Source: http://www.google.com/patents/US6456882?dq=5,966,702
Timestamp: 2014-10-02 17:48:10
Document Index: 164735150

Matched Legal Cases: ['art 28', 'art 28', 'art 28', 'art 28', 'art 28', 'Application No. 60']

Patent US6456882 - Implantable cardiac stimulation device having automatic capture/threshold ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsAn improved system and method for performing automatic capture/threshold detection in an implantable cardiac stimulation device or any device capable of stimulating some organ or tissue in the body. In existing systems a threshold stimulation energy level is periodically determined and a working stimulation...http://www.google.com/patents/US6456882?utm_source=gb-gplus-sharePatent US6456882 - Implantable cardiac stimulation device having automatic capture/threshold capability using a dynamically adjustable safety marginAdvanced Patent SearchPublication numberUS6456882 B1Publication typeGrantApplication numberUS 09/684,153Publication dateSep 24, 2002Filing dateOct 6, 2000Priority dateMay 15, 2000Fee statusPaidPublication number09684153, 684153, US 6456882 B1, US 6456882B1, US-B1-6456882, US6456882 B1, US6456882B1InventorsHarold C. SchlossOriginal AssigneePacesetter, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (13), Non-Patent Citations (2), Referenced by (18), Classifications (5), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetImplantable cardiac stimulation device having automatic capture/threshold capability using a dynamically adjustable safety marginUS 6456882 B1Abstract An improved system and method for performing automatic capture/threshold detection in an implantable cardiac stimulation device or any device capable of stimulating some organ or tissue in the body. In existing systems a threshold stimulation energy level is periodically determined and a working stimulation energy level is then set by increasing the threshold stimulation energy level by a fixed or preprogrammed safety margin, e.g., a fixed voltage level or a percentage safety margin. However, in certain circumstances this safety margin may not be sufficient, resulting in either frequent threshold level determinations or losses-of-capture. To avoid these situations which may be wasteful of battery energy or dangerous for the patient, embodiments of the present invention periodically increase and/or decrease the safety margin according to the performance of the stimulation device, i.e., based upon the frequency of capture.
FIELD OF THE INVENTION The present invention is generally directed to an implantable medical device, e.g., a cardiac stimulation device, and is particularly directed to an automatic capture/threshold pacing method for use in such a device.
It is well known that the amplitude of a pulse that will reliably stimulate a patient's heart i.e., its threshold value will change over time after implantation and will vary with the patient's activity level and other physiological factors. To accommodate for these changes, pacemakers may be programmed manually by a medical practitioner to deliver a pulse at an amplitude well above an observed threshold value. To avoid wasting battery energy, the capability was developed to automatically adjust the pulse amplitude to accommodate for these long and short-term physiological changes. In an existing device, the Affinity� DR, Model 5330 L/R Dual-Chamber Pulse Generator, manufactured by the assignee of the present invention an AutoCapture� pacing system is provided. The User's Manual, �1998 St. Jude Medical, which describes this capability is incorporated herein by reference. In this system, the threshold amplitude level is automatically determined for a predetermined duration level in a threshold search routine and capture is maintained by a capture verification routine. Once the threshold search routine has determined a pulse amplitude that will reliably stimulate i.e., capture, the patient's heart, the capture verification routine monitors signals from the patient's heart to identify pulses that do not stimulate the patient's heart (indicating a loss-of-capture). Should a loss-of-capture (LOC) occur the capture verification routine will generate a large amplitude (e.g., 4.5 volt) backup pulse shortly after (typically within 80-100 ms.) the original (primary) stimulation pulse. This capture verification occurs on a pulse-by-pulse basis and thus, the patient's heart will not miss a beat. However while capture verification ensures the patient's safety, the delivery of two stimulation pulses (with the second stimulation pulse typically being much larger in amplitude) is potentially wasteful of a limited resource, the battery capacity. To avoid this condition the existing device, monitors for two consecutive loss-of-capture events and only increases the amplitude of the primary stimulation pulse should two consecutive loss-of-capture (LOC) events occur i.e., according to a loss-of-capture criteria. This procedure is repeated, if necessary, until two consecutive pulses are captured, at which time a threshold search routine will occur. The threshold search routine decreases the primary stimulation pulse amplitude until capture is lost on two consecutive pulses and then, in a similar manner to that previously described, increases the pulse amplitude until two consecutive captures are detected. This is defined as the capture threshold. The primary pulse amplitude is then increased by a safety margin value, e.g., 0.3 volts to ensure a primary stimulation pulse whose amplitude will exceed the threshold value and thus reliably capture the patient's heart without the need for frequent backup pulses. In a copending, commonly-assigned application to Paul A. Levine, entitled �An Implantable Cardiac Stimulation Device Having Autocapture/Autothreshold Capability�, improved loss-of-capture criteria are disclosed which are based upon X out of the last Y beats, where Y is greater than 2 and X is less than Y. The Levine application is incorporated herein by reference in its entirety.
