Abstract: An apparatus and method for assessing the status of well-being of patients being treated for CHF using cardiac pacing as a therapy. By sampling the output from an activity sensor or the like, and by noting the frequency with which the averaged rectified sensor output exceeds a preset threshold following changes in the pacing mode, the efficacy of the new mode compared to the previous one can be evaluated.

Abstract: A method and apparatus for attenuating polarization voltages or "afterpotentials" which develop at the heart tissue/electrode interface following the delivery of a pacing stimulus to the heart tissue such that the evoked response of the heart may be accurately detected to determine whether each pacing stimulus resulted in heart capture or contraction, thereby facilitating improved tracking of the capture threshold and minimizing power consumption while assuring therapeutic efficacy. The conventional large capacitance coupling capacitor used to suppress DC components of the pacing spike has another, much lower capacitance capacitor connected in series with it. The lower capacitance capacitor may be operable in either the autothreshold mode or in the normal pacing mode such that its value can be selectively inserted in series with the larger capacitance coupling capacitor to effectively lower the overall capacitance of the coupling capacitor following delivery of the pacing stimulus.

Abstract: Based upon patient studies indices a high degree of correlation was found between HRV and VO2.sub.max, i.e., the patient's exercise capacity. Based on this finding, a pacing therapy optimization protocol for treating patients with CHF has been devised. The protocol involves first pacing the patient's heart with a pacemaker programmed to operate in a first mode for a predetermined time period and then collecting electrogram data from which a HRV index is derived. The mode is then changed and the steps repeated until all possible modes have been utilized. At that time, a determination is made as to which of the modes is associated with the largest HRV index and the pacemaker is then programmed to function in that mode. Alternatively, the method of the present invention can be applied to changes in drug therapy instead of or in combination with pacing therapy.

Abstract: An apparatus and method for assessing the status of well-being of patients being treated for CHF using cardiac pacing as a therapy. By sampling the output from an activity sensor or the like, and by noting the frequency with which the averaged rectified sensor output exceeds a preset threshold following changes in the pacing mode, the efficacy of the new mode compared to the previous one can be evaluated.

Abstract: A method and apparatus for attenuating polarization voltages or "afterpotentials" which develop at the heart tissue/electrode interface following the delivery of a pacing stimulus to the heart tissue such that the evoked response of the heart may be accurately detected to determine whether each pacing stimulus resulted in heart capture or contraction, thereby facilitating improved tracking of the capture threshold for minimizing power consumption while assuring therapeutic efficacy. The conventional large capacitance coupling capacitor used to suppress DC components of the pacing spike has a second, much lower capacitance capacitor connector in series with it, the second capacitor being shunted by a switch so that its value can be selectively inserted in series with the coupling capacitor to effectively lower the overall capacitance of the coupling capacitor following delivery of the pacing spike.

Abstract: An implantable cardiac rhythm management device includes an accelerometer along with apparatus for processing the analog signal output from the accelerometer for deriving therefrom the time of occurrence of a selected heart sound in relation to a previously occurring ventricular depolarization event. The thus-derived heart sound information can be used to establish a hemodynamic upper rate limit for a rate adaptive pacemaker.

Abstract: An implantable cardiac rhythm management device (pacemaker or defibrillator) having circuitry for determining the interval between two successive natural ventricular depolarization signals, includes the capability of computing and storing histogram arrays of heart rate variability data over a prolonged period, such as 24 hours. By utilizing an algorithm for generating a histographic log and a time domain log wherein a logarithmic data compression technique is implemented, the volume of HRV data collected for later telemetered readout to an external device does not exceed the memory and power capabilities of the implanted device.

Abstract: A cardiac rhythm management device and method includes a dual-chamber pacemaker especially designed for treating congestive heart failure and a defibrillator as a back-up measure. The device incorporates a programmed microcontroller which is operative to adjust the AV delay of the pacemaker to a minimum or maximum length consistent with optimal cardiac function. The cardiac stimulator includes apparatus for sensing cardiac function from cycle-to-cycle and determining whether incremental changes made to the AV delay interval enhances or worsens the measured cardiac function. On each iterative cycle, the AV delay interval is changed, either incremented or decremented, until a cross-over point is reached in which it is noted that the cardiac function ceases to improve and this is followed with a further incremental adjustment in an opposite direction to compensate for any overshoot.

Abstract: A cardiac stimulating system incorporating a microprocessor-based controller is designed to automatically optimize both the pacing mode and one or more pacing cycle parameters in a way that results in optimization of a cardiac performance parameter, such as cardiac output. For each of a plurality of modes in which a DDD cardiac pacer can operate, a pacing parameter such as the AV interval of the pacer is incrementally adjusted and following that, an observation is made as to the effect of the adjustment on cardiac output. After the process has been repeated for all possible pacing modes, a determination is made to find the pacing mode and the AV interval or other pacing parameter that results in the maximum cardiac output or other optimal cardiac performance parameter. It is these pacing parameters that are then programmed into the microcontroller for causing the pacemaker to function in the desired mode and at the desired parameter values.

