Patent Application
20070213774
This document generally relates to cardiac rhythm management (CRM) systems and particularly to a system for testing defibrillation threshold (DFT) during implantation of an implantable medical device such as an implantable cardioverter defibrillator (ICD).
Tachyarrhythmias are abnormal heart rhythms characterized by a rapid heart rate. Tachyarrhythmias generally include supraventricular tachyarrhythmia (SVT, including atrial tachyarrhythmia, AT) and ventricular tachyarrhythmia (VT). Fibrillation is a form of tachyarrhythmia further characterized by an irregular heart rhythm. In a normal heart, the sinoatrial node, the heart's predominant natural pacemaker, generates electrical impulses, called action potentials, that propagate through an electrical conduction system to the atria and then to the ventricles of the heart to excite the myocardial tissues. The atria and ventricles contract in the normal atrio-ventricular sequence and synchrony to result in efficient blood-pumping functions indicated by a normal hemodynamic performance. VT occurs when the electrical impulses propagate along a pathologically formed self-sustaining conductive loop within the ventricles or when a natural pacemaker in a ventricle usurps control of the heart rate from the sinoatrial node. When the atria and the ventricles become dissociated during VT, the ventricles may contract before they are properly filed with blood, resulting in diminished blood flow throughout the body. This condition becomes life-threatening when the brain is deprived of sufficient oxygen supply. Ventricular fibrillation (VF), in particular, stops blood flow within seconds and, if not timely and effectively treated, causes immediate death. In very few instances a heart recovers from VF without treatment.
Implantable cardioverter defibrillators (ICDs) are used to treat most tachyarrhythmias, including AT, VT, and VF. An ICD is an implantable medical device that delivers a defibrillation pulse (shock) to terminate a detected tachyarrhythmia episode. The electric defibrillation pulse depolarizes portions of the myocardium and renders it refractory. During the implantation of an ICD to a patient anticipating tachyarrhythmia episodes, a defibrillation threshold (DFT) test is performed to determine the DFT, which is the energy level of the defibrillation pulse required to terminate a tachyarrhythmia episode of that patient. The energy level of each defibrillation pulse is then programmed to a level exceeding the DFT by a safety margin. The programmable energy level for each defibrillation pulse is limited to the ICD energy level.
During a DFT test, several energy levels are programmed to be tested. A VF episode is induced, such as by delivering a defibrillation pulse during a ventricular repolarization (on a T wave). A defibrillation pulse at the programmed minimum energy level is delivered from the ICD to terminate the induced VF. If the defibrillation pulse does not terminate the VF, another defibrillation pulse at the programmed next, stepped-up energy level is delivered. The delivery of the defibrillation pulses is repeated until the VF episode is terminated or until the programmed maximum energy level has been tested. If the VF episode is terminated, the last energy level (the energy level of the defibrillation pulse that terminated the VF episode) is the DFT. If the VF episode is not terminated, the VF episode is to be terminated without using the ICD. This may happen, for example, when the patient's DFT exceeds the programmed maximum energy level, or when defibrillation electrodes are not properly positioned in the patient. Thus, for the safety of the patient, there is a need for a device capable of terminating an arrhythmia episode, such as a VF episode, induced for a DFT test, in addition to the ICD.
A system for conducting a defibrillation threshold (DFT) test for programming an implantable medical device such as an implantable cardioverter defibrillator (ICD) during its implantation includes an external defibrillator as a back up device. The system reduces the risk to the patient by performing an automated external defibrillation procedure when external defibrillation is needed to recover the patient from an arrhythmia episode induced for the DFT test.
In one embodiment, a system for conducting a DFT test for programming an implantable medical device includes an external defibrillator and a medical device programmer. The external defibrillator is communicatively coupled to the medical device programmer. The external defibrillator delivers one or more external defibrillation pulses in response to an external defibrillation command. The medical device programmer programs the implantable medical device to perform the DFT test and produces the external defibrillation command if an arrhythmia episode induced prior to the DFT test sustains after the DFT test.
