Abstract: A system and method are provided for inducing ventricular tachycardia in a patient to enable testing to determine the optimum parameters for anti-tachycardia stimulation. The implantable device provides for overdrive pacing of the heart for a short sequence, followed by delivery of a series of pulse pairs. Each pulse pair has a first stimulus pulse delivered at the same or similar overdrive rate, and an inducing pulse which is delivered in timed relation to the evoked T-wave, preferably during the falling edge portion of the T-wave. In this way, each cycle the inducing pulse is timed for efficaciously inducing tachycardia. The timing of the inducing pulse is enhanced by near field sensing of the T-wave at about the location where the pulses are delivered, preferably using bipolar sensing and/or sense circuitry designed to recover the signal with an optimum time response.

Abstract: There is provided a pacing system having special functions for treating the patient's atrium with atrial pacing so as to reduce the probability of occurrence of dangerous atrial arrhythmias. The pacemaker of the system provides for atrial Pace.sub.-- Conditioning, whereby the patient's normal intrinsic atrial rate is overridden by higher rate pacing whenever a predetermined sequence of intrinsic heartbeats is sensed. The pacemaker also provides for special pacing routines following the detection of one or more PACs. The PAC response routines include pacing at an elevated rate for a predetermined time or number of beats, and smoothing out pacing intervals for one or several cycles following the occurrence of a PAC.

Abstract: A system and method are provided for inducing ventricular tachycardia in a patient to enable testing to determine the optimum parameters for anti-tachycardia stimulation. The implantable device provides for overdrive pacing of the heart for a short sequence, followed by delivery of a series of pulse pairs. Each pulse pair has a first stimulus pulse delivered at the same or similar overdrive rate, and an inducing pulse which is delivered in timed relation to the evoked T-wave, preferably during the falling edge portion of the T-wave. In this way, each cycle the inducing pulse is timed for efficaciously inducing tachycardia. The timing of the inducing pulse is enhanced by near field sensing of the T-wave at about the location where the pulses are delivered, preferably using bipolar sensing and/or sense circuitry designed to recover the signal with an optimum time response. In one preferred embodiment, near field sensing is enabled by use of an FDC circuit.

Abstract: A pacemaker system is provided which provides for more flexibility in re-programming of the control software, or program which is controlling an implanted pacemaker. The system comprises an external programmer device which is capable both of programming the implanted device in a conventional way, and also downloading new control software to the implanted device, subject to predetermined system conditions. All implanted devices, e.g., pacemakers within the system of the invention, share a hardware platform, and are identified as belonging to a given one of a plurality of groups, each group being characterized as providing therapy aimed at a different condition. Each pacemaker also carries type data, indicating the type of pacemaker within the group, and a set of permissions data representative of different types within the group to which it is permitted to be programmed.

Abstract: A rate responsive pacemaker and method of pacing, having circuitry for controlling the rate of change of pacing rate in response to varying rate sensor signals. The pacemaker increments or decrements pacing rate each cycle, the change in rate being limited as a function of pacing rate, rate of change of sensor rate; the magnitude of the difference between sensor rate and pacing rate; whether prior cycles ended in sense or pace events; and/or a separate fast response sensor.

Abstract: A rate adaptive pacemaker and method of operation, where the sensor-indicated rate is adjusted as a function of sensed sinus rate. The pacemaker is particularly adapted for VDDR operation. The natural sinus rate is compared to the sensor-indicated rate at one or more rates, and the sensor response function is adjusted, or adapted as a function of such comparisons, so as to optimize sensing of the atrial rate and maintenance of synchronous operation. The rate response function may be adjusted specifically at upper pacing limit, and may also be adjusted as a function of comparisons made at other rates.

Abstract: A pacemaker for providing optimized inhibit and trigger responses, operating in a VVD or AAD mode. For each pacemaker cycle, the pacemaker is controlled to time out a refractory interval, an inhibit interval or range following a refractory interval, and a trigger interval or range which follows the inhibit interval and ends at the time out of the scheduled escape interval. A signal sensed during the inhibit range results in no pace pulse delivery, the pacemaker goes to the trigger mode and extends the escape interval. Any signal thereafter sensed before the time out of the extended escape interval results in delivery of a trigger pulse and restarting of a new pacemaker cycle. If no signal is sensed during the inhibit range, any signal sensed during the trigger range results in generation of a trigger pulse and the start of a new pacemaker cycle.

