Abstract: A rate-responsive pacemaker which is provided with a closed-loop control system whose rate control parameter is the depolarization gradient. Any difference between the measured value of the rate control parameter and a target value is used to change the pacing rate in a direction which tends to minimize the difference. To calibrate the system for long-term changes due to drugs and the like, the target value is changed in each measurement cycle in accordance with prescribed rules.

Abstract: A rate-responsive pacemaker which is provided with a closed-loop control system whose rate control parameter is the depolarization gradient. Any difference between the measured value of the rate control parameter and a target value is used to change the pacing rate in a direction which tends to minimize the difference. To calibrate the system for long-term changes due to drugs and the like, the target value is changed in each measurement cycle in accordance with prescribed rules.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fusion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fusion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fusion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fusion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fashion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fusion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fusion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: A multi-programmable ROM-less cardiac pacer employs an intermittent microprocessor turned ON and OFF by a pacer timer clockwise independent of the processor to time intervals preset by the processor. Sensed activity and external communications restart the processor with an interrupt request. Five antitachycardia mechanisms are externally programmable: programmed burst, burst rate scanning, automatic overdrive, programmed critically timed and critically timed scanning. In scanning mechanisms, the interval changes progressively until the tachycardia is terminated by a successful interval which is stored. Runaway protection is executed in the software. For telemetry, the pacer collects the following monitored pacing data over a programmable period of time: percent pacing, average rate, maximum rate, number of tachycardia episodes and maximum tachycardia duration.

Abstract: A multi-programmable ROM-less cardiac pacer employs an intermittent microprocessor turned ON and OFF by a pacer timer clockwise independent of the processor to time intervals preset by the processor. Sensed activity and external communications restart the processor with an interrupt request. Five antitachycardia mechanism are externally programmable: programmed burst, burst rate scanning, automatic overdrive, programmed critically timed and critically timed scanning. In scanning mechanisms, the interval changes progressively until the tachycardia is terminated by a successful interval which is stored. Runaway protection is executed in the software. For telemetry, the pacer collects the following monitored pacing data over a programmable period of time: percent pacing, average rate, maximum rate, number of tachycardia episodes and maximum tachycardia duration.

Abstract: A multi-programmable ROM-less cardiac pacer employs an intermittent microprocessor turned ON and OFF by a pacer timer clockwise independent of the processor to time intervals preset by the processor. Sensed activity and external communications restart the processor with an interrupt request. Five antitachycardia mechanisms are externally programmable: programmed burst, burst rate scanning, automatic overdrive, programmed critically timed and critically timed scanning. In scanning mechanisms, the interval changes progressively until the tachycardia is terminated by a successful interval which is stored. Runaway protection is executed in the software. For telemetry, the pacer collects the following monitored pacing data over a programmable period of time: percent pacing, average rate, maximum rate, number of tachycardia episodes and maximum tachycardia duration.

Abstract: An instruction memory for a microprocessor based cardiac pacer is equipped with code means defining improved pacing routines for accomplishing a programmably selectable 2:1 block mode in which every other atrial sense output is automatically ignored above a programmed maximum atrial rate. The 2:1 block option is preselected via the initialization routine. The atrial refractory period becomes programmable by equating it with the programmed maximum rate interval. As an alternative to 2:1 block mode, the pacer also offers VVI fallback pacing routine which can be automatically substituted for the main pacing routine. While atrial tachycardia continues to be monitored during the fallback routine, the criteria for resuming normal pacing are made different from the criteria for entering the fallback routine. In addition, before exiting the fallback routine, the R-R interval is lengthened by an amount to shift the phase of R-waves relative to P-waves.