In one embodiment, a method for conducting a DFT test for programming an implantable medical device is provided. The DFT test is performed using the implantable medical device. Whether an arrhythmia episode induced prior to the DFT test sustains following the DFT test is determined using a medical device programmer. If the induced arrhythmia episode sustains following the DFT test, an external defibrillation command is produced using the medical device programmer. A delivery of one or more external defibrillation pulses is controlled according to an automated external defibrillation procedure in response to the external defibrillation command using at least one of the medical device programmer and an external defibrillator. The one or more external defibrillation pulses are delivered from the external defibrillator.
This Summary is an overview of some of the teachings of the present application and not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description and appended claims. Other aspects of the invention will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof. The scope of the present invention is defined by the appended claims and their legal equivalents.
The drawings illustrate generally, by way of example, various embodiments discussed in the present document. The drawings are for illustrative purposes only and may not be to scale.
FIGS. 5A-B are each a portion of a block diagram illustrating an embodiment of an external defibrillator system and a programmer system of the CRM system.
FIGS. 6A-B are each a portion of a block diagram illustrating another embodiment of the external defibrillator system and the programmer system.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that the embodiments may be combined, or that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the spirit and scope of the present invention. References to “an”, “one”, or “various” embodiments in this disclosure are not necessarily to the same embodiment, and such references contemplate more than one embodiment. The following detailed description provides examples, and the scope of the present invention is defined by the appended claims and their legal equivalents.
This document discusses a system for conducting a DFT test for programming an ICD during its implantation. The system includes an external defibrillator as a back up device. The external defibrillator is automatically activated to defibrillate the patient when the ICD fails to recover the patient from an arrhythmia episode induced for the DFT. A medical device programmer of the system controls the ICD to perform the DFT test and controls the external defibrillator to recover the patient from the induced arrhythmia episode if the induced arrhythmia episode sustains after the DFT test or has lasted beyond a predetermined period of time (such as about 30-40 seconds). In one embodiment, the external defibrillator is an automated external defibrillator (AED) that delivers defibrillation pulses and performs an automated external defibrillation procedure to control the delivery of the defibrillation pulses in response to a command issued by the medical device programmer. In another embodiment, the external defibrillator delivers the defibrillation pulses, and the medical device programmer performs the automated external defibrillation procedure to control the delivery of the defibrillation pulses from the external defibrillator. In a further embodiment, the system includes an external arrhythmia induction system for inducting the arrhythmia episode prior to the DFT test.
Implantable medical device 101 delivers anti-tachyarrhythmia therapies including cardioversion and defibrillation therapies. In one embodiment, implantable medical device 101 is an ICD. In a specific embodiment, the ICD includes a cardiac pacemaker that delivers cardiac pacing pulses. In various embodiments, in addition to a cardioverter defibrillator, implantable medical device 101 includes one or more of other monitoring and/or therapeutic devices such as a cardiac pacemaker, a neural stimulator, a drug delivery device, and a biological therapy device. Implantable medical device 101 includes a hermetically sealed can housing an electronic circuit that senses physiological signals and delivers therapeutic electrical pulses. The hermetically sealed can also functions as an electrode for sensing and/or pulse delivery purposes. In one embodiment, as illustrated in
During implantation of implantable medical device 101 into a patient, a DFT test is conducted to determine the DFT, which is the energy level required for a defibrillation pulse to terminate a VT or VF episode in the patient. To ensure successful defibrillation when needed, implantable medical device 101 is to be programmed to deliver defibrillation pulses each with an energy level that exceeds the DFT by a safety margin. During the DFT test, at least distal end of 112 of lead 110 is inserted into heart 199 such that electrodes 112, 114, and 115 are placed for sensing one or more ventricular electrograms and delivering ventricular defibrillation pulses. In one embodiment, both distal end 112 of leads 110 and distal end 107 of lead 105 are inserted into heart for the proper operation of implantable medical device 101. Implantable medical device 101 is connected to the lead(s) but not implanted during the DFT test. In one embodiment, implantable medical device 101 induces an arrhythmia episode, such as a VF episode, prior to the DFT test, and delivers one or more defibrillation pulses in attempt to terminate the induced arrhythmia episode during the DFT. In a specific embodiment, implantable medical device 101 induces a VF episode by delivering at least one defibrillation pulse during a ventricular repolarization (i.e., on a T wave).