Abstract: A dual chamber pacemaker system is provided having an improved Wenckebach response for optimizing tracking of atrial signals having rates within a rate range above the normal tracking range, i.e., in a designated Wenckebach range. When an atrial sense occurs in the Wenckebach range, the AV delay is extended up to a predetermined maximum extension to enable delivery of a ventricular pulse at the ventricular upper rate limit (dynamic tracking limit). When the AV delay would have to be extended beyond the maximum extension in order to pace the ventricle at the dynamic tracking limit, the next ventricular stimulus is delivered asynchronously at an escape interval greater than the escape interval corresponding to the dynamic tracking limit, e.g., at a predetermined lower pacing limit.

Abstract: A dual chamber pacemaker system is provided having means for determining when sensed atrial signals have a physiological rate, and tracking only such sensed atrial signals as are found to have physiological rates. The pacemaker provides logic means for continuously determining a physiological rate as a function of sensed atrial rate, whereby physiological rate substantially tracks the rate of sensed physiological atrial signals. The pacemaker also determines dynamic decision rates which are coupled to follow the physiological rate. The decision rates comprise a dynamic pacing limit, which sets the pacing escape interval; a dynamic tracking limit, which sets the upper limit of the physiological range of rates which are tracked; and the dynamic Wenckebach limit, which defines the upper rate for a dynamic Wenckebach range.

Abstract: A dual chamber pacemaker is provided having incorporated therein a VA conduction test for concurrently testing for the conditions of retrograde conduction (RC) and far field R wave sensing (FFRS). The pacemaker changes the AV or VV interval to a predetermined interval over a number of pacemaker cycles, and determines whether the VA interval remains substantially unchanged, i.e., the VA intervals are substantially equal. When VA interval equality is determined, the pacemaker checks the measure of VA interval with stored RC and FFRS criteria to determine whether either can be verified. Respective corrective steps are taken if either RC or FFRS is verified.

Abstract: A pacing system and method for delivering atrial stimulus pulses is provided, wherein detected AV interval is utilized for increasing or decreasing atrial pacing interval. The AV interval is compared with an AV reference value each cycle to determine direction of change of pacing, the AV reference being updated each cycle in accordance with a predetermined correlation of change of pacing interval and change of AV reference. The pacing system may be either DDDR or AAIR. In the AAIR embodiment, a single atrial lead is used and the far field ventricular R wave signal is sensed from the total electrocardiogram signal obtained from the atrial lead.

Abstract: A pacemaker system is provided for rate responsive pacing, wherein rate is controlled as a function of two or more sensor inputs, each sensor providing a signal representing a respective different control parameter. Preferably a first sensor signal represents a physiologically accurate although slow response signal such as OT interval, and a second sensor represents a relatively fast response such as activity. The two parameter signals are processed so that they are directly comparable and can be compared as indicators of pacing rate throughout the desired pacing range. The algorithm utilizes a parameter control reference curve for each respective parameter, such reference curve representing the desired correlation between pacing rate and the parameter signal.

Abstract: A rate adaptive pacemaker system, and method of operation, is provided which has a pacemaker which generates pacing pulses at a controlled pacing rate as a function of at least one monitored patient variable. The correlation of pacing rate with the patient variable is nonlinear, or dynamic, and is adapted to actual patient conditions. The value of the relationship between the pacing rate and the monitoring variable is determined at the lower rate limit and the upper rate limit, and the dynamic characteristic between these limits is automatically adjusted.

Abstract: A cardiac pacemaker and method of operation of such pacemaker is disclosed comprising a single lead having conventional ventricular pacing and sensing electrode means as well as atrial sensors adapted to be positioned in the patient's atrim without any contact with the atrial wall, for sensing atrial wall movement and for generating information signals representative of the atrial wall movement. The free-floating atrial sensor is utilized in providing information for making a determination of a number of cardiac conditions, including analysis of direction of P waves to determine whether sensed signals are anterograde or retrograde.

Abstract: A clamping device for clamping onto a support element, the device being made of a semi-rigid material having a high coefficient of elasticity and preferably in the form of a unitary piece. The device has a peripheral portion with a geometry such as a parallelogram whereby when pressure is applied from opposite sides along the shorter axis the device expands along its longer axis. A pair of fingers are formed extending lengthwise along the longer axis, to provide gripping surfaces at about the center of the device, whereby the applied pressure moves the gripping surfaces away from the support element, and release of such pressure results in their returning into a gripping condition.