Output pulse artifact rejection in demand pacemakers and sensing circuits employed in conjunction therewith

Abstract

An atrial-ventricular demand pacemaker having improved atrial pulse artifact rejection includes a blanking circuit (30, 100) connected in the signal path from the ventricular output terminal (17) to the sensing amplifier (21) to blank the signal during an atrial pulse. A holding circuit including a low-pass filter (46, 137) and a switching element (43, 112) stores a prior signal value at the sensing amplifier input during the blanking interval, and delays return to normal operation until after the blanking circuit has returned to normal. Artifact rejection is also improved by limiting atrial pulse output circuit recharge time and by limiting polarization current driven into the ventricular output circuitry by an atrial output pulse.

What is claimed: .[.1. A heart pacemaker comprising: 
     
        pulse artifact is prevented from entering the sense amplifier..]. .[.3.  A heart pacemaker according to claim 2 wherein said first switching means comprises a series switching element connected in series with said terminal means and said sensing amplifier and a shunt switching element connected between said signal path and signal ground both selectively operative in response to said timing means for blocking the passage of signals along said signal path..]. .[.4. A heart pacemaker according to claim 2 wherein said signal holding means includes a shunt capacitor connected between the signal path and signal ground and a shunt resistor connected between said signal path and signal ground to form a discharge path for said capacitor, with said second switching means connected in series in said signal path between said resistor and said capacitor..]. .[.5. A heart pacemaker according to claim 2 wherein said timing means includes means for actuating said first and second switching means just prior to delivery of an atrial pulse..]. .[.6. A heart pacemaker according to claim 2 wherein said timing means includes means operative at the end of an atrial pulse for delaying the return of said second switching means to normal operation until after the return of said first switching means to normal operation, to prevent switching artifact from entering said sensing amplifier..]. .[.7. A heart pacemaker comprising: terminal means for connection to a patient's heart for delivering atrial and ventricular stimulation thereto;   generating means for delivering sequential atrial and ventricular electrical stimulation pulses to said terminal means at a predetermined repetition rate;   a sensing amplifier for sensing electrical signals indicative of the patient's heartbeat;   demand control means connected to said sensing amplifier and operative for preventing delivery of said stimulating pulses if a heartbeat occurs within a predetermined time interval following a preceding heartbeat;   blanking means for normally connecting said terminal means to said sensing amplifier for conveying the patient's heartbeat signals thereto, and for selectively decoupling said sensing amplifier from said terminal means during delivery from said terminal means during delivery of an atrial stimulation pulse, said blanking means including holding circuit means operative during a blanking interval to hold a prior signal level at the input to the sensing amplifier..]. .[.8. A heart pacemaker according to claim 7 wherein said blanking means includes timing means for sequentially returning the blanking means and the holding means to normal operation at   
     
     
        the end of the atrial stimulation pulse..]. .Iadd.9.  A heart pacemaker comprising pulse generator means for generating electrical stimulation pulses in a first chamber of a heart; storage means for temporarily storing representations of natural electrical heartbeat signals occurring in a second chamber of a heart;   sensing means coupled to said storage means for sensing said natural electrical heartbeat signals;   circuit path means for coupling said signals to said storage means comprising capacitive coupling means associated with said path through which said signals are transmitted;   terminal means for coupling said stimulation pulses from said pulse generator to the first chamber of the heart and for coupling said signals from the second chamber of the heart to said circuit path means;   blanking means comprising timing means for timing out a first and a second period of time, means for preventing the transmission of signals through said circuit path means for said first period of time that begins prior to the generation of an electrical stimulation pulse and lasts until after the termination of said pulse, means for preventing further storage in said storage means for said second period of time which begins before the termination of said first period and lasts until after the termination of said first period; and discharging means for discharging said capacitive coupling means after the generation of a stimulation pulse before the   
     
     
        termination of said first period of time. .Iaddend. .Iadd.10.  A heart pacemaker as claimed in claim 9 wherein said circuit path means comprises resistive means coupled to said capacitive coupling means; said capacitive means and said resistive means are coupled together so as to provide signal differentiation for said signals, and said storage means provide signal integration. .Iaddend.