External system 120 includes a programmer system 122, an external defibrillator system 124, and a communication link 123. Programmer system 122 communicates with implantable medical device 101 via telemetry link 103 and allows for control of the DFT test. External defibrillator system 124 provides for recovery of the patient using external defibrillation if the arrhythmia episode induced for the DFT test is not terminated by the DFT test. Communication link 123 allows for communication between programmer system 122 and external defibrillator system 124.
Telemetry link 103 is a wireless communication link providing for bidirectional data transmission between implantable medical device 101 and programmer system 122. In one embodiment, telemetry link 103 is an inductive telemetry link. In an alternative embodiment, telemetry link 103 is a far-field radio-frequency telemetry link.
External system 220 is another embodiment of external system 120 and includes programmer system 122, external defibrillator system 124, an arrhythmia induction system 226, communication link 123, and another communication link 225. That is, in addition to the components of CRM system 100, CRM system 200 includes arrhythmia induction system 226 and communication link 225 as part of its external system.
Arrhythmia induction system 226 allows for induction of the arrhythmia episode prior to the DFT test by delivery electrical stimulation such as cardiac pacing pulses, a low-voltage DC current, or a low-voltage AC current. Arrhythmia induction system 226 provides induction of the arrhythmia episode without consuming the battery energy of implantable medical device 101. In various embodiments, the cardiac pacing pulses, the low-voltage DC current, or the low-voltage AC current provides an alternative or supplement to the defibrillation pulse in inducing the arrhythmia episode. Cardiac pacing at a high pacing rate is a relatively painless way to induce VF in a patient, but is not uniformly successful. Delivering a DC current at about 5-12 V has a high rate of success, but may cause plating of the electrodes. Delivering an AC current of 50 or 60 Hz also has a high rate of success, but is known to cause skeletal muscular contractions. In one embodiment, arrhythmia induction system 226 is capable of delivering two or more of the cardiac pacing pulses, the low-voltage DC current, and the low-voltage AC current for inducing VF, to allow selection by the physician conducting the DFT test. Communication link 225 allows for communication between programmer system 122 and arrhythmia induction system 226.
Programmer system 322 is a specific embodiment of programmer system 122 and includes a medical device programmer 330, surface ECG electrodes 331A-D, and a surface ECG cable 329 for connecting surface ECG electrodes 331A-D to medical device programmer 330. Medical device programmer 330 allows for programming of implantable medical device 101 to perform the DFT test and initiates external defibrillation if the arrhythmia episode induced prior to the DFT test sustains after the DFT test or lasts beyond a predetermined period of time (such as about 30-40 seconds). In one embodiment, medical device programmer 330 also controls the delivery of each external defibrillation pulses from external defibrillator system 324 according to an automated external defibrillation procedure. In one embodiment, surface ECG electrodes 333A-B are adhesive electrode patches for attachment to the skin of body 302 as illustrated in
External defibrillator system 324 is a specific embodiment of external defibrillator system 124 and includes an external defibrillator 332, external defibrillation electrodes 333A-B, and an external defibrillation cable 335 for connecting external defibrillation electrodes 333A-B to external defibrillator 332. In one embodiment, external defibrillator 332 is an AED that performs the automated external defibrillation procedure in response to an external defibrillation command produced by medical device programmer 330. In another embodiment, external defibrillator 332 delivers each defibrillation pulses in response to a pulse delivery command produced by medical device programmer 330 according to the automated external defibrillation procedure. In one embodiment, external defibrillation electrodes 333A-B are adhesive electrode pads for attachment to the skin of body 302 as illustrated in
Arrhythmia induction system 326 is a specific embodiment of arrhythmia induction system 226 and includes an arrhythmia induction device 334 coupled to heart 199 via lead system 310. Arrhythmia induction device 334 allows for induction of the arrhythmia episode prior to the DFT test. In one embodiment, medical device programmer 330 produces an arrhythmia induction command before programming implantable medical device 101 to perform the DFT test. Arrhythmia induction device 334 delivers electrical stimulation to heart 199 to induce the arrhythmia episode in response to the arrhythmia induction command. In various embodiments, arrhythmia induction device 334 delivers one or more of the cardiac pacing pulses, the low-voltage DC current, and the low-voltage AC current that are known to induce a VF episode in the patient.
