摘要:
A cardiac stimulator lead (10) is provided that includes a connector (16) for connecting to a cardiac stimulator (24) and a tubular insulating sleeve (12) that has a first end (14) coupled to the connector and a second end (18). An electrode (20) is coupled to the second end and has a longitudinal bore. An extendable/retractable corkscrew (26) is positioned in the bore. In one aspect, the lead includes a radiopaque member moveable with the corkscrew to verify axial movement. In another aspect, the bore is configured so that the corkscrew will not extend fully unless tissue is present to engage the corkscrew. In another aspect, a shape-memory polymeric washer is included to restrict fluid influx after corkscrew deployment.
摘要:
A cardiac stimulator capable of measuring pacing impedance includes a tank capacitor for delivering charge to the heart via device leads, a shunt resistor, and high-impedance buffers for measuring pacing current through the shunt resistor. Soon after the leading edge of the stimulation pulse, the voltage across the shunt resistor, as sampled by a high-impendance buffer, indicates lead and cardiac tissue resistance. Just prior to opening the pacing switch to terminate the stimulation pulse, the voltage across the shunt resistor is sampled by a high-impedance buffer and held once against to allow the capacitance of the lead/heart tissue to be calculated. In alternative embodiments, a high-impedance buffer measures the voltage between the tank capacitor and ground immediately following the stimulation pulse to allow estimation of the lead/heart tissue capacitance. In one alternative embodiment, a look-up table is created in main memory and searched to find the closest lead/heart tissue capacitance estimate to any arbitrary degree of accuracy. In another alternative embodiment, the lead/heart tissue capacitance is estimated by successive approximation to any arbitrary degree of accuracy. When the lead/heart tissue capacitance and lead resistance have been determined, a plurality of parameters of importance for analyzing and optimizing a cardiac stimulation system may be calculated, such as the instantaneous current, the average current, the charge, and the energy delivered to the cardiac tissue.
摘要:
A cardiac lead is provided that is capable of deforming in situ to accommodate difficult myocardial structures. The lead includes a connector for coupling to a cardiac stimulator and a flexible tubular sleeve coupled to the connector. The sleeve is composed of a thermally-sensitive shape-memory polymeric material and is deformable in situ into a permanent shape. An electrode is coupled to the sleeve and a conductor wire is coupled to the connector and to the first electrode.
摘要:
An implantable medical device electrically stimulates the heart to beat and senses electrical activity in the heart. The medical device generally includes a processor, a plurality of electrodes, and a sense amplifier. The medical device is capable of performing a variety of diagnostic tests, such as a sensing test in which a suitable sensitivity setting is computed for the sense amplifier. An external programmer is also provided to initiate the diagnostic tests. The programmer transmits a start signal to the implantable medical device and the medical device's processor initiates the diagnostic test specified by the programmer via the start signal. The implantable device is capable of completing the diagnostic test without further communication from the programmer or may initiate communication with the programmer during a refractory period in which signals from the programmer will not interfere with the diagnostic test. In the latter case, the programmer responds before the refractory period ends.
摘要:
An implantable medical device (1) is disclosed having an electrically insulative coating material (7) on a portion of the titanium housing (2). A high definition window (8, 18) is prepared in the coating by pulsed excimer laser radiation ablating an organic coating, such as parylene or a similar polymer, to micromachine a conductive window having sharply defined boundaries or edges.
摘要:
An implantable medical device (100) for electrically stimulating the heart to beat generally includes a processor (170), a plurality of electrodes (101, 110, 120, 140, 150), a sense amplifier (162, 164), a pulse generator (168), and a heart status monitor. The processor can determine when the patient has entered an environment of high electromagnetic interference. When this occurs, the processor forces the implantable device into a safe noise mode. While in the same noise mode (which preferably continues while the patient is experiencing the electromagnetic interference), the implantable device paces the heart on demand and inhibits pacing during the vulnerable period. The processor determines when the vulnerable period is occurring and when the heart needs to be paced by monitoring a status signal from the heart status monitor. The heart status monitor preferably includes an impedance measurement circuit, but may include any type of cardiac sensor that can generate a status signal from which the processor can determine the beginning and ending of the vulnerable period.
摘要:
An implantable cardiac stimulation system (10) having a patient warning system (78) and an elongated electrode (26) mounted near the can of the system for providing reliable stimulation for warning. The electrode (26) has an extended length (34) and a short width (36). The length is preferably at least double the width and more preferably at least four times the width. This extended length increases the probability that contact with the surrounding tissue will be achieved. The short width and rounded profile of the width, forming an 'edge', on the other hand, increases the probability that a high enough current density will be achieved, causing stimulation to occur. The electrode may also be curved along its length, which tends to promote a 'point' or small area contact between the electrode and the patient's tissue. The electrode may be mounted directly on the can or header of the cardiac stimulator or may be part of a separate pin electrode. If a pin electrode is used, a hood configuration can be used to surround at least part of the header, reducing rotation of the pin electrode. By making only a portion of the surface of the pin electrode conductive, and particularly edges or corners, an elongated electrode, as described herein, is formed which produces a higher electric current density and more efficient stimulation.
摘要:
A method of communicating data between an external device and an implantable medical device wherein a first pulse is transmitted as electromagnetic energy from one device to the other, is received and stored as electrostatic energy in the second device and, after a delay period representing data to be communicated, the stored energy is released and transmitted as electromagnetic energy back to the first device. A communications circuit in the implantable device for accomplishing the method includes an antenna coil, a non-linear electronic component in circuit communication with the antenna coil, a storage capacitor in circuit communication with the antenna coil and non-linear electronic component for storing energy received by the antenna coil, and a switch for selectively connecting the charged storage capacitor and the antenna coil to discharge the charge stored in the capacitor into the antenna coil.
摘要:
An implantable medical device (100) for electrically stimulating the heart to beat includes a sense circuit (208, 218) for detecting cardiac electrical activity. The sense circuit includes an amplifier (210, 220) with a dynamically adjustable gain to provide increased sensitivity to the electrogram during atrial fibrillation. Alternatively, sensitivity control is provided by dynamically adjusting threshold limits associated with a threshold detector included in the sense circuit. The sensitivity level of the medical device to the electrogram can be repeatedly adjusted after implantation and preferably is increased upon detection of the loss of normal sinus rhythm (NSR) in the heart's atria. The medical device is calibrated with the aid of a calibration device (400) external to the body to determine appropriate sensitivity levels. A method for calibrating and operating an implanted medical device with dynamically adjustable sensitivity is also disclosed for improving the medical device's sensitivity to atrial fibrillation.
摘要:
A lead assembly (10) adapted for endocardial fixation to a human heart is provided. The lead assembly (10) includes a lead body (12) that has a proximal end provided with a connector (16) for electrical connection to a cardiac stimulator (18). The cardiac stimulator may be a pacemaker, a cardioverter/defibrillator, or a sensing instrument. The distal end of the lead body is connected to an electrode (23). The lead body consists of one or more noncoiled conductor cables (25) surrounded by a coextensive insulating sleeve (26). Each conductor cable consists of a conducting element covered by a coextensive insulating coating (29). The conducting element may be a single filament wire or a plurality of individual conductor wires. In contrast to conventional leads, the lead body of the present invention does not require coiled conductor wires. Lead body diameters of 1.04 mm or smaller are possible.