Cardiac arrhythmia detection system for an implantable stimulation device

An implantable cardiac event detection system for eliminating sensing of high amplitude T-waves, the cardiac event detection system including an implantable lead that transmits an electrogram signal from a heart, comprising:

• an amplifier, coupled to the implantable lead, for amplifying an electrogram signal;
• threshold detection means, coupled to the amplifier, for detecting an occurrence of an R-wave in the electrogram signal whenever the magnitude of the electrogram signal exceeds a threshold value;
• and
• control means, responsive to the detection of the R-wave, for dynamically changing the threshold value from an initial value to a temporary value, for maintaining the threshold value at the temporary value for a programmable time period, and then for gradually returning the threshold value from the temporary value back to the initial value in a predetermined stepwise fashion within a prescribed time period, the prescribed time period being selected to return the threshold value to its initial value prior to the occurrence of a succesive R-wave, so that a high amplitude T-wave that follows the R-wave is not sensed.

An implantable cardiac event detection system for eliminating sensing of high amplitude T-waves, the system including an implantable lead that transmits an electrogram signal from a heart, comprising:

• an amplifier, coupled to the implantable lead, for amplifying an electrogram signal;
• threshold detection means, coupled to the amplifier, for detecting an occurrence of an R-wave in the electrogram signal whenever the magnitude of the electrogram signal exceeds a threshold value;
• and
• control means, responsive to the detection of the R-wave, for dynamically changing the threshold value from an initial value to a temporary value, and then for returning the threshold value from the temporary value to the initial value in accordance with an adjustable recovery curve so that a T-wave that follows an R-wave is not sensed.

An implantable cardiac event detection system for eliminating sensing of high amplitude T-waves, the system including an implantable lead that transmits an electrogram signal from a heart, comprising:

• an amplifier, coupled to the implantable lead, for amplifying an electrogram signal, the amplifier having a plurality of programmable gains;
• first control means for automatically adjusting the gain of the amplifier so that the electrogram signal is within an optimum dynamic range even in the presence of changing cardiac signal morphology such that an R-wave within the electrogram signal is not clipped and a T-wave is proportionally reduced relative to the R-wave;
• threshold detection means, coupled to the amplifier, for detecting an occurrence of an R-wave in the electrogram signal whenever the magnitude of the electrogram signal exceeds a threshold value;
• and
• second control means, responsive to the detection of the R-wave, for dynamically changing the threshold value from an initial value to a temporary value, and then for gradually returning the threshold value from the temporary value to the initial value prior to the occurrence of a successive R-wave;
• whereby a T-wave that follows the R-wave is not sensed.

An implantable cardiac event detection system, the system including an implantable lead that transmits an electrogram signal from a heart, comprising:

• sensing means, coupled to the implantable lead, for sensing an R-wave in the electrogram signal, the sensing means having a gain factor which can be programmably adjusted;
• means, coupled to the sensing means, for determining a baseline value of the electrogram signal;
• and
• amplitude detecting means, coupled to the sensing means, for detecting an amplitude value of the R-wave;
• means for automatically adjusting the gain factor of the sensing means based on the difference between the amplitude value of the R-wave and the baseline value;
• threshold detection means, coupled to the sensing means, for detecting an occurrence of an R-wave in the electrogram signal whenever the magnitude of the electrogram signal exceeds a threshold value;
• control means, responsive to the detection of the R-wave, for dynamically changing the threshold value from an initial value to a temporary value, and then for gradually returning the threshold value from the temporary value back to the initial value prior to the occurrence of a successive R-wave, the initial value and the temporary value each being automatically adjusted as a function of the average baseline value and the average amplitude value;
• whereby a T-wave that follows the R-wave is not sensed as a result of the adjustment of the gain factor of the sensing means and as a result of the temporary threshold value being adjusted above the T-wave amplitude even in the presence of changing cardiac morphology.