Multi chamber capture detection

A pacing system for pacing multiple chambers of the heart and sensing signals from the myocardium of multiple chambers of the heart which will allow the verification of a cardiac evoked response resulting from a delivered charge to the heart tissue, the pacing system having a pacing circuit capable of pacing multiple chambers of the heart the pacing system comprising:

• a preamplifier system having:
• a) a DC coupled buffer amplifier stage,
• b) a switch matrix following the buffer amplifiers allowing sensing of the differential between any two electrodes implanted in the heart,
• c) a next stage of differential amplifiers providing gain to either the differential between any two electrode Inputs or one Input to ground, and
• d) a next stage wideband bandpass filter with gain, having an output and internal switches capable of discharging charges transferred across the Input allowing the output of bandpass filter to be reset to analog ground.

A method for operating a pacing system for determining the presence of an evoked response of the myocardium, the method including the following steps:

• a) delivering a programmable stimulating monophasic pulse, followed by a programmable autoshort period which is shorter than the time between the end of the pace pulse and the beginning of an evoked response signal,
• b) Opening the switches in front of the buffer amplifiers during the delivering of the pulse and the autoshort period, and closing the switches in front of the buffer amplifiers immediately at the end of the autoshort period,
• c) at the same time during the delivering of the pulse and the autoshort period opening all blanking switches and setting all amplifier inputs in the filter stages to system ground,
• d) closing the matrix switches of the switch matrix and placing sensed signals at the inputs of the differential amplifiers,
• e) closing the switch connecting the output of the differential amplifier to the fast high pass filter,
• f) discharging the charge transferred across the high pass capacitor to system ground, The output of the first high pass is then switched to a low pass filter,
• g) switching the signal to the next high pass filter,
• h) discharging the charge transferred across the high pass capacitor to system ground,
• i) sending the output of the second high pass stage to the final low pass filter,
• j) switching the output of the final low pass filter, to the bandpass filter stage, and
• k) connecting the outputs of the bandpass filters to programmable threshold detectors.