SUMMARY OF THE INVENTION The present invention provides an improved system and method for performing automatic capture and threshold detection in an implantable cardiac stimulation device. In existing systems, a threshold stimulation energy level is periodically determined and a working stimulation energy level is then set by increasing the threshold stimulation energy level by a fixed or preprogrammed safety margin, e.g., a fixed voltage level or a percentage safety margin. However, in certain circumstances this safety margin may not be sufficient, resulting in either frequent threshold level determinations or losses-of-capture. To avoid these situations which may be wasteful of battery energy or dangerous for the patient embodiments of the present invention periodically increase and/or decrease the safety margin according to the performance of the stimulation device i.e., based upon the frequency of capture.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a simplified functional block diagram of an implantable cardioverter/defibrillator (ICD), which represents one type of implantable cardiac stimulation device with which the present invention may be used.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims.
In FIG. 2, a simplified block diagram of the circuitry needed for a dual-chamber pacemaker 70 is illustrated. The pacemaker 70 is coupled to heart 28 by way of leads 74 and 76, the lead 74 having an electrode 75 that is in electrical and preferably physical contact with one of the atria of the heart 28, and the lead 76 having an electrode 77 that is in electrical and preferably physical contact with one of the ventricles of the heart 28. The leads 74 and 76 are electrically and physically connected to the pacemaker 70 through a connector 73 that forms an integral part of the housing wherein the circuits of the pacemaker are housed. Typically, leads 74 and 76 are operated in a bipolar mode where a signal is generated by measuring the voltage difference between the voltage present at a �tip� portion and the �ring� portion on the same lead. Alternatively, leads 74 and 76 can operate in a unipolar mode where the voltage is measured from the �tip� portion of each lead to a conductive case 116 which surrounds the pacemaker 70.
The leads 74 and 76 carry stimulation pulses to the electrodes 75 and 77 from an atrial pulse generator (A-PG) 78 and a ventricular pulse generator (V-PG) 80, respectively. Further, electrical signals from an atrium are carried from the electrode 75, through the lead 74, to the input terminal of an atrial channel sense amplifier (A-AMP) 82; and electrical signals from a ventricle are carried from the electrode 77 through the lead 76, to the input terminal of a ventricular channel sense amplifier (V-AMP) 84. Similarly, electrical signals from both the atrium and the ventricle are applied to the inputs of an intracardiac electrogram amplifier (IEGM) 85. The amplifier 85 is typically configured to detect an evoked response from the heart 28, i.e., a response to an applied stimulation pulse, thereby aiding in the detection of �capture�. Capture occurs when an electrical stimulus applied to the heart is of sufficient energy to depolarize the cardiac tissue, thereby causing the heart muscle to contract, or in other words, causing the heart to beat. Capture does not occur when an electrical stimulus applied to the heart is of insufficient energy to depolarize the cardiac tissue. Following each stimulation pulse which causes capture, the associated cardiac tissue (i.e., the atrium or the ventricle) enters into a physiologic refractory period during which it cannot be re-stimulated.
The dual-chamber pacemaker 70 is controlled by a control and timing circuit (hereinafter referred to as a control/timing circuit) 86 that typically includes a microprocessor programmed to carry out control and timing functions. The control/timing circuit 86 receives the sensed signals from the atrial (A-AMP) amplifier 82 over signal line 88. Similarly, the control/timing circuit 86 receives the output signals from the ventricular (V-AMP) amplifier 84 over signal line 90, and the output signals from the IEGM amplifier 85 over signal line 91. These output signals are used to detect intrinsic events, such as R-waves or P-waves. These output signals may also be used to measure the response following a pacing pulse. The control/timing circuit 86 uses these signals to determine if the pacing pulse was captured. Also, the control/timing circuit may be used to measure the polarization artifact present on the electrodes 75 and/or 77 when calibrating the evoked response detection system by pacing when the heart is known to be in a refractory state. The control/timing circuit 86 also generates trigger signals that are sent to the atrial pulse generator (A-PG) 78 and the ventricular pulse generator (V-PG) 80 over signal lines 92 and 94, respectively, to control the energy level (comprised of amplitude and duration components) of the signals delivered to the electrodes, 75 and 77. These trigger signals are generated each time that a stimulation pulse is to be generated by the respective pulse generator 78 or 80. The atrial trigger signal is referred to simply as the �A-trigger�,and the ventricular trigger signal is referred to as the �V-trigger�.
