Abstract: An implantable medical device employing a random access memory for storage of data relating the physiologic condition of the patient in which the device is implanted and/or information related to the functioning of the device. The memory and associated addressing circuitry are reconfigurable to allow for storage and display of information in either a histogram or trend line format.

Abstract: A pacing system analyzer is constructed to provide verification that an implantable cardiac pacer operating in a demand mode will not itself produce tachycardia in a patient because of abnormally long patient retrograde conduction time. The analyzer when performing the retrograde conduction test provides an intercardiac electrogram, changes the ventricular sense amplifier to asynchronous and samples to determine the maximum amplitude signals over a sampling period to select an amplifier gain factor. After the gain factor is set additional signal samples are collected, peak-to-peak amplitude is measured and interpolation between data is made to provide waveform "segments" and the best waveform segment to employ for testing for retrograde conduction is selected. The time periods from pacing to these segments are measured and utilized to determine if retrograde conduction is present.

Abstract: A pacing system analyzer as connected to an implantable cardiac pacer and if an atrial pacing pulse is detected only, the analyzer sends a simulated P-wave to the pacer and determines the response of the simulated P-wave to determine if the pacing mode is AAI, AAT, or AOO. In the event a ventricular output pulse only is detected by the analyzer, a simulated R-wave is sent to the pacer and if the pacer responds either by a triggered ventricular pulse or by not changing its response, the analyzer determines that the pacer is in a VVT or VOO mode. On the other hand, if the pacer is inhibited a subsequent simulated P-wave is sent to it and the response of this P-wave determines whether or not the pacer is in a VVI or VDD mode. In the event that both atrial and ventricular pacing pulses are detected by the analyzer, the simulated R-wave is first sent to the pacer and an unchanged response determines that the pacer is in a DOO mode.

Abstract: A marker channel telemetry system for use with a pacemaker or other medical device for transmitting event identifying codes to a remote receiver to indicate the occurrence of specific events such as sensed and paced events in a dual chamber pacemaker. The structure of the system includes latches to store event information and for forming the marker codes. The system also includes a serial telemetry transmitter for transmitting the data to the remote receiver.