Communication link 123 allows for communication between programmer system 322 and external defibrillator system 324. In one embodiment, communication link 123 is a wired link that provides for electrical connection between medical device programmer 330 and external defibrillator 332. In one embodiment, communication link 123 is a wireless link that provides for communication between medical device programmer 330 and external defibrillator 332 via telemetry.
Communication link 225 allows for communication between programmer system 322 and arrhythmia induction system 326. In one embodiment, communication link 225 is a wired link that provides for electrical connection between medical device programmer 330 and arrhythmia induction device 334. In one embodiment, communication link 225 is a wireless link that provides for communication between medical device programmer 330 and arrhythmia induction device 334.
In one embodiment, medical device programmer 330, external defibrillator 332, and arrhythmia induction device 334 are three physically separate units communicatively coupled to each other via wired and/or wireless communication links. In another embodiment, medical device programmer 330, external defibrillator 332, and arrhythmia induction device 334 are physically integrated into one external device. In another embodiment, medical device programmer 330 and external defibrillator 332 are physically integrated into one external device that is communicatively coupled to arrhythmia induction device 334 via a wired and/or wireless communication link. In another embodiment, medical device programmer 330 and arrhythmia induction device 334 are physically integrated into one external device that is communicatively coupled to external defibrillator 332 via a wired and/or wireless communication link. In another embodiment, arrhythmia induction device 334 and external defibrillator 332 are physically integrated into one external device that is communicatively coupled to medical device programmer 330 via a wired and/or wireless communication link.
In addition to controlling the DFT test, medical device programmer 330 generally allows for programming of implantable medical device 101 and receives signals acquired by implantable medical device 101. Telemetry link 103 provides for communication between medical device programmer 330 and implantable medical device 101. In one embodiment, telemetry link 103 is an inductive telemetry link. In an alternative embodiment, telemetry link 103 is a far-field radio-frequency telemetry link. Telemetry link 103 provides for data transmission from implantable medical device 101 to medical device programmer 330. This may include, for example, transmitting real-time physiological data acquired by implantable medical device 101, extracting physiological data acquired by and stored in implantable medical device 101, extracting therapy history data stored in implantable medical device 101, and extracting data indicating an operational status of implantable medical device 101 (e.g., battery status and lead impedance). Telemetry link 103 also provides for data transmission from medical device programmer 330 to implantable medical device 101. This may include, for example, programming implantable medical device 101 to acquire physiological data, programming implantable medical device 101 to perform at least one self-diagnostic test (such as for a device operational status), programming implantable medical device 101 to enable an available monitoring or therapeutic function, programming implantable medical device 101 to adjust therapeutic parameters such as pacing, cardioversion, and defibrillation parameters, programming the implantable medical device 101 to induce an arrhythmia episode for a DFT test, and programming the implantable medical device 101 to perform the DFT test.
Sensing circuit 440 senses one or more electrograms from heart 199 via lead system 310. Implant defibrillation circuit 442 delivers internal defibrillation pulses to heart 199 via lead system 310. When used in this document, “internal defibrillation pulses” refers to defibrillation pulses delivered using electrodes placed within the body of the patient, while “external defibrillation pulses” refers to defibrillation pulses delivered using electrodes attached to the skin of the patient. Tachyarrhythmia detection and classification module 444 detects tachyarrhythmia episodes and classifies each detected tachyarrhythmia episode by its type and/or origin using the one or more electrograms. In one embodiment, tachyarrhythmia detection and classification module 444 classifies the detected tachyarrhythmia episode as one of VT and SVT by comparing the morphology of the cardiac signal sensed during the detected tachyarrhythmia episode to a template morphology associated with a known cardiac rhythm such as a normal sinus rhythm (NSR). The classification of the detected tachyarrhythmia episode determines whether an internal defibrillation pulse is to be delivered based on whether the detected tachyarrhythmia episode is of a type and/or origin for which a defibrillation therapy is applicable.
