Rejection of noises caused by postural changes during acute myocardial infarction detection

A method comprising:

• sensing at least one cardiac signal representative of cardiac activity of a subject using an implantable medical device (IMD);
• calculating, from the cardiac signal, a first dominant vector corresponding to a direction and magnitude of maximum signal power of a first segment of a cardiac cycle and a second dominant vector corresponding to a direction and magnitude of maximum signal power of a second segment of a cardiac cycle;
• measuring a change in the first dominant vector;
• measuring a change in the second dominant vector;
• and
• subtracting the change in the second dominant vector from the measured change in the first dominant vector to form a difference.

A system comprising

• an implantable medical device (IMD) comprising:
• a plurality of implantable electrodes adapted for spatial distribution within a subject;
• and
• at least one cardiac signal sensing circuit in communication with the electrodes, the cardiac signal sensing circuit operable to produce an electrical cardiac signal representative of cardiac activity of the subject;
• and
• means for calculating, from the electrical cardiac signal, a first dominant vector corresponding to a direction and magnitude of maximum signal power of a first segment of at least one cardiac cycle of the subject and at least a second dominant vector corresponding to a direction and magnitude of maximum signal power of a second segment of the cardiac cycle, and forming a difference by subtracting a measured change in the second dominant vector from a measured change in the first dominant vector, and using the difference to reduce noise in the measured change in the first dominant vector.