Pacing schemes for revealing t-wave alternans (twa) at low to moderate heart rates

Abstract

Implantable systems that can monitor myocardial electrical stability, and methods for use therewith, are provided. Also provided are novel pacing sequences that are used in such monitoring. Such pacing sequences are designed to reveal alternans at low to moderate heart rates.

1 . In an implantable system, a method for monitoring myocardial electrical stability, comprising:
 (a) pacing a patient's heart in accordance with a pacing sequence that includes a short beat set of a plurality of short beats that get successively shorter or longer from the beginning to the end of the short beat set, followed by a regular beat set of a plurality of regular beats, wherein each said short beat is shorter than each said regular beat;   (b) measuring at least one metric of T-waves in two or more beats that follow each change in beat length;   (c) determining magnitudes of alternation based on the measured T-wave metrics; and   (d) monitoring myocardial electrical stability based on the determined magnitudes of alternation.   
   
   
       2 . The method of  claim 1 , wherein step (d) comprises determining, based on the determined magnitudes of alternation, whether T-wave alternans are present. 
   
   
       3 . The method of  claim 1 , wherein step (d) comprises tracking changes in the magnitudes of alternation as steps (a), (b) and (c) are repeated over time, to thereby track changes in myocardial electrical stability. 
   
   
       4 . The method of  claim 1 , wherein the pacing sequence includes a long beat set of a plurality of long beats that follows the regular beat set, wherein each said long beat is longer than each said regular beat. 
   
   
       5 . The method of  claim 4 , wherein:
 the long beat set includes long beats that get successively longer from the beginning to the end of the long beat set.   
   
   
       6 . The method of  claim 4 , wherein:
 the long beat set includes long beats that get successively shorter from the beginning to the end of the long beat set.   
   
   
       7 . The method of  claim 1 , wherein step (b) includes measuring at least one of the following T-wave metrics: T-wave amplitude; T-wave width; T-wave slope; T-wave area; T-wave morphology; QT interval; and evoked QT interval. 
   
   
       8 . In an implantable system, a method for monitoring myocardial electrical stability, comprising:
 (a) pacing a patient's heart in accordance with a pacing sequence that includes a short beat set of a plurality of short beats that get successively shorter or longer from the beginning to the end of the short beat set, followed by a long beat set of a plurality of long beats, wherein each said short beat is shorter than each said long beat;   (b) measuring at least one metric of T-waves in two or more beats that follow each change in beat length;   (c) determining magnitudes of alternation based on the measured T-wave metrics; and   (d) monitoring myocardial electrical stability based on the determined magnitudes of alternation.   
   
   
       9 . The method of  claim 8 , wherein step (d) comprises determining, based on the determined magnitudes of alternation, whether T-wave alternans are present. 
   
   
       10 . The method of  claim 8 , wherein step (d) comprises tracking changes in the magnitudes of alternation as steps (a), (b) and (c) are repeated over time, to thereby track changes in myocardial electrical stability. 
   
   
       11 . The method of  claim 8 , wherein the pacing sequence includes a regular beat set of a plurality of regular beats that follow the long beat set. 
   
   
       12 . The method of  claim 8 , wherein step (b) includes measuring at least one of the following T-wave metrics: T-wave amplitude; T-wave width; T-wave slope; T-wave area; T-wave morphology; QT interval; and evoked QT interval.