Abstract: An implantable activity-based variable rate pacemaker includes an accelerometer for detecting movements of the patient, and discriminates between those of the detected movements indicative of physical exercise by the patient and those of the detected movements indicative of non-exercise. The pacemaker is responsive to detected movements indicative of physical exercise to select a pacing rate according to the level of the physical exercise. Separately, a parameter of the patient which varies in proportion to physical exercise but differs from direct detection of patient movement is sensed to generate an output representing the present state of physical exercise of the patient.

Abstract: An activity-based variable rate pacemaker senses motion in a preselected low frequency range to detect physical activity of the patient and produce an electrical signal having amplitude maxima and minima representative of the speed and intensity of the physical activity. The electrical signal is selectively limited to appreciable amplitude values for detected physical activity which is related to true physical exercise by the patient, in contrast to detected physical activity which is related to internal and external disturbances on the patient. The amplitude maxima and minima of the selectively limited signal are detected in successive equal intervals of time, the results obtained for consecutive blocks of time each containing the same number of successive equal intervals of time are compared to determine whether the physical exercise is more vigorous or less vigorous than that determined for a predetermined number of immediately preceding blocks, and the pacing rate is adjusted accordingly.

Abstract: An implantable variable rate pacemaker adaptive to patient exercise detects movements of the patient, and discriminates between detected movements indicative of physical exercise by the patient and detected movements indicative of non-exercise. The pacemaker responds to the detected movements indicative of physical exercise by incrementally adjusting the pacing rate according to the level of the physical exercise. The detection of movement is performed by an accelerometer in the form of a mechanoelectrical transducer which converts mechanical movements to an electrical signal having a designated parameter representative of the intensity of the mechanical movements. The accelerometer is housed within and isolated from the pulse generator case of the pacemaker and is implemented as part of a semiconductor device.

Abstract: A method for detecting and treating ventricular tachyrhythmias of a patient's heart includes the steps of selectively dividing the heart rate continuum into regions including at least two classes of tachycardia, contiguous to each other and of progressively higher heart rate ranges, the lowest and highest of the tachycardia classes being bounded respectively by a sinus rate region and a fibrillation region of the continuum; selectively adjusting the boundaries between the tachycardia classes and between the lowest and highest of those classes and the respective sinus rate and fibrillation regions, to correspondingly adjust the rate ranges of the classes; selectively detecting cardiac events anywhere within the continuum and distinguishing between normal and abnormal tachycardias among the detected events; selectively treating a detected abnormal tachycardia with any of a multiplicity of therapy regimens of differing degrees of aggressiveness, toward terminating the detected tachycardia; with the improvement o

Abstract: A dual chamber pacemaker with variable V-A delay based on detection of multiple criteria before lengthening the V-A delay period. Before the V-A delay period can be extended, the pacemaker must be stimulating the ventricle at a maximum ventricular rate, and an atrial event must be sensed in a relative atrial refractory period. During this interval the pacemaker would not respond to an atrial event that was sensed, but the occurrence of the event would be detected. To optimize a ventricular blanking period, in each cardiac cycle, the energy level of the atrial output pulse and the sensitivity of the ventricular sense amplifier are sampled. Based on these dynamic parameters, the duration of the ventricle blanking period is adjusted for each cycle so that a minimum ventricular blanking period can be maintained without cross-talk.

Abstract: An implantable endocardial lead with retractable fixation apparatus. The fixation apparatus comprises a sharpened helix which can be repeatedly both retracted within an electrode at a distal end of the lead and displaced outside the electrode by action of a flexible, tubular lanyard. The lanyard passes through a lumen from a proximal end of the lead to the distal end of the lead, where the lanyard is attached to a piston supporting the helix. At the proximal end of the lead, a jig moves the lanyard with respect to a longitudinal axis of the lead. When the helix is in an exposed position, torque can be transmitted from the proximal end of the lead to the distal end thereof, through the electrode to the piston and then to the helix to screw the helix into the endocardial tissue. To stiffen the lead during implantation, a stylet can be inserted into a lumen in the lanyard.