Implant defibrillation controller 446 controls the delivery of the internal defibrillation pulses based on the classification of each detected tachyarrhythmia as well as in response to commands sent from medical device programmer 330. Implant defibrillation controller 446 includes a DFT testing module 447. DFT testing module 447 performs a DFT test in response to a DFT testing command. The DFT test includes delivering one or more internal defibrillation pulses each at a specified energy level. In one embodiment, the DFT test includes delivering a sequence of internal defibrillation pulses at programmed substantially different energy levels to terminate an induced arrhythmia episode. In a specific embodiment, the delivery of the sequence of internal defibrillation pulses starts with delivering an internal defibrillation pulse at the programmed minimum energy level and is stopped if the induced arrhythmia episode is terminated before the delivery of the entire sequence of internal defibrillation pulses. If a defibrillation pulse of the sequence of defibrillation pulses fails to terminate the induced arrhythmia episode, another defibrillation pulse of the sequence of defibrillation pulses at the next, stepped-up energy levels is delivered. This continues until the defibrillation pulse at the programmed maximum energy level is delivered. If the induced arrhythmia episode is not terminated after the delivery of the defibrillation pulse at the programmed maximum energy level, external defibrillation is to be performed to recover the patient.
ICD switch 448 starts and stops operation of ICD 401. In response to an ICD-off command, ICD switch stops the operation of the ICD 401. ICD 401 includes a mechanism protecting its electronic circuitry from being damaged and/or malfunctioning during external defibrillation. However, if desired, ICD switch 448 allows ICD 401 to stop its operation when external defibrillator 330 starts operating.
Implant telemetry circuit 450 transmits signals from ICD 401 to medical device programmer 330 and receives signals transmitted from medical device programmer 330 to ICD 401. Examples of the signals received using implant telemetry circuit 450 include the DFT testing command, the programmed energy levels of the internal defibrillation pulses, and the ICD-off command.
FIGS. 5A-B are each a portion of a block diagram illustrating an embodiment of an external defibrillator system 524 and a programmer system 522. In this embodiment, programmer system 522 sends the external defibrillation command to external defibrillator system 524 to start the external defibrillation. External defibrillator system 524 delivers external defibrillation pulses and controls the delivery of external defibrillation pulses according to the automated external defibrillation procedure.
External defibrillation cable and electrodes 533 provide for an interface between external defibrillator 532 and body 302 through which one or more external defibrillation pulses are delivered from external defibrillator 532 to body 302. In one embodiment, external defibrillation cable and electrodes 533 include external defibrillation cable 335 and external defibrillation electrodes 333A-B as discussed above with reference to
External defibrillator 532 is a specific embodiment of external defibrillator 332 and includes an external sensing circuit 552, an external defibrillation circuit 554, an external defibrillation controller 556, an AED switch 558, a command receiver 560, and a user interface 562. In the embodiment illustrated in
External sensing circuit 552 senses an external cardiac signal via external defibrillation electrodes 533. External defibrillation circuit 554 delivers the external defibrillation pulses. External defibrillation controller 556 controls the delivery of the external defibrillation pulses according to the automated external defibrillation procedure. External defibrillation controller 556 includes an AED rhythm analyzer 557 that analyzes the external cardiac signal to determine whether each external defibrillation pulse is to be delivered. In one embodiment, AED rhythm analyzer 557 detects VF. External defibrillation controller 556 causes the delivery of an external defibrillation pulse from external defibrillation circuit 554 when VF is detected. In one embodiment, external defibrillation controller 556 produces a therapy failure signal when the detected VF or cardiac arrest is still detected after the predetermined number of defibrillation pulses are delivered or after the predetermined time interval has elapsed.
