Accelerometer-based method for cardiac function and therapy assessment

Abstract

A method for determining a change in function of a patient's heart that includes the steps of collecting seismocardiographic (SCG) data corresponding to a heart motion of the patient's heart; determining a hemodynamic parameter based on the SCG data; and comparing the parameter with a predetermined measure of cardiac performance. The system used with the method includes one or more accelerometer sensors, a computer data analysis module, and may also include a 2D and 3D visual graphic display of analytic results, i.e. a Ventricular Contraction Map.

1 . A method for determining a change in function of a patient's heart, comprising the steps of: 
 (a) collecting seismocardiographic (SCG) data from an external surface of a patient corresponding to a heart motion of said patient's heart;    (b) determining a hemodynamic parameter based on the SCG data of step (a); and    (c) comparing said parameter of step (b) with a predetermined measure of cardiac performance.    
   
   
       2 . The method of  claim 1 , wherein step (b) further comprises determining one or more parameters selected from the group consisting of isovolumetric contraction time (IVCT), isovolumetric relaxation time (IVCT), and left ventricle ejection time.  
   
   
       3 . The method of  claim 1 , wherein said hemodynamic parameter of step (b) is selected from the group consisting of one or more of the following: a pre-ejection period, a rate of contraction of left ventricle, a duration of systole, a duration of an isovolumic relaxation period, a rate of change of ventricular pressure, and an ejection fraction.  
   
   
       4 . The method of  claim 1 , wherein the SCG data of step (a) are collected by an accelerometer.  
   
   
       5 . The method of  claim 1 , wherein said SCG data of step (a) are selected from the group consisting of one or more of the following: acceleration, velocity, and time intervals of valve sounds.  
   
   
       6 . The method of  claim 1 , wherein said predetermined measure of cardiac performance comprises a change in cardiac contractility based on a change in the height or rate of rise of curves based on said SCG data.  
   
   
       7 . The method of  claim 1 , wherein said predetermined measure of cardiac performance comprises a change in SCG data velocity or acceleration during early diastole as an indication of hypertophic cardiomyopathy.  
   
   
       8 . The method of  claim 1 , wherein said predetermined measure of cardiac performance comprises a change in SCG data velocity or acceleration during early diastole of a tilt test as an indication of reflex sympathetic stimulation.  
   
   
       9 . The method of  claim 1 , wherein said hemodynamic parameter comprises a heart valve sound at a designated frequency range.  
   
   
       10 . The method of  claim 1 , further including the step of comparing the SCG data of step (b) with data produced by a non-accelerometer-based technique to determine any correlation between a measure of cardiac function produced by said technique and said SCG data.  
   
   
       11 . The method of  claim 1 , wherein step (b) further comprises subjecting a patient's heart to biventricular pacing and determining whether there is a shorter isovolumetric contraction time as an indication that biventricular pacing is increasing heart contraction.  
   
   
       12 . The method of  claim 1 , further including the step of subjecting a patient's heart to sub-threshold pacing and determining whether there is a shorter isovolumetric contraction time as an indication that sub-threshold pacing is increasing heart contraction.  
   
   
       13 . The method of  claim 1 , wherein step (a) further comprises providing a plurality of accelerometer sensors for collecting said SCG data.  
   
   
       14 . The method of  claim 13 , wherein step (a) further comprises disposing said plurality of accelerometer sensors upon a neck, a chest apex, and a chest sternum of said patient.  
   
   
       15 . The method of  claim 1 , wherein step (a) comprises collecting SCG data during cardiac motion corresponding to unpaced beats only.  
   
   
       16 . A method for testing or evaluation of a cardiac function, comprising the steps of: 
 (a) collecting seismocardiographic (SCG) data corresponding to heart motion of a patient's heart during a non-testing condition;    (b) determining a hemodynamic parameter based on the SCG data of step (a);    (c) imposing a test condition upon said patient;    (d) collecting seismocardiographic (SCG) data corresponding to heart motion of said patient's heart during said test condition;    (e) determining said hemodynamic parameter based on the SCG data of step (d); and    (f) comparing information from steps (b) and (e) to determine said cardiac function.    
   
   
       17 . The method of  claim 16 , wherein the SCG data of steps (a) and (d) are collected by an accelerometer sensor.  
   
   
       18 . The method of  claim 16 , wherein said hemodynamic parameter of steps (b) and (e) is selected from the group consisting of one or more of the following: a pre-ejection period, a rate of contraction of left ventricle, a duration of systole, a duration of an isovolumic relaxation period, a rate of change of ventricular pressure, and an ejection fraction.  
   
   
       19 . The method of  claim 16 , wherein said test condition is selected from the group consisting of stress testing and tilt testing.  
   
   
       20 . The method of  claim 16 , wherein step (e) further comprises determining that heart contractility does not shorten, or the time of contractility lengthens, during a stress test as an indication of coronary blockage.  
   
   
       21 . The method of  claim 16 , wherein step (e) further comprises determining that an amplitude of a rapid filling wave becomes larger during a stress test as an indication of a coronary blockage.  
   
   
       22 . A system for determining a change in function of a patient's heart, comprising: 
 means for collecting seismocardiographic (SCG) data from an exterior surface of a said patient corresponding to a heart motion of said patient's heart;    means for determining a hemodynamic parameter based on said SCG data; and    a processing device that compares said hemodynamic parameter with a predetermined measure of cardiac performance.    
   
   
       23 . The apparatus of  claim 22 , wherein said means for collecting SCG data comprises an accelerometer.  
   
   
       24 . The apparatus of  claim 23 , wherein said accelerometer is adapted for wireless communication with said means for determining a hemodynamic parameter.  
   
   
       25 . The apparatus of  claim 22 , wherein said means for determining a hemodynamic parameter is adapted for wireless communication with said processing device.