Abstract: A series of test signals are generated by a microprocessor of a pacemaker to determine whether a bipolar or unipolar lead is attached to an implanted cardiac pacemaker restricting programming of said pacemaker to only an unipolar pacing mode unless the presence of an operational bipolar lead is detected. Detection is accomplished by generating a series of low frequency high impedance pulses, applying them to lead contacts and sensing a return signal. If a return signal is detected, then that indicates either a unipolar lead is connected to the pacemaker or that the ring conductor of a bipolar lead is open and bipolar pacing must be inhibited.

Abstract: A replacement connector for implanted leads. The proximal end of the implanted lead is cut away and discarded. A slip-on seal is placed on the remaining end of the lead. The replacement connector is connected to the implanted lead using an eccentric locking mechanism both to secure the implanted lead and the replacement connector together and to achieve a positive electrical connection. A boot mates with the slip-on seal to protect the connection from body fluids.

Abstract: An implantable variable rate pacemaker adaptive to patient exercise detects movements of the patient, and discriminates between detected movements indicative of true physical exercise by the patient and detected movements which are not true physical exercise. An activity sensor converts mechanical movements of the patient to an electrical signal representative thereof. Only a portion of the electrical signal in a frequency range below 4 Hz is processed by the pacemaker's electrical circuitry, to discriminate against signal components arising from other than physical exercise of the patient. As a result of this signal processing, a predetermined variable signal component is recovered, other than frequency of amplitude crossings relative to a threshold value, to produce an output signal representative of true physical body exercise.

Abstract: An implantable endocardial lead with retractable fixation device. The fixation device comprises a sharpened helix which can be repeatedly both retracted within a distal end of the lead and displaced outside the lead. A threaded stylet passes through a lumen from a proximal end of the lead to the distal end of the lead, where the threaded stylet is screwed into a piston supporting the helix. When the helix is in an exposed position, torque can be transmitted from the proximal end of the lead through the distal end to the piston and thence to the helix to screw the helix into the endocardial tissue.

Abstract: A transvenous lead for defibrillation and pacing of the heart includes a single defibrillating coil electrode adapted to be introduced into the right ventricle of the heart. The coil constitutes a relatively long flexible large surface area electrode conformable to the shape of the ventricle and thereby readily disposed along the entire length of the vertricle for use in delivering defibrillating shocks. A pacing electrode at the tip of the lead is used both in stimulating the heart with pacing pulses and in sensing the response of the heart to the pulses and to shocks. The coil electrode is multi-filar, composed of a plurality of wires tightly wound side by side, each wire composed of copper-zirconium alloy wrapped with tantalum, and is flared from the diameter at its ends to a lager diameter intermediate its ends to increase the exposed surface area thereof in the ventricle.

Abstract: A body function assistance device, capable of analyzing changing but cyclic physiologic needs of a patient and generating a response based on the analysis. A microprocessor in the body function assistance device controls the response of the device to various external events and internal timer events. The microprocessor recognized variations in patterns of recurrent events and adjusts the output of the body function assistance device in response to the detected variations. In a particular embodiment, an implantable cardiac pacer is responsive to a circadian wake-sleep cycle.

Abstract: A lead assembly for a cardiac pacemaker is formed by an electrical conductor having one end connected to the pacemaker and a heart engaging electrode member attached to the opposite end. The electrode member has a profiled contact surface having at least one diametrically extending groove and a coating of iridium oxide thereon. The profiled electrode member offers at least a pair of edges to both grip the heart tissue to reduce relative movement of the electrode while focusing the discharge of the pulses thereby allowing reduction in the polarizing pacing voltage.

Abstract: An implantable lead for a cardiac stimulator has an electrode at its distal end, and resilient, non-penetrating, tissue-contacting elements integral with the lead in the vicinity of the electrode. The resilient elements are movable from a first unextended position for ease of insertion or withdrawal of the lead through the vein of a patient to a second extended position for contacting tissue to retain the electrode in a selected location in the heart of the patient. A device operable along the lead serves to selectively move the resilient elements from the unextended to the extended position or vice versa.

