Cardiac Pacemakers, Inc.

Brian D Pederson

Rodney W Salo

John Anderson Hauck

Arthur L Olive

Bruce Alan Tockman

Ronald W Heil, Jr

Veerichetty A Kadhiresan

Robert C Owens

William L Zimmer

Renold J Russie

Michael W Dooley

Donald L Villalta

Brian P Citak

A cardiac pacing and sensing system includes a body implantable unit for generating tissue stimulation pulses and manipulating information based on sensed signals, and a catheter for transmitting pulses from the unit to a pacing electrode adjacent myocardial tissue. The unit incorporates circuitry for generating response values, one associated with each stimulation pulse, based on a predetermined characteristic or parameter of the signals evoked by the pulses. To evaluate the efficacy of the parameter in distinguishing capture versus non-capture, the stimulation pulses are generated according to a protocol of high energy pulses guaranteed to effect capture interspersed with low energy pulses guaranteed not to effect capture. Data, accumulated and sorted into separate 'capture' and 'non-capture' sets, provides respective capture and non-capture composite values. The ratio of the composite values is compared to a predetermined threshold, to generate an indication either accepting or rejecting the chosen parameter. A parameter, once accepted, can be employed in a self-test that either increments or decrements stimulation of signals to evaluate the capture threshold. Optionally, two or more designated parameters can be screened simultaneously and compared, with the most favorable ratio then being compared to the threshold.

Self-calibration system for capture verification in pacing devices

A rate adaptive cardiac pacer is described in which the impedance versus time information derived using impedance plethysmography or the pressure versus time information derived from a pressure transducer in a ventricular chamber is signal processed to recover a modulating envelope due to volume or pressure changes occasioned by respiratory activity. Either or both of the respiratory interval or respiratory depth may be combined in an appropriate rate control algorithm with other parameters also derived from the impedance versus time signal to develop a rate control signal for an implanted pacer.

Variation in cardiac chamber volume or pressure as a controlling

An endocardial lead having first and second spaced apart electrodes resides in a patient's heart. The first electrode is a sensing electrode and the second electrode is a carrier signal driving electrode. The lead has a conductor coupling a source of alternating current carrier signals of a predetermined frequency to the second electrode. A third electrode is in electrical contact with body tissues. A cardiac pacer apparatus includes a pacer can which functions as a fourth electrode and has a plastic top wherein the third electrode is located. Said third electrode acts in cooperation with the first electrode to form a pair of sensing electrodes. The sensing electrode pair is further coupled to a sense amplifier for receiving an amplifying modulated electrical signals developed across the sensing electrode pair. A demodulator and filters circuit for demodulating the modulated carrier signal and recovering the modulating signal therefrom is connected to the output of the sense amplifier. The modulating signal is proportional to instantaneous stroke volume of the patient's heart and the demodulator and filters circuit develops a control signal therefrom called a stroke volume signal. The control signal is applied to the pulse generator so as to control the rate of stimulating pulses.

Dual indifferent electrode pacemaker

A biomedical apparatus capable of sensing changes in the heart's ventricular volume or stroke volume and then changing the operating performance of the device in a fashion as a function of stroke volume. A relatively low frequency signal (under 5 KHz) is applied between spaced electrodes disposed in the heart and the beating action of the heart serves to modulate this signal due to changes in impedance being sensed between these or other electrodes within the heart. The modulated carrier signal is then processed to remove R-wave and other electrical artifacts and then demodulated to remove the carrier frequency component leaving the envelope which is proportional to instantaneous ventricular volume. This envelope signal then contains stroke volume and ventricular volume information which can be used by the biomedical apparatus to vary its operating parameters. For example, a current proportional to changes in stroke volume may be injected into the timing circuit of a demand-type cardiac pacer pulse generator whereby the interpulse interval of the pulse generator is varied as a function of stroke volume.

Biomedical method and apparatus for controlling the administration of

Variable rate cardiac pacer

A variable rate cardiac pacer apparatus is responsive to the physical activity of the patient. A source of alternating current carrier signals of a predetermined frequency is coupled to the pacer housing. At least one sensing electrode is coupled to the carrier signals. The sensing electrode and the pacer housing are structured and arranged to operate as a pair of interface sensing electrodes. A sense amplifier apparatus is coupled to the sensing electrodes for receiving and amplifying modulated electrical signals developed across the sensing electrodes. A demodulator circuit apparatus is structured and arranged to receive the amplified modulated carrier signal which is proportional to the impedance field around the sensing electrode. The frequency of the demodulated signal is proportional to the patient's rate of movement. A signal processing apparatus receives the demodulated signal and provides a processed signal proportional to impedance changes sensed at the interface. A rate control apparatus determines the rate at which the heart stimulating pulse will be generated in response to the processed signal.

