     
         5 . The method of  claim 4 ,
 wherein the first parameter comprises a first predetermined range,   wherein the second parameter comprises a second predetermined range,   wherein the third parameter comprises a predetermined value,   wherein determining for the window that the value of the cost function meets the first parameter comprises determining for the window that the value of the cost function is within the first predetermined range;   wherein determining that the quantity of occurrences that the speed-amplitude crosses the first threshold over the window meets the second parameter comprises determining that the quantity of occurrences that the speed-amplitude crosses the first threshold is within the second predetermined range; and   wherein determining that the quantity of occurrences that the speed-amplitude crosses the second threshold meets the third parameter comprises determining that the quantity of occurrences that the speed-amplitude crosses the second threshold exceeds the predetermined value.   
     
     
         6 . The method of  claim 4 , further comprising:
 determining for one or more other windows consecutive to the window:   a quantity of occurrences that a speed-amplitude determined for the one or more other windows crosses the first threshold,   a value of the cost function of the speed-amplitude for the one or more other windows, and   a quantity of occurrences that the speed amplitude for the one or more consecutive windows crosses the second threshold; and   wherein identifying the onset or offset of the ventricular fibrillation event comprises determining for the one or more other windows that:
 the value of the cost function for the one or more other windows meets the first parameter, 
 the quantity of occurrences that the speed-amplitude for the one or more other windows crosses the second threshold meets the second parameter, and 
 the quantity of occurrences that the speed-amplitude for the one or more other windows crosses the third threshold meets the third parameter. 
   
     
     
         7 . The method of  claim 1 ,
 wherein the ECG signal comprises a signal for a first channel and a signal for a second channel;   and further comprising:   determining for the window a maximum of a value of the cost function of the signal for the first channel and a value of the cost function of the signal for second channel, and   determining a maximum value of a quantity of occurrences that the signal for the first channel crosses a predetermined ECG threshold and a quantity of occurrences that the signal for the second channel crosses the predetermined ECG threshold; and wherein identifying the onset or offset of a ventricular fibrillation event comprises determining the onset or offset of the ventricular fibrillation based on the maximum value of the cost functions for the first channel and the second channel and the maximum value of the quantity of occurrences that the ECG signal crosses the predetermined ECG threshold for the first channel and the second channel.   
     
     
         8 . The method of  claim 1 ,
 wherein the ECG signal comprises a signal for a first channel and a signal for a second channel; and   wherein determining a speed-amplitude from the analytical pair comprises determining an average of a speed-amplitude for the signal of the first channel and a speed-amplitude for the signal of the second channel.   
     
     
         9 - 11 . (canceled) 
     
     
         12 . A machine-readable medium encoding a computer program product operable to cause data processing apparatus to perform operations comprising:
 applying a transform to an ECG signal to obtain an analytical pair, the analytical pair including the ECG signal and the transformed ECG signal;   determining a speed-amplitude from the analytical pair; and   identifying an onset or offset of a ventricular fibrillation event based on a value of a cost function of the speed-amplitude over a window.   
     
     
         13 . The machine-readable medium of  claim 12 , wherein the transformation comprises a Hilbert transformation. 
     
     
         14 . The machine-readable medium of  claim 12 ,
 wherein the threshold comprises a first threshold; and   wherein identifying the onset or offset of the ventricular fibrillation event comprises identifying the onset or offset of the ventricular fibrillation based on:   the value of the cost function of the speed-amplitude over the window,   the quantity of occurrences that the speed-amplitude crosses the first threshold over the window, and   a quantity of occurrences that the speed amplitude crosses a second, different threshold over the window.   
     
     
         15 . The machine-readable medium of  claim 14 , wherein identifying the onset or offset of the ventricular fibrillation event comprises determining for the window that:
 the value of the cost function meets a first parameter,   the quantity of occurrences that the speed-amplitude crosses the first threshold over the window meets a second parameter, and   the quantity of occurrences that the speed amplitude crosses the second threshold meets a third parameter.   
     