It is noted that the pacemaker 70 in FIG. 2 is referred to as a dual-chamber pacemaker because it interfaces with both an atrium and a ventricle of the heart 28. Those portions of the pacemaker 70 that interface with the atrium, e.g., the lead 74, the P-wave sense amplifier 82 the atrial pulse generator 78, and corresponding portions of the control/timing circuit 86, are commonly referred to as the �atrial channel�. Similarly, those portions of the pacemaker 70 that interface with the ventricle, e.g., the lead 76, the R-wave sense amplifier 84, the ventricular pulse generator 80 and corresponding portions of the control/timing circuit 86, are commonly referred to as the �ventricular channel�. While a dual chamber pacemaker includes a single atrial channel and a single ventricular channel, multichamber devices may include more than one atrial channel and/or more than one ventricular channel.
As needed for certain applications, the pacemaker 70 may further include at least one sensor 112 that is connected to the control/timing circuit 86 of the pacemaker 70 over a suitable connection line 114. While this sensor 112 is illustrated in FIG. 2 as being included within the pacemaker 70, it is to be understood that the sensor may also be external to the pacemaker 70, yet still be implanted within or carried by the patient. A common type of sensor is an activity sensor, such as a piezoelectric crystal, that is mounted to the case of the pacemaker. Other types of sensors are also known, such as sensors that sense the oxygen content of blood, respiration rate, pH of blood body motion, and the like. The type of sensor used is not critical to the present invention. Any sensor or combination of sensors capable of sensing a physiological or physical parameter relatable to the rate at which the heart should be beating (i.e., relatable to the metabolic need of the patient), and/or relatable to whether a tachyarrhythmia is likely to soon occur, can be used. Such sensors are commonly used with �rate-responsive� or �rate-modulated� pacemakers in order to adjust the rate (pacing cycle) of the pacemaker in a manner that tracks the physiological or metabolic needs of the patient.
Representative of the types of control/timing circuits that may be used with the invention is the microprocessor-based control/timing circuit described in U.S. Pat. No. 4,940,052, entitled �Microprocessor Controlled Rate-Responsive Pacemaker Having Automatic Rate Response Threshold Adjustment.� Reference is also made to U.S. Pat. Nos. 4,712,555 and 4,944,298, wherein a state-machine type of operation for a pacemaker is described; and U.S. Pat. No. 4,788,980, wherein the various timing intervals used within the pacemaker and their inter-relationship are more thoroughly described. The '052, '555, '298 and '980 patents are incorporated herein by reference.
Accordingly, what has been shown is an improved automatic capture/threshold procedure for use in an implantable cardiac stimulation device where the safety margin value adaptively varies in response to the loss-of-capture performance of the device. While the invention has been described by means of specific embodiments and applications thereo,f it is understood that numerous modifications and variations could be made thereto by those skilled in the art without departing from the spirit and scope of the invention. For example, while the description of the safety margin has primarily described adding a value to the amplitude of a threshold stimulation pulse, safety margins that increase the duration of the stimulation pulse is also considered to be within the scope of the present invention. Additionally, embodiments where the safety margin is achieved by increasing the amplitude and duration of the stimulation pulse are also considered to be within the scope of the present invention. Such a safety margin has been described in a copending, commonly-assigned U.S. Provisional Application No. 60/204,317, entitled �Method and Device For Optimally Altering Stimulation Energy to Maintain Capture of Cardiac Tissue� (to Mandell), the teachings of which are incorporated herein by reference in their entirety. It is therefore to be understood that within the scope of the claims, the invention may be practiced otherwise than as specifically described herein.
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EventsDateCodeEventDescriptionMar 24, 2014FPAYFee paymentYear of fee payment: 12Mar 24, 2010FPAYFee paymentYear of fee payment: 8Mar 24, 2006FPAYFee paymentYear of fee payment: 4Oct 6, 2000ASAssignmentOwner name: PACESETTER, INC., CALIFORNIAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SCHLOSS, HAROLD C.;REEL/FRAME:011291/0977Effective date: 20000922Owner name: PACESETTER, INC. 15900 VALLEY VIEW COURT SYLMAR CARotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google