Ischemia detection

Abstract

Techniques for detection and treatment of myocardial ischemia are described that monitor both the electrical and dynamic mechanical activity of the heart to detect and verify the occurrence of myocardial ischemia in a more reliable manner. The occurrence of myocardial ischemia can be detected by monitoring changes in an electrical signal such as an ECG or EGM, and changes in dynamic mechanical activity of the heart. Dynamic mechanical activity can be represented, for example, by a heart acceleration signal or pressure signal. The electrical signal can be obtained from a set of implanted or external electrodes. The heart acceleration signal can be obtained from an accelerometer or pressure sensor deployed within or near the heart. The techniques correlate contractility changes detected by an accelerometer or pressure sensor with changes in the ST electrogram segment detected by the electrodes to increase the reliability of ischemia detection.

1 . A system for detecting myocardial ischemia, the system comprising: 
 means for generating a first signal indicative of contractile activity of a heart;    means for obtaining a second signal indicative of electrical activity of the heart; and    means for detecting myocardial ischemia based on both the first signal and the second signal.    
     
     
         2 . A system according to  claim 1 , further comprising means for controlling, subsequent to when myocardial ischemia is detected, delivering a therapy to alleviate effects of the ischemia within the heart.  
     
     
         3 . A system according to  claim 1 , wherein the therapy includes at least one of a drug delivery therapy, an electrical stimulation therapy, a combination of the drug delivery therapy and the electrical stimulation therapy.  
     
     
         4 . A system according to  claim 1 , wherein the means for generating the first signal includes an implanted accelerometer and the first signal comprises a heart acceleration signal.  
     
     
         5 . A system according to  claim 4 , wherein the accelerometer mechanically couples to a distal portion of a lead adapted to be implantable one of within and on an exterior portion of the heart.  
     
     
         6 . A system according to  claim 1 , wherein the means for obtaining the second signal indicative of electrical activity of the heart includes a subcutaneous electrode array (SEA).  
     
     
         7 . A system according to  claim 6 , wherein the system further comprises a subcutaneous ischemia monitoring circuit means disposed within a substantially hermetic housing in electrical communication with said SEA.  
     
     
         8 . A system according to  claim 1 , wherein the means for obtaining the second signal indicative of electrical activity of the heart includes at least one endocardial electrode disposed within a chamber or vasculature of the heart.  
     
     
         9 . A system according to  claim 1 , wherein the means for obtaining the second signal indicative of electrical activity of the heart includes at least one externally mounted electrode adapted to be coupled to a portion of epidermis of a subject.  
     
     
         10 . A computer-readable medium containing instructions to produce a technical effect via at least one computer processor, comprising: 
 obtaining a first signal indicative of dynamic mechanical activity of a heart;    obtaining a second signal indicative of electrical activity of the heart; and    detecting a relative degree of an episode of myocardial ischemia based at least in part on both the first signal and the second signal.    
     
     
         11 . A computer computer-readable medium according to  claim 10 , wherein the first signal is derived from one of an implanted pressure transducer, an accelerometer, a velocity sensing apparatus.  
     
     
         12 . A computer-readable medium according to  claim 10 , wherein the first signal relates to one of a right ventricular contractile activity and a left ventricular contractile activity.  
     
     
         13 . A computer-readable medium according to  claim 12 , wherein the right ventricular contractile activity is provided from an endocardial location.  
     
     
         14 . A computer-readable medium according to  claim 12 , wherein the left ventricular contractile activity is provided from one of an epicardial location, a pericardial location, a location within a portion of a great vein or coronary sinus.  
     
     
         15 . A computer-readable medium according to  claim 12 , wherein the relative degree of the episode of myocardial ischemia is determined along at least a plurality of axes of one of said first signal and said second signal.  
     
     
         16 . A computer-readable medium according to  claim 11 , wherein the accelerometer mechanically couples to a distal portion of a lead adapted to be implantable one of: within a chamber of the heart, on an exterior portion of the heart, within a portion of vasculature of the heart.  
     
     
         17 . A computer-readable medium according to  claim 10 , wherein obtaining the second signal indicative of electrical activity of the heart includes a signal derived from a subcutaneous electrode array (SEA).  
     
     
         18 . A computer-readable medium according to  claim 17 , further comprising a subcutaneous ischemia monitoring circuit means disposed within a substantially hermetic housing in electrical communication with said SEA.  
     
     
         19 . A computer-readable medium according to  claim 10 , wherein obtaining the second signal indicative of electrical activity of the heart includes at least one endocardial electrode disposed within a chamber or a portion of vasculature of the heart.  
     
     
         20 . A computer-readable medium according to  claim 10 , wherein obtaining the second signal indicative of electrical activity of the heart includes at least one externally mounted electrode adapted to be coupled to a portion of epidermis of a subject.