     
         16 . The machine-readable medium of  claim 15 ,
 wherein the first parameter comprises a first predetermined range,   wherein the second parameter comprises a second predetermined range,   wherein the third parameter comprises a predetermined value,   wherein determining for the window that the value of the cost function meets the first parameter comprises determining for the window that the value of the cost function is within the first predetermined range;   wherein determining that the quantity of occurrences that the speed-amplitude crosses the first threshold over the window meets the second parameter comprises determining that the quantity of occurrences that the speed-amplitude crosses the first threshold is within the second predetermined range; and   wherein determining that the quantity of occurrences that the speed-amplitude crosses the second threshold meets the third parameter comprises determining that the quantity of occurrences that the speed-amplitude crosses the second threshold exceeds the predetermined value.   
     
     
         17 . The machine-readable medium of  claim 15 , the operations further comprising:
 determining for one or more other windows consecutive to the window:   a quantity of occurrences that a speed-amplitude determined for the one or more other windows crosses the first threshold,   a value of the cost function of the speed-amplitude for the one or more other windows, and   a quantity of occurrences that the speed amplitude for the one or more consecutive windows crosses the second threshold; and   wherein identifying the onset or offset of the ventricular fibrillation event comprises determining for the one or more other windows that:   the value of the cost function for the one or more other windows meets the first parameter,   the quantity of occurrences that the speed-amplitude for the one or more other windows crosses the second threshold meets the second parameter, and   the quantity of occurrences that the speed-amplitude for the one or more other windows crosses the third threshold meets the third parameter.   
     
     
         18 . The machine-readable medium of  claim 12 ,
 wherein the ECG signal comprises a signal for a first channel and a signal for a second channel;   and the operations further comprising:   determining for the window a maximum of a value of the cost function of the signal for the first channel and a value of the cost function of the signal for second channel, and   determining a maximum value of a quantity of occurrences that the signal for the first channel crosses a predetermined ECG threshold and a quantity of occurrences that the signal for the second channel crosses the predetermined ECG threshold; and   wherein identifying the onset or offset of a ventricular fibrillation event comprises determining the onset or offset of the ventricular fibrillation based on the maximum value of the cost functions for the first channel and the second channel and the maximum value of the quantity of occurrences that the ECG signal crosses the predetermined ECG threshold for the first channel and the second channel.   
     
     
         19 . The machine-readable medium of  claim 12 ,
 wherein the ECG signal comprises a signal for a first channel and a signal for a second channel; and   wherein determining a speed-amplitude from the analytical pair comprises determining an average of a speed-amplitude for the signal of the first channel and a speed-amplitude for the signal of the second channel.   
     
     
         20 - 33 . (canceled) 
     
     
         34 . A cardiac monitoring apparatus comprising:
 an input element;   a processor; and   a machine-readable medium encoding instructions operable to cause the processor to perform operations comprising:   applying a transform to an ECG signal to obtain an analytical pair, the analytical pair including the ECG signal and the transformed ECG signal;   determining a speed-amplitude from the analytical pair; and   identifying an onset or offset of a ventricular fibrillation event based on a value of a cost function of the speed-amplitude over a window.   
     
     
         35 . The cardiac monitoring apparatus of  claim 34 , wherein the transformation comprises a Hilbert transformation. 
     
     
         36 . The cardiac monitoring apparatus of  claim 34 ,
 wherein the threshold comprises a first threshold; and   wherein identifying the onset or offset of the ventricular fibrillation event comprises identifying the onset or offset of the ventricular fibrillation based on:   the value of the cost function of the speed-amplitude over the window,   the quantity of occurrences that the speed-amplitude crosses the first threshold over the window, and   a quantity of occurrences that the speed amplitude crosses a second, different threshold over the window.   
     