Abstract: A cardiac pacemaker has a sense amplifier responsive to signals representative of cardiac activity for passing signal components lying in a selectively variable pass band and for selectively varying the gain of the passed signal. A pair of signal comparators constituting switched capacitor amplifiers, associated with the sense amplifier, are responsive to the filtered and gain adjusted signal for comparison of its magnitude to predetermined target levels for determination of heart rate and the need for change of rate. Two target levels are provided in each comparator for comparison with the level of the detected signal, by multiplexing the switched capacitors. Another switched capacitor amplifier is used to develop a voltage reference level insensitive to temperature, supply voltage, and circuit components, for deriving the target levels for the comparison.

Abstract: An implantable cardiac stimulator for detecting and treating bradycardias includes a sense amplifier responsive to sensed cardiac signals for detecting cardiac activity. The sense amplifier includes an automatic gain control amplifier, a filter and quad comparator having a pair of signal channels to establish sensing thresholds, margins and signal gain. The sense amplifier has a feedback loop containing a microprocessor which implements preselected algorithms in conjunction with the outputs of the quad comparator to variably adjust the amplifier gain and to programmably control the sensing margin.

Abstract: A cardiac pacemaker pulse generator is adapted to .generate electrical stimuli at a first pacing rate, and to selectively increase the rate to a second higher pacing rate. A timer triggers the rate increase to establish the higher rate as an exercise rate folloing the passage of a preset period of time after the timer is enabled. An external magnet controlled by the patient activates a reed switch to enable the timer to commence timing. The pulse generator is further adapted to respond to a second pass of the magnet over the reed switch after enabling of the timer to thereupon disable the timer before the preset period of time has expired. If the second pass of the magnet occurs after the exercise rate has begun, the element for increasing the rate is disabled to return the pulse generator to the lower pacing rate. The change in pacing rates is made in steps.

Abstract: An implantable cardiac stimulator for detecting and treating cardiac arrhythmias includes a sense amplifier responsive to sensed cardiac signals for detecting and distinguishing normal and abnormal cardiac activity within the sensed signals. The sense amplifier includes an automatic gain control amplifier, a filter and quad comparator having a pair of signal channels for processing the sensed signals according to different frequency bandpass characteristics to establish sensing thresholds, margins and signal gain. The sense amplifier has a feedback loop containing a microprocessor which implements preselected algorithms in conjunction with the outputs of the quad comparator to variably adjust the amplifier gain and to programmably control the sensing margin.

Abstract: A heart pacemaker detects pace-terminable tachycardia conditions in the atrium of the heart in accordance with selected high rate, rate stability, sudden onset and sustained high rate criteria. When a pace-terminable tachycardia is detected, programmed treatment modalities are applied to attempt to terminate the tachycardia. The tachycardia is treated by applying timed bursts of electrical pulses in formats defined by programmed primary and secondary treatment modalities. The primary and secondary treatments may be applied in an order which is dependent upon the prior successful treatment of similar tachycardias. The pacemaker may also utilize remembered treatment values which were successfully applied to treat similar tachycardias. The pacemaker may be programmed to restart the primary and secondary modes of treatment in the event that the modes initially failed to terminate a tachycardia. The pacemaker may also be programmed to limit the rate of burst pulses to avoid overstimulating the heart.

Abstract: A heart pacemaker detects pace-terminable tachycardia conditions in the atrium of the heart in accordance with selected high rate, rate stability, sudden onset and sustained high rate criteria. When a pace-terminable tachycardia is detected, programmed treatment modalities are applied to attempt to terminate the tachycardia. The tachycardia is treated by applying timed bursts of electrical pulses in formats defined by programmed primary and secondary treatment modalities. The primary and secondary treatments may be applied in an order which is dependent upon the prior successful treatment of similar tachycardias. The pacemaker may also utilize remembered treatment values which were successfully applied to treat similar tachycardias. The pacemaker may be programmed to restart the primary and secondary modes of treatment in the event that the modes initially failed to terminate a tachycardia. The pacemaker may also be programmed to limit the rate of burst pulses to avoid overstimulating the heart.