AED switch 558 starts and stops operation of external defibrillator 532. In response to the external defibrillation command received from medical device programmer 330 or a user signal requesting external defibrillation, AED switch 558 starts the automated external defibrillation procedure. Command receiver 560 receives the external defibrillation command from medical device programmer 330 via communication link 123. User interface 562 includes a presentation device 563 and a user input device 564. Presentation device 563 includes a visual and/or audio indication of the states of the operation of external defibrillator 532 and a visual presentation device and/or a speaker to guide the user through the automated external defibrillation procedure. User input device 564 includes a user defibrillation switch 565, which receives the user signal requesting external defibrillation, thereby allowing the user to manually start the automated external defibrillation procedure when needed.
Surface ECG cable and electrodes 531 allow for monitoring of the patient's surface ECG. In one embodiment, surface ECG cable and electrodes 531 include surface ECG cable 329 and surface ECG electrodes 331A-D, as discussed above with reference to
Medical device programmer 530 is a specific embodiment of medical device programmer 330 and includes a surface ECG monitor 568, an external defibrillation initiator 570, an external telemetry circuit 572, a DFT controller 573, and a user interface 574. While components relevant to the DFT test are illustrated in
Surface ECG monitor 568 senses one or more surface ECG signals. In one embodiment, surface ECG monitor 568 senses a surface ECG signal using surface ECG electrodes 331A-D attached to the patient and connected to surface ECG monitor 568 via surface ECG cable 329.
External defibrillation initiator 570 produces the external defibrillation command to start the operation of external defibrillator 532. The external defibrillation command is sent to external defibrillator 532 via communication link 123. In one embodiment, when desired, external defibrillation initiator 570 also produces the ICD-off command to stop the operation of implantable medical device 101. The ICD-off command is sent to implantable medical device 101 via telemetry link 103. External defibrillation initiator 570 includes a programmer rhythm analyzer 571. Programmer rhythm analyzer 571 analyzes the surface ECG signal(s) sensed by surface ECG monitor 568 to determine whether to produce the external defibrillation command. In one embodiment, programmer rhythm analyzer 571 detects VF from a surface ECG signal when the surface ECG signal becomes available following the DFT test and produces the external defibrillation command if VF is detected.
External telemetry circuit 572 transmits signals from medical device programmer 530 to implantable medical device 101 and receives signals transmitted from implantable medical device 101 to medical device programmer 530. Implant telemetry circuit 450 and external telemetry circuit 572 form telemetry link 103.
DFT controller 573 programs implantable medical device 101 to perform the DFT test. DFT controller 573 produces the DFT testing command and transmits the DFT testing command and the programmed energy levels to implantable medical device 101 via telemetry link 103 in response to a user command for initiating the DFT test. In one embodiment, DFT controller 573 also produces the arrhythmia induction command for inducing the arrhythmia episode prior to the DFT test. The arrhythmia induction command is sent to implantable medical device 101 via telemetry link 103 and/or arrhythmia induction device 334 via communication link 225. In one embodiment, the delivery of each of the internal defibrillation pulses is controlled by DFT testing module 447 of ICD 401 (specific embodiment of implantable medical device 101), as discussed above with reference to
User interface 574 includes a presentation device 575 and a user input device 576. Presentation device 575 includes a display screen that displays the surface ECG signal(s) and signals received from implantable medical device 101, including the one or more electrograms. User input device 576 receives the user command for initiating the DFT test and the programmed energy levels. In one embodiment, user interface 574 includes an interactive screen that integrates portions of presentation device 575 and portions of user input device 576. In one embodiment, user interfaces 562 and 574 are each part of an integrated user interface.
FIGS. 6A-B are each a portion of a block diagram illustrating an embodiment of an external defibrillator system 624 and a programmer system 622. In this embodiment, programmer system 622 initiates and controls the automated external defibrillation procedure by sending the pulse delivery commands to external defibrillator system 624. External defibrillator system 624 delivers the external defibrillation pulses in response to the pulse delivery commands received from programmer system 626.