     
         37 . The cardiac monitoring apparatus of  claim 36 , wherein identifying the onset or offset of the ventricular fibrillation event comprises determining for the window that:
 the value of the cost function meets a first parameter,   the quantity of occurrences that the speed-amplitude crosses the first threshold over the window meets a second parameter, and   the quantity of occurrences that the speed amplitude crosses the second threshold meets a third parameter.   
     
     
         38 . The cardiac monitoring apparatus of  claim 37 ,
 wherein the first parameter comprises a first predetermined range,   wherein the second parameter comprises a second predetermined range,   wherein the third parameter comprises a predetermined value,   wherein determining for the window that the value of the cost function meets the first parameter comprises determining for the window that the value of the cost function is within the first predetermined range;   wherein determining that the quantity of occurrences that the speed-amplitude crosses the first threshold over the window meets the second parameter comprises determining that the quantity of occurrences that the speed-amplitude crosses the first threshold is within the second predetermined range; and   wherein determining that the quantity of occurrences that the speed-amplitude crosses the second threshold meets the third parameter comprises determining that the quantity of occurrences that the speed-amplitude crosses the second threshold exceeds the predetermined value.   
     
     
         39 . The cardiac monitoring apparatus of  claim 37 , the operations further comprising:
 determining for one or more other windows consecutive to the window:   a quantity of occurrences that a speed-amplitude determined for the one or more other windows crosses the first threshold,   a value of the cost function of the speed-amplitude for the one or more other windows, and   a quantity of occurrences that the speed amplitude for the one or more consecutive windows crosses the second threshold; and   wherein identifying the onset or offset of the ventricular fibrillation event comprises determining for the one or more other windows that:   the value of the cost function for the one or more other windows meets the first parameter,   the quantity of occurrences that the speed-amplitude for the one or more other windows crosses the second threshold meets the second parameter, and   the quantity of occurrences that the speed-amplitude for the one or more other windows crosses the third threshold meets the third parameter.   
     
     
         40 . The cardiac monitoring apparatus of  claim 34 ,
 wherein the ECG signal comprises a signal for a first channel and a signal for a second channel;   and the operations further comprising:   determining for the window a maximum of a value of the cost function of the signal for the first channel and a value of the cost function of the signal for second channel, and   determining a maximum value of a quantity of occurrences that the signal for the first channel crosses a predetermined ECG threshold and a quantity of occurrences that the signal for the second channel crosses the predetermined ECG threshold; and   wherein identifying the onset or offset of a ventricular fibrillation event comprises determining the onset or offset of the ventricular fibrillation based on the maximum value of the cost functions for the first channel and the second channel and the maximum value of the quantity of occurrences that the ECG signal crosses the predetermined ECG threshold for the first channel and the second channel.   
     
     
         41 . The cardiac monitoring apparatus of  claim 34 ,
 wherein the ECG signal comprises a signal for a first channel and a signal for a second channel; and   wherein determining a speed-amplitude from the analytical pair comprises determining an average of a speed-amplitude for the signal of the first channel and a speed-amplitude for the signal of the second channel.   
     
     
         42 . A cardiac monitoring apparatus comprising:
 an input element;   a processor; and   a machine-readable medium encoding instructions operable to cause the processor to perform operations comprising:   applying a transform to an ECG signal to obtain an analytical pair, the analytical pair including the ECG signal and the transformed ECG signal;   determining a speed-amplitude from the analytical pair; and   identifying an onset or offset of a ventricular fibrillation event based on a value of a cost function of the speed-amplitude over a window.   
     
     
         43 . The cardiac monitoring apparatus of  claim 42 , wherein the transform comprises a Hilbert transform. 
     
     
         44 . The cardiac monitoring apparatus of  claim 42 , wherein identifying the offset of the ventricular fibrillation event comprises:
 determining the onset or offset of the ventricular fibrillation event based on the quantity of occurrences that the speed-amplitude over a window crosses a predetermined threshold and based on a quantity of occurrences that a speed-amplitude for one or more other windows consecutive to the window crosses the predetermined threshold.