Rate responsive pacemaker apparatus having an electrode interface sensor

A method for matching the distance spanned by a plurality of surface electrodes on an impedance measuring catheter to the size of a ventricular chamber to be measured is disclosed. The catheter includes a plurality of longitudinally spaced electrodes extending from its distal end and spanning a distance known to be greater than the maximum length of a ventricular chamber. With the distal end of the catheter located at the apex of the ventricle, an AC drive signal is applied between the distal electrode and a proximal electrode known to be outside of the ventricle. By then sensing the resulting voltage between successive adjacent electrode pairs and comparing same, the pair where a different characteristic is exhibited is known to be at the transition between the ventricle and the atrium.

Method for matching the sense length of an impedance measuring catheter

A resistivity cell formed integrally with or attached to the proximal end of a diagnostic catheter, allowing blood resistivity to be more easily and accurately measured. The cell comprises generally cylindrical body having an internal longitudinal bore of a known cross-sectional area and extending through the wall of the body are first and second pairs of longitudinally aligned electrodes. By joining a syringe to the proximal end of the assembly, a known volume of blood can be drawn into the cell. By applying an alternating current driving signal across the two outer electrodes and measuring the resistance between the two center electrodes, the blood's resistivity can be measured using the equation .rho.=AR/1. By connecting the cell directly to the vascular catheter, the need to maintain the blood sample at body temperature is alleviated.

Flow-through resistivity cell

An implantable cardiac pacing lead includes a porous, platinum electrode, a flexible electrically conductive coil, and a crimp tube coupling the electrode to the distal end of the coil. A recess in the crimp tube, open to the electrode at the crimp tube distal end, houses a matrix impregnated with a therapeutic drug. The electrode is highly porous and loaded with a therapeutic drug in liquid or solid form. Immediately upon implant of the electrode at a selected myocardial location, the electrode begins dispensing the therapeutic drug. Meanwhile, the matrix begins to elute its drug at a rate more suited to chronic treatment. If desired, the recess can extend through the crimp tube to permit proximal end loading of the drug carrying matrix. A silicone plug, or an additional and proximal crimp tube section, is inserted into the recess after loading of the matrix to provide the required fluid seal. Finally, a variety of different matrices can be housed in the recess, to provide elution of different drugs and at differing rates.

Cardiac electrode with drug delivery capabilities

A multi-pole pacing/sensing lead is used to measure the instantaneous impedance in the right ventricle of a patient's heart. The resulting impedance waveform is signal processed to obtain a measure of the time interval beginning with the occurrence of a paced beat or a spontaneous QRS complex (systole marker) and ending with the point where the impedance versus time signal crosses the zero axis in the positive direction following the paced or spontaneous QRS complex initiating the interval or some other predetermined point along the positive-going waveform. The resulting time interval is inversely proportional to the contractility of the heart and is found to decrease with exercise and the introduction of catecholamines. Thus, it can be used as a control parameter for a demand-type cardiac pacemaker. A means for obviating changes in pacing rate due to long-term drift in the impedance sensing circuitry is also disclosed.

Physiologic control of pacemaker rate using pre-ejection interval as the

A cardiac pacer of the type having an implantable pulse generator and electrical leads deployed in the right ventricular chamber of the heart. The lead has a stimulating electrode as well as a plurality of sensing electrodes coupled to the pulse generator. Certain control circuitry associated with the implantable pacer provides for measurement of the impedance variations occasioned by the pumping action of the heart and a differentiating circuit operatively coupled to the impedance sensing circuit for developing a control signal corresponding to the rate of change of the impedance with respect to time. This control signal may be coupled to the timing circuit of the implantable pulse generator, allowing the pacing rate to be altered in accordance with the level of physiologic activity of the person in whom the pacer is implanted.

Closed loop control of cardiac stimulator utilizing rate of change of

An improved dilation catheter for use in the conduct of transluminal angioplasty techniques whereby measurements may be taken to determine patency during the course of the procedure. The catheter comprises an elongated tubular member having an inelastic expander member proximate its distal end. The expander is adapted to be inflated and deflated through the introduction of a suitable fluid into the lumen of the tubular member. Disposed on either side of the expander member are sets of electrodes, preferably ring electrodes. Associated with each such electrode is a conductor which runs the length of the catheter from an associated ring electrode to the proximal end of the catheter where such conductors are connected to circuitry for performing impedance plethysmography. Thus, as the improved catheter is routed through the vascular system, the cross-sectional size of the blood vessel at plural points proximate the distal end of the catheter can be assessed, both for locating stenotic lesions to be treated and for later determining the efficacy of the treatment process.

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Saint Paul, MN, United States of America

Brian D Pederson