External defibrillator 632 is another specific embodiment of external defibrillator 332 and includes external sensing circuit 552, external defibrillation circuit 554, an external defibrillator controller 656, an external defibrillator switch 658, command receiver 560, and a user interface 662. In the embodiment illustrated in
External defibrillator controller 656 causes the delivery of each external defibrillation pulse upon receiving a pulse delivery command. External defibrillator switch 658 starts and stops operation of external defibrillator 632. In response to the external defibrillation command received from medical device programmer 330 or the user signal for turning external defibrillator 632 on, external defibrillator switch 658 activates external defibrillator 632 in preparation of receiving the pulse delivery commands and delivering the defibrillation pulses. Command receiver 560 receives the external defibrillation command from medical device programmer 330 via communication link 123. After external defibrillator 632 is turned on, command receiver 560 receives the pulse delivery command(s) from medical device programmer 330 via communication link 123.
User interface 662 includes a presentation device 663 and a user input device 664. Presentation device 663 includes a visual and/or audio indication of the states of the operation of external defibrillator 632. User input device 664 includes user defibrillation switch 665, which receives the signal for turning external defibrillator 532 on and/or the pulse delivery commands entered by the user. This allows the user to manually start and perform an external defibrillation procedure.
Medical device programmer 630 is a specific embodiment of medical device programmer 330 and includes surface ECG monitor 568, an external defibrillation controller 670, external telemetry circuit 572, DFT controller 573, and user interface 574. While components relevant to the DFT test are illustrated in
External defibrillation controller 670 produces the external defibrillation command to start the performance of the automated external defibrillation procedure. The external defibrillation command is sent to external defibrillator 632 via communication link 123 to activate external defibrillator 632 and also starts the control of the delivery of one or more external defibrillation pulses from external defibrillation 632 according to the automated external defibrillation procedure using medical device programmer 630. In one embodiment, when desired, external defibrillation controller 670 also produces the ICD-off command to stop the operation of implantable medical device 101. The ICD-off command is sent to implantable medical device 101 via telemetry link 103. External defibrillation controller 670 includes programmer rhythm analyzer 571. Following the DFT test, programmer rhythm analyzer 571 analyzes the surface ECG signal(s) sensed by surface ECG monitor 568 to determine whether to produce the external defibrillation command. In one embodiment, programmer rhythm analyzer 571 detects VF from a surface ECG signal when the surface ECG signal becomes available following the DFT test and produces the external defibrillation command if VF is detected. Then, programmer rhythm analyzer 571 detects VF from the surface ECG signal following the delivery of each defibrillation pulse from external defibrillator 632 and/or before each defibrillation pulse is ready to be delivered from external defibrillator 632. If the VF is detected, external defibrillation controller 670 produces a pulse delivery command and sends the pulse delivery command to external defibrillator 632 via communication link 123.
Lead(s) 710 provides the electrical connection between heart 199 and PSA 734 through which pacing pulses are delivered to heart 199. In one embodiment, lead(s) 610 include one or both of leads 110 and 105 as discussed above with reference to
PSA 734 is a specific embodiment of arrhythmia induction device 334 and includes a PSA sensing circuit 780, a pacing circuit 782, a pacing controller 784, and a user interface 786. In one embodiment, PSA 734 is an external (non-implantable) pacing and measuring device used during implantation of an implantable pacemaker or ICD to ensure adequate lead placement, maintain basic cardiac functions, evaluate pacing parameters for an initial programming of the implantable pacemaker, and/or induce an arrhythmia episode for a DFT test. PSA sensing circuit 780 senses one or more electrograms from heart 199 via lead(s) 710. Pacing circuit 782 delivers pacing pulses to heart 199 via lead(s) 710. Pacing controller 784 controls the delivery of the pacing pulses from pacing circuit 782. User interface 786 includes a presentation device 787 and a user input device 788. Presentation device 787 displays the sensed one or more electrograms, indications of each sensed and paced event, and/or measurement parameters such as lead impedances. User input device 788 allows the user to start, stop, and adjust the delivery of the pacing pulses. For the purpose of inducing the arrhythmia episode for a DFT test, pacing controller 784 causes pacing circuit 782 to deliver the pacing pulses at a pacing rate high enough to induce fast VT or VF. In one embodiment, user interfaces 562, 574, and 786 are each part of an integrated user interface.
In various embodiments, in addition to or instead of inducing the arrhythmia episode for the DFT test, PSA 734 is used to ensure that lead(s) are properly positioned before the DFT test. It may also provide for life support when necessary during the procedure of implanting implantable medical device 101.