Abstract: A method and apparatus for automatically optimizing a cardiac performance parameter of the heart, such as its cardiac output mean arterial pressure pO.sub.2 or pCO.sub.2. The performance parameter is optimized by periodically pacing the heart for a short period of time with stimulating pulses having a modified pacing parameter value. The intrinsic operation of the heart is monitored a majority of the time and establishes a baseline value for the cardiac performance parameter. The heart is then paced with the modified pacing parameter value during an interval that is approximately a 1:4 ratio with respect to the baseline monitoring interval. The method of the present invention can be achieved using a totally implanted pacemaker, an implanted pulse generator in combination with external equipment communicating with the pacemaker via telemetry, or by using equipment located external the patient.

Abstract: A DDD-type cardiac pacemaker having a microprocessor-based controller is programmed to automatically determine and utilize and optimize A-V delay for the patient in whom the device is implanted. The microprocessor-based controller periodically changes the A-V delay and then computes heart rate variability over an insuing predetermined period. The particular A-V delay value associated with the minimum heart rate variability index is determined to be the optimum. Heart rate variability may be determined by performing a power spectrum analysis on cyclic variations in R-R intervals, preferably using a FFT signal processing chip, or by a time domain analysis based upon the standard deviation of R-R intervals during a prescribed period of time and a calculated value of respiratory sinus arrhythmia. The apparatus is also operative to optimize the A-V delay interval following a change in the pacing mode of the DDD-type pacemaker.

Abstract: A pacemaker including a marker code generator generating marker codes between an indifferent electrode disposed on the pacemaker housing and the pacemaker can serving as a reference electrode. Marker code signals are generated proximate the pacemaker rather than proximate cardiac tissue, and thus can be generated at a large potential for sensing by surface EKG, and can also be generated simultaneously while pacing the heart and not necessarily in the refractory period. The pacemaker facilitates the interpretation of surface EKG, and can be sensed and recorded by commercially available two-channel holter monitors which can be taken home with the patient. Thus, marker code signals can be sensed and recorded while at home and played back for the physician at a later time for analysis. The marker code generator can be selectively turned on by the external programmer such that battery life depreciation is not appreciable. The pacemaker can be adapted with either a unipolar or bipolar endocardial lead.

Abstract: A cardiac rhythm management device includes a dual-chamber pacemaker especially designed for treating congestive heart failure and a defibrillator as a back-up measure. The device incorporates a programmed microcontroller which is operative to adjust the AV delay of the pacemaker to a minimum or maximum length consistent with optimal cardiac function. The cardiac stimulator includes apparatus for sensing cardiac function from cycle-to-cycle and determining whether incremental changes made to the AV delay interval enhances or worsens the measured cardiac function. On each iterative cycle, the AV delay interval is changed, either incremented or decremented, until a cross-over point is reached in which it is noted that the cardiac function ceases to improve and this is followed with a further incremental adjustment in an opposite direction to compensate for any overshoot.

Abstract: A cardiac pacemaker signal processing circuit adapted to obtain an evoked ECG signal. The circuit senses the electrical signals of the ring and tip electrodes in the unipolar mode from the bipolar lead after the electrical pacing stimulus has been applied to contract the ventricle of the heart. The residual oppositely polarized potentials at the ring and tip electrode, as well as the sensed evoked ECG signals, are added together to cancel out the opposing residual potentials, but to add the common polarized ECG signal. Thus, a high quality evoked ECG signal is obtained, free of the residual potentials, and subsequently utilized by R-wave detection circuits for sensing the QRS complex. The circuit includes compensating signal processing circuits to provide time domain signal processing weighting functions to match exponential time delay of the tip and ring electrodes, and includes amplitude adjusting compensation as well.

Abstract: A DDD pacemaker including stimulating means to stimulate the ventricles of a heart after a predetermined A-V delay period includes means for adjusting the A-V delay period to enhance the probability of detecting naturally occurring ventricular depolarization signals when such signals are being detected at a predetermined rate and switching to a more hemodynamically appropriate A-V delay period when paced beats predominate. The invention is implemented in software run on a microprogrammable controller comprising the DDD pacemaker.

Abstract: A cardiac rhythm management device is described in which the rate controlling parameter of a rate adaptive pacemaker is the heart's total active time. The active time is evaluated using the intraventricular impedance technique, the active time being the length of the interval between the onset of contraction and the point where a line passing through two points on the fast filling segment of the impedance wave form reaches the impedance level corresponding to the end-diastole impedance of the preceding beat. The approach results in a upper rate limit corresponding to the maximum heart rate that does not compromise circulatory function, e.g., result in a decrease in cardiac output, or an increase in cardiac workload without an associated increase in cardiac output. The application also teaches the use of the heart's total active time as an indication of hemodynamic instability for triggering a defibrillation.

Abstract: A rate adaptive pacemaker of the type having a variable rate cardiac stimulating pulse generator and a sensor for monitoring some physiologic parameter whereby the pulse generator stimulating rate can be adjusted to meet physiologic demand is further provided with a hemodynamic sensor which is operative to provide an output signal representing the pumping performance of the heart in response to the pacing stimulation. The signal from the hemodynamic sensor is processed and then used in an algorithm to determine whether further rate increase should be permitted based upon whether the rate increase would be accompanied by a further increase in cardiac output, a plateau or a decrease in cardiac output. Hence, the adaptive rate pacemaker is provided with a real-time, hemodynamic maximum pacing rate instead of a preprogrammed, fixed, maximum rate.