To perform the DFT test, a process as illustrated in
An external defibrillator is connected to the patient at 804. This includes attaching external defibrillation electrodes onto the patient and electrically connects the external defibrillation electrodes to the external defibrillator using a cable. The external defibrillator is activated by an external defibrillation command is produced by the medical device programmer. In one embodiment, the external defibrillator is an AED that performs an automated external defibrillation procedure in response to the external defibrillation command. In another embodiment, the external defibrillator is activated by the external defibrillation command and delivers each external defibrillation pulse in response to a pulse delivery command produced by the medical device programmer.
One or more pacing and/or defibrillation leads are inserted to the patient at 806, with electrodes for sensing, pacing, and defibrillation placed in or on the heart of the patient. The leads are then connected to the ICD, which has not been implanted, at 808.
An arrhythmia episode is induced at 810. In one embodiment, the arrhythmia episode is induced using the ICD. In a specific embodiment, a fast VT or VF episode is induced by an internal defibrillation pulse delivered from the ICD during a ventricular repolarization (i.e., on a T wave). In another embodiment, the arrhythmia episode is induced using an external arrhythmia induction device. The medical device programmer sends an arrhythmia induction command to the ICD or the external fibrillation induction to induce the arrhythmia episode.
The DFT test is performed using the ICD at 812. The medical device programmer sends a DFT testing command to the ICD to initiate the DFT test. During the DFT test, one or more internal defibrillation pulses are delivered from the ICD to terminate the induced arrhythmia episode. The one or more internal defibrillation pulses each have a programmed energy level. In one embodiment, a sequence of internal defibrillation pulses at programmed substantially different energy levels is delivered to terminate the induced arrhythmia episode. In a specific embodiment, the delivery of the sequence of internal defibrillation pulses starts with the programmed minimum energy level and stops if and when the induced arrhythmia episode is terminated before the entire sequence of internal defibrillation pulses has been delivered. If an internal defibrillation pulse of the sequence of internal defibrillation pulses fails to terminate the induced arrhythmia episode, another internal defibrillation pulse of the sequence of internal defibrillation pulses at the next, stepped-up energy levels is delivered. This continues until either the induced arrhythmic episode is terminated or the internal defibrillation pulse at the programmed maximum energy level has been delivered.
If the patient is recovered by the end of the DFT test at 814, the process illustrated in
In response to the external defibrillation command, an automated external defibrillation procedure is performed at 820. In one embodiment, the automated external defibrillation procedure is performed by the external defibrillator that is an AED. During the automated external defibrillation procedure, an external cardiac signal is sensed by the AED using the external defibrillation electrodes. If a need for defibrillation in indicated in the external cardiac signal, an external defibrillation pulse is delivered from the AED. After the delivery of the external defibrillation pulse, whether the induced arrhythmia episode sustains is determined. If the induced arrhythmia episode sustains, another defibrillation pulse is delivered from the AED. The AED repeats the delivery of the external defibrillation pulse and the determination of whether the induced arrhythmia episode sustains until the induced arrhythmia episode no longer sustains, until a predetermined number of defibrillation pulses have been delivered, or until a predetermined time interval has expired. In another embodiment, the automated external defibrillation procedure is performed by the external defibrillator and the medical device programmer. During the automated external defibrillation procedure, if a need for defibrillation is detected by the medical device programmer from the one or more surface ECG signals, a pulse delivery command is sent to the external defibrillator to cause the delivery of an external defibrillation pulse. After the delivery of the external defibrillation pulse, whether the induced arrhythmia episode sustains is determined by the medical device programmer. If the induced arrhythmia episode sustains, another pulse delivery command is sent to the external defibrillator to cause the delivery of another defibrillation pulse. The medical device programmer repeatedly sends the pulse delivery command to the external defibrillator and determines whether the induced arrhythmia episode sustains until the induced arrhythmia episode no longer sustains, until a predetermined number of defibrillation pulses have been delivered, or until a predetermined time interval has expired.
The process illustrated in
It is to be understood that the above detailed description is intended to be illustrative, and